Vibration Analysis Manual Rev0

OPERATIONS/ MAINTENANCE VIBRATION MANUAL

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INDICE INDICE

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CHAPTER 1

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1.1 INTRODUCTION ............................................................................................. 4 1.2 CONDITIONS FOR SUCCESS .................................................................................. 4 1.3 DEFINITION OF GOALS AND OBJECTIVES .................................................................... 5 1.4. MANAGEMENT'S SUPPORT .................................................................................. 6 1.5. PERSONNEL IN CHARGE OF THE PREVENTIVE-PREDICTIVE MAINTENANCE SYSTEM ........................... 6 1.6. IDEAL CHARACTERISTICS OF A VIBRATION ANALYST ........................................................ 7 1.7 IDEAL CHARACTERISTICS OF A PERSON IN CHARGE OF MAINTENANCE ......................................... 8 CHAPTER 2

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2.1 INTRODUCTION ........................................................................................... 2.2 FORMATION OF THE PREDICTIVE MAINTENANCE GROUP .................................................... 2.3 PLANT'S MAINTENANCE DIRECTOR ......................................................................... 2.4 VIBRATION ANALYST ...................................................................................... 2.5 THE PERSON IN CHARGE OF MAINTENANCE ................................................................ 2.6 TECHNICAL DEPARTMENT ................................................................................. 2.7 CONCLUSIONS ............................................................................................ CHAPTER 3

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3.1 INTRODUCTION ........................................................................................... 3.2 MINIMUM TRAINING REQUIREMENTS ....................................................................... 3.3 BASIC LEVEL IN VIBRATION ANALYSIS ..................................................................... 3.4 INTERMEDIATE LEVEL IN VIBRATION ANALYSIS ............................................................. 3.5 ADVANCED LEVEL IN VIBRATION ANALYSIS ................................................................. 3.6 TRAINING IN THE USE OF INSTRUMENTS AND THE PREDICTIVE MAINTENANCE SYSTEM ...................... 3.7 VIBRATION ANALYSIS QUESTIONNAIRE ..................................................................... 3.8 ADDITIONAL TRAINING .................................................................................... CHAPTER 4

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4.1 INTRODUCTION ........................................................................................... 4.2 SELECTION PROCEDURE ................................................................................... 4.3 PRIORITY 1, VERY CRITICAL EQUIPMENT .................................................................. 4.4 PRIORITY 2, CRITICAL EQUIPMENT ........................................................................ 4.5 PRIORITY 3, EQUIPMENT WITH NORMAL PRIORITY ......................................................... 4.6 PRIORITY 4, EQUIPMENT WITH LOW PRIORITY............................................................. 4.7 CONCLUSIONS ............................................................................................ CHAPTER 5

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5.1 INTRODUCTION ........................................................................................... 35 5.2 COMMENTS ABOUT THE FORMATS ......................................................................... 35 CHAPTER 6

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6.1 INTRODUCTION ........................................................................................... 6.2 DIFFERENT TYPES OF SPECTRAL BAND ALARMS ............................................................ 6.3 VIBRATION-MOVEMENT, SPEED AND ACCELERATION PARAMETERS .......................................... 6.4 PROBLEMS THAT CAN BE DETECTED WITH VIBRATION ANALYSIS ............................................ 6.5 VIBRATION GLOBAL VALUE (GV) SPECIFICATIONS ......................................................... 6.6 ALARM LEVELS AND SPECTRAL BAND WIDTH SPECIFICATIONS ............................................... 6.7 CASE A - GENERAL EQUIPMENT WITH COG TOOTH OR BLADE BEARINGS .................................... 6.8 CASE B - GENERAL EQUIPMENT LIKE FLAT STRENGTHENING PLATES WITHOUT COG TEETH OR BLADES. ..... 6.9 CASE C - GEAR BOX, HIGH FREQUENCY POINTS WITH A KNOWN NUMBER OF TEETH ........................ 6.10 CASE D - GEAR BOXES, HIGH FREQUENCY POINTS WITH AN UNKNOWN NUMBER OF TEETH ................ 6.11 CASE E - MEASUREMENT POINT FOR THE ROTOR ROD PASSAGE FREQUENCY IN INDUCTION MOTORS ....... 6.12 CASE F - LOW FREQUENCY MEASUREMENT POINT FOR THE DETECTION OF ELECTRIC FREQUENCY.......... 6.13 CASE G - SPECIAL EQUIPMENT .......................................................................... 6.14 THE DETECTION OF HIGH FREQUENCY IN THE BEARING CONDITION DIAGNOSTICS.......................... CHAPTER 7

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7.1 INTRODUCTION ........................................................................................... 7.2 THE PRINCIPLES FOR CORRECT MOUNTING OF VIBRATION TRANSDUCERS ................................... 7.3 SELECTION OF MEASUREMENT POINTS ON THE EQUIPMENT ................................................. 7.4 EFFICIENT TRACING OF MONITORING ROUTES ............................................................. 7.5 DEFINITION OF MONITORING PRIORITIES ................................................................... CHAPTER 8

55 56 56 58 58 60 60 61 62 62 63 63 64 65 74 74 77 79 80

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8.1 INTRODUCTION ........................................................................................... 82 8.2 SELECTION OF THE OPTIMAL PARAMETER FOR THE LOW FREQUENCY MEASUREMENTS (ACCELERATION, VELOCITY AND MOVEMENT) ............................................................................ 82 8.3 REQUIRED EQUIPMENT FOR LOW FREQUENCY ANALYSIS .................................................... 83 8.4 BEARING EVALUATION IN THE EQUIPMENT WITH LOW SPINNING VELOCITY. ................................. 86 8.5 SPECIFICATIONS FOR THE ALARM LEVELS IN THE SPECTRAL BAND FOR THE LOW SPINNING VELOCITY EQUIPMENT ....................................................................................................... 87 CHAPTER 9

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9.1 INTRODUCTION ........................................................................................... 9.2 DEMODULATION BASIC PRINCIPLES ........................................................................ 9.3 FUNCTIONS OF THE CSI DEMODULATOR 750 .............................................................. 9.4 EXAMPLE OF DEMODULATOR 750'S USE ................................................................... 9.5 CONCLUSIONS ............................................................................................ CHAPTER 10

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10.1 INTRODUCTION ......................................................................................... 95 10.2 MAINTENANCE INDICATORS .............................................................................. 95 10.3 CONCLUSIONS........................................................................................... 96 CHAPTER 11

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11.1 INTRODUCTION ......................................................................................... 99 11.2 VIBRATION ANALYSIS REPORT ........................................................................... 99 11.3 REPORT OF THE RESULTS OBTAINED .................................................................... 100



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CHAPTER 12

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12.1 INTRODUCTION ........................................................................................ 106 12.2 PRECISION ALIGNMENT ................................................................................. 106 12.3 PRECISION BALANCING ................................................................................. 107 12.4 BASES AND ANCHORING ................................................................................ 107 12.5 DOCUMENTING THE PRECISION CORRECTIONS ........................................................... 109 12.5 DOCUMENTING THE PRECISION CORRECTIONS ........................................................... 110 12.6 FINANCIAL SAVINGS .................................................................................... 110 CHAPTER 13

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13.1 INTRODUCTION ........................................................................................ 113 13.2 MANAGEMENT SUPPORT AND PLANT'S CULTURE ......................................................... 113 13.3 PROGRAM ORGANIZATION .............................................................................. 114 13.4 PREDICTIVE MAINTENANCE TECHNOLOGIES.............................................................. 114 13.5 PROACTIVE MAINTENANCE .............................................................................. 114 13.6 TRAINING DEVELOPMENT ............................................................................... 115 13.7 MAINTENANCE INDICATORS ............................................................................. 115 13.8 EXAMPLES OF THE EVALUATION QUESTIONS. ............................................................ 115 CHAPTER 14

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GLOSSARY ................................................................................................... 117 CHAPTER 15

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ANNEXES .................................................................................................... 123



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CHAPTER 1

effective evaluation system of advantages is put to use.

Definition of the effective organization of the personnel assigned to the PreventivePredictive Maintenance (PPM).

The success or failure will depend directly from the effort realized in the beginning of the program's implementation.

1.1 Introduction The decision to establish a PreventivePredictive Maintenance System in the plant is the first stage in obtaining the total cost of the maintenance and substantial improvements in the efficiency of the production process. There are a great number of plants today, which operate successfully with the predictive maintenance system. However, there are factories that have failed during the first three years of the operation, coming to the point of abandoning completely the Predictive maintenance systems. The primary causes of the failure are the lack of programs' formal, clear objectives and goals before its initiation. The primary purpose of the first chapter is to give to the reader general rules for the definition of the objectives and goals. The reader will also learn about the general bases for personnel selection, which will form the Predictive Maintenance Group and the manner in which they will be organized. 1.2 Conditions for success A successful Preventive-Predictive Maintenance System should be able to quantify obtained advantages. This could be achieved only if the program was established appropriately, if the adequate predictive maintenance techniques were used, and if an

An appropriate implementation of a Preventive-Predictive Maintenance System should include the following elements: - Clearly defined objectives and goals - Recording system of advantages obtained - General support a) Human resources b) Financial resources c) Long term planning - Effective organization of the PPM personnel - Dedicated personnel which is independent from the plant's operations - Various persons' blend of experiences - Teamwork - Training strategies a) Training program b) Continuous training - Efficient procedures for the collection and analysis of the obtained data - Practical work a) Precision alignment b) Precision balancing - Implementation of precision corrections - Establishment of standards of acceptance for suppliers - Perseverance - Communication programs - Obey for the main PPM In the following chapters most of these elements will be explained in detail. With respect to this chapter, we shall concentrate on the definition of the objectives and goals and on the efficient organization of the personnel that will be assigned to the Preventive-Predictive Maintenance system.


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The predictive maintenance uses various techniques; however, we shall refer only to the analysis of vibrations program because it is the technology with the fastest implementation and it provides the best investment returns. 1.3 Definition of Goals and Objectives Every constructive action comes from a wellestablished purpose. The PreventivePredictive Maintenance System's goals and objectives should be developed and adopted by the work groups in the operative areas in coordination with the plant's general advisors. It is important to remember that the PPM should not be an ideal excuse for the purchase of sophisticated equipment in the area of data collection and analysis, or the justification for employing a numerous group of people in charge of taking data from various types of equipment. The real purpose of a PPM is to minimize equipment failures, maintenance costs and the unplanned stoppages. The PPM should also try to increase the efficiency and the quality of the plant's product. This will be achieved through the periodic monitoring of the equipments' mechanical condition, equipment and process' efficiency, as well as a close observation of other parameters, which define the plant's operational conditions. This manual focuses on the mechanical conditions of the equipment through the vibration analysis. The objectives and goals vary from plant to plant; however, as the information pertinent to the actual situation is needed, it will be necessary to determine the conditions for the

most important maintenance indicators, such as: -

monthly maintenance cost maintenance cost per production unit time percentage of extra labor plant's availability monthly electric consumption total cost of parts' stock etc.

In chapter 10, these indicators will be explained in detail. As the reference data pertinent to these indicators will be used to evaluate the PPM, the following data will be the minimum required: maintenance personnel's labor cost and maintenance personnel's extra time. As in some plants the adequate observation of the indicators is not correctly recorded, the calculation phase of the reference values causes great difficulty in the implementation of the PPM because it is necessary to obtain the information generated in the administrative files. The long-term objectives of the PreventivePredictive Maintenance system are: - Eliminate unnecessary maintenance - Minimize the production loss caused by equipment breakdowns - Reduce the inventory of replacement parts - Increase the process efficiency - Improve quality production - Prolong the utility of different components of the factory - Increase the production capacity - Reduce the maintenance total cost - Increase the factory's total profitability All the objectives previously mentioned are measurable; consequently, value references should be acquired before the implementation of the PPM and realistic goals should be established for each element. Vibration Analysis Manual Page 5 of 143


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1.4. Management's support The implementation of the PreventivePredictive Maintenance System involves the capital investment in taking data and acquiring equipment, as well as in personnel. In order to implement the PPM and to reach its goals, it is necessary that management make a commitment to provide the necessary resources. The management should also facilitate the communication ties between different departments in order to promote the exchange of necessary information for the registration and calculation of maintenance indicators. In some cases, the information is not found directly in the maintenance department, for example: the energy cost, the total processed products, etc. It's important to mention that in the factories that failed in its Predictive Maintenance systems, the management provided for the initial purchase of measuring equipment. However, the necessary resources were not invested into the PPM staff, the personal training and the independent consultants; and they are all necessary components in the successful implementation of the program. One of these programs, with deficient administration, will fail within the first year. Programs have failed because the management was not informed correctly of the PPM way of operation. It is essential that the manager know that the most important benefits are obtained in the long term. The absence of this information could make the manager pressure the personnel because of the investment and lack of results. An important aspect to consider is the fact that during the first year of the system's

operation, the personnel in charge will find equipment with the most failures and problems. These personnel will generate corresponding reports for the solution of the equipment problems. After the first year of the system's operation, the most serious problems will be completely resolved, and the personnel's reports will show few or no major corrective actions. In order to realize initial corrective actions it will be necessary to invest resources for the solution of the problems. As an example we can cite: precision balancing, precision alignment, improvements in consolidation and support mechanisms, hiring of independent consultants, etc. If one does not have a clear view of this implementation stage, the management will probably conclude that the program is not succeeding in obtaining the benefits which justify the assigning of major human resources and an investment in additional technologies, as are precision balancing and alignment.

1.5. Personnel in charge of the PreventivePredictive Maintenance System All the successful Preventive-Predictive Maintenance Systems dedicate full-time personnel to form the PPM group. In some cases, these groups cover various areas of the plant, and in others, several factories at the same time. In any case, a successful PPM will need a selected group of persons dedicated exclusively to the tasks of predictive maintenance in order to fully concentrate on the achievement of goals and objectives established at the beginning of the program.



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Even though some successful plants have assigned part time personnel to these tasks, this approach is not recommended. It is very probable that due to an excessive workload, the personnel cannot maintain the proper monitoring frequency and equipment analysis. The continuity in monitoring and analysis is critical for the success in a predictive maintenance program. It is important to remember that the Predictive Maintenance Group will be the plant's profit generating center from the moment the system is implemented. The factories that have implemented successfully the MMP report production increase from 10% to 30%, the typical cost maintenance reduction from 25% to 50% and the total profits increase of 50% in the most favorable cases. In all the factories that have successfully implemented the PPM, it was noted that the management has offered a great support, which contributed to these results. Its protagonist roll is based on the assignment of economic and human resources to promote the program's development. The management also has the roll of a mediator in the interaction between the maintenance department (provider) and the production (client) with the purpose of programming the repair work in the most efficient way. When we talk about World Class Maintenance, we can only talk about an organization with high proficiency in the maintenance department and the precision correction in equipment. In the beginning, the precision corrections will take longer than usual repairs. However, the time invested is justified because it increases the functional duration

of equipment and decreases considerably the vibration levels. Due to the fact that the solution to equipment problems requires an analysis before and after the correction, we shall present the ideal vibration analysis attributes as well as the necessary qualities of the personnel in charge of maintenance. 1.6.

Ideal characteristics of a vibration analyst

One of the most important attributes in obtaining a success in a predictive maintenance program based on a vibration analysis will be an adequate selection of the personnel who will be in charge of the project. Even though there is very much information about vibration analysis as well as programs and seminars that facilitate the learning, it will be important to select the adequate personnel who will be in charge of the program and which complies with the following principles. The ideal attributes of a vibration analyst are: -

A recognized leader Self-motivated Experienced in mechanical maintenance Skillful in verbal and written communication Decision taker With mechanical inclination Analytical Decisive Competent Willing to learning new techniques Skillful in computer use Focused on details Always looking for the cause Good observer Consistent in his work Capable in making propositions Gifted in abstract thinking Vibration Analysis Manual Page 7 of 143


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- Dedicated in report generating tasks - High performer - Consistent in follow-ups

- Inclination for meticulous work - High performer - Consistent follow-ups

The key characteristics in this person are:

The correct selection of the personnel in charge of the system will result in the program's success, which implies the analysis, follow-ups and precision corrections.

- Willingness to approach the task - Willingness to learn It is important to mention that the major developments in technologies and training programs are elaborated in the United States and consequently an additional element could be the proficiency in English. However, this requirement should not be absolutely indispensable. 1.7 Ideal characteristics of a person in charge of maintenance

The complete success in the predictive maintenance program will not only depend on the vibration analyst, but also on the rest of the team, such as: the management, the person in charge of maintenance and the production department. The roles and responsibilities of every group member, as well as their interrelation, will be described in Chapter 2.

In the majority of successful predictive maintenance programs, we find a person in charge of maintenance who is responsible for precision corrections and retro alimentation to the vibration analyst regarding the work done. The person in charge of maintenance collaborates with the vibration analyst from the moment the system is implemented. As he will have some similar responsibilities to the ones of the analyst, their profiles will be alike: -

Self-motivated Experienced in mechanical maintenance With mechanical inclination Analytical Decisive Competent Willing to learning new techniques Skillful in computer use Focused on details Always looking for the cause Good observer Consistent in his work Vibration Analysis Manual Page 8 of 143

CHAPTER 1

IMPLEMENTATION PROCEDURE FOR A PREVENTIVE-PREDICTIVE MAINTENANCE SYSTEM BASED ON VIBRATION ANALYSIS

Personnel Selection Vibration Analyst

Defining the parameters of the Spectral Band Analysis and Alarm levels for the Critical Equipment

Selection of the monitoring Chapter 1 and 2

d2

Team who will consider the Priorities and Maintenance Costs

Chapter 6 Chapter 4

Evaluation of Analyst's Diagnostic Ability

Chapter 3

The technical data recording of the equipment necessary for the System

Vibration Analyst's training program definition

Chapter 5

Selection of the appropriate Transducers for each equipment and Particular Measurement point

Chapter 7

Chapter 3

Selection and identification of measurement points Training in the use of the instruments and Software

Chapter 5 according to the supplier

Optimal arrangement of the data bases, space and equipment to be recorded in the Software

according to the structural organization of the software

Data generation in the Predictive Maint. Software: - Space - Equipment - Measurement Points - Analysis parameters - Alarm levels - Typical failure frequency - External system

Efficient selection of Monitoring Routes and the definition of monitoring intervals

Chapter 7


CHAPTER 1

PROCEDURE TO FOLLOW FOR THE OPERATION OF A PREVENTIVE-PREDICTIVE MAINTENANCE SYSTEM BASED ON VIBRATION ANALYSIS Analyst's/Collector's Routing responsibility according to the monitoring duties

2

1

Analyzing the wave spectra and shapes obtained according to the list of the "Alarm priorities"

Data collection from equipment

ї Activated alarms in the field?

No Computer registration by the Analyst/Collector

Yes

Recording of the Additional spectra with an increased resolution, if necessary ,to facilitate the diagnostic, data collection of the phase, resonance testing, etc.

Elaborate a report informing about the present situation

No

Yes Reduce to one half the Monitoring interval

Write a report with Recommendations and Steps for the solution

Schedule the stoppage according to the recommendations and make the repair

2 No

Is it an urgent problem?

Is there enough Information to make a conclusion? Monitoring the initial states to see whether there are improvements

Yes Printing of an Exceptional report Elaborate Diagnostics

1 Printing of the "Alarm report" according to priority

1

No

Problem resolved?

Yes

Compare results with those of the Expert System

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CHAPTER 2 Definition of the members' Roles and responsibilities in the Preventive-Predictive Maintenance System 2.1 Introduction In Chapter 1, we described the importance of the measurable objectives and goals in a Preventive-Predictive Maintenance System, as well as the importance of the ideal attributes of the vibration analyst and the person in charge of maintenance. In this chapter, we shall focus on describing the roles and responsibilities of each member of the group who will be responsible for the PPM implementation and operation. 2.2

Formation of maintenance group

the

Predictive

The Preventive-Predictive Maintenance System involves each one of the following employees in the formation of the working group: Plant's Maintenance Director Vibration analyst The person in charge of maintenance Technical Director of the group Each member of the group will fulfill his roles and responsibilities in such a way that working together the group will make the program successful. 2.3 Plant's maintenance director The plant's maintenance director will be a partial member of the Predictive Maintenance group due to his additional responsibilities in the organization. However, he will have the following responsibilities in the Work group:

1. He will be responsible for the acquisition of all the instruments and computer systems necessary for the analyst and the person in charge of maintenance. 2. He will collaborate with the production personnel to define which of the plant's equipment will be observed and to establish its monitoring intervals. The criteria for the equipment selection will be presented in Chapter 4. 3. He will be responsible for the arrangements necessary for the analyst's and technician's training. He should be informed of all the seminars and conferences available during the whole year. 4. In agreement with the analyst, he will define the equipment's codification in order to incorporate it into the system. 5. In collaboration with the analyst, he will define the Spectral Band Alarm Levels for all the equipment in the system (see chapter 6). 6. The Maintenance directors, the analyst and the personnel of the Systems department will define the adequate procedures to make a back up (reserve) copy of the stored information. 7. He will determine what equipment will be included in the Preventive-Predictive Maintenance System, and the technologies that will be used. For this reason, he will have to elaborate a schedule with deadlines, covering all the equipment to which a predictive technology will be applied. 8. He will prepare and publish monthly Preventive-Predictive Maintenance System reports, including the description of the progress and successes achieved by the Program. In order to do this, he should seek Vibration Analysis Manual Page 11 of 143


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support from the analyst and the person responsible for maintenance. 9. He will make sure that the plant's maintenance personnel know the objectives of the PPM and that he will create the necessary seminars to improve the maintenance, especially in precision correction and precision alignment. 10. He should be subscribed to specialized reviews in Predictive Maintenance in order to be informed about technological improvements and new ways of finding potential problems in equipment. 11. He should be in contact with the Technical Section in order to be informed about available classes and seminars for the members of the Preventive-Predictive Maintenance system. 12. He should have the knowledge about precision alignment, precision balancing, basic vibration analysis and the content of the Preventive-Predictive Maintenance System that is used at the plant. 13. He should elaborate the acceptance specifications for the suppliers' work with respect to alignment and balancing, as well as the acceptance criteria for new machines. 2.4 Vibration analyst The vibration analyst is a group member who will be working full time at his responsibilities: 1. Maintaining and updating the databases generated for the vibration analysis: a. The study of the equipment manuals and their assembling diagrams in order to have all the necessary information for the introduction of new equipment into the system.

b. Selection and measurement marking of the equipment included in the system. c. Incorporate equipment into the system with the person responsible for the maintenance. d. To establish in collaboration with the maintenance director the alarm levels for the spectral band for each type of machines, which should be included in the system. This information should be included in the computer system (see chapter 6). e. Elaborate and arrange in the most efficient way the monitoring routes in order to record the equipment's vibration (see chapter 7). 2. He will take vibration data from the equipment and he will write special reports to determine which equipment needs a detailed analysis based on the obtained spectra. He will analyze present and past readings in order to have a complete view of the vibration record and be able to predict potential failures. 3. He will prepare the necessary "action reports" and generate work orders for the corrective maintenance. He will turn in this report and the work order to the maintenance coordinator indicating potential problems. A model report is found in chapter 11. 4. He will readjust the equipment's monitoring schedule according to the changes that take place and he will shorten the period between monitoring sessions for the equipment that presents signs of deterioration. In the equipment that presents no significant data, he will extend the period between monitoring session; but only, if and Vibration Analysis Manual Page 12 of 143


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when the equipment in question is not critical for the production. 5. He will contact the maintenance director, the members of the technical section or an independent consultant when he needs a second opinion regarding the vibration analysis. 6. Together with the person responsible for maintenance, he will file maintenance supervisor's reports that contain the description of the work done as was recommended by the analyst or technician. 7. He will collect the information from various sources regarding the savings and benefits in order to annex it to the records. This information will be necessary in the elaboration of the director's monthly maintenance reports. The documentation about achieved goals will be a justification for more support from the plant's management. 8. He will add more equipment to the system when he feels that it is necessary to take readings from additional equipment. 9. He will take samples from the gearboxes for the Ferro graphic analysis from the equipment whose vibration levels are abnormal, especially when the gearing frequency amplitudes increase. The results from the oil analysis will confirm the interpretation of the spectral vibration. 10. He will use other preventive maintenance techniques applicable to equipment's condition. These approaches could be obtained from independent consultants if there is a lack of equipment or necessary experience. It is important that the analyst is familiar with different predictive maintenance techniques in order to use them adequately when they are needed.

11. He will take classes and take part in training seminars in vibration analysis. He should also attend conferences and expositions where the latest market achievements in instruments and advanced analysis techniques are demonstrated. 12. He will need the necessary knowledge in precision alignment and balancing. He will need to realize at least one precision alignment per month. The same should be done regarding precision balancing with all the equipment that needs it. He will record "influence coefficients" obtained during balancing in order to save time in future balancing with the same equipment. The updating of this information will be his responsibility. 13. He will need to check the vibration levels of the new and repaired equipment to ensure that it complies with specifications that were given to the supplier. 14. He will need to write a monthly report with a resolved case that had a positive impact for the plant by decreasing the maintenance cost and/or has achieved a significant decrease in vibration levels. In this report, the information should contain the total vibration tendency of all the equipment that is monitored at the plant. This indicator is crucial in the observation of the precision corrections. 2.5 The person in charge of maintenance A person in charge of maintenance is included in the predictive maintenance group because it will be necessary to do precision corrections and these corrections will be a port of his responsibilities. The number of members of this department will depend on the plant's size. The responsibilities of this department include: Vibration Analysis Manual Page 13 of 143


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1. The department will be in charge of coordinating, in collaboration with the vibration analyst, the precision balancing at the plant. He should participate in the balancing tasks performed by the analyst in order to obtain the lowest vibration levels. 2. The department will be responsible for the precision alignment of the most critical equipment; the personnel should be at least trained in the modern techniques of precision alignment, either with the reversed indicators or with laser based instruments. 3. It will file the records of all the alignments in order to have them available for future alignments. 4. It will file the corresponding information in par with the equipment's operation before and after the precision alignment in order to calculate energy savings. These results will justify the acquisition of the latest technologies in alignment, such as the laser method. 5. It will be responsible for ensuring the quality of repairs done by independent companies and it should ask for the precision balancing and precision alignment certificates when outsourcing does the work. 6. It should supply the vibration analyst with the most relevant information about the repairs. If necessary, a group member should ask for analyst's help during repairs in order to resolve collaboratively the most critical equipment problems. 2.6 Technical Department The technical department of will be an additional complement to the predictive group. Even though the technical department will not be an active member in

the every day activities, it will have staff responsibilities, which will have a positive impact on the program's success: 1. They will elaborate implementation strategies for each predictive technique that will be implemented in the , as is the case of this manual. These strategies will have the essential objective to facilitate the implementation and operation of various predictive techniques applicable to the teamwork. 2. They will present to the Director of every plant the elaborated strategies for each technique. 3. They will develop vibration analysis classes and seminars for the whole group in order to train the plant's personnel. The advantage of these seminars is to unify the group's criteria. 4. They will help directly when confronted with equipment vibration problems using their own experience or the help from another plant, as well as with the independent consultants in the field. 5. During the implementation stage, they will offer assistance to all the plants that need it to facilitate the process. For this purpose, the technical department will be able to seek assistance from independent specialists. 6. They will maintain the plant's personnel informed about new technologies in the market, as well as about the most recent and innovative techniques for resolving problems. 7. They will evaluate instruments, services and analysis techniques of various suppliers to achieve group standardization. For such effect, they should be trained in various techniques of predictive maintenance, as are vibration, thermography, oil analysis, ultrasound, etc. Vibration Analysis Manual Page 14 of 143


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8. They will define the world-class evaluation processes, which will be applied to all the company plants. Thanks to this approach, it will be known which plants in the company are similar to Benchmark's position in order to apply similar strategies in the rest of the plants. 9. They will apply the world-class evaluations in the plants that have the predictive maintenance system in operation for at least six months.

The program's success or failure will be seen sooner or later with the maintenance indicators, pay off indicators and plant's profitability. Even though the actual instruments are sophisticated and provide great advantages in the analysis tasks, they will not resolve communication problems that could exist among the members of the Predictive Maintenance group and the final user, the production department. The relation between the integral parts of the group is shown in the diagram 2.1.

2.7 Conclusions All the previously mentioned parts of the Preventive-Predictive Maintenance System should work in close collaboration and as a whole. The common goal of this group is the successful implementation and continuous operation of the PreventivePredictive Maintenance System. Each integral group should accomplish its responsibilities previously assigned to achieve the common goal. These responsibilities can vary according to the maturity phase of the system and the number of plant members. However, this approximation will be a good start to ensure the program's success. It is important to remember that one should not temper (politicize) with the system, as it is the essential element for the successful realization of the Preventive-Predictive Maintenance program. The previous comment refers to the necessity to eradicate all types of politics from the fundamental activities of the program. This project requires that all the members of the group focus positively their energy in order to facilitate the system's implementation and continuous operation.


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STAFF Maintenance Management

Vibration analyst

Technical Department

Person in charge of Maintenance

Diagram 2.1 Operation chart of the Preventive-Predictive Maintenance System.



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CHAPTER 3

3.2 Minimum training requirements

Training: Definition, Planning and Scheduling of the training requirements

The vibration analyst should have at least the following knowledge:

3.1 Introduction

-Personal computer use, Windows various text processor software.

To be successful in the implementation stage of the Preventive-Predictive Maintenance System, the members of the group will be required to have consolidated knowledge about the equipment's operational dynamics in the PreventivePredictive Maintenance System and about the instruments used to collect and analyze vibration data. For the plants that incorporate for the first time a Preventive-Predictive Maintenance System, it will be fundamental to define, plan and schedule the implementation of the minimum requirements necessary for the program. In this chapter, the training needs for the initial stages of the program's implementation will be defined, and a proper scheduling will be presented to promote the personnel's knowledge in par with the program's development. An evaluation questionnaire (test) for the determination of the personnel's proficiency level is annexed to this chapter in order to determine the training needs in vibration analysis. The design of this questionnaire is based on the selection of one answer in order for the results to be calculated by adding all the positive answers. The final score will define the personnel's training needs for the vibration analysis.

-Basic level of Vibration analysis and

-Data analyzer/collector's basic functions -The use and configuration of the Preventive-Predictive Maintenance System. To obtain a better training result, it is recommended to plan the training stages according to the previously established schedule. It is possible that one already has the necessary knowledge in vibration analysis and the computer use. If one already knows how to use computers, this stage can be eliminated from the training plan. If one already has some experience and knowledge in the vibration analysis, he/she will need to answer the questionnaire annexed to this chapter to define his/her training needs. Depending on the results obtained in the questionnaire, the personnel should be scheduled for any of the three following courses: Basic level in vibration analysis Intermediary level in vibration analysis Advanced level in vibration analysis The suggested content for each of these courses is presented bellow and an independent consultant or a specialized enterprise in this field of training could prepare it. 3.3 Basic level in vibration analysis Vibration Analysis Manual Page 17 of 143

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This course will have the following content: 1. Basic vibration principles -amplitude - phase - frequency 2. Different types of measuring instruments

The maintenance director will be very important in the promotion of the continuous training program in order to obtain the maximum results. The number of problems resolved at the plant will depend directly on the knowledge in diagnostics and problem solving acquired by the group.

3. Different types of vibration sensors 3.4 4. Resonance 5. Most common failure diagnostic, using phase spectra: - unbalance - lack of alignment - bent rotors - bearing failure - loose machine parts - belt and pulley problems - friction - gear box 6. Vibration tolerance levels In general, this is the material that is required for the personnel's initiation into the vibration analysis. The knowledge acquired in the first course will be used in detecting the most common failures at the plant. However, there will be cases of defective equipment that will require a more advanced, analyst's knowledge. For this reason, an intermediary course on vibration analysis is recommended six months after the beginning of the system's initiation. If a complex vibration problem is presented during the first 6 months, it is recommended to contact an independent adviser in order to find the solution. The plant's personnel will learn the manner in which the problem was resolved, reinforcing the knowledge of the group.

Intermediate analysis

level

in

vibration

The content of the intermediary level course: 1. Analysis of the wave shape 2. Analyzer's advanced functions: -

synchronous averaging negative averaging averaging by tracking ordinates polar diagrams demodulation technique current's spectral analysis

3. Electric problems - induction motors - direct current motors - synchronous motors 4. Gear box Identifying lateral bands use of demodulation 5. Bearings finding lateral bands use of the wave shape demodulation use Normally, the knowledge acquired in this course will be applicable to the existent technology at the beginning of the Predictive Maintenance. The advanced level course in vibration analysis, that will be seen bellow, will require the acquisition Vibration Analysis Manual Page 18 of 143


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of advanced technology in analysis and special computer packages. 3.5 Advanced level in vibration analysis This course is recommended for the plants that have solidified Predictive maintenance programs in which they have obtained favorable results in maintenance. However, the maintenance group has on occasions faced problems that it could not resolve with the knowledge acquired in the first two courses. To resolve complex problems in vibration analysis, it is recommended to acquire multi-channel analysis technology, which could be used to localize complex equipment failures. Once the plant has come to this stage of maturity, it is recommended to take an advanced course with the following content: 1. Course in multi-channel analysis 2. Study of transitory events 3. Modal analysis 4. Use of ODS (Operational deflection shape) to observe the vibration mode of an equipment in a computer system. 5. Relative phase between two measuring points 6. Transference function 7. Coherence It is important to mention that on occasions it is not necessary to pursue the specialization to this point, especially when there are consultants who can resolve these specific problems. However, in this case, additional technology can be acquired according to the specific needs regarding some old equipment problems. It is recommended that the plants have among their staff at least two persons with this level of proficiency in

order to resolve the most complex problems. Even though it is possible to have only one specialist in a large plant with the aforementioned qualifications. 3.6 Training in the use of instruments and the Predictive Maintenance System With respect to the use of the data analyzer/collector, as well as in the use and configuration of the Predictive Maintenance system, the supplier of the instruments according to the stipulated purchase clauses should teach the latter. However, it is amply recommended to hire an independent consultant to initialize the system, defining the alarm levels for each type of equipment and facilitating the critical equipments' configuration stage in the system. Additionally, this consultant could realize the first analysis of the equipment that could be a review and practice of the acquired knowledge in the Basic level of vibration analysis by the Predictive Maintenance Group. Among the basic functions of the vibration collector/analyzer equipment CSI model 2115, we can mention the following: Data collection in programmed routes Outside of the route configuration mode Information transference analyzer's routing load PC data loading analysis functions real time spectrum wave shape in real time global value vs. time peak and phase monitoring The functions and configurations of the Predictive Maintenance system CSI Master Trend include: Vibration Analysis Manual Page 19 of 143


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data creation archive equipment configuration measurement points configuration assignation of analysis parameters assignation of spectral band alarms configuration of expert systems report generation spectral display communication with the analyzer data base maintenance information printing frequency failure display programs for typical frequency calculation in bearings, gears and various types of failure. Program for recording equipment failure information and follow-ups. and others. The estimated time for the training in the use of this technique is approximately 10 days, either at the plant or at the supplier's installations. In case of the training at the plant, the information recording will be swifter because the examples used will include the plant's equipment. 3.7 Vibration analysis questionnaire As was previously mentioned in this chapter, the primary objective of this questionnaire is to evaluate the actual level of knowledge of the Predictive Maintenance Group members in order to define the initial training needs in vibration analysis. The questionnaire is presented in Table 1 and the answers in Table II. On the right side of Table I, one needs to mark one point for each correct answer and o points for each wrong answer. The first 25 questions are used to define the basic level of knowledge in vibration analysis. The questions 26 through 30 deal with a more complex subject matter and

they will serve as an evaluation tool for the members' capacity to make an advanced diagnostic. Based on the results from the first 25 questions, we conclude: a) If the total score is less than 17 in the first 25 points, the questions 26 through 30 do not need to be answered. It is recommended to take the Basic Vibration course to acquire the content, which was suggested earlier in this chapter. b) If the score is higher than 17 in the first 25 questions, and the score for the questions 26 through 30 is higher than or equal to 4, it is recommended to take a course in Advanced Vibration.

3.8 Additional training The original goal of the PreventivePredictive Maintenance System is to, remembering the content of chapter 1, increase the availability of the equipment and their duration. The diagnostic of the equipment's problem is only one necessary stage in the achievement of this goal. The implementation of the precision correction to resolve the vibration problems, is another necessary stage on the path to plant's operational excellence. For this motive, the personnel of the Predictive Maintenance Group will need to have necessary knowledge in order to support the maintenance personnel in the correction tasks. For this reason, the personnel of this group should be trained in the following areas: Multi-plane balancing Precision alignment In case the personnel of the group do not do the balancing, it will be necessary to know Vibration Analysis Manual Page 20 of 143


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the balancing techniques in order to solicit the maximum quality from the suppliers. In chapter 13, we shall see acceptable balancing criteria. In case of the precision alignment, the most usual arrangement is that each plant has its personnel for these tasks. For this reason, special precision alignment techniques should be performed, such as alignment with the inverted indicators or laser alignment. The selection of a particular

technology will depend on plant's profile. The laser system is easier and has a greater precision. On the implementation schedule for the Preventive-Predictive Maintenance System, it is recommended to program courses on these topics for the Predictive Group three months after the system is initiated.


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TABLE 1. VIBRATION ANALYSIS QUESTIONNAIRE No.

QUESTION

ANSWERS

1

Which of the following elements will indicate the vibration seriousness?

__ a. phase __ b. amplitude __ c. frequency

2

The vibration unit most used to measure the residual unbalances in the equipment is:

__ a. mils peak __ b. mils peak-peak __ c. in./sec. peak

3

The most used vibration parameter to measure the "health" level of an equipment with spinning frequency ranges from 600 and 10,000 rpm is: The acceleration vibration is most commonly used to measure the vibration levels in the area of:

__ a. movement __ b. acceleration __ c. speed

5

When an axle spins at 100 rpm the most suitable method to obtain the phase is:

__ a. stroboscopic lamp __ b. optic tachometer __ c. the phase can not be taken

6

The minimum recommended frequency for the use of the speed sensor, or seismic sensor, is:

__ a. __ b. __ c. __ d. (cp.)

7

The movement (displacement) sensor is based on the principle of:

__ a. superficial contact __ b. no contact __ c. variable air gap

8

The vertical and horizontal phases are set at 0 or 180° in a ventilator fit with pulleys when there is a problem concerning:

__ a. excessive unbalance __ b. eccentric pulley __ c. misalignment (lack of alignment) __ d. none of the above

4

Pts.

__ a. high frequencies __ b. low frequencies __ c. none of the above

6 cpm (cp.) 60 cpm (cp.) 6000 cpm (cp.) none of the above



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No.

QUESTION

ANSWERS

9

When a rotor is unbalanced, the phase difference between vertical and horizontal positions should be:

__ __ __ __

a. 0° b. 180° c. 45° d. none of the above

10

Which of the following options is not considered to be a cause of vibration:

__ __ __ __

a. lack of alignment b. unbalance c. resonance d. all of the above

11

The phase value in the resonance peak in comparison with phase value before entering the resonance curve will be set at:

__ __ __ __

a. 180° b. 45° c. greater than 180° d. none of the above

12

If there is a unbalance and the spinning frequency increases three times, theoretically, the vibration will increase:

__ __ __ __

a. 9 times b. 3 times c. 6 times d. none of the above

13

The system's natural frequency will be increased when:

__ a. its mass is increased __ b. the spinning frequency increases __ c. its rigidity increases __ d. none of the above

14

The rotors that operate at a higher than normal frequency are known as:

__ a. resonant motors __ b. semi-rigid motors __ c. flexible rotors __ d. none of the above

15

The shock test that is used to calculate the resonance will help us determine:

__ a. the second critique __ b. the third critique __ c. the none bending mode __ d. none of the above

16

It is possible to distinguish between unbalance and lack of alignment only with the analysis of vibration's global values.

__ a. yes __ b. no

Pts.



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No.

QUESTION

ANSWERS

17

When the axial vibration is 50% greater than the radial vibration, the vibration's most probable cause is:

__ __ __ __

18

When there is a looseness problem in a gear box, the typical spectrum will present:

__ a. harmonic frequency __ b. high vibration at 1X rpm __ c. harmonic multiples of 1X __ d. none of the above

19

If by loosening a screw in a motor that is in operation, the vibration decreases; it is probable that the problem is:

__ __ __ __

a. residual unbalance b. unstable leg c. lack of alignment d. all of the above

20

. If after 30 minutes of functioning, the vibration of a screw compressor set at 1X and 2X RPM increases considerably, the most probable cause of this increase is:

__ __ __ __

a. residual unbalance b. lack of lubrication c. lack of alignment d. all of the above

21

If the axial phase readings, taken in the same direction at each of the ventilator supports, shows a 180° difference, then the most probable cause is:

__ a. lack of alignment __ b. unbalance __ c. looseness __ d. bent axle __ e. none of the above

22

The instability originated by oil shaking in the flat strengthening plates will cause vibration in the following range:

__ __ __ __

a. high frequency b. very high frequency c. sub-harmonic range d. none of the above

23

At which of the following bearing failure frequencies, the axle spinning frequency acts as a lateral belt:

__ __ __ __

a. roller failure b. cage (box) failure c. internal track d. none of the above

Pts.

a. resonance b. unbalance c. eccentricity d. none of the above



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No.

QUESTIONS

ANSWERS

24

In case of a turbulence in a centrifugal pomp, the vibration will be generated randomly in:

__ __ __ __

25

Will the gearing frequency be similar for each pair of gears even if they spin at different frequencies?

__ a. yes __ b. no

Pts.

a. high frequency b. blade's frequency c. sub-harmonic range d. none of the above

TOTAL NUMBER OF POINTS IN THE FIRST 25 QUESTIONS 26

The information acquired by the separation of the lateral frequency bands (belts) in the gearing frequency will help us determine:

__ a. the severity of gear's unbalance __ b. the intensity applied to the gear __ c. which gear has been severely damaged __ d. none of the above

27

The best way to detect broken gear teeth is to analyze the vibration wave in the following units:

__ a. mils __ b. g's __ c. in./sec.

28

Which one of the following frequencies will be presented as lateral belts (bands) around the spinning frequency when there are loose rods in the rotor or an induction motor?

__ a. slipping frequency __ b. pole's passage frequency __ c. frequency of an electric line __ d. rod's frequency in a rotor __ e. none of the above

29

Which one of the following electric problems in induction motors causes pulsing and rhythmic vibrations at the spinning frequency of the motor:

__ a. eccentric motor __ b. loose stator __ c. rotor rolling in short circuit __ d. none of the above __ e. all of the above



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30

Which one of the following averaging techniques is used to obtain spectra in a variable velocity equipment?

__ a. peak maintenance __ b. negative averaging __ c. synchronous averaging __ d. following (tracking) ordinates __ e. normal with prefilter __ f. none of the above TOTAL SCORE OF THE LAST 5 QUESTIONS

Important note: If there is a scoring card with less than 17 correct answers, the person should not answer questions 26 through 30.



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TABLE II. ANSWERS TO THE TABLE I QUESTIONNAIRE QUESTION #

ANSWERS

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

b b c a b d b b d c d a c c d a d c b c d c d c a c b b d d

COMMENTS

the minimum recommended freq. is 600 cpm

the phase difference will be 90° the phase difference will be 90°

the first critique is determined lack of alignment

loose or cracked rods in the rotor



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CHAPTER 4 Criteria for the selection of the critical equipment

is installed and operating in the plant because it would be wearisome for the analyst who is just starting his analysis, and his attention can be sidetracked to the equipment that is not critical for the process or the maintenance costs.

4.1 Introduction When a Predictive-Preventive Maintenance System is implemented, one of the most significant objectives is to minimize the equipment failures in order to reduce the number of unplanned stoppages and to achieve the maximum availability of the production plant. Besides this objective, it is important to reduce the total maintenance cost. In order to achieve these goals from the very beginning of the system's implementation, it will be necessary to identify the critical equipment for the plant. Once the objectives of the Preventive Maintenance Group were defined, the next step in the implementation of the system will be make the correct selection of the equipment which should be included in the program. There are various criteria for the selection of the equipment that should be included in the system. In this chapter, we shall define them using the selection criteria for the critical equipment, which is based on the plant's importance of production and its maintenance cost. Both selection criteria will be important in achieving the maximum results during the first months of the program's operation. It is not recommended to initiate the program monitoring all the equipment that

4.2 Selection procedure In order to proceed to the selection of the equipment with which the system will be initiated, a list, which includes all the installed equipment in the plant, should be elaborated, and each one of them should be classified in accordance to its priority in the system. The table I, shows the order in which the plant's equipment should be prioritized. The list can be elaborated in a data base package and afterward a priority list should be made. For the elaboration of the general lists of the equipment, it is recommended to have the plant's layouts at hand. It is very easy to omit equipment or components while elaborating the list; therefore, all the precautions should be taken to ensure that all the equipment that affects the production and its costs is included on the list. To determine the priorities according to the production and costs, one should take into account the following principles: 4.3 Priority 1, Very critical equipment PRODUCTION PRIORITY On this list should be included all the equipment which has to be in operation for a continuous production. In other words, the loss or failure of any of them would result in a total stoppage of the plant or its production line, causing a total loss of Vibration Analysis Manual Page 28 of 143

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production during a major period of time, 12 hours. COST PRIORITY IN MAINTENANCE With respect to maintenance costs, the equipment whose repairs and maintenance are excessively high will be included in this group.

All the equipment that at the moment of a failure has a negative impact of more than 30% of the plant's production should be included on this list. If there are various production lines, each one should be considered as a separate plant. COST PRIORITY IN MAINTENANCE

We shall include in this category the equipment whose parts or components need to be ordered with great anticipation because of the prolonged delivery time or the need for special parts, even when this equipment does not represent a loss in production when they are idling for the sake of repairs. Summarizing, there is equipment whose costs of repairs are very low, however the fact that these machines idle has a great impact on the production, as can be the case of a small lubrication pump of a reducer or a turbo compressor. On other hand, there will be situations in which some teams will not cause a production stoppage; however, their repair costs and maintenance will be very elevated, lowering the company's profits. Consequently, it will be important to take into account both criteria for the classification of critical equipment that should be included in Priority 1. In this priority section, we can include as examples: furnace components, mills and cement plants' crushers. 4.4 Priority 2, Critical equipment PRODUCTION PRIORITY

For the evaluation of the critical equipment with respect to maintenance costs, one should include the equipment with high maintenance costs, or the equipment that has required frequent maintenance interventions caused by a design problem or the tasks performed. It will be necessary to review the equipment record to establish its priority. 4.5 Priority 3, Equipment with normal priority PRODUCTION PRIORITY In this selection will be included the equipment which does not have a great impact on the production if it stops functioning. A typical example would be redundant systems, or the ones that have replacements, which have the so-called "stand by" status. However, this equipment will have a considerable maintenance costs. The equipment that could be repaired in less than one hour could also be considered as normal priority. COST PRIORITY IN MAINTENANCE With respect to maintenance costs, one should classify as normal priority the equipment that has relatively normal maintenance costs, and also the equipment that is repaired by independent personal. For example, a screw compressor which has Vibration Analysis Manual Page 29 of 143


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a redundant system and whose repair would be provided by its supplier.

4.6

Priority priority

4,

Equipment

with

low

In this group should be included the rest of the plant equipment which has an impact on the production and/or maintenance costs. It is necessary to make an evaluation in order to determine, according to the equipment, the convenience of including it in the monitoring list. In some cases, the replacement costs are smaller than the annual costs required for the monitoring of the equipment in this priority section.

Critical (Priorities 1 and 2) during the first six months of the system's operation. This way, the maximum investment return efficiency will be realized. As the program matures, the equipment that was classified as Priority 3 and 4 will be annexed. The Predictive Maintenance Group will have to scrupulously review the initial list that includes all the plant equipment, and it should courteously involve the members of the production and maintenance in this process. The more information one has about the maintenance and repair time, the easier the classification task will be.

There is equipment that operates under the status of preventive maintenance, and there might also be equipment that operates till it brakes down. This does not imply that no sufficient attention has been dedicated to it. Typical examples of this equipment are cooling ventilators of some frequency converters or direct current converters. In case some of these little ventilators suddenly stop, the panel's temperature monitoring system will send a warning on time and a stoppage could be prevented with another cooling method. This is only an example; the best selection criteria will depend on the plant's working profile. 4.7 Conclusions To achieve a successful implementation of the Preventive Maintenance System, the efforts need to be focused on the equipment catalogued as Very critical or Vibration Analysis Manual Page 30 of 143

CAPITULO 4 Dirección de Tecnología

TABLE 1. PRIORITY ASSIGNATION OF THE PREDICTIVE MAINTENANCE SYSTEM POSITION

EQUIPMENT

CODE

SECTION

PRODUCTION PRIORITY

COST PRIORITY

VERY CRITICAL VERY CRITICAL VERY CRITICAL VERY CRITICAL

VERY CRITICAL CRITICAL NORMAL LOW

CRITICAL NORMAL LOW

VERY CRITICAL VERY CRITICAL VERY CRITICAL

CRITICAL CRITICAL CRITICAL

CRITICAL NORMAL LOW

NORMAL LOW

CRITICAL CRITICAL

PRIORITY 1, VERY CRITICAL FOR THE PLANT PRODUCTION 1 2 3 4

PRIORITY 1, VERY CRITICAL BECAUSE OF THE VERY HIGH MAINTENANCE COSTS 5 6 7

PRIORITY 2, CRITICAL FOR THE PLANT PRODUCTION 8 9 10

PRIORITY 2, CRITICAL BECAUSE OF THE HIGH MAINTENANCE COSTS OR FREQUENT STOPPAGE 11 12

PRIORITY 3, NORMAL PRIORITY INCLUDES REDUNDANT MACHINES AND/OR WITH MODERATE MAINTENANCE COSTS 13 14 15

NORMAL NORMAL LOW

NORMAL LOW NORMAL

LOW

LOW

PRIORITY 4, LOW PRIORITY FOR THE PRODUCTION AND LOW MAINTENANCE COSTS 16


CAPITULO 4 Technology

SUGGESTED EQUIPMENT FOR IMPLEMENTATION IN THE PREDICTIVE MAINTENANCE SYSTEM

PRIORITY 1 1 1 1 1

TRITURATION PRIMARY CRUSHER SECONDARY CRUSHER VIBRATING SIEVE STACKER RECLAIMER

QUANTITY 1 1 1 1 1

2 2 2

GRINDING (RAW MATERIALS AND CEMENT): MILL TRANSMISSION SEPARATOR'S TRANSMISSION SWEEPING IDF

2 2 2

1 1 1 2 2 1 2

CALCINATION: KILN TRANSMISSION TRANSMISSION COOLER GRATE CLINKER CRUSHER CLINKER COOLER FANS BURNER'S PRIMARY AIR FANS PREHEATER IDF. COLLECTOR IDF

1 3 1 7 2 1 2

GENERAL TRANSPORTATION: WEIGHT FEEDER FEEDER PLATES CONVEYOR BELT FULLER PUMP HAULING CHAIN FULLER COMPRESSOR BUCKET ELEVATOR BUCKET CARRIER PLATE CARRIER

6 3 6 2 1 2 8 1 1

2 1,2 1,2 1,2 1 1,2 1,2 1 1


CAPITULO 4 Technology PRIORITY 2 1

PACKING PALLETIZING ROTARY PACKER TRANSMISSION MOTOR PULLEYS

QUANTITY 2 4

3 2 3 3 3

SERVICES: CENTRIFUGAL PUMP (HORIZONTAL AND VERTICAL) THERMICAL OIL PUMP FUEL OIL PUMP DEEP WELL PUMP AIR COMPRESSOR

4 2 4 3 8

2 2 2 2 3 3

VARIOUS EQUIPMENT: LUBRICATION PUMP HYDRAULIC PUMP LUBRICATION COMPRESSOR TURBO VENTILATORS DUST COLLECTOR VENTILATORS PRESSURIZER VENTILATORS

8 4 1 10 15 10

APPROXIMATE EQUIPMENT QUANTITY 141

THIS EQUIPMENT AND ITS PRIORITY ARE AN EXAMPLE OF RECOMMENDED EQUIPMENT TO BE TAKEN INTO ACCOUNT IN A PREDICTIVE MAINTENANCE SYSTEM FOR A SINGLE PRODUCTION LINE. THIS LIST SHOULD BE MODIFIED ACCORDING TO THE PRODUCTION LINE NEEDS AND THE PLANT'S SPECIFIC CRITERIA.



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CHAPTER 5 Technical information equipment type.

by

5.1 Introduction One of the most important aspects in the Preventive-Predictive Maintenance System is the available information about the equipment parts. The more complete information about equipment components the easier will be the configuration process of the spectral alarm bands, as it will be seen in Chapter 6. In addition, the spectral analysis will be improved considerably with complete data information. In this chapter, necessary forms will be presented to store the minimum required information of various equipment components. Due to the great diversity of equipment types, the major kinds of the most typical equipment in industry will be presented. However, the user can elaborate a similar format for the types of equipment that are not included in this chapter. 5.2 Comments about the formats The formats that are included in this chapter have in the right upper corner general information about the equipment. The first three spaces were designed with appropriate lengths to include the appropriate information into the CSI Master Trend software. We are going to comment on different segments of this format.

The name of the equipment should be registered in alphabetical order with the maximum of 10 characters. CSI Master Trend will locate the equipment thanks to the assigned identification. The same identification will appear in the data collector, as well as in all the system's wave spectra and shapes reports. Consequently, it is very important to identify them according to plant's usage. SECTION In this space of 28 characters, one should include the name of the section to which the equipment belongs. For example: Equipment: North Induced Draft Ventilator Identification: 5205-84 Section: Cement Kiln 2 TYPE OF EQUIPMENT The specific work type performed by the equipment should be selected. This information will determine the way the information is registered. For example, when the velocity is constant and the load varies, it is recommended to record the load at the time of reading. The Master Trend software requires this information when the equipment is included into the system. MONITORING FREQUENCY The schedule for the equipment's vibration reading needs to be determined. This decision depends on the equipment's priority in the process. The usual time sequence for the industrial equipment reading is one month (monthly). The rest of the spaces is reserved for the specific data of each equipment part.

EQUIPMENT IDENTIFICATION

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In addition, a schematic diagram of the equipment is included to show the place where the measurements should be taken. The equipment's nomenclature of the measuring points is shown in each diagram. The letters H, V and A will show the position of the sensor; which are respectively Horizontal, Vertical and Axial. In case of the induction motors, E1H and E2H points will be added to record the low and high frequency spectra respectively in order to be able to counteract possible electric problems. The configuration of these measurement points will be explained in Chapter 6, Table III, pages 6-18. In case of the gear boxes, it will be necessary to define additional monitoring points to record the gearing frequency. In the schematic diagrams, these measurement points should be identified. The configuration of these points is shown on Table III, page 6-17. ANALYSIS PARAMETERS On the back of each form, the definition of the analysis parameters of the spectral bandwidth is included, as well as the alarm level that each band will have. In some cases, the analysis parameters will be similar when they are in the same equipment subdivision, and it will be only necessary to refer to the equipment that has its parameters established in order to use them in the information recording. In order to fill in correctly this table, it will be necessary to use the information from tables II and III, which are included in chapter 6.


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SCHEMATIC EQUIPMENT DIAGRAM MEASUREMENT POINTS 4H 4V 4A

3H 3V 3A

IDENTIFICATION: SECTION:

F A N

TYPE OF EQUIPMENT: CONSTANT VELOCITY, CONSTANT LOAD CONSTANT VELOCITY, VARIABLE LOAD VARIABLE VELOCITY, CONSTANT LOAD VARIABLE VELOCITY, VARIABLE LOAD

MOTOR

1H, 1V 1A, E1H

EQUIPMENT DESCRIPTION:

2H, 2V 2A, E2H

E1H and E2H will be used to detect electrical frequencies.

MONITORING FREQUENCY: WEEKLY MONTHLY FORTNIGHTLY BIMESTRIAL

OTHER:

ANALYST: _________________________________

SPECIFIC FAN INFORMATION

Brand:___________________________ Serial number: _______________________ HP: ________________________________ Plate current: ________________________ Voltage: ____________________________

Brand: _____________________________ Serial no: _________________________ CFM flow: _______________________ Operation temperature: _____________ Number of blades: ____________________ Ventilator type:

Motor Type:

MOTOR INFORMATION:

Induction: Synchronous: RPM reference: __________ No. poles: ______ No. rotor rods (bars) _______ No. stator grooves: ______ No. commutator grooves

Direct current:

Type of support: 1. Free side

Ball bearing Brand and no.: _______

2. Loading side

Forced type Induced type Closed circuit

Diameter of the motor's pulley (Dm): ______ Diameter of the ventilator's pulley (Dv): ____ Groove number and the section type: ______ Distance between axle centers: ________ Spinning velocity: RPM fan = RPM motor X (Dm/Dv)= _____


Type of support: Ball bearing Brand and no.: _______


1. Free side

2. Loading side

Roller bearing Brand and no.: _______


Journal bearing

Journal bearing



The spectral bandwidth and its alarm levels are on the backside of this form.

Journal bearing

Journal bearing

Note: If a motor has a cooling ventilator it will be considered as additional equipment.



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4H 4V 4A

F A N



MOTOR

2H, 2V 2A, E2H


1H, 1V 1A, E1H



OTHER:

ANALYST: _________________________________

SPECIFIC FAN INFORMATION MOTOR INFORMATION: Brand:___________________________ Serial number: _______________________ HP: ________________________________ Plate current: ________________________ Voltage: ____________________________

Motor Type: Induction: Synchronous: RPM reference: __________ No. poles: ______ No. rotor rods (bars) _______ No. stator grooves: ______ No. commutator grooves

Direct current:



Diameter of the motor's pulley (Dm): ______ Diameter of the ventilator's pulley (Dv): ____ Groove number and the section type: ______ Distance between axle centers: ________

2. Loading side

Spinning velocity: RPM fan = RPM motor X (Dm/Dv)= _____



Type of support:





Journal bearing

Journal bearing


1. Free side

2. Loading side




Journal bearing

Journal bearing




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4H 4V 4A

F A N

MOTOR

1H 1V 1A E1H

EQUIPMENT DESCRIPTION: IDENTIFICATION: SECTION:

TYPE OF EQUIPMENT: CONSTANT VELOCITY, CONSTANT LOAD CONSTANT VELOCITY, VARIABLE LOAD VARIABLE VELOCITY, CONSTANT LOAD VARIABLE VELOCITY, VARIABLE LOAD MONITORING FREQUENCY: WEEKLY MONTHLY FORTNIGHTLY BIMESTRIAL

2H 2V 2A E2H

OTHER:

ANALYST: _________________________________

E1H and E2H will be used to detect electrical




Motor Type:

MOTOR INFORMATION:


Direct current:




2. Loading side




Type of support:





Journal bearing

Journal bearing

1. Free side

2. Loading side




Journal bearing

Journal bearing




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4H 4V 4A

IDENTIFICATION:

F A N

SECTION:


MOTOR

1H, 1V 1A, E1H


2H, 2V 2A, E2H



OTHER:

ANALYST: _________________________________

MOTOR INFORMATION: Brand:___________________________ Serial number: _______________________ HP: ________________________________ Plate current: ________________________ Voltage: ____________________________


Direct current:






2. Loading side






Type of support:

Journal bearing

Journal bearing







Journal bearing

Journal bearing

1. Free side

2. Loading side



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SCHEMATIC EQUIPMENT DIAGRAM MEASUREMENT POINTS

EQUIPMENT DESCRIPTION: IDENTIFICATION:

FAN

SECTION: MOTOR

1H 1V 1A E1H

2H 2V 2A E2H


OTHER:


ANALYST: _________________________________

SPECIFIC FAN INFORMATION MOTOR INFORMATION: Brand:___________________________ Serial number: _______________________ HP: ________________________________ Plate current: ________________________ Voltage: ____________________________


Direct current:





2. Loading side




Type of support:





Journal bearing

Journal bearing



Journal bearing

Journal bearing

The spectral bandwidth and its alarm levels are on the backside of this form. Note: If a motor has a cooling ventilator it will be considered as additional equipment.

1. Free side

2. Loading side



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Code . . .



FAN

SECTION: MOTOR

1H 1V 1A E1H

2H 2V 2A E2H



OTHER:

ANALYST: _________________________________




Direct current:


Diameter of the motor's pulley (Dm): ______ Diameter of the ventilator's pulley (Dv): ____ Groove number and the section type: ______ Distance between axle centers: ________ Spinning velocity: RPM fan = RPM motor X (Dm/Dv)= _____



2. Loading side


2. Loading side







Journal bearing

Journal bearing



Journal bearing

Journal bearing

The spectral bandwidth and its alarm levels are on the backside of this form. Note: If a motor has a cooling ventilator it will be considered as additional equipment.



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SCHEMATIC EQUIPMENT DIAGRAM THAT SHOWS MEASUREMENT POINTS


MOTOR

1H 1V 1A E1H

IM PU LS E TU R BI NE

2H 2V 2A E2H


OTHER:

ANALYST: _________________________________ E1H and E2H will be used to detect electrical frequencies.

SPECIFIC PUMP INFORMATION



Direct current:

Brand: _____________________________ Serial no.:________________________ Flow in gallons/min.:_________________ Operating temperature__________ Number of blades :___________ Pump type:

Centrifugal

Hydraulic Positive displacement

Coupling type: __________ Coupling brand: __________________________


2. Loading side





Journal bearing

Journal bearing

The spectral bandwidth and its alarm levels are on the backside of this form. Note: If a motor has a cooling ventilator it will be considered as additional equipment


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SCHEMATIC EQUIPMENT DIAGRAM MEASUREMENT POINTS EQUIPMENT DESCRIPTION:

1A 1P

2P

M O T O R

1F, E1F

SECTION:

2A 2F, E2F

3A 3P F = fluid direction P = perpendicular with the flow

IDENTIFICATION:

3F

P U M P


OTHER:


SPECIFIC PUMP INFORMATION



Direct current:

Brand: _____________________________ Serial no.:________________________ Flow in gallons/min.:_________________ Operating temperature__________ Number of blades :___________ Pump type:

Centrifugal

Hydraulic Positive displacement

Coupling type: __________ Coupling brand: ____________________________


2. Loading side


2. Loading side







Journal bearing

Journal bearing



Journal bearing

Journal bearing




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4H 4V 4A


MOTOR

1H,1V 1A, E1H

2H, 2V 2A, E2H

SCREW COMPRESSOR

SECTION:

5H 5V 5A


6H 6V 6A

E1H and E2H will be used to detect electrical frequencies..

MONITORING FREQUENCY: WEEKLY MONTHLY FORTNIGHTLY BIMESTRIAL Brand:___________________________ Serial number: _______________________ HP: ________________________________ Plate current: ________________________ Voltage: ____________________________

Motor Type: Direct current:


SPECIFIC COMPRESSOR INFORMATION Brand: ___________Serial no.: _______________ Maximum working pressure: _________________ Operational flow in CFM: ___________________ Coupling brand: ___________________________ No. of parts: ______________________________ No. of pinion entrance teeth (Np): _____________ No. of high velocity globe axles (La): __________ No. of low velocity globe axles (Lb): ___________ RPM high axle = RPM motor x (Np/Nc) RPM low axle = RPM high axle X (La/Lb)

2. Loading side

Type of high velocity axle support:





Journal bearing

Journal bearing

OTHER:

ANALYST: _________________________________

MOTOR INFORMATION:



3. Loading side ball bearing roller bearing pillow block

4. Free side ball bearing roller bearing pillow block

6. Free side ball bearing roller bearing pillow block

brand and no.: _____________

Type of low velocity axle support:

5. Loading side ball bearing roller bearing pillow block brand and no.: _____________

The spectral band width and its alarm levels are on the backside of this form


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3H 3V 3A



Crusher

MOTOR

1H, 1V 1A, E1H

2H, 2V 2A, E2H


OTHER:


ANALYST: _________________________________

SPECIFIC CRUSHER INFORMATION



Direct current:

Brand: _____________________________ Serial no.: __________________________ Grinding material: ___________________ Operational temperature: ______________ Number of hammers: _________________ Diameter of the motor's pulley (Dm):_____ Diameter of the mill's pulley (Dt): _______ No. grooves and section type: ________ Distance between axle centers: _________ Spinning velocity: RPM crusher = RPM


2. Loading side

motor

x (Dm/Dt)= __________


2. Loading side









Journal bearing

Journal bearing

Journal bearing

Journal bearing


The spectral band width and its alarm levels are on the backside of this form.

Note: If a motor has a cooling ventilator it will be considered as additional equipment


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1H 1V 1A E1H

2H 2V 2A E2H

3H 3V 3A

SECTION:

CONE TRITURATOR MOTOR


OTHER:


ANALYST: _________________________________



Direct current:

Brand: ____________________________ Serial no.: _________________________ Grinding material: ______ Operational temperature: ______________ Number of cones: ____________________ Coupling type: _______________________ Coupling brand: _____________________

Type of support:


SPECIFIC TRITURATOR INFORMATION

1. Free side

2. Loading side





Journal bearing

Journal bearing


2. Loading side





Journal bearing

Journal bearing


Note: If a motor has a cooling ventilator it will be considered as additional equipment .


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Code . . .


1H 1V 1A E1H

2H 2V 2A E2H

3H 3V 3A


CONE TRITURATOR

MOTOR

E1H and E2H will be used to detect electrical frequencies..


OTHER:

ANALYST: _________________________________



Direct current:


2. Loading side

SPECIFIC TRITURATOR INFORMATION Brand: ____________________________ Serial no.: _________________________ Grinding material: ______ Operational temperature: ______________ Number of cones: ____________________ Diameter of the motor's pulley (Dm): ____ Diameter of the mill's pulley (Dt): _______ Number of grooves and the section type: ______ Distance between axle centers: __________ Spinning speed: mill=

RPM motor x (Dm/Dt)= __________



RPM



Type of support:

Journal bearing

Journal bearing







Journal bearing

Journal bearing

1. Free side

2. Loading side



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SCHEMATIC EQUIPMENT DIAGRAM MEASUREMENT POINTS 8H,8V,8A,G8H 7H,7V,7A 5H,5V,5A MOTOR

9H 9V 9A

10H 10V 10A

2H 2V 2A E2H


N4 N2

N3

N1

TRANSPORTER'S PULLEY

6H,6V,6A,G6H

REDUCER

1H 1V 1A E1H



3H 4H 3V 4V 3A 4A G3H

OTHER:



Direct current:

Supports 3 and 4 Supports 5 and 6 Supports 7 and 8 ball bearing ball bearing ball bearing roller bearing roller bearing roller bearing Journal bearing Journal bearing.: _____

Special checking frequency:


Number or reduction steps: Spinning frequency: RPMgearN1 = RPM motor (reference) = _________ RPMgearN2/N3 = RPM motor X (N1/N2) = ______ RPMgearN4 = RPMgearN2/N3 X (N3/N4) = _____

Type of support:


SPECIAL REDUCER INFORMATION: Brand: ____________________________ Serial No.: _________________________

2. Loading side

The points G3H, G6H and G8H are used to obtain spectra that include the gearing frequency and their maximum frequency should not be less than:



FMAXG3H = 3 X N1 X RPMMOTOR = __________ X RPMMOTOR FMAXG6H = 3 X N3 X RPMGEARN/2N3 = _________ X RPMGEARN2/N3 FMAXG8H = 3 X N4 X RPMGEARN4 = ___________ X RPMGEARN4



SPECIAL PULLEY INFORMATION:

Journal bearing

Journal bearing

RPM pulley = RPM gearN4 = _____


9. Free side ball bearing roller bearing flat strengthening brand and no.: _________

The spectral bandwidth and its alarm levels are on the backside of this form



10. Loading side ball bearing roller bearing flat strengthening brand and no.: _____


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SCHEMATIC EQUIPMENT DIAGRAM MEASUREMENT POINTS 8H,8V,8A,G8H 7H,7V,7A 5H,5V,5A MOTOR

1H 1V 1A E1H

2H 2V 2A E2H

9H 9V 9A

10H 10V 10A


N4 N2

THREAD

N3

N1

6H,6V,6A,G6H

REDUCTOR

3H 4H 3V 4V 3A 4A G3H



OTHER:

ANALYST: _________________________________


SPECIAL REDUCER INFORMATION: Brand: ____________________________ Serial No.: _________________________ Coupling type on the entrance side________ Coupling type on the exit side: ________ Number or reduction steps:

Motor Type:

Spinning frequency:

MOTOR INFORMATION:


Direct current:

Type of support:


RPMgearN1 = RPM motor (reference) = _________ RPMgearN2/N3 = RPM motor X (N1/N2) = ______ RPMgearN4 = RPMgearN2/N3 X (N3/N4) = _____

2. Loading side





Journal bearing

Journal bearing

The spectral bandwidth and its alarm levels are on the backside of this form. Note: If a motor has a cooling ventilator it will be considered as additional equipment The spectral bandwidth and its alarm levels are on the backside of this form

Supports 3 and 4 ball bearing roller bearing Journal bearing

Supports 5 and 6 ball bearing roller bearing Journal bearing:


Special checking frequency: The points G3H, G6H and G8H are used to obtain spectra that include the gearing frequency and their maximum frequency should not be less than: FMAXG3H = 3 X N1 X RPMMOTOR = __________ X RPMMOTOR FMAXG6H = 3 X N3 X RPMGEARN/2N3 = _________ X RPMGEARN2/N3 FMAXG8H = 3 X N4 X RPMGEARN4 = ___________ X RPMGEARN4 SPECIAL TREAD INFORMATION: RPM pulley = RPMgearN4 = _____ 9. Free side 10. Loading side Ball bearing Ball bearing Roller bearing Roller bearing Journal bearing Journal bearing Brand and no.: _______ Brand and no.: _______ The spectral bandwidth and its alarm levels are on the backside of this form


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SCHEMATIC EQUIPMENT DIAGRAM MEASUREMENT POINTS 8H,8V,8A,G8H

9H 9V 9A

10H 10V 10A

7H,7V,7A N4

5H,5V,5A MOTOR

N2

N3

N1

SPROCKET

6H,6V,6A,G6H

REDUCER

1H 1V 1A E1H

2H 2V 2A E2H

SECTION:


OTHER:

ANALYST: _________________________________



Motor Type: Direct current:

SPECIAL REDUCER INFORMATION: Brand: ____________________________ Serial No.: _________________________ Coupling type on the entrance side: _____ Coupling type on the exit side: ________ Number or reduction steps:___________________ Spinning frequency: RPMgearN1 = RPM motor (reference) = _________ RPMgearN2/N3 = RPM motor X (N1/N2) = _______ RPMgearN4 = RPMgearN2/N3 X (N3/N4) = _____ Type of support: Supports 3 and 4 ball bearing roller bearing Journal bearing





IDENTIFICATION:


3H 4H 3V 4V 3A 4A G3H



2. Loading side

The points G3H, G6H and G8H are used to obtain spectra that include the gearing frequency and their maximum frequency should not be less than: FMAXG3H = 3 X N1 X RPMMOTOR = __________ X RPMMOTOR FMAXG6H = 3 X N3 X RPMGEARN/2N3 = _________ X RPMGEARN2/N3 FMAXG8H = 3 X N4 X RPMGEARN4 = ___________ X RPMGEARN4





SPECIAL SPROCKET INFORMATION: RPM sprocket = RPMgearN4 = _____

Journal bearing

Journal bearing

SPECIAL TREAD INFORMATION:


RPM pulley = RPMgearN4 = _____ 9. Free side 10. Loading side Ball bearing Ball bearing Roller bearing Roller bearing Journal bearing Journal bearing Brand and no.: _______ Brand and no.: _______





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8H,8V,8A,G8H

10H 10V 10A

7H,7V,7A


N4

5H,5V,5A MOTOR

N2

N3

N1

DRIVING PINION

6H,6V,6A,G6H

REDUCER

1H 1V 1A E1H

2H 2V 2A E2H

3H 4H 3V 4V 3A 4A G3H


OTHER:




Direct current:






SPECIAL REDUCER INFORMATION: Brand: ____________________________ Serial No.: _________________________ Coupling type on the entrance side: _____ Coupling type on the exit side: ________ Number or reduction steps:___________________ Spinning frequency: RPMgearN1 = RPM motor (reference) = _________ RPMgearN2/N3 = RPM motor X (N1/N2) = _______ RPMgearN4 = RPMgearN2/N3 X (N3/N4) = _____ Type of support:

2. Loading side





Journal bearing

Journal bearing

The spectral bandwidth and its alarm levels are on the backside of this form. Note: If a motor has a cooling ventilator it will be considered as additional equipment The spectral bandwidth and its alarm levels are on the backside of this form

The points G3H, G6H and G8H are used to obtain spectra that include the gearing frequency and their maximum frequency should not be less than: FMAXG3H = 3 X N1 X RPMMOTOR = __________ X RPMMOTOR FMAXG6H = 3 X N3 X RPMGEARN/2N3 = _________ X RPMGEARN2/N3 FMAXG8H = 3 X N4 X RPMGEARN4 = ___________ X RPMGEARN4

SPECIAL PINION INFORMATION: RPM pinion = RPMgearN4 = _____ 9. Free side Ball bearing Roller bearing Journal bearing Brand and no.: _______

10. Loading side Ball bearing Roller bearing Journal bearing Brand and no.: _______

Number of pinion teeth: __________



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SCHEMATIC EQUIPMENT DIAGRAM MEASUREMENT POINTS 6V 6A G6V

8H 8V 8A

5H 5V G5V


N3=

N4=

N2=

N3=

N1=


N2=

2H,G2H

7V 7A G7V

1V,G1V 0A,G0A

COUPLER

CIH,CIV,CIA

4V 4A G4V


OTHER:

APOYO “C” COUPLER

MCH,MCV,MCA

ANALYST: _________________________________

C = COUPLING SIDE MOTOR L = FREE SIDE

MLH,MLV,MLA

SPECIAL REDUCER INFORMATION: Brand: ____________________________ Serial No.: _________________________ Coupling type on the entrance side: _____ Coupling type on the exit side: _________


Type of support:


Direct current:

2. Loading side





Journal bearing

Journal bearing



Coupling side entrance


Spinning frequency: RPMgearN2/N3 = RPM motor X (N1/N2) = ________ RPMgearN4 = RPMgearN2/N3 X (N3/N4) = _______


9. Free side Ball bearing Roller bearing Journal bearing Brand and no.: _______


Pinion side entrance 10. Loading side Ball bearing Roller bearing Journal bearing Brand and no.: _______

Special checking frequency: The points G3H, G6H and G8H are used to obtain spectra that include the gearing frequency and their maximum frequency should not be less than: FMAXG0A/G1V = 3 X N1 X RPMMOTOR = _________ X RPMMOTOR FMAXG4V/G7V = 3 X N2 X RPMGEARN2/N3 = _________ X RPMGEARN2/N3 FMAXG5V/G6V = 3 X N3 X RPMGEARN2/N3 = ________ X RPMGEARN2/N3



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SCHEMATIC EQUIPMENT DIAGRAM THAT SHOWS MEASUREMENT POINTS 1H 1V 1A E1H

2H 2V 2A E2H


REDUCING MAAG

4H 4G 3H,3V 3A,3G

N4

SECTION:

N1 X X

MOTOR

IDENTIFICATION:

N3

X X

X X

N2 X X




OTHER:

ANALYST: _________________________________

SPECIAL REDUCER INFORMATION: Brand: ____________________________ Serial No.: _________________________ Number of reduction steps: _________


Spinning frequency:


Type of support: Supports N1


RPMgearN1 = RPM motor (reference) = _________ RPMgearN2/N3 = RPM motor X (N1/N2) = _______

Direct current:

2. Loading side





Journal bearing

Journal bearing


ball bearing roller bearing Journal bearing

Supports N2

ball bearing roller bearing Journal bearing

Special checking frequency: The points G3H, G6H and G8H are used to obtain spectra that include the gearing frequency and their maximum frequency should not be less than: FMAXG3A = 3 X N1 X RPMMOTOR = _________ X RPMMOTOR FMAXG4H = 3 X N3 X RPMGEARN2/N3 = ________ X RPMGEARN2/N3 The spectral band width and its alarm levels are on the back side of this form.

Note: If a motor has a cooling ventilator it will be considered as additional equipment The spectral bandwidth and its alarm levels are on the backside of this form



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CHAPTER 6 General procedure for the assignation of the narrow band alarm levels for different types of equipment. 6.1 Introduction Even though there is a lot of available literature on problem diagnosis using the vibration analysis approach, there is very little material on the appropriate method to specify effectively the perimeters of the spectral band alarms for various types of equipment. If these bands are used during the analysis process, the user can save thousands of pesos in maintenance expenses and they can significantly increase the plant's profitability. First, one has to determine that equipment has a problem, and second, one has to diagnose its cause and severity. The purpose of this chapter is to provide the user with a technical document which shows how to specify the alarm levels in peak velocity and the manner in which to define the spectral band frequencies in order to measure the vibrations levels in general processing equipment and in the service area. When these spectral bands and their alarm levels are appropriately defined for the specific type of equipment, bearing type and spinning frequency, valuable information will be obtained in order to prevent "false alarms".

This chapter's information is primarily applied to the preventive maintenance software which has 6 alarms spectral bands

as is the case of CSI Master Trend Plus system. The main part of the predictive maintenance system is based on the appropriate definition of the spectral band alarm levels that will provide the necessary information for the potentially serious problem detection in equipment. Even if we could obtain the "perfect" alarm specification value for the total equipment vibration, very serious potential problems could arise; these would have an almost imperceptible effect on the global vibration. However, these problems can be observed in the spectrum. But if the user does not use the spectral band technique for the alarm levels specification, it is probable that he will not detect a significant change in the global vibration levels, however the equipment could have a serious problem that was not detected. We are suggesting potential problems like worn out gear, gears in poor condition or an electric problem. For example, failure frequency of a bearing could increase by a factor of 4, from 0.03 to 0.12 in./sec. and cause an insignificant change in the vibration's global value if the 1X and 2X were respectively 35 in./sec. and 0.20 in./sec. (in this case the vibration's global value would be approximately from 0.4 to 0.42 in./sec.). Consequently, it is not recommended to use only the vibration's global value. Consequently, the fundamental objective of this chapter is to offer a procedure to specify the correct spectral band alarms for different equipment configurations. This procedure is summarized in Table III.



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6.2

Different types of spectral band alarms

It is important to note that there are two types of the preventive maintenance spectral band alarms that most software salesmen offer: 1) absolute peak, and 2) power band. The CSI Master Trend software uses power bands. The absolute peak systems help the user specify the maximum permissible amplitude of each peak within each defined narrow band. If any of these peaks equals or exceeds this value, the alarm of this specific band will be activated. On the other hand, the power band systems calculate the total energy within each band which is created by all the peaks from the same band. The total power of each band is calculated using the same equation that is used for the global value calculation for the complete spectrum: n

VG =

∑ Fi2 i =1

EQUATION 1

NBF VG = Vibration Global Value n = Number of resolution lines Fi = Spectral line amplitude NBF = Noise, as of chosen window = 1.5 Hanning window For the power band case, note that it is not necessary that only one individual peak in the band equals or exceeds the alarm value to activate it. For example, if a band that is defined from 0.5 FMAX to FMAX using 400 resolution lines for the spectrum, the equation 1 will be used to calculate the line range for the resolution of 200 to 400, which corresponds to the area of 0.5 FMAX to FMAX.

If we define the alarm level of 0.2 in./sec., two peaks of 0.175 in./sec. and 0.185 in./sec. will be sufficient to activate the alarm. Note that none of the two peaks exceeds the value of 0.2 in./sec. These power bands will be used in Table III because they are a good indicator of what occurs in the spectral band. 6.3

Vibration-Movement, speed acceleration parameters

and

Two important points will be taken into account before defining the spectral band alarms. First, the analyst should know which frequencies are generated by different parts of the equipment. For example, ball and roller bearings, strengthening plates, gears, electric problems, unbalance, movement, etc. Second, the analyst will have to define which vibration parameters (movement, speed or acceleration) he will use to detect in the best possible way the problems that can be observed in equipment. Table 1 shows that while the movement is a good indicator in measuring the low frequencies, lower than 600 CPM, it will not detect major frequency problems as can be caused by damaged bearings or worn out gears. For example, assume that we have a blower coupled by pulleys and bands where the engine has a normal operational velocity of 3600 RPM. The motor presents a bearing failure of 0.3 in./sec. at a spinning frequency (1X RPM).


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Code . . .

As

the

normal

alarm

levels

for

this

LOGARITHMIC AMPLITUDE

LOGARITHMIC AMPLITUDE LOGARITHMIC AMPLITUDE

MO VEM ENT

ATO DIC R IN E W PO

ON AT I LER E C AC

(mil s)

R

(g)

SPEED

FATIGUE INDICATOR

AREA OF SEVERE SIMILITUDE

EFF O

LOGARITHMIC FREQUENCY

RT

IND

ICA T

OR

COMPARISON OF VIBRATION LEVELS FOR MOVEMENT, SPEED AND ACCELERATION

FIGURE 1

If the peak-peak movement is used to evaluate this equipment and according to Table 1, we observe that at the frequency of 60,000 CPM, the spinning vibration will be only 1,5 mils.

equipment are 2 mils, the amplitude at the spinning frequency could be well observed on a linear spectral scale, while the vibration at 60,000 CPM will not be observed adequately. It's very probable that the analyst will not notice the bearing failure with the movement parameter, but the use of the velocity spectrum will allow a clear indication of the spinning frequency and the bearing failure frequency. The latter is a cause of major preoccupation even though the amplitude is similar to the one of unbalance at the spinning frequency. However, the spectra obtained in velocity also have limitations. For example, let's assume that we have an air centrifugal turbo compressor that spins at 3580 RPM and has a 344 tooth motive gear. The gear frequency (GMF) of this compressor will be approximately 1,231,500 CPM. In order to make an adequate observation of the gear situation, it is necessary to obtain spectra of at least 2.5 times the gear frequency.



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For this type of equipment, the normal values that are twice the engine frequency are 6 G's; on other hand, when wearing out problems start, this value can increase ten times. If we have a vibration level of 60 G's at 2X GMF, which is equivalent in this case to 2,263,000 CPM, the vibration velocity at this frequency is 0.089 in./sec. and with a movement of only 0.0007 mil. Consequently, the best indicator of the gear state for this kind of equipment is the acceleration, especially if one needs to analyze frequencies greater than 300,000 CPM. However, the speed spectra have proven to be the best indicators of most vibration problems. Consequently, the alarms analyzed in this chapter will be defined in peak units. The Tables I and II contain values in peak velocity; however, if one wishes to use RMS velocity it will only be necessary to multiply the peak value by 0.07071. 6.4 Problems that can be detected with vibration analysis In order to define adequately the spectral band alarms, it is necessary to clearly understand which problems can be detected through the vibration analysis, the manner in which they are detected and the level of severity. During years, many investigations have taken place to determine the way of evaluating typical problems, as are the cases of: unbalance, alignment, bearing

and gear condition, electrical conditions, etc. The Nexus A graphs show us a summary of the most common vibration problem diagnostics. The nexus A will help to compress the primordial causes. In these graphs, one will find typical spectra of different vibration problems. However, they will not be necessarily the only ones used in different failure types. For example, for the angular lack of alignment graph, note that while typical spectrum shows high amplitudes at 1X RPM and 2X RPM in the axial direction, at times high amplitudes will be shown at 1X, 2X and 3X RPM which dominate all the spectra, whether they are axial or radial readings. Additionally, there will be equipment that simultaneously presents various problems, as can be the case of high unbalance combined with the mechanical looseness at the base. In this case, both problems present high amplitudes at 1X RPM with harmonic multiples of spinning frequency. In some graphs, the phases of two points are presented in order to improve the analyst's diagnostic. Hopefully, the Nexus A graphs will help the analyst diagnose a great variety of equipment problems. Today, experiments and investigations are conducted in the field to complement the information that is presented in the annexed graphs. 6.5 Vibration global value (GV) specifications Even today, a lot of investigation is conducted to establish permissible vibration standards.



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Some international committees, formed by experienced professors, have studied the task of formulating the vibration criteria. The International Standard Organization (ISO) establishes the permissible vibration levels in accordance with ISO 2372, as is shown in: Table I. Severity criteria ISO 2372 for the equipment with the spinning velocity range from 600 to 12,000 RPM.

ventilators, etc.) Classification Vibration in the equipment supports (in./sec. peak) Very good < 0.07 (1.75 mm/s) Good < 0.20 (5.00 mm/s) Precaution < 0.50 (13.0 mm/s) Unacceptable > 0.50 (13.0 mm/s)

Various intents similar to ISO norms have been made to offer severity vibration criteria for different types of equipment. This is important because even with the same power there will be variations in the normal vibration levels.

For example, a reciprocating air compressor will have different vibration values from those of a screw compressor. Also, equipment will Class 1. Small equipment (for example electricalhave different vibration levels depending on motors up to 20 HP, tool machines,the type and the location of anti-vibrators, the natural frequency of the whole equipment, etc.) Classification Vibration in the equipmentthe relation of the center of gravity with supports (in./sec. peak) respect to the insulators, etc. Very good Good Precaution Unacceptable

< 0.02 (0.50 mm/s) < 0.05 (1.25 mm/s) < 0.13 (3.3 mm/s) > 0.13 (3.3 mm/s)

Consequently, the analyst will have to take into account the type of equipment and its assembling for the proper assignation of the vibration global levels in the predictive Class 2. Medium size equipment (for examplemaintenance software that is used.

electrical motors up to 100 HP, pumps, etc.) Classification Vibration in the equipment In this chapter, we shall use Table II, which supports (in./sec. peak) was developed by James Berry (Technical Very good < 0.03 (0.75 mm/s) Association of Charlotte), it's the best starting Good < 0.08 (2.00 mm/s) point for the criteria definition regarding the Precaution < 0.20 (5.00 mm/s) global vibration levels in in./sec. peak and Unacceptable > 0.20 (5.00 mm/s)

mm/sec. peak.

Class 3. Large equipment in cement industry (for example steam turbines, centrifugalThe table II is the starting point in defining the compressors, etc.) vibration criteria; in no way should it be taken Classification Vibration in the equipmentas a conclusive reference to equipment's supports (in./sec. peak) condition. These initial criteria should be Very good < 0.05 (1.25 mm/s) followed by the user's further analysis after Good < 0.13 (3.30 mm/s) having analyzed the vibration indicators at Precaution < 0.30 (7.50 mm/s) each measurement point in the system. Unacceptable > 0.30 (7.50 mm/s)

In the Table II, there are three vibration level

Class 4. Large equipment in cement industry (for example large turbo generators, largesections: "GOOD", "REGULAR" and "ALARM".



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After the global level revision of the vibration in equipment in good condition, it is probable that most of the points are located in the good or regular section. However, even though all the measurement points are located in the acceptable section, there is a possibility that the equipment has serious functional problems. Therefore, it is in this situation that spectral band alarms will be used. The global vibration values presented in Table II will be used as direct indicators in the definition of alarm levels in the Table III sections. 6.6 Alarm levels and spectral band width specifications The Table III shows the definition of the alarms and spectral bandwidths for various types of equipment, as well as different configurations when using predictive maintenance software that allows the formation of at least six spectral bands. The CSI Master Trend software facilitates the formation of no more than 12 spectral bands, consequently this Table can be used for the same purpose, and even new bands can be added if necessary. Before using Table III, the user should identify in the Table II the type of equipment in question in order to define the global value that will be used for this equipment. This information is the global vibration value which will be used directly in Table III. If the equipment selected for examination is not included in Table II,

it will be necessary to consult the supplier of the equipment in order to obtain the necessary information regarding the acceptable vibration levels. If this information is not received, one should use the equipment vibration levels of the most similar type. In Table III “DESCRIPTION” there are various sections. The "BAND'S MINIMUM FREQUENCY" defines at what frequency each band should initiate. It is important to notice that this minimum band frequency starts at 1% of the FMAX instead of 0 CPM. This frequency does not initiate at 0 CPM because most data collectors and spectral analyzers have a "noise" in the area of the first three spectral lines, especially when the data is collected with an accelerometer and are converted into speed with digital integration. The "MAXIMUM BAND FREQUENCY" specifies the maximum frequency of each band. We shall see bellow a section "BAND ALARMS" which defines the alarm level as a total value percentage (in some cases a direct value is used) of each band. In conclusion, at the end of the column, the "FREQUENCY RANGES ON A BAND" are defined to allow the user to distinguish the failure type that can occur in every frequency band. 6.7 Case A - General equipment with cog tooth or blade bearings The case A is applicable to a variety of driving as well as driven equipment of rotating kind which have ball and roller bearings or needle type supports. Before using the Case A from Table III, it will be necessary to identify the type of equipment


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in Table II in order to use the global vibration value defined in Table II.

possible without information.

The equipment's Global Value (VG) obtained in Table II will be substituted in each spectral band by taking the percentage that corresponds to each band.

As the last point in case A, note that each defined band has a specific purpose in the area that it covers. For example, the band A covers the sub-synchronous vibration area that is fundamental for the spin. In this area are located tabulated problems: looseness, bearing box spinning frequency, unbalance, bent axle, eccentricity, etc.

It is important to note in the Case A that for the equipment with spinning velocity ranging from 500 to 999 RPM, the FMAX should be taken at 60X RPM. The reason for this procedure is to ensure that the first stages of bearing damage can be observed, especially at natural speeds of the equipment. This range prevents that only the final stages of the bearing failure are observed. If in the Case A, the FMAX ranges are set too low, the important high frequency information will be lost; and consequently, we shall not have the information pertinent to the first stages of bearing failure. In the Nexus A, the typical spectra of the initial bearing failure are presented. On the other hand, if the FMAX ranges are defined too high, one will have a low spectral resolution, which could cause confusion at the time of elaborating a diagnostic. In the second place, all the information in the area of low frequencies as are unbalance, lack of alignment and the sub-harmonic waves will be piled up on the spectrum's left side, losing the potential information for diagnostics. In general, there is a rule for the FMAX definition: maintain it as low as

losing

any

important

The bands 2 and 3 cover the two harmonic waves (2X and 3X RPM) where potential problems can be found as are slipping, mechanical looseness, etc. The band 4 covers the fundamental frequencies of most bearing failures (BPFI, BPFO and BSF). In a similar way, bands 5 and 6 cover areas of bearing's natural frequencies as well as the harmonic waves of the fundamental bearing frequencies. 6.8 Case B - General equipment like flat strengthening plates without cog teeth or blades. The case B is similar to case A but with the difference that this case could be applied to equipment with flat strengthening plates. The cases in which the motor has bearings and the driven equipment has flat strengthening plates, then, the case A should be applied to the motor, while the case B should be applied to the equipment which is driven. It is important to note that FMAX for the flat strengthening plates is of only 20X RPM in comparison with 50X or 60X RPM for the equipment with bearings which present areas of high frequency. Additionally, the flat strengthening plates could cause serious problems in the area of sub-synchronous frequency, as is the case with



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oil squirts. Consequently, the frequency range should be minor and one should have a good resolution in the sub-synchronous area in order to detect correctly these problems. For this reason, the band 1 is exclusively selected for the detection of sub-synchronous vibration. The maximum percentage of global value is assigned to band 2 while a very low value is assigned to the band 6 because in its area the vibration will be insignificant. 6.9 Case C - Gear box, high frequency points with a known number of teeth The gearboxes will need two measurement definitions in some places due to a possible problem with unbalance, lack of alignment, looseness in the area of low frequency, as well as frequencies generated by the gears in the area of high frequencies. Taking into account the aforementioned and with the goal of obtaining the best possible information in the area of equipment's condition, it will be necessary to: a) Define in each axle support points that consist of the gear boxes, alarms and the frequencies that correspond to cases A and B, depending on the support types, bearings or strengthening plates that they have respectively. b) Define the second pair of alarms and spectral bands with a 2.75X GMF (gear frequency) at the points closest to the gears, preferably in the direction of their common contact points.

It is very common that the second gear harmonic frequency has higher vibration values than the fundamental 1X GMF when there are gear problems. Consequently, the second harmonic frequency and its lateral bands should be covered. In addition, some gear looseness cases will be observed in the GMF harmonic wave area. It will not be absolutely necessary to define the two alarm pairs of the spectral bands for each measurement point. However, it is recommended to check from time to time the points whose global values have increased considerably, and no increase has been noted in the low frequencies. In the gear boxes with various reduction stages, it is important to take into account the number of teeth of each analyzed gear, as well as the spinning frequency of each axle, especially for the definition of the bands required for A and B cases and for the high gear-frequency points. 6.10 Case D - Gear boxes, high frequency points with an unknown number of teeth Unfortunately, in the majority of the gearboxes, the teeth number is not known. In some gears, the spinning frequency of each axle is also unknown. Despite these problems, it is possible to effectively define the spectral band alarms, which can be used temporarily, while the correct teeth number and spinning frequency information of each monitored point is sought. In the case D, a maximum frequency of 160X RPM is specified; it will be applied at each measurement point on each axle that contains gears.



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If the spinning frequency of each axle is unknown, it is recommended to provisionally define spinning frequencies for each axle considering the increase (or decrease, depending on the specific case) in the same proportion for each axle based on the Increasing or Decreasing Factors data that is specified on the gear box plate. Once the teeth number for each gear and the axle spinning frequencies that contain the gears are known, the charge side of the motor will need to be modified, making sure to use at least 1,600 resolution lines to separate adequately the alarms and spectral bands of this equipment, following the procedures seen in case C.

This high frequency measurement point for the detection of rotor rod problems is normally defined on the horizontal axle and on the back of the induction motors, using as a minimum of 1600 resolution lines to easily observe the lateral bands. It is important to remember that this is an additional point to those already established in the cases A and B, depending on the motor support type. Due to the unknown number of rotor rods in most motors, it was decided to determine the maximum velocity of 240,000 CPM in order to cover most motors seen on the market, in which the number of rods various from 37 to 70.

6.11 Case E - Measurement point for the rotor rod passage frequency in induction motors

6.12 Case F - Low frequency measurement point for the detection of electric frequency.

The specific purpose for adding this point in each induction motor is to detect the first two harmonic rotor rod passage frequencies (RBPF = rod no. X motor spinning freq.), and the lateral bands of double electric line frequency (7200 CPM) that normally accompany the rod frequency.

The fundamental purpose of this additional point in each induction motor is to separate adequately the vibration frequencies generated by mechanical failure induced by an electrical problem.

When high rotor rod passage frequency amplitudes or the second harmonic wave are detected, one suspects that a loose rod and/or a motor eccentricity is present; particularly when these frequencies are followed with 2X electric frequency lateral bands and/or 2X slipping frequency. In the Nexus A, the induction motor functions with regard to electric vibration are explained more clearly.

The valuable information in the low frequency spectrum and high resolution is found in the area of 3,600 CPM, equivalent to the electric frequency, as well as the double value of this frequency, 7,200 CPM. It is common in the maintenance predictive systems to find frequencies of 7,200 CPM, its amplitude is high and there is a possibility of an electric problem in the motor as can be the case of the stator eccentricity or cracked rods in the rotor. In the Nexus A, these symptoms are explained in detail.



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The measurement point additional to those configured in cases A or B should be assigned to the horizontal position in the mechanic-electric problems. 6.13 Case G - Special equipment The purpose of this section is to cover various types of special equipment that for some reason requires different configuration of spectral bands from those seen in cases A and B, Table III. For example, the primary objective in specifically defining the bands of centrifugal equipment (pumps and ventilators) defined in the Types 1 through 4 in case G is to separate the cog tooth and blade passage frequency from the bearing failure frequency. However, the amplitudes permitted for the cog tooth or blade passage frequency will not be sufficient for the bearing failure frequency, they will be excessively high to detect bearing failures.

higher alarm level will be defined than it was defined in the levels programmed for the bearing problem detection. In Type 1, Table III, the band 4 has a fundamental frequency for the cog tooth passage and the first harmonic wave of lateral bands that could be detected above or bellow this warping frequency. On this band, the permitted vibration level is 70% of the Global Value (VG). Bands 3 and 5, adjacent to band 4, will have minor values for the bearing problem detection. In addition to bearings low harmonic waves, the band 5 will detect cog tooth harmonic frequency wave that is an indicator of the pulsing flow problem.

Type 2 - Centrifugal equipment with an unknown number of cog teeth or blades and bearings

Consequently, in the cases where one or various typical bearing failures and the cog tooth passage are in the same band, it will be impossible to separate alarms levels of the two vibration sources.

This configuration will include the equipment for which we know that there are cog teeth and bearing supports, but the exact number of cog teeth or blades is unknown. Different from the previously mentioned Type 1, the band 4 will cover the frequencies ranging from 4X to 6X RPM because most of the centrifugal equipment like pumps and ventilators have from 4 to 6 blades.

Type 1 - Centrifugal equipment with a known number of cog teeth or blades and bearings

The previous statement is not necessarily true in all the cases, because the width of this band can be adjusted.

If the number of blades, cog teeth or lobes in a ventilator, pump or compressor is known, it will be possible to add a separate band to record the passage frequency of the cog teeth, blades or lobes (BPF). In this band, a

Once the information about the number of cog teeth or blades is obtained, it will be necessary to reconfigure the equipment using the information from Table 1.



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Type 3 - Centrifugal equipment with the known number of cog teeth or blades and flat strengthening plates. In this case, the maximum frequency goes up to only 20X RPM, in comparison with 50X or 60X RPM for equipment with bearings. The band 5 will be used to calculate the information generated by the cog tooth frequency and its possible bands of the first spinning frequency harmonic wave. The alarm level will be 70% of the Global Value (VG), while the levels of bands 4 and 6 will be only 30% of the global value. The maximum frequency will be defined up to 1.2X the number of blades (BPF), in the case where this multiplication is greater than 20X RPM. Type 4 - Centrifugal equipment with the unknown number of cog teeth or blades and flat strengthening plates In this case, the band 4 will record the possible cog tooth or blade passage frequencies for pumps and ventilators. The band 6 with a range from 10X to 20X RPM will record the cog tooth or blade passage harmonic wave frequencies to detect pulsing flow problems. It is important to mention again that it will be necessary to reconfigure the equipment with the information from Type 3, once the information about the number of cog teeth or blades is obtained. 6.14 The detection of high frequency in the bearing condition diagnostics

In addition to the use of different alarms and spectral bands in the case of equipment with bearings, there is an additional predictive maintenance software tool called High Frequency Detection (HFD). This bearing condition indicator is based on the detection of acceleration levels in the high frequency area, typically from 5,000 to 20,000 Hz. The value obtained with these filters will be expressed in acceleration units (G's), and the tendency of this value will help to determine the analyzed bearing condition. When a bearing starts to deteriorate, the balls and rollers will start to fall into the microscopic "potholes" created on the track, and thus exciting the bearings and their components natural frequencies in a high frequency area. It will be possible to detect with the HFD these premature deterioration stages in the fenders, but in the normal spectrum it will be almost impossible to appreciate the fundamental bearing failure frequencies in this deterioration stage. In the case of CSI, the Master Trend software allows to define an additional band thanks to the HFD configuration, it has even preconfigured the band width and very similar alarms to those seen in previous sections. It is recommended in general to place the value "REGULAR" to 1.5 G's RMS and "ALARM" level to 3.0 G's RMS. Even though this HFD parameter is a good indicator of bearings condition, one should use additional tools as seen in the case of demodulation (chapter 9) to confirm the bearings state, especially in the most critical company equipment. In addition, the filter HFD will also serve to detect possible problems caused by lack of lubrication, the problem occurs because the



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lack of lubrication in the bearings, especially in the case of grease lubrication, makes the contact metalmetal very probable between balls and tracks, generating very high frequencies that could be detected with the HFD. In case of a subtle increase in the HFD values between readings, it is recommended to re-lubricate the bearings and retake measurements to see the effects at high frequencies. In case the values have diminished considerably, it will be necessary to retake measurements in 24 hours to ensure that they did not return to their previous level. When the HFD go back to their previous values after this time lapse, it is very probable that the bearing is in its initial failing stage. The adjusting of the accelerometer will need to be done using a magnetic band or it should be screwed to the equipment to obtain reliable HFD information. In no way should this measurement be taken with a manual measuring point accelerometer. In conclusion, it is important to remember that in the bearing case, the natural frequencies do not change with the increase or decrease in the spinning frequency of the equipment. This is important at the moment of spectrum evaluation with natural bearing frequencies.


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TABLE II. CRITERIA FOR RANGES IN GLOBAL VALUE VIBRATION CONDITIONS (VIBRATION VELOCITY, PEAK IN IN./SEC.). See notes bellow: TYPE OF EQUIPMENT COOLING TOWER TRANSMISSIONS Long floating axle transmission Pulleys and bands transmission Direct coupling transmission COMPRESSORS Reciprocating Screws Centrifugal with or without external gear boxes Centrifugal with integrated gear (axial reading) Centrifugal with integrated gear (radial reading) VENTILATORS AND BLOWERS Rotator lobe Blower fit with pulleys and bands Directly fit ventilators Primary air ventilators Large forced draft ventilators Large induced draft ventilators Ventilators fit on the axle of a motor Axial flow ventilators MOTOR-GENERATOR Belt coupled coupler coupled COOLING SYSTEM Reciprocating Open centrifugal Hermetic centrifugal LARGE TURBOGENERATORS 3600 RPM turbo generators 1800 RPM turbo generators CENTRIFUGAL PUMPS Vertical pumps (height ranging from 4 to 7 meters) Vertical pumps (height ranging from 2.5 to 4 meters) Vertical pumps (height ranging from 1.5 to 2.5 meters) Vertical pumps (height ranging from 0 to 1.5 meters) General use horizontal pumps Boiler supplier pump Hydraulic pumps TOOL-MACHINES Motor entrance to the gear box Exit from the gear box Spindles a. Cutting operations b. Platter finish c. Critical tolerance platter

GOOD

REGULAR Alert limit

ALARM failure limit

0 - .375 0 - .275 0 - .200

.375 - .600 .275 - .425 .200 - .300

> .600 > .425 > .300

0 - .325 0 - .275 0 - .200 0 - .200 0 - .150

.325 - .500 .275 - .425 .200 - .300 .200 - .300 .150 - .250

> .500 > .425 > .300 > .300 > .250

0 - .300 0 - .275 0 - .250 0 - .250 0 - .200 0 - .175 0 - .175 0 - .150

.300 - .450 .275 - .425 .250 - .375 .250 - .375 .200 - .300 .175 - .275 .175 - .275 .150 - .250

> 450 > .425 > .375 > .375 > .300 > .275 > .275 > .250

0 - .275 0 - .200

.275 - .425 .200 - .250

> .425 > .300

0 - .250 0 - .200 0 - .150

.250 - 400 .200 - .300 .150 - .225

> .400 > .300 > .225

0 - .250 0 - .175

.250 - .400 .175 - .275

> .375 > .275

0 - .375 0 - .325 0 - .250 0 - .200 0 - .200 0 - .200 0 - .125

.375 - .600 .325 - .500 .250 - .400 .200 - .300 .200 - .300 .200 - .300 .125 - .200

> .600 > .500 > .400 > .300 > .300 > .300 > .200

0 - .100 0 - .150 0 - .100

.100 - .175 .150 - .225 .100 - .175

> .175 > .225 > .175

0 - .075 0 - .050 0 - .030

.075 - .125 .050 - .075 .030 - .050

> .125 > .075 > .050

Notes: 1. Assuming an equipment spinning velocity from 500 to 60,000 CPM. 2. Assuming readings taken with accelerometer or velocity seismic sensor closest to bearings or strengthening plates. 3. Assuming that the equipment is not on insulators (for insulated equipment increase the alarm level 30 to 50%. 4. Set the alarms of similar motors to driven equipment. 5. Set the external gear box alarms 25% higher than the levels of driven equipment


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TABLE II. CRITERIA FOR RANGES IN GLOBAL VALUE VIBRATION CONDITIONS (VIBRATION VELOCITY, PEAK IN MM./SEC.). See notes bellow: TYPE OF EQUIPMENT COOLING TOWER TRANSMISSIONS Long floating axle transmission Pulleys and bands transmission Direct coupling transmission COMPRESSORS Reciprocating Screws Centrifugal with or without external gear boxes Centrifugal with integrated gear (axial reading) Centrifugal with integrated gear (radial reading) VENTILATORS AND BLOWERS Rotator lobe Blower fit with pulleys and bands Directly fit ventilators Primary air ventilators Large forced draft ventilators Large induced draft ventilators Ventilators fit on the axle of a motor Axial flow ventilators MOTOR-GENERATOR Belt coupled coupler coupled COOLING SYSTEM Reciprocating Open centrifugal Hermetic centrifugal LARGE TURBOGENERATORS 3600 RPM turbo generators 1800 RPM turbo generators CENTRIFUGAL PUMPS Vertical pumps (height ranging from 4 to 7 meters) Vertical pumps (height ranging from 2.5 to 4 meters) Vertical pumps (height ranging from 1.5 to 2.5 meters) Vertical pumps (height ranging from 0 to 1.5 meters) General use horizontal pumps Boiler supplier pump Hydraulic pumps TOOL-MACHINES Motor entrance to the gear box Exit from the gear box Spindles a. Cutting operations b. Platter finish c. Critical tolerance platter

GOOD

REGULAR Alert limit

ALARM failure limit

0 - 9.50 0 - 7.00 0 - 5.00

9.50 - 15.25 7.00 - 10.80 5.00 - 7.50

> 15.25 > 10.80 > 7.50

0 - 8.25 0 - 7.00 0 - 5.00 0 - 5.00 0 - 3.80

8.25 - 12.70 7.00- 10.80 5.00 - 7.50 5.00 - 7.50 3.80 - 6.40

> 12.70 > 10.80 > 7.50 > 7.50 > 6.40

0 - 7.50 0 - 7.00 0 - 6.40 0 - 6.40 0 - 5.00 0 - 4.50 0 - 4.50 0 - 3.80

7.50 - 11.50 7.00 - 10.80 6.40 - 9.50 6.40 - 9.50 5.00 - 7.50 4.50 - 7.00 4.50 - 7.00 3.80 - 6.40

> 11.50 > 10.80 > 9.50 > 9.50 > 7.50 > 7.00 > 7.00 > 6.40

0 - 7.00 0 - 5.00

7.00 - 10.80 5.00 - 7.50

> 10.80 > 7.50

0 - 6.40 0 - 5.00 0 - 3.80

6.40 - 10.00 5.00 - 7.50 3.80 - 5.70

> 10.00 > 7.50 > 5.70

0 - 6.40 0 - 4.50

6.40 - 9.50 4.50 - 7.00

> 9.50 > 7.00

0 - 9.50 0 - 8.25 0 - 6.40 0 - 5.00 0 - 5.00 0 - 5.00 0 - 3.20

9.50 - 15.25 8.25 - 12.70 6.40 - 10.00 5.00 - 7.50 5.00 - 7.50 5.00 - 7.50 3.20 - 5.00

> 15.25 > 12.70 > 10.00 > 7.50 > 7.50 > 7.50 > 5.00

0 - 5.50 0 - 3.80 0 - 2.50

2.50 - 4.50 3.80 - 5.70 2.50 - 4.50

> 4.50 > 5.70 > 4.50

0 - 2.00 0 - 1.25 0 - 0.75

2.00 - 3.20 1.25 - 2.00 0.75 - 1.25

> .3.20 > .2.00 > 1.25

Notes: 1. Assuming an equipment spinning velocity from 500 to 60,000 CPM. 2. Assuming readings taken with accelerometer or velocity seismic sensor closest to bearings or strengthening plates. 3. Assuming that the equipment is not on insulators (for insulated equipment increase the alarm level 30 to 50%. 4. Set the alarms of similar motors to driven equipment. 5. Set the external gearbox alarms 25% higher than the levels of driven equipment.


CAPITULO 6

Technology TABLE III. RECOMMENDED SPECTRAL BAND ALARM SYSTEM SPECIFICATIONS FOR VARIOUS EQUIPMENTS (See notes 1 and 2 bellow). (PEAK VELOCITY BANDS FOR NO INSULATED EQUIPMENT BOX MEASUREMENTS AND AT A VELOCITY GREATER THAN 500 RPM). CASE A. MACHINES IN GENERAL WITH BEARINGS WITHOUT COG TEETH OR BLADES --Set FMAX = 50X RPM (if the spinning velocity < 1500RPM DESCRIPTION BAND 1 BAND 2 BAND 3 BAND 4 BAND 5 MINIMUM BAND FREQ. MAXIMUM BAND FREQ. ALARM BANDS

5% Fmax 1.2X RPM 90% OF VG ALARM

1.2X RPM 2.2X RPM 50% OF VG ALARM

FREQUENCY RANGE COVERED BY THE BAND

Subsynchronous freq. and 1X RPM

1.5 - 2.0X RPM

2.2X RPM 3.2X RPM 40% OF VG ALARM 2.5 -3.0X RPM

see case A notes) BAND 6


12.2X RPM 50% Fmax 25% OF VG ALARM

50% Fmax 100% Fmax 20% OF VG ALARM

Fundamental frequencies for failing bearings

Low bearing harmonic wave frequency

High bearing harmonic wave frequencies and natural bearing frequencies

NOTE: To obtain alarm values of Global Values (VG) go back to TABLE II "CRITERIA FOR RANGES...". NOTE: FMAX = Spectral maximum frequency NOTE: If the spinning velocity is between 500 and 999 RPM set the FMAX = 60X RPM to detect possible natural bearing frequencies. CASE B. MACHINES IN GENERAL WITH FLAT STRENGTHENING PLATES WITHOUT COG TEETH OR BLADES --Set FMAX = 20X RPM DESCRIPTION MINIMUM BAND FREQ. MAXIMUM BAND FREQ. ALARM BANDS FREQUENCY RANGE COVERED BY THE BAND

BAND 1

BAND 2



Subsynchronous band

1X - 1.5X RPM

BAND 3 1.8X RPM 2.8X RPM 50% OF VG ALARM 2X - 2.5X RPM

BAND 4

BAND 5



3X - 3.5X RPM

4X - 10X RPM

BAND 6 10.2X RPM 100% Fmax 20% OF VG ALARM 10.5X - Fmax

NOTES: 1. These spectral band alarm specifications are applied to standard process and service equipment as are centrifugal pumps, blowers, motors, forced and induced draft ventilators, generators, coolers, centrifugal compressors, vacuum pumps, reducers, etc. 2.

These specifications are not applicable to reciprocating equipment, diesel motors, gas turbines, great power generators, exciters, pulverizes, etc. The spectral bands for this type of equipment should be designed by the user after obtaining and analyzing spectra.


CAPITULO 6

Technology TABLE III. RECOMMENDED SPECTRAL BAND ALARM SYSTEM SPECIFICATIONS FOR VARIOUS EQUIPMENT (See notes 1 and 2 bellow). (PEAK VELOCITY BANDS FOR NO INSULATED EQUIPMENT BOX MEASUREMENTS AND AT A VELOCITY GREATER THAN 500 RPM).

CASE C. GEAR BOXES, HIGH FREQUENCY POINTS WITH KNOWN NUMBER OF TEETH --Set FMAX = 2.75X RPM Gear Freq. (GMF)- See case C note) DESCRIPTION

BAND 1

BAND 2

MINIMUM BAND FREQ. MAXIMUM BAND FREQ. ALARM BANDS

1% Fmax 0.1X GMF 90% OF VG ALARM

0.1X GMF 0.25X GMF 40% OF VG ALARM


Low harmonic waves

High harmonic waves

BAND 3 0.25X GMF 0.75X GMF 30% OF VG ALARM 0.5X GMF and its lateral bands

BAND 4

BAND 5

BAND 6

0.75X GMF 1.25X GMF 70% OF VG GMF

1.25X GMF 1.75X GMF 30% OF VG ALARM

1.75X GMF 100% MAX 50% OF VG ALARM

GMF and its lateral bands

1.5X GMF and its lateral bands

2X GMF, 2.5X GMF and its lateral bands

NOTE: In gear boxes, it will be necessary to specify if there are points with high frequency ranges in addition to the normal frequency range points, as was described in cases A and B. Place the sensor closest to the axle gear that should be checked. It is important to remember that the natural acceleration frequency can be excited, consequently it is recommended to use the magnetic disc or to place fast switch breakers to avoid these problems. NOTE: GMF = gear frequency = No. of gear teeth in question multiplied by its spinning frequency. CASE D. GEAR BOX, HIGH FREQUENCY POINTS WITH UNKNOWN NUMBER OF TEETH --Set FMAX = 160X RPM of the axle to be checked--See note C DESCRIPTION

BAND 1


1% Fmax 10X RPM 70% OF VG ALARM


1.6 - 10X RPM

BAND 2 10X RPM 40X RPM 60% OF VG ALARM 10 - 40X RPM

BAND 3 40X RPM 70X RPM 60% OF VG ALARM

BAND 4

BAND 5

BAND 6

70X RPM 100X RPM 60% OF VG ALARM

100X RPM 130X RPM 40% OF VG ALARM

130X RPM 100% Fmax 40% OF VG ALARM

70 - 100X RPM

100 - 130X RPM

130X - Fmax

40 - 70X RPM

NOTE: The 160X RPM frequency range should be applied to each axle that is checked, taking into account the spinning velocity or each axle. One should additionally take spectra with the cases A and B frequency ranges. Once the number of gear teeth is acquired, immediately replace the spectral band alarm levels with those of the case C. NOTES: 1. These spectral band alarm specifications are applied to standard process and service equipment as are centrifugal pumps, blowers, motors, forced and induced draft ventilators, generators, coolers, centrifugal compressors, vacuum pumps, reducers, etc. 2. These specifications are not applicable to reciprocating equipment, diesel motors, gas turbines, great power generators, exciters, pulverizers, etc. The spectral bands for this type of equipment should be designed by the user after obtaining and analyzing spectra.


CAPITULO 6

Technology TABLE III. RECOMMENDED SPECTRAL BAND ALARM SYSTEM SPECIFICATIONS FOR VARIOUS EQUIPMENT (See notes 1 and 2 bellow). (PEAK VELOCITY BANDS FOR NO INSULATED EQUIPMENT BOX MEASUREMENTS AND AT A VELOCITY GREATER THAN 500 RPM). CASE E.

FREQUENCY MEASUREMENT POINTS FOR THE INDUCTION MOTOR ROTOR ROD --Set FMAX = 240,000 RPM (See case E note) DESCRIPTION

MINIMUM BAND FREQ. MAXIMUM BAND FREQ. ALARM BANDS FREQUENCY RANGE COVERED BY THE BAND

BAND 1 30,000 RPM 65,000 RPM .08 in./sec. (2mm/sec.)

BAND 2 65,000 RPM 100,000 RPM .06 in./sec. (1.5 mm/sec.) 65K - 100K

BAND 3 100,000 RPM 135,000 RPM 0.06 in./sec. (1.5 mm/sec.) 100K - 135K

30K - 65K

BAND 4 135,000 RPM 170,000 RPM 0.06 in./sec. (1.5 mm/sec.)


135K - 170K


NOTE: The purpose of including this additional point in horizontal position on the back of the motor is to detect possible rotor motor passage frequencies and the appearance of its lateral bands which are twice higher than the electric frequency. This case is applicable to spinning velocity motors which range from 900 to 3600 RPM. The transducer should be well installed, using the magnetic base or quick connection. CASE F. LOW FREQUENCY MEASUREMENT POINTS TO DETECT ELECTRIC FREQUENCY --Set FMAX = 12,000 RPM (600 to 3600 RPM motors) DESCRIPTION MINIMUM BAND FREQ. MAXIMUM BAND FREQ. ALARM BANDS

BAND 1 240 RPM 2,000 RPM

BAND 2 2,000 RPM 4,000 RPM

BAND 3 4,000 RPM 6,000 RPM

BAND 4 6,000 RPM 8,000 RPM

BAND 5 8,000 RPM 10,000 RPM

BAND 6 10,000 RPM 12,000 RPM

90% OF VG ALARM 50% OF VG ALARM 50% OF VG 35% OF VG ALARM 30% OF VG ALARM 30% OF VG ALARM 30% OF VG ALARM FREQUENCY RANGE COVERED 90% OF VG ALARM ALARM BY THE BAND 120 to 2000 RPM motors 2000 to 4000 RPM motors NOTE: The purpose of including this additional point in the horizontal position on the motor's charge side is to separate mechanic from electric peaks, especially in the area of 1X RPM and twice the electric frequency (7,200 RPM for Mexico). NOTES: 1. These spectral band alarm specifications are applied to standard process and service equipment as are centrifugal pumps, blowers, motors, forced and induced draft ventilators, generators, coolers, centrifugal compressors, vacuum pumps, reducers, etc. 2.

These specifications are not applicable to reciprocating equipment, diesel motors, gas turbines, great power generators, exciters, pulverizers, etc. The spectral bands for this type of equipment should be designed by the user after obtaining and analyzing spectra.


CAPITULO 6

Technology TABLE III. RECOMMENDED SPECTRAL BAND ALARM SYSTEM SPECIFICATIONS FOR VARIOUS EQUIPMENT (See notes 1 and 2 bellow).

(PEAK VELOCITY BANDS FOR NO INSULATED EQUIPMENT BOX MEASUREMENTS AND AT A VELOCITY GREATER THAN 500 RPM).

CASE G. SPECIAL MACHINES TYPE 1. CENTRIFUGAL MACHINES WITH THE KNOWN NUMBER OF COG TEETH OR BLADES AND BEARINGS-- Set FMAX = 50X RPM (See notes) DESCRIPTION BAND 1 BAND 2 BAND 3 BAND 4 BAND 5 MINIMUM BAND FREQ. MAXIMUM BAND FREQ. ALARM BANDS FREQUENCY RANGE COVERED BY THE BAND




1.5 - 2.0X RPM

2.2X RPM BPF - 1.2X RPM* 40% OF VG ALARM 2.5X Fundamental frequencies for failing bearings

BAND 6

BPF - 1.2X RPM* BPF + 1.2X RPM* 70% OF VG ALARM

BPF + 1.2X RPM* 50% Fmax 35% OF VG ALARM


Cog tooth and blade passing frequency (BPF)

Bearing's low harmonic wave frequency

Bearing's high harmonic wave frequencies and natural bearing frequencies

NOTE: "BPF" = Passing cog bearing or blade freq. = No. of cog bearings or blades multiplied by spinning RPM. NOTE: If the spinning velocity is between 500 and 999 RPM set the FMAX = 60X RPM to detect possible bearing's natural frequencies.

CASE G. SPECIAL MACHINES TYPE 2. CENTRIFUGAL MACHINES WITH THE UNKNOWN NUMBER OF COG TEETH OR BLADES AND BEARINGS-- Set FMAX = 50X RPM (See notes) DESCRIPTION

BAND 1

BAND 2


0.5% Fmax 1.2X RPM 90% OF VG ALARM




1.5 - 2.0X RPM

BAND 3 2.2X RPM 3.2X RPM 40% OF VG ALARM 2.5 -3.0X RPM

BAND 4

BAND 5

BAND 6




Possible cog tooth and blade passing frequencies (BPF) for pumps and ventilators

Bearing's low harmonic wave frequency

Bearing's high harmonic wave frequencies and natural bearing frequencies

NOTE: Once the number of cog teeth or blades is obtained, replace these spectral band alarm levels with those from type 1. NOTE: If the spinning velocity is between 500 and 999 RPM set the FMAX = 60X RPM to detect possible natural bearing frequencies. NOTES: 1. These spectral band alarm specifications are applied to standard process and service equipment as are centrifugal pumps, blowers, motors, forced and induced draft ventilators, generators, coolers, centrifugal compressors, vacuum pumps, reducers, etc. 2. These specifications are not applicable to reciprocating equipment, diesel motors, gas turbines, great power generator, exciters, pulverizers, etc. The spectral bands for this type of equipment should be designed by the user after obtaining and analyzing spectra.


CAPITULO 6

Technology

TABLE III. RECOMMENDED SPECTRAL BAND ALARM SYSTEM SPECIFICATIONS FOR VARIOUS EQUIPMENT (See notes 1 and 2 bellow).

(PEAK VELOCITY BANDS FOR NO INSULATED EQUIPMENT BOX MEASUREMENTS AND AT A VELOCITY GREATER THAN 500 RPM).

CASE G. SPECIAL MACHINES TYPE 3. CENTRIFUGAL MACHINES WITH THE KNOWN NUMBER OF COG TEETH OR BLADES AND FLAT STRENGTHENING PLATES-- Set FMAX = 20X RPM or 1.2X BPF DESCRIPTION

BAND 1

BAND 2


0.1% Fmax 0.8X RPM 30% OF VG ALARM



Subsynchronous band

1X - 1.5X RPM

BAND 3 1.8X RPM 3.8X RPM 50% OF VG ALARM 2X - 3.5X RPM

BAND 4

BAND 5

BAND 6

3.8X RPM BPF - 1.2X RPM* 30% OF VG ALARM

BPF - 1.2X RPM* BPF + 1.2X RPM* 70% OF VG ALARM

BPF + 1.2X RPM* 100% Fmax 30% OF VG ALARM

4X - Low spinning harmonic wave frequency

Cod tooth or blade passing frequency (BPF) and lateral 1X bands.

High spinning harmonic wave frequency

* NOTE: "BPF" = Passing cog bearing or blade freq. = No. of cog bearings or blades multiplied by spinning RPM. CASE G. SPECIAL MACHINES TYPE 4. CENTRIFUGAL MACHINES WITH THE UNKNOWN NUMBER OF COG TEETH OR BLADES AND BEARINGS-- Set FMAX = 20X RPM DESCRIPTION BAND 1 BAND 2 BAND 3 BAND 4 BAND 5 MINIMUM BAND FREQ. MAXIMUM BAND FREQ. ALARM BANDS




Subsynchronous band

1X - 1.5X RPM


BAND 6




4X - 6.5X RPM

7X - 9.5X RPM

10X - Fmax

2X - 3.5X RPM

NOTE: Once the number of cog teeth or blades is obtained, replace these spectral band alarm levels with those from type 3. NOTES: 1. These spectral band alarm specifications are applied to standard process and service equipment as are centrifugal pumps, blowers, motors, forced and induced draft ventilators, generators, coolers, centrifugal compressors, vacuum pumps, reducers, etc. 2. These specifications are not applicable to reciprocating equipment, diesel motors, gas turbines, great power generators, exciters, pulverizers, etc. The spectral bands for this type of equipment should be designed by the user after obtaining and analyzing spectra.


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CHAPTER 7 Principles for monitoring routes

planning

We do not intend at all to exclude the movement and velocity transducers, but due to their limited applications they will not be analyzed in this manual. In case one needs information about them, necessary bibliography will be annexed to this manual.

7.1 Introduction An important part of the Predictive Maintenance System based on the vibration analysis is the planning of monitoring routes. Various aspects will influence an adequate planning of monitoring routes. In this chapter, we shall mention the most important aspects that should be taken into account when implementing the monitoring routes, as well as general principles for the selection of monitoring points on the equipment, adequate mounting of vibration transducers and the principles for storing obtained information. 7.2 The principles for correct mounting of vibration transducers Today, there are three types of transducers, which are used to measure vibration levels. These three types of transducers contain movement, velocity and acceleration sensors. The three systems are based on the principle of transforming the mechanical vibration into an analog electrical signal that represents the mechanical movement. Even though the three systems have their particular characteristics and applications, in this chapter we shall focus on the description of the accelerometer and its different forms of mounting because the transducers cover most of the diagnostic applications for equipment problems.

7.2.1 Accelerometer description The accelerometers transform the mechanic movement into an analog signal proportional to the vibration acceleration in the system. Most of the accelerometers use piezoelectric materials (generally quartz or polycrystalline ceramics) as the main sensitive transducer component. The quartz is the most durable and it has smaller signal vibrations with temperature changes. The piezoelectric material produces an electric voltage when it is exposed to an external force. The material's atoms are compressed and the electrons are moved creating a voltage proportional to the force. In figure 1, the "compression mode" accelerometer is shown. A mass is pressed against a piezoelectric material to produce a reference force. When an accelerometer is submitted to a vibration force (equivalent to the mass multiplied by acceleration), this force is added to and subtracted from the reference generated by the screw inserted into the piezoelectric crystal, producing a voltage proportional to the change in force.

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piezoelectric crystal

that needs to be measured in each specific case. When an inadequate mount is used to measure a certain frequency range, it is very probable that the acquired signal will be of low quality.

Figure 1. Compression type accelerometer

For example, if it is necessary to take data of high frequency levels and a manual tracing point is used, it is very probable that the high frequency information does not appear. These details will be discussed bellow, referring to Table 1.

This accelerometer mechanism will have its natural, operational frequency that will depend on the installed mass and the constant spring of the system. The frequency range is limited to 10% of the natural frequency.

The direct mounting to equipment is the most adequate manner for obtaining reliable vibration readings, while the usage of quick connectors, magnetic bases and tracing points will diminish the high frequency sensitivity.

The high frequency accelerometers (greater than 10 KHz) are usually small, while the low frequency accelerometers (0.001 at 1 KHz) are usually large and heavy.

To obtain the correct, direct mounting on the equipment, it will be necessary to adequate the place where the sensor will be mounted. One should make sure that the diameter of the equipment is larger than the sensor's, the measurement place should be flat in an area not larger than 5 thousandths of an inch, have a finish of at least 10 micro inches and the thread should be perpendicular to the base.

The advantages of accelerometers are:

vibration

reading

- They take acceleration readings, which is an advantage when it is necessary to measure bearing failure and gear frequency. - They are small. - They are light. - They are economical. - They have a wide frequency range. 7.2.2 Accelerometer mounting types and their frequency response The accelerometers can be mounted on equipment using threaded screws, quick connectors, magnetic bases or tracing points connected to the accelerometer for the manual data taking. The adequate mount type will be chosen for each usage taking into account the frequency range

On the other hand, the accelerometer should have a pair of appropriate fasteners that should have in most cases a value of 26 pounds/inch. However, it will not be always possible to install screw sensors to equipment; in those cases, it is recommended to use fast connectors or magnetic bases. The table II shows the frequency response curves according to different mounts. In the curve that corresponds to the direct mounting on the surface, one observes that the accelerometer could be used to measure frequencies of up to 10,000 Hz Vibration Analysis ManualPage 75 of 143


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without any resonance problems in the sensor. Quick connection mounting is obtained by providing the measuring equipment with a threaded base fitted with cement or a screw. On the other hand, the accelerometer will have a special connector with internal threads. When the sensor is fixed to the base, a good coupling is formed. The connection is managed quickly and the frequency of 8,000 Hz is obtained.

In the case of the magnetic base mount, if and when the measuring spot is free of grease and perfectly clean, one can record frequencies in the order of 6,000 Hz. The choice will depend on the user and his finances.



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Table 1. Accelerometer mounting types FREQUENCY RESPONSE CURVES 1. Direct to the surface mount

FREQUENCY IN HZ

2. Quick connector mount

FREQUENCY IN HZ

3. Magnetic-base mount

FREQUENCY IN HZ

4. Threaded tracing point

FREQUENCY IN HZ

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The selection of measurement points on the equipment will greatly depend on the sensor's mount and on the accessibility of the measurement points. In chapter 5, we presented different formats for the registration of the acquired information, and using the previously presented points it is recommended to collect the most possible information from the equipment which means taking vibration data in horizontal, vertical and axial directions at each measurement point. This information will be valuable for the problem diagnostic when the vibration levels go beyond the limits established in Table III, Chapter 6. As a general norm, the measurement points should be located as close as possible to the equipment supports in order to register a reliable information at each point. When the measurement points are far from the supports, there is a risk of getting a weak signal which could create a situation in which the alarm levels are never reached.

The tangential readings will only cause the capping of alarm levels when the equipment is operating in good condition; thus, causing the analyst's time loss and confusion. In case of the disc placement as magnet bases or threaded discs for the quick connectors, it is recommended to identify them with a letter to avoid confusion among the personnel that collects data. As a general rule, it is recommended to use the letters H, V and A for the horizontal, vertical and axial readings respectively. In addition, it is recommended to place protective covers on each disc to prevent a grease or dust collection. This procedure will shorten the data collection time because there will be no need to constantly clean the equipment. These covers can be plastic. In figure 2, there is a typical arrangement of the strengthening plate measurement points.

However, at times it will be impossible to reach the points closest to the supports. In these situations, it is recommended to observe attentively the spectra obtained in search for any frequency generated by bearing or gear failures. The readings of the horizontal and vertical directions will be taken following a radial pattern. It is not recommended to take these readings in a tangential manner, for example, on top of a motor or pump. We have this situation because the tangential readings are greater than radial readings. This difference is caused by the equipment' movements and possible bending (deviations).

Figure 2. Measurement points. The markings for horizontal, vertical and axial axles will be respectively H, V, and A. In the case of the vertically installed equipment, both radial readings will be in Vibration Analysis ManualPage 78 of 143


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the horizontal position and for this reason it is recommended to use different abbreviations for the identification of the measurement points. Cardinal axis could be used for the identification of the process route; for example, a radial reading for a vertical pump is usually taken in the direction of the tube's exit and the other at 90°. The reading in the direction of the fluid movement could be identified with the letter F and the one at 90° from it with the letter P, showing in such a way that it is a perpendicular reading in the direction of the fluid's movement. 7.4 Efficient tracing of monitoring routes In most predictive maintenance software, the monitoring routes could be configured in accordance with the user's needs, which is the case of the CSI Master Trend System. Normally the data collecting personnel establish the monitoring routes according to the physical distribution of the equipment in order to optimize the data recording time. In this way the information is recorded in one or more plant sections and it is sent to the computer. However, in some plants the time element has been sacrificed in a way that seems to be attractive: recording the information by "family" groups (equipment with common characteristics). This recording method requires the monitoring routes to be organized according to equipment's characteristics. For example: pumps, ventilators, gearboxes, blowers, etc.

The primary objective of these routes is to group equipment according to its characteristics and thus facilitate the analytical process. Thanks to this method, the spectra analysis will be easier because the analyst will be focused on the specific type of equipment; and he could use methods like spectra comparison, as well as the specialized and comparative equipment of the same type. Either of the two ways monitoring routes is correct; selection of the adequate depend on the plant size and of common type equipment.

for planning however, the method will the existence

If the distance between machines of the same type is great, it is preferable to use topographic routes. In either of the two cases, it is important to take into account the following suggestions: 1. In the initial stages of the system's implementation, it will be necessary to take spectra of high resolution in all measurement points (at least 1600 lines) with the purpose of obtaining the initial equipment reference. Record the wave spectra and form. 2. Adding additional measurement points, as is the case with electric or gear frequency measurement points, take into account that these points should be selected immediately after the usual measurements. For example, for the electric frequency readings, the measurement point with this range of frequency should be defined after the point with the normal bearing frequency rage. The previous recommendation is offered with the intention of taking advantage of the sensor's connection to the base and the opportunity to take two readings from the Vibration Analysis ManualPage 79 of 143


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same measurement point without taking it off and putting it on again. 3. The later readings could have 400 or 800 resolution lines to avoid the saturation of the computer's memory; the exception to this principle could be the points that require a higher resolution like electric frequency points. 4. Do not saturate the data collector with too many routes because it is often necessary to take additional readings with high resolution when potentially chronic problems are detected in the work area. The unnecessary data diminishes the available computer memory, and it prevents the recording of the rest of the equipment's measuring points. It is important to unload the information continuously in order to be always capable of storing new spectra information. 5. Preferably, record the vibration wave shape only when the alarm levels were triggered in the collector. The analysis of the wave shape will be an important tool when problems are presented in bearings and gears, and in many different kinds of problems. In the software, it will be possible to select the time for the wave shape recording and the spectrum depending on the alarms going off as it was previously described. It is not necessary to always store the wave shapes in order not to saturate the computer's hard disk, unless it has a great capacity. In the equipment that is not critical for the process, it is recommended to record the spectrum and the wave shape only when the established alarms are triggered.

7.5 Definition of monitoring priorities After establishing a vibration-monitoring program, it will be necessary to define the schedule for the data collection from the equipment. The monitoring periods will vary according to the type of the equipment that is monitored and its priority for the production. According to general practice, a 30-day period is considered to be adequate for most industrial equipment. However, it will be necessary to diminish this period when the alarm vibration levels are detected in critical machines for the process. The previous is applicable to equipment that has spinning frequencies higher than 600 CPM. In machines with spinning frequencies lower than 600 CPM, it is recommended to apply 60 day monitoring periods. This is due to the fact that they will present minor problems in comparison with the equipment with major velocity. However, in case of a reading abnormality, it is recommended to diminish the monitoring frequency. On the other hand, in the equipment that has not presented any problems in several readings, it is recommended to extend the monitoring period, for example, from 30 to 60 days. In addition, it is important to mention that in order to have an adequate Predictive Maintenance System, it will be necessary to have sufficient data for the effective calculations that are performed by software. When there is a meager amount of data in the system, the prognostics will not be as precise as when there is a complete record. Vibration Analysis ManualPage 80 of 143


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Consequently, it is not recommended to have monitoring sessions scheduled for more than 60 days apart because the quantity of accumulated data will be low and the analyst will not be able to predict adequately the behavior of the equipment. If on the contrary, the monitoring sessions are too frequent, for example every 15 days, the collection task will be wearisome and it is very probable that the computer hard disk gets saturated prematurely.

Thus, it will be necessary to define monitoring periods in accordance with the plant machines, paying close attention to the equipment that is very critical for the process.



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CHAPTER 8 Monitoring procedure for the low spinning velocity equipment (lower than 600 CPM)

amplitude difference in the area of low frequency. In this chapter, we shall explain the general procedures for the correct vibration level measuring of low spinning frequency, and the recommended alarm levels for this equipment will be seen.

8.1 Introduction A lot of specialists have considerable experience in the area, but there is insufficient or no work experience with the equipment with low spinning frequency in the range of 1.5 to 300 rpm. In some cases, even the most necessary type of the equipment used to make the precision monitoring sessions is unknown. Due to this lack of knowledge, when initiating the Predictive Maintenance System, it is common that the low spinning velocity equipment remains excluded from the program, even though these can be critical for the process. Generally, the equipment of low spinning frequency has an axle diameter from 4 to 20 inches or more, and they are typically large in size. Consequently, when the bearing failures start in these units, the resulting vibration in the bearing box will be very low. Consequently, it is possible that some potentially serious problems remain unheeded. For example, in units spinning at velocities lower than 20 rpm, it will be almost impossible to detect a bearing failure using a spectral analysis; however, it could be detected through the wave's shape analysis (time domain). Additionally, the criteria for the severity of normal vibrations, as seen in Table I of chapter 6, will not apply to equipment with low spinning velocity due to the great

8.2

Selection of the optimal parameter for the low frequency measurements (acceleration, velocity and movement)

In accordance with Figure I shown in chapter 6, pages 63, we can summarize that every measurement unit, movement, velocity and acceleration have their specific applications depending on the frequency range that one wished to measure. Referring to this chapter's subject matter, when it is necessary to obtain information in very low frequencies, it is recommended to use movement as a measurement parameter. Its usage will be focused on detecting the failures like unbalance, lack of alignment or eccentricity in the axle or other components that spin at a low velocity, inferior to 600 cpm. However, the movement will have very little sensibility for the events that occur at frequencies higher than 600 cpm, especially when there are multiple harmonic waves that could be generated, for example, by a loose bearing in its box. For the frequencies that are ranging from 600 to 60,000 cpm, it is recommended to use the velocity as the optimal measurement parameter. Even though the equipment spins, for example, at 60 cpm, it is very probable that the bearing failure frequency of this axle is above 600 cpm. Vibration Analysis ManualPage 82 of 143


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Consequently, It is recommended to use the movement as an optimal parameter to measure equipment's unbalance and lack of alignment; and to use velocity to evaluate the bearing condition. In figures 8.1 and 8.2, the spectra of the bearing on the coupler's side of an induced draft ventilator that spins at 250 rpm approximately are presented. As it can be observed, the movement spectra do not provide any information about the bearing condition, we can only see that the vibration at spinning frequency is low. The velocity spectrum presents in the clearest manner a series of corresponding failing frequencies of this roller, which is damaged because of the inadequate lubrication. The acceleration will only be used when the frequencies go beyond 300,000 cpm, which indicates that this parameter will not be useful for low frequencies.

Two important factors should be taken into account at the time of taking measurements for the equipment of low spinning frequency. The first one refers to integration processes that take place in the moment the signal that comes from the accelerometer, is integrated into the velocity or movement data. Today, most of the available equipment is supplied with special filters to avoid the noise at low frequencies. Consequently, it will be necessary to pay close attention when selecting the instruments that will be used for these measurements. The main objective of these readings is to consistently provide reliable information. When the readings are not consistent, the equipment's behavior will be unpredictable if we base our findings on the accumulated vibration level tendencies.

As one of the main functions of the predictive maintenance system is focused on the vibration level tendencies, especially on the bearing vibration tendencies, in this chapter, we shall see that the best parameter for the analysis of the equipment, that spins at frequencies higher than 60 rpm, will be the vibration velocity. 8.3

Required equipment frequency analysis

for

low



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SPINNING FREQUENCY 1X RPM (249.2 cpm)

SPECTRUM OBTAINED IN MOVEMENT

harmonic wave activities or bearing frequency failure are not observed

Table 8.1 Spectrum obtained in movement (mils peak-peak)

SPINNING FREQUENCY 1X RPM (249.2 cpm)

SPECTRUM OBTAINED IN VELOCITY ventilator bearing failure frequency

Table 8.2 Spectrum obtained in velocity (in./sec. peak)



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In conclusion, as the equipment is a very important factor, it is recommended to use integrated analog spectra with a narrow band width, for example: 20,000 cpm for spinning frequencies of 60 rpm and a high resolution equal or higher than 1600 lines. The transducer is the second important factor for the low frequency measurement that should be used to obtain reliable and quality readings for analysis. Most of the accelerometers used in the industry for its preventive maintenance systems have a measuring range of 120 cpm and higher. Actually, there are high frequency accelerometers that measure from 120 cpm to 600,000 cpm. Normally, these accelerometers are used to detect problems related to bearings, gears and the first harmonic wave spinning frequencies in which one might observe problems related to unbalance, lack of alignment, etc. However, this type of accelerometers could not be used to measure frequencies that go beyond its minimal level. For such purpose, low frequency accelerometers have been developed, thanks to them reliable data could be obtained in the range of low frequencies, but it will have limitations with respect to high frequencies. The typical operation range of these sensors is from 6 to 60,000 cpm, and its weight varies from 135 to 1,000 grams. They are larger than normal accelerometers.

Its resonance frequencies initiate in the range of 390,000 cpm and its sensitivity varies from 500 to 10,000 mV/g.

Some low frequency accelerometer that could be found on the market are: - Wilcoxon Research mod. 793L (c) - Wilcoxon Research mod. 793L (c) - CSI mod. 320L (c) - PCB mod. 326A02 (s) - PCB mod. 326A03 (s) - B & K mod. 8318 (s) Each one of them has its characteristic properties with respect to frequency and sensitivity. All of them could be used for low frequency measurements. Some of them are compression type (c) and others cut type (s). When using a compression type accelerometer, it is recommended to wait for at least 3 minutes so that the sensor temperature can be stabilized. In the cut type accelerometers, it will not be necessary to wait for the temperature to stabilize. Actually, they are most recommended for low frequency measurements. In addition, it is recommended that the sensors have at least a sensitivity of 500 mV/g, and preferably 1 V/g. The preferred mount for this type of low frequency accelerometers is a fast connector or a magnetic base. However, one will obtain better results when screwing the measuring equipment to the surface in question. It is very important to mention that during the low spinning frequency reading, the total time of measurement should be at least from 2 to 3 minutes due to the low frequency range and high resolution lines. Due to the previously stated, one should try not to move the accelerometer's cable and not to place it near motors or transformers Vibration Analysis ManualPage 85 of 143


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to avoid electromagnetic interference (EMI). This interference would cause erroneous readings in the spectrum. 8.4 Bearing evaluation in the equipment with low spinning velocity. The rollers or bearings could be evaluated satisfactorily even in the equipment with as low spinning velocity as 1.5 rpm. However, one should take into account the equipment as well as the mere sensor, with respect to what was seen in the previous segment. In addition, one needs to take into account the spinning frequency of 1X RPM as well as the bearing failure frequency; low values will be recorded for large equipment and low spinning frequency. Consequently, it will be very important that the sensor is located in the bearings' charge zone in order to detect its problems. This will be of considerable importance especially when the ball rollers are large because the internal tolerance among balls and tracks allow that in some bearing sections the balls have no contact with external tracks, especially at 180° from the charge zone.

It is important to note that the components' natural frequencies will remain constant, independently of the bearing spinning frequency. The frequency difference is not observed between a spinning velocity of 10,000 RPM and 100 RPM. Of course, the only unique difference that will exist is the quantity of energy generated by the impacts, the axle that spins at 10,000 RPM has greater energy peaks than the axle that spins at 100 RPM. Consequently, the vibration amplitude in the natural frequency zone will be much greater than in the equipment of high spinning velocity. The normal frequency range established through the bearing observation in the equipment is 50 to 60 times the spinning frequency. However, for the equipment of low velocity, for example equipment that spins at 100 CPM, the maximum checking frequency will be 6,000 CPM. In this frequency range, we can observe the final stages of the bearings' damage, but the initial stages are not presented when their natural frequency is excited because the natural bearing frequencies are found in the range of 30,000 to 120,000 CPM.

If the sensor is placed exactly in this area, it will be impossible to obtain spectra with bearing failure frequency information. Consequently, it will be necessary for the sensor to be positioned in the charge zone, either in radial or axial direction.

Due to the previous statement, it will be necessary to define additional checking points in key areas of the equipment with a frequency range of at least 150,000 CPM, with the purpose of observing the initial damage stages.

The Table A-12 of the Nexus A shows the four classical stages that 80% of bearings undergo. It is important to emphasize that during the second stage of bearing failure, their natural frequencies are excited. This occurs when the wearing has progressed to the point of causing shocks within the bearing components.

As the last point, it is important to capture and accumulate the wave vibration shape that was obtained in acceleration, especially in equipment with spinning velocity smaller than 60 CPM. It will be possible to observe the impacts caused when the ball and rollers enter in contact with the damaged part, either on the internal or external track. Vibration Analysis ManualPage 86 of 143


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The reciprocal time period between the impacts will be the BPFO, BPFI and BSF frequencies, depending on the location of the damaged part.

This value will be used to define all spectral bands in accordance with the procedure previously seen in chapter 6.

8.5 Specifications for the alarm levels in the spectral band for the low spinning velocity equipment The narrow bands that were defined in Table III, chapter 6, will not be applicable to the analysis of low spinning velocity equipment because the vibration velocity looses sensitivity when the frequencies are lower than 600 CPM. However, the existing relation between the movement and velocity at frequencies lower than 600 CPM is linear. Consequently, the following empirical formula can be used to define the spectral band alarms following the chapter 6 procedures: Alarm

BF

= (Alarm FM) (Fi/600)

in which: Alarm BF = Alarm level for low frequency (Fi) which is calculated in in./sec. Alarm FM = Alarm lever for moderate frequencies obtained from the Table II, chapter 6, in in./sec. Fi = Frequencies on which one wishes to set the alarm levels in CPM. For example, in the table II, chapter 6, for a general-purpose horizontal pump, we have an alarm level of moderate frequency, 0.3000 in./sec. Supposing that the pump spins at 100 CPM, the alarm level would be at: Alarm

= (0.3000) (100/600) = 0.050 in. per sec.

BF



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CHAPTER 9 Application procedures of the demodulation techniques 9.1 Introduction One of the most valuable tools for the premature detection of failures in gears and bearings is the demodulation technique. In this chapter, we shall describe a demodulation technique as well as its application using a CSI Demodulator model 750 in conjunction with an Analyzer 2115. Recommendations for an adequate use will be offered and a practical example will be presented. 9.2 Demodulation basic principles In the initial failure stages of bearings or gears, as well as in friction and lack of lubrication problems, vibration levels at high frequencies will be generated. Thus, it will be very difficult to determine which one of the previous causes is creating these vibration levels at very high frequency; especially when they are combined in one equipment, gear and bearing, as well as in a mechanical seal. Especially for the bearings, the vibration level value was used in the area of high frequency (Spike Energy or HFD) to determine their replacement date. However, in some experiments realized, no failure was found on the bearing track. It was discovered in an investigation that in the premature bearing damage, the damage itself originates in an area between 4 and 6 thousandths of an inch on the inside part of the bearing tracks.

The passage of balls or rollers through this failure area excites natural frequencies of the transducer or in the region of an ultrasonic frequency. Therefore, the ball's passing frequency through the tracks will modulate the natural frequencies that will be excited. The demodulation technique will work in these areas of high frequencies using the wave shape that comes from the transducer and that could contain the bearing's harmonic wave frequencies, as well as the natural frequencies of the transducer or components of the equipment's structure. The demodulation process consists of the rectification of the complete wave from which it determines the existent spacing of the excitable frequencies (bearings and gear). The wave shape obtained through this process is submitted to a low passage filter with the purpose of eliminating the resonant or "transported" frequency. Finishing this process, a demodulated spectrum could be obtained which will contain only the frequencies that excite very high frequencies. These frequencies, also called "carriers", could correspond also to bearing failure or to the spinning frequency of a specific gear that is causing problems in a gearbox. This way, the analyst could adequately monitor the initial stages of bearing or gear failures of the most critical plant equipment. In the case of bearings, it is important to specify that insufficient lubrication will also show on the demodulated spectrum the bearing failure frequency. It is recommended to lubricate the part in question and take another demodulated spectrum after the lubrication. Vibration Analysis ManualPage 88 of 143


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The equipment should be checked 24 hours after the lubrication to observe whether the demodulated spectrum still presents bearing failure frequency. In case the bearing failure frequencies reappear, one can conclude that the bearing is in the initial failure stage, predicting an additional 20% of its "life expectancy". As the demodulation technique is applied to vibration levels of very high frequency, it will be very important to select an appropriate accelerometer for the equipment type as well as its mount in accordance with the information presented in chapter 7. In the specific case of CSI Master Trend software, it is possible to determine measurement points with demodulation, when using one of the seven filters that the Demodulator 750 has. In this way, one can use demodulated spectra to detect premature bearing and gear failures. 9.3 Functions of the CSI Demodulator 750 The Demodulator/Pre-processor 750 is the Analyzer 2115 accessory and it is adhered to its back. The Analyzer provides energy and it can remain connected even when it is not in use. The Demodulator/Processor 750 offers three main functions: - It permits the use of a low noise preamplifier to improve the function of the Analyzer 2115 in case of very weak entrance amplitude. - It permits the selection and use of any of the six filters (or none). - It permits the use of demodulating circuit as an entrance signal processor for the analyzer.

The functional diagram of the Demodulator 750 is shown on the Table 9.1. On this diagram, the following functions will be explained: Preamplifier The first step in the Processor 750 is the preamplifier, which has a purpose of incrementing the signal's entrance level of low amplitude to the point of boosting the signal to the level that can be processed in the following stages eliminating the problems of the coefficient signal/noise. In this stage the amplification can be configured in such a way that it becomes automatically adjustable or to chose a value of 0.2, 1, 10 or 50. The manual selection of amplification can be used only in the mode "Analyze" of the Analyzer 2115. For the effects of the signal transmission to the demodulator, it is recommended to use the Auto range mode. Filter options The following stage in the use of the preprocessor is the selection of filters, one of the eight filters can be chosen. Five of these filters are "high pass", two are "band pass" and one permits all the frequency signals or "bypass". The appropriate filter selection requires the knowledge about the entering signal that will be analyzed. The filters of high pass avoid the level reduction of the transported signal whose frequencies are above the specific filter and represent an important attenuation of the signal frequencies that are bellow the cutting limit.



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The demodulator has 4 general-purpose passing filters with frequencies of 500, 1000, 2000 and 5000 Hz. In order to better illustrate the use of these filters, let's suppose that the signal transmitted for analysis is in the frequency range from 2500 to 4000 Hz (this can be realistic for the beginning of the bearing failure) and the spectrum shows in addition a gear frequency in the range from 400 to 500 Hz that comes from the gear frequency of this equipment. For this particular case, the appropriate filter should be selected from the 1000 and 2000 Hz pass filters. This way, the spectrum signal that comes from the gear will be attenuated, leaving only the bearing signal. An additional, fifth, high-pass filter with the frequency limit of 100 Hz will be added in order to detect no uniform air gaps in induction motors. This filter attenuates the fundamental frequency of the electric line

stage, it presents useful frequencies as are the pole passage frequencies that function as lateral bands in case of eccentricities in the air gap and even in situations of loose rotor rods. (See "Electric problems" in Nexus A) The example that is presented in this chapter is about loose rods. In addition, this filter of 100 Hz can be used for general purposes in the applications that require it, we recommend it in the case of low spinning velocity reducer in which one could observe the gear frequencies. The passing filters of the existing bands will be used for the electric frequency analysis with the purpose of eliminating all the signals that are not included in the selected band. There are filters from 50 to 60 Hz depending on the electric frequency of the line. These filters should be used only when the induction motor current is measured.

ENTRANCE

PREAMPLIFICATOR

FILTER 1 OF 7

AMPLIFICATOR:

DEMULATOR

FILTER EXIT

Table 9.1 Fundamental diagram of the CSI Demodulator/Processor model 750. and, in coordination with the demodulation Demodulation stage Vibration Analysis ManualPage 90 of 143


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The fourth and last stage of the Processor 750 is demodulation. The demodulator accepts at the entrance the signal known as "transported". The exit signal of the demodulator will be known as "base band". This base band signal will contain the necessary information for the analyst because in this base band will be included signals known as "carriers" and that could be the bearing failure frequencies, the spinning frequency of a damaged gear, or the lateral bands corresponding to the pole passing frequency for electric problems. The minimum frequency of the base band is normally constant at zero or very close to zero, while the maximum frequency is known as Fmax. It will be very important to set permanently Fmax of the base band mostly at one half of the expected frequency of the transported signal. In other words, if one estimates that the transported signal has a frequency of 120,000 CPM, the Fmax of the base band should not be greater than 60,000 CPM. The previous is due to the fact that the base band Fmax is greater than 50% of the transported signal frequency; it is possible that the lateral bands of the transported signal overlap with the higher portion of the base band frequency range distorting the signal that might confuse the analyst. It is important to remember that the transporting or modulating frequencies brought to the spectrum appear as lateral bands of the transported frequency. Consequently, these lateral bands should be included in the high passing filter of 400 Hz in order to eliminate the residual components of the transported frequency. If these components are not eliminated they will impact the spectral base band result.

As a general rule, when the demodulation function is in use, the analyzer's Fmax should not exceed 400 Hz or half of the transported signal's frequency, using the lower value. 9.4 Example of Demodulator 750's use We shall present a typical case of the Demodulator 750's use for the loose rotor rod detection in induction motors. The case is based on the ventilator motor that is attached directly to an axle. The power of the motor is 75 HP and it is attached to vibration insulators. This motor has been experiencing continuous changes in bearings and it was also rewound in two occasions during the last two years.

In addition, a rhythmic noise could be heard in the motor and the 1X RPM vibration amplitude would rise and dip en par with the noise rhythm. This type of rhythmic vibration could be coming from another machine located in close parameters which is spinning at a frequency very closely related to this motor (see page A-20 of Nexus A). However, in this case the motor in question is isolated and distant from the rest of the ventilators of the group that belong to the same production line. Another possible cause of rhythmic vibrations at the spinning frequency is the existence of loose or cracked rods in the motor's rotor. The lateral bands that are in the spinning frequency and in their harmonic waves produce this rhythmic vibration, and their distance is equivalent to the passing frequency of the poles, or Fp (See A-17 and A-18 of Nexus A). Vibration Analysis ManualPage 91 of 143


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It was proceeded to acquire a spectrum in the horizontal direction on the charge side of the motor with a frequency range of 12,000 CPM and a maximum resolution of 3,200 lines which is shown on Table 9-2. In this no demodulated spectrum, it is observed that the first 3 harmonic spinning frequency waves (1x, 2x and 3X RPM) show acceptable vibration levels. However, even though the amplitudes are very low, the lateral bands of low separation frequency are piled up in each one of the bands. The lateral bands in the first spinning frequency harmonic waves indicates loose or cracked rods in the rotors of induction motors, if and when these lateral bands are spaced according to the pole passing frequency or Fp. The pole passing frequency Fp is defined in the following manner: Fp = Np * Fs

Formula 9.1

where: Fp = pole passing frequency Np = number of stator poles Fs = Slipping frequency

Fmax was set at 3,000 CPM and a high pass filter of 100 Hz was used in order to cover all the spinning harmonic wave frequencies. The demodulated spectrum is presented on the Table 9.3. In this spectrum, one observes pole passing frequency Fp and its harmonic waves. From the information related to this spectrum, it was concluded that this motor rotor had one or more rotor rods loose or cracked. Additionally, a spectrum analysis of this motor's current was done, and it was corroborated that there were loose rods. Based on this diagnostic, it was decided to replace this motor because it was impractical to repair it. 9.5 Conclusions When it is appropriately used, the demodulation technique offers valuable information that could not be obtained from a normal spectrum, especially when it is a question of initial failures of bearings and gears.

The slipping frequency Fs is calculated subtracting real spinning frequency from synchronic spinning frequency. For this motor, the spinning synchronous frequency is approximately 3598 RPM (the line's electric frequency was 59.96 Hz), and the real spinning frequency is approximately 3573 RPM. Because this motor is made of two poles, the passing pole frequency, as suggested in Formula 9.1, will be 50 CPM. To obtain the modulation frequency, also called lateral bands, in the spectrum without demodulation of Figure 9.2, an additional spectrum was taken on the same place using Demodulator 750. Vibration Analysis ManualPage 92 of 143


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For the adequate application of this technique, it will be necessary to initially know the relevant frequencies of the signals known as "transported", knowing them it will be possible to set correctly the passage filters, as well as to chose the band and the Fmax which should be defined.

It is important to remember that the minimum frequency of a demodulated spectrum could be zero that is impossible for normal spectra, in which the first three resolution lines are eliminated because of the low frequency noise created by the integration process.

VENTILATOR NUMBER 3

Spinning Frequency

2X electric freq.

3X spinning freq. with lateral bands

Table 9.2 Spectrum with motor demodulator



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VENTILATOR NUMBER 3

pole passing harmonic wave frequency

DEMODULATED SPECTRUM

High passage filter of 100 Hz

Table 9.3 Demodulated motor spectrum at 100 Hz

Comment [MPC1]:



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CHAPTER 10 Criteria for measuring results Maintenance indicators 10.1 Introduction As it was mentioned in chapter 1, the fundamental objectives in the implementation of the PredictivePreventive Maintenance System are the control of maintenance costs and the efficiency increase in the productive process. In order for the Predictive-Preventive Maintenance program to be successful, it needs to quantify the obtained results. The objective can be reached with the use of some base indicators of the system's function. In this chapter, we shall see the subject of maintenance indicators that were used to quantify the implementation benefits of the Predictive Maintenance System. Most of the indicators were mentioned and a detailed description will be made of those that are most recommended and generally used in industry. The calculation of these indicators could be automatically done in the plants, which have a computerized maintenance administration system. However, in the plants that do not have such systems, the effort made in obtaining the information and calculating the indicators will be rewarded when the benefits obtained are presented. On the other hand, it will be necessary to have the initial indicators data when starting to implement the system, in order to have the starting and comparison points for the future work.

In some plants, this will not be a major problem because they count with most of the information. For the plants that are only introducing the system of indicators, it is recommended to make an additional effort before initiating the predictive maintenance system. 10.2 Maintenance Indicators For the recording of the obtained benefits with the implementation and operation of the Predictive Maintenance System, it will be necessary to use the following Maintenance Indicators: - Percentage of the "out of service" time for maintenance reasons, as a total time function (availability). - Emergency hours vs. total hours of labor. - Maintenance cost per tone of product. - Number of problems detected vibration analysis per month.

with

- A vibration average in relation to the global value for the whole plant or the production line. - The percentage of the problems resolved vs. detected problems with vibration analysis (percentage of corrective action). The first six indicators are the most important ones for the continuation of the Predictive-Preventive Maintenance System. However, we are going to present some others that could be used: - Total departmental maintenance cost per month. - Number of corrections made thanks to the Predictive-Preventive Maintenance System per month. Vibration Analysis ManualPage 95 of 143


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Tones of the produced product per month.

information in order to have it constantly available.

- Total of the defective units or monthly loss.

In this aspect, the work done by the Maintenance Director will be finished. As the leader of the Predictive Maintenance Group, the director should establish communication ties with the departments that have the information necessary for the calculation of the indicators.

- Percentage of waste or defective parts vs. total production - Number of incidents beyond the tolerance level per month. - Extra time as a percentage of total hours of labor. - Percentage of time that the equipment was used vs. the time of its availability. - Number of problems found by the Predictive-Preventive Maintenance System. - Percentage of the equipment included in the Predictive Maintenance. - Consumption and cost of the electric energy per month. - Monthly cost of replacement parts. - Monthly cost of the inventory parts. - Number of inventory parts eliminated from the shop per month due to the maintenance improvements. - Average time between repairs replacements of the equipment.

or

- Number of detected problems thanks to the vibration analysis that have not been resolved per month.

The Maintenance Predictive Group should process this information in order to elaborate the monthly report of the Predictive-Preventive Maintenance System, showing the progress and benefits of the program. It is recommended to make tendency graphs with each one of the indicators to show the progress of the Predictive Maintenance System. This report should be circulated at the plant and directed to the General Management. It is recommended to send a copy to the Technical Department for the evaluation of each plant and be able to determine which plant has obtained the best results. While waiting to establish communication channels in order to obtain all the necessary information for the recording of the indicators, it is recommended to start with the Table 1 indicators. The 6 indicators from Table I could be used as an initial step in the program's evaluation. In most of the plants, the sufficient information is available to elaborate these indicators.

- Number of problems detected thanks to the vibration analysis that have not been resolved in more than 3 months.

10.3 Conclusions

Even though there are many indicators that deserve attention, a procedure can be elaborated to record the necessary

The elaboration and continued analysis of the maintenance indicators will be very important for the Predictive-Preventive Maintenance System. The reason is very Vibration Analysis ManualPage 96 of 143


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simple; they are the "measurement instruments" for the system's condition. The same way we evaluate the conditions of the specific machines, we should evaluate the progress and benefits of the System. Special attention should be paid to the reports of potential benefits gained by corrections; in other words, report the cost of the repair done on time with the cost of a catastrophic failure if the failure had not been prevented. The reports of the obtained results, which will be discussed in chapter 11, will be very important in the initial implementation of the system. This type of specific situation reports will give a boost to the system and gain support and confidence from the rest or the plant's staff, including of course the General Management.


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TABLE I. CALCULATION OF THE MOST IMPORTANT MAINTENANCE INDICATORS MAINTENANCE INDICATORS 1. AVAILABILITY --

Availability =

OBJECTIVES

Stoppage time due to maintenance 1 - ---------------------------------------------------------------------

90% first year 96% second year

Total time during production time 2. MAINTENANCE UNIT COST PER TONE PRODUCED Cost/Unit =

Total maintenance cost during the period -------------------------------------------------------------------Number of tones produced during the period

lowering tendency

3. PERCENTAGE OF MAINTENANCE EXTRA TIME Extra time total during the period Extra T. % = ------------------------------------------------------------------------Total of the normal working time during the period

less than 10% during the first year less than 5% during the second year

4. PERCENTAGE OF HOURS SPENT IN CORRECTIVE MAINTENANCE

-

---

% of corrective maintenance labor =

Total hours of labor in emergencies ----------------------------------------------------------------Total hours of labor in maintenance

Number of emergency interventions % of corrective labor = ---------------------------------------------------------------

less than 20% during the first year less than 10% during the second year

Total number of jobs done 5. PERCENTAGE OF THE EQUIPMENT INCLUDED IN THE PREDICTIVE MAINTENAN Number of machines included in the program % of the achievement = ----------------------------------------------------------Number of potential machines for Predictive Maintenance

More than 75% during first semester 100% at the end of the first year

6. PERCENTAGE OF THE REALIZED CORRECTIONS % of implementation =

Number of failures detected by and corrected ---------------------------------------------------------------Total number of failures detected by Predictive M

Note: The failure is considered to be corrected when its vibration levels are within the permissible limits

More than 50% during first semester 100% at the end of the first year



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CHAPTER 11 Writing reports 11.1 Introduction One of the PPM personnel's most tedious obligations is writing reports. Essentially, there are two types of reports: a technical report which contains the analysis results and recommendations for problem resolutions; and the second report is for the management in which is included the benefit accretion gained by problem resolutions. The latter should also include a brief diagnostic of the situation and the work accomplished. In this chapter, we shall see the importance that both reports have in the PredictivePreventive Maintenance System, and the recommended format shall be elaborated in order to have the optimal impact on the person who will receive it. 11.2 Vibration Analysis report The vibration analysis reports should be elaborated when the following situations occur: a. When equipment has high vibration levels, which were presented during the first monitoring session at the initiation of the system. b. When equipment presents abrupt changes in vibration levels which were measured in two consecutive monitoring sessions. c. When the vibration level tendency has incremented in such a way that it requires an action in the next 30 days.

d. When there is a need to analyze an equipment that for some reason was not included in the system. These reports will be submitted to the director of the area in which the equipment is located, and if such person is not available, it should be presented to the Maintenance Director of the plant. The primary objective of this report will be to describe to the plant maintenance personnel the exact vibration condition of the equipment. For this reason, one should include in the report the following section in accord with Table 11.1. SCHEMATIC DIAGRAM In this section, one should elaborate a schematic diagram of the equipment, showing its measurement points. Today, there is a large number of computer packages for a simple elaboration of these diagrams and their interface with word processors. The report from Figure 11.1 was elaborated with a package called VISIO that runs on Windows. Other kinds of packages that could be used are: CorelDraw 4.0, Word for Windows, etc. EQUIPMENT IDENTIFICATION In this section, the equipment information should be included: its name and identification, section to which it belongs, date when the data were taken and the date when the analysis report was elaborated. The name and the signature of the analyst should be included also. NUMBER OF THE WORK ORDER The number of the work order will be important in order to follow up with the Vibration Analysis ManualPage 99 of 143


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work that was done in this equipment. In case there is an Administrative Maintenance System interface at the plant, this number could be assigned directly from the PPM. This will depend on the system that was implemented at each plant. VIBRATION LEVELS In this report, five levels of vibration that show the operational conditions of the equipment will be defined. Depending on the actual equipment condition, one should select one of the five severity vibration criteria. This way, the person who receives the equipment will know in which condition the equipment is operating. REPAIR PRIORITY Depending on the vibration severity and the equipment priority as far as the critical equipment is concerned, one should determine the action plan and the follow up, either repairing or monitoring at short intervals. PROBLEM DESCRIPTION In this section, one should include a brief explanation of the problem, mentioning the possible causes of the vibration and in which measurement points the problem was discovered. The potential dangers and losses that could be suffered in case no action is taken in the time frame established by the analyst should also be included in this section.

mentioned for the problem correction in a specific machine. It will be very important to explain in the clearest possible manner the recommendations because thanks to them one will obtain the solution to the problem. As the last point suggestion, one should annex in the right lower corner the most important spectra that led to the diagnostic. It is recommended that the alarm limits, which are registered in the system, appear in these spectra, and that annotations of the most important frequencies that led to the spectrum interpretation should be made. The CSI MasterTrend Software offers the possibility to file the spectra in files .BMP or .PCX in such a way that any text processor could retrieve them. In figure 11.2, we show a model report, elaborated with the information obtained from a Symetro reducer that presented serious pitting problems. No spectrum was obtained after the pinion replacement; consequently, the report of the obtained results, which are explained in the following section, will show another model case. In conclusion, a vibration analysis report should not contain complicated technical information that could confuse the maintenance personnel. One should explain the problem in a simple manner and make very clear recommendations.

RECOMMENDATIONS In this section, one should include the steps that should be followed in order to resolve the vibration problem. These steps should preferably be listed chronologically or following a procedure that was previously

11.3 Report of the results obtained This is one of the most important reports in the Predictive Maintenance System because it is directed to the Plant Management. Vibration Analysis ManualPage 100 of 143

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This report should be elaborated in a simple and clear manner in order to attract the attention of the high administrators and consequently obtain their support for the continuation of the system. The acquisition of the new predictive technologies will depend greatly on their support, which will also serve as the necessary boost for the training improvement of the Predictive Maintenance personnel. In this report, one should include the problems that were detected thanks to the vibration analysis and the correction results. The following should be mentioned in the report: PRECEDENTS A brief description of the failure record pertinent to a specific machine should be included. It is recommended to use the data from the last two years.

WORK DONE RESOLUTION

DURING

THE

PROBLEM

It should contain brief description of the action taken to resolve the problem, involving the maintenance personnel that collaborated in problem solving. It is recommended to include comparative spectra where the improvement is shown. Special attention should be paid to presenting these spectra. The axle frequency scale and the axle amplitude scale will need to be similar in order to avoid confusion when the reader observes them. It will be very easy to appreciate the achievements in the previously described presentation. Bellow, we present a model.

BRIEF DESCRIPTION OF THE PROBLEM In this section, a brief description of the analysis results will be made, paying attention not to use too complex technical results, only the most important information.



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20 de Agosto de 1993 August 20, 1993 For:

Ing. Ricardo Navarro / General Director Ing. Mariano Romero / Production Director Ing. Roberto Marrjo / Maintenance Director

From: Ing. Jorge Gutiérrez Villarreal / Predictive Maintenance Subject: Vibration analysis report and the improvement in the machine M-85 in the stretching area. 1. PRECEDENTS In the last 24 months, the stretching machine M-85 required continuous transmission bearing replacements; they have been replaced approximately every six months. The total stoppage time due to repairs was 33 hours in the last 24 months. As the plant is operating at its full capacity, these unexpected stoppages have directly impacted the sales because 80% of the raw material is processed through it. The estimated losses due to this stoppage time rise to $235,000.00 with respect to sales, $24,800.00 in maintenance costs and the personnel's extra time. External personnel were balancing the inertia steering wheel without satisfactory results. It was decided to make a vibration analysis with the instruments acquired by the company. It was managed to find the excellence range, and we expect a continuous operation of this production line with high reliability. This machine was annexed to the Predictive Maintenance System that is in its implementation stage. An analysis reports follows, as well as the results obtained. 2. PROBLEM DESCRIPTION AND THE IMPLEMENTED CORRECTIONS High-level vibrations were detected at the entrance of the reducer, especially in the vertical direction and at the pinion spinning frequency. The vibration in the horizontal directions was in average less than 30% of the vertical readings. Looseness was suspected at the base and it was checked with hands. It was discovered that 3 of the 4 anchor screws were loose. In coordination with the maintenance personnel, we proceeded to tighten the screws while we monitored the vibration levels in order to stop the process in case of an increase in vibration levels that could occur if the assembly motor-reducer is destabilized during the screw tightening.



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You will find bellow, the comparative spectra before and after the screw tightening. In a planned stoppage, we shall proceed to apply a cement grout to eliminate looseness in one anchor that could not be tightened.

Sincerely, Ing. Jorge Gutiérrez Villarreal Analyst Predictive Maintenance Department



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TYPICAL ARRANGEMENT OF EQUIPMENT WITH MEASUREMENT POINTS

Identification: Section: Monitoring date: Date of the general report: Analyst's name: Analyst's signature:

Work order number:__________________ VIBRATION LEVELS: REPAIR PRIORITY:

Description of the problem:

Recommendations:

SEVERE, greater than 2X LF IMMEDIATE ATTENTION VERY HIGH, greater than LF PROGRAM IN _________ DAYS HIGH, grater than 0.9X LF REPAIR NEXT MAINT. REGULAR, greater than LA MONITOR IN _______ DAYS NORMAL, weaker than 0.9X LA CONTINUE MONITORING

LA = alarm limit = ___________ in./sec. LF = failure limit = ___________ in./sec.

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TYPICAL EQUIPMENT DISTRIBUTION WITH MEASUREMENT POINTS 6V 6A G6A

N3= 42

8H 8V 8A

5V 5A G5V

N4= 176

No. of work order: CMV-0188-9880

N3= 42

VIBRATION LEVELS:

SYMETRO REDUCER

N2= 297

7V 7A G7V

N1= 38

Equipment: Symetro Reducer Mill M. Primes 2 Identification: MMP-2 Section: Raw materials mill Date of monitoring: 31-08-93 Date of report writing: 02-09-93 Name of the analyst: Oscar Jiménez Yenny Analyst's signature:

SEVERE, greater than 2X LF IMMEDIATE ATTENTION VERY HIGH, greater than LF PROGRAM IN _________ DAYS HIGH, grater than 0.9X LF REPAIR NEXT MAINT REGULAR, greater than LA MONITOR IN _______ DAYS NORMAL, weaker than 0.9X LA CONTINUE MONITORING

N2= 297

2H,G2H 1V,G1V 0A,G0A

4V 4A G4V

LA = alarm limit = 0.12 in./sec. LF = failure limit = 0.15 in./sec.

Problem description: 1. High vibration levels were detected at the point IV located at the reducer's entrance. The vibration is 0.762 in./sec. at gear frequency and it shows lateral bands distanced from each other at the spinning frequency. The gear frequency is 38X RPM spin. 2. The vibration at the point 2H shows also the components of the pinion gearing frequency. 3. The probable cause of this vibration is the excessive pitting at the pinion entrance. 4. The reducer bearings are in good condition. 5. There is a potential risk of the second step reduction crown getting damaged if the reducer continues working with the same vibration levels.

Recommendations: 1. Take a sample of the reducer's oil and analyze it in order to obtain information about metal particles that are found in oil. 2. Have a reserve pinion ready at the moment of reducer inspection. 3. Stop the unit, inspect the pinion entrance and replace it in case of an excessive pitting evidence. Adjacent crowns should be checked also. 4. It is recommended to immediately monitor the repair to make sure it was realized correctly.



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CHAPTER 12 Importance Corrections

traditional alignment method, as are "face and edge" or "inverted indicators".

of

Precision

12.1 Introduction In this chapter, we shall talk about the definition and importance of precision corrections. It was previously mentioned that the two major vibration causes in the rotating equipment are lack of alignment and unbalance. Consequently, we shall focus on the precision alignment and balancing. 12.2 Precision alignment

The precision alignment is very important because it will help minimize the damage in couplers, bearings, seals, etc., and reduce the vibration levels in the equipment. Poorly aligned or not aligned equipment will generate too much vibration in and/or effort on the driving and driven equipment. Consequently, the bearings, seals, couplers, etc. will fail in the most inopportune moments. In general, all the equipment should be precision aligned, either when it is installed for the first time or when a program of this type is initiated.

Precision alignment is the process with which an adequately trained person, with equipment and necessary tools, takes the time and makes an effort to make two or more equipment parts stay aligned within a previously established tolerance.

However, it is practically impossible to align all the equipment from one day to another. So, it will be necessary to classify the equipment according to its importance in the process, maintenance costs and failure frequency in parts (bearings, couplers, etc.).

This tolerance will depend on the spinning velocity of the equipment, coupler type, distance between two axles and its function while it operates under certain temperature and load conditions. In other words, it is a result of a technological alignment that is adequately implemented.

Basing ourselves on the previous statement, we shall present an alignment verification and precision alignment corrections program in order to accomplish the goals of precision alignment with all the prioritized equipment within a reasonable time period.

On Table I, the acceptable tolerance for the precision alignment jobs is presented. This table is an analysis summary for the tables used by Benchmark companies today. The precision alignment is not necessarily related to a specific method with which it is performed. For example, a person with very little training and with a laser alignment system will make a worse alignment than a person with great ability and experience that implements a

It is amply recommended to take readings of the workflow before initiating an alignment program, and to retake readings after precision alignment in order to calculate the electric energy savings. It is normal to obtain savings greater than 10% in electricity consumption. Another important part of the precision alignment is the pole alignment. Because one might think that the belts are flexible, in many occasions one does not pay due attention to the precision alignment between poles. Vibration Analysis ManualPage 106 of 143


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An excessive lack of alignment between poles will generate high axial vibration levels, reducing the life expectancy of the belts and bearings, and even wearing the poles. It will be very important to check that both poles are actually concentric; if not, there will be high radial vibration. Generally, one aligns the pulleys taking as reference their faces, however one should be careful in establishing equal distances between the face and the first groove in both pulleys. Otherwise, there will be a lack of alignment between grooves and consequently between belts, as it is shown on Table 12.1. A correct alignment between poles implies aligning grooves, and not the faces of both pulleys. 12.3 Precision balancing The term balancing is defined as a "procedure which verifies the rotor mass distribution, and if necessary, it is adjusted to ensure that the residual unbalance or the vibration at the corresponding frequency are within the specified limits". The table II shows the balancing tolerance for rigid and flexible motors according to precision standards.

As in the case of precision alignment, it is important to make previous verifications before performing precision balancing. Among recommended verifications, we emphasize the following: concentricity of axles, couplers and pulleys, bearing temperatures, condition of the attachment screws, condition and type of transmission belts (if there are any), structure conditions (looseness, cracks, corrosion, etc.), base and foundation conditions, etc. Two of the most important predictive maintenance system functions are the problem identification and the prolongation of equipment's durability. The vibration analysis is much more precise when there are no high spinning frequencies caused by an unbalance. The lack of alignment and other vibration causes are more easily detected if one has faith in precision balancing. In addition, any residual unbalance or induced vibration wastes energy, reducing efficiency and shortening the durability of bearings and other components. The precision balancing is undertaken in order to maintain the product quality, reduce the production time loss, increase the life of equipment's components, save energy and increase the operational safety. It is also very important because it can decrease maintenance costs. 12.4 Bases and anchoring

LACK OF PULLEY GROOVE ALIGNMENT

Table 12.1

There was a lot of discussion, during the precision alignment and precision balancing about the importance of examining the conditions of the equipment's base and anchoring. To attain the precision levels, it is fundamental to be able to count on adequate bases and anchoring, and they Vibration Analysis ManualPage 107 of 143


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1316 – SHELF 16 -MIH MOTOR SIDE HORIZONTAL-CHARGE

should be in good condition. Some might say, "The foundation for a good analysis is a good base verification". A typical problem with bases and foundations is shown bellow. The spectra shown in Tables 12.2 and 12.3 correspond to the horizontal readings on the charge side of an 1,000 HP motor that drives a mill of an iron plant. This motor is relatively new as it was installed 3 months before this monitoring in order to increase the power in the lamination process. The anchoring modifications were not made, and the motor now weighs double of its original weight.

It is recommended to stop the unit and repair the deteriorated section of concrete, applying grout cement to achieve high resistance in a short period of setting time. The results obtained with this repair can be observed in the Table 12.3 spectrum. Once this motor was functioning at full power, spinning frequency vibration of only 0.17 in./sec. was observed. This vibration amplitude is within this equipment's limits. This example is sufficient to underline the importance that bases and anchoring have in achieving low levels in vibration and prolonging equipment's durability when they are used correctly.

Before taking the reading, a revision by hand was made at the foundation, finding that one of the anchors was completely detached from the foundation. In the spectrum of the Figure 12.2, one observes that the original vibration at spinning frequency was 1.29 in./sec. Vibration Analysis ManualPage 108 of 143


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Table 12.2 Spectrum taken before the anchor repair

1316 – SHELF 16 -MIH MOTOR SIDE HORIZONTAL-CHARGE

Table 12.3 Spectrum taken after the anchor repair. Vibration Analysis ManualPage 109 of 143


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12.5 Documenting corrections

the

precision

the working conditions of the equipment through precision balancing and alignment.

One of the stages that takes most time when making an alignment is the verification and correction of the prealignment. For example, before initiating an alignment job in equipment, the first thing that should be done is ensuring that both axles and couplers are concentric. Then, one should see whether there is a loose leg, adverse conditions in the screws, base, anchor, etc.; and afterward, one should correct the problem.

The operation costs could be decreased the following way:

Each one of these conditions will have an effect on the equipment's operation and alignment. The documentation of the verifications and corrections realized will be very useful because the future realignment's time consumption will be considerably shorter. For example, a loose leg will not appear suddenly among alignment tasks. If the problem was found and corrected, it will not be necessary to check the loose leg again.

- energy saving by decreasing the energy consumption - increase the bearing duration by reducing the load and temperature. - cost reduction in maintenance labor - cost reduction in parts replacement - product's quality increase - decrease the production time loss If we consider the fact that the energy costs directly influence the plant's profitability, we can deduce that if we improve the operational conditions of the inefficient equipment, we will contribute directly to the increase in profits. In this step lies the importance of precision correction, it is worth trying to implement it.

For a balancing job, if the influence coefficients, the distribution of the correction weight, the documented quantities and the sensors are all in place; when the technician proceeds to balance the equipment, he could repeat initial parameters without a great time loss. As a result, a technician will be able to determine a correction weight without having to place again a trial weight, saving time, money and effort. 12.6 Financial savings It is unquestionable that considerable amounts of money could be saved improving Vibration Analysis ManualPage 110 of 143

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TABLE 1 TOLERANCE FOR THE PRECISION ALIGNMENT

1. SHORT COUPLERS (DIRECT COUPLING WITHOUT SPACER AXLE) EXCELLENT SPINNING FREQUENCY IN RPM < 500 500 - 1250 1250 - 2000 2000 - 3500 3500 - 7000 > 7000

PARALLEL (mils)

ANGULAR (mils/in. of coupler diameter)

5.0 4.0 3.0 2.0 1.0 0.5

1.5 1.0 0.5 0.3 0.25 0.2

ACCEPTABLE PARALLEL (mils)

ANGULAR (mils/in. coupler diameter)

6.0 5.0 4.0 3.0 2.0 1.0

2.0 1.5 1.0 0.5 0.3 0.25

2. SPACER AXLE EXCELLENT SPINNING FREQUENCY IN RPM

< 500 500 - 1250 1250 - 2000 2000 - 3500 3500 - 7000 > 7000

PARALLEL/LONGITUDE INCH OF THE SPACER AXLE (mils/in. of coupler diameter)

1.8 1.2 0.9 0.6 0.3 0.15

ACCEPTABLE PARALLEL/LONGITUDE INCH OF THE SPACER AXLE (mils/in. of coupler diameter)

3 2 1.5 1.0 0.5 0.25

Source: CSI tolerance for the precision alignment Note: In case the coupler tolerance is inferior, one should use the tolerance specified by the provider Vibration Analysis ManualPage 111 of 143


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TABLE II. TOLERANCE FOR THE PRECISION BEARING ACCEPTANCE

SPINNING FREQUENCY IN RPM

EQUATION USED TO CALCULATE THE PERMISSIBLE RESID UNBALANCE UPER IN GRAMS/INCH

< 150

until 1000

> 1000

U PER = 5.018 x W U PER = 113400 x W / N 2

U PER = 113.4 x W / N

where: UPER = permissible rotor unbalance in grams-inch W = rotor weight in pounds N = RPM rotor service For the dynamic balancing in two planes, one should divide the result by 2 and this tolerance will be applie each measurement plane. Only one plane will be considered when the relation diameter/width of the rotor greater than 6. In this case, the resulting tolerance will be applied directly to each rotor support. The balancing provider should offer a Balancing Certificate that confirms that a verification experiment was conducted after the balancing in which a weight was placed at six different positions (60° each). The certif weight would be 10 times the residual unbalance that was solicited. These readings should be included in tabular form certificate and its average value should be shown. To accept the rotor repair as effectively done, all the readings should be in the range of the promised value 12%. If some readings are outside of this range, the motor should not be accepted. IMPORTANT NOTE: For the balancing done in the field where the rotors are balanced on their supports and at the operational velocity, it is recommended to use an acceptable criteria of 0.05 in./sec. max peak, in horizontal and vertic positions, taking measurements on the frame supports.

Source: United States marine tolerance, NAVSEA STANDARD ITEM 009-15



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CHAPTER 13 Criteria for Certification

13.2 Management support and plant's culture

the

World

Class

13.1 Introduction In various chapters of this manual, we mentioned the terms "World Class" or "Benchmark", but we did not give their definition or explanation. A "World Class" or "Benchmark" company is an enterprise whose administrative organization, production processes, technology, human resources, maintenance programs and other characteristics are worthy of being considered as development models and/or examples to follow. The World Class maintenance starts with a clear understanding of the manner in which the maintenance should be done. Then, and only then, it is possible to specify with certainty what human resources are necessary to realize it, which parts are necessary to support its infrastructure and what systems are necessary to control it. In this chapter, we shall focus on the programs and maintenance systems used by the World Class companies; as well as the most important criteria for the World Class Certification. In order to evaluate a maintenance system and be able to compare it with World Class Systems, it will be necessary to evaluate each one of its sections or parts, which integrate the whole program. Bellow, you will find a summary of each one of the program's integral parts and the evaluation standards.

One of the fundamental parts for the implementation, development and maintenance of the World Class Maintenance System is the unconditional support from the Management and an adequate cooperation among the plant's staff. The management needs to establish the objectives and goals for its system in a clear and concise manner, emphasizing not only the plan for the implementation of new techniques but also its expectations for its personnel's involvement. It is essential to establish the Mission for the maintenance department. The relation established with the management and the support for the predictive maintenance system from the line operators should create the adequate social ambiance which should help to realize the plant's goals and objectives, and which should be known by everyone involved. The consistency of a maintenance department and the presence of a dedicated predictive maintenance group are essential elements in the development and maintenance of the World Class Maintenance program. In conclusion, the system should use all the equipment records and data obtained in the monitoring stage to identify and program all kinds of interventions (predictive maintenance, planned stoppage, equipment repairs, acceptable levels of repaired equipment, etc.), with the purpose of attaining a higher availability of the machines and estimating the most realistic maintenance costs. Vibration Analysis ManualPage 113 of 143

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13.3 Program organization A necessary infrastructure should be developed for an appropriate blend of corrective, preventive, predictive and proactive maintenance in order to realize the objectives of World Class Maintenance. An effective communication should be established between the department of predictive maintenance and the department of programmed or corrective job implementation. The predictive maintenance department will send to the repair personnel a report containing the diagnostic of the equipment and corrective actions. The department of work implementation should send to the predictive maintenance department the information corresponding to the details pertinent to repairs and commentaries about special findings. This type of reciprocal communication will ensure the success and continuous development of the program. The vibration spectrum of equipment before and after the maintenance is a clear manner of showing the importance of communication and the achievement obtained by operators, mechanics and managers. The necessary information for the elaboration of these reports could be found in chapter 11. The benefits of the vibration analysis and other monitoring efforts should be communicated in an official manner to all the levels of the organization in a routine manner. The World Class companies have a Computerized Administrative Maintenance System (SCAM, based on its title in Spanish) to achieve the previously mentioned goals; in other words, the automatic integration of

corrective, preventive, proactive maintenance.

predictive

and

The computerized program should also interconnect the purchase and storage departments in order to generate, with respect to needs and monitoring conditions, the work orders for part purchases that are necessary in the performance of an effective maintenance. 13.4 Predictive maintenance technologies An evaluation of the percentages of the equipment included at this time (critical or no critical) in the monitoring program, in accordance with the predictive maintenance implementation techniques (analysis of the vibrations, thermography, oil, ultrasonic, etc.) and the manner in which the rest or the equipment could be included. Besides these tasks, the program members will evaluate the methods and techniques used for the application of the aforementioned technologies. In the case of the vibration analysis, one should review the parameters and techniques of inspection, alarm level functions, frequency or interval monitoring and other aspects of the program according to the principles established in this manual.

13.5 Proactive maintenance A study will be conducted to determine the use or storage of the proactive maintenance techniques: - Development of specifications or acceptability criteria for the repaired equipment, either in internal or external shops, as well as for the new equipment. Vibration Analysis ManualPage 114 of 143

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- Use of the advanced techniques (modal and multi- hannel analysis, demodulation, negative averaging, etc.) for the determination and solution of the "root causes" of the identified problems. - Working relation between predictive maintenance department and the engineering department in the development and installation specifications for new equipment. - Use of the precision alignment and balancing techniques, with their respective specifications.

It is important to remember that a World Class Maintenance program is dynamic and in constant improvement, and the maintenance indicator program should be constantly evaluated, justified and communicated to the whole organization. 13.8 Examples of the evaluation questions. We shall show a list of questions that can be used to evaluate a predictive maintenance system: 13.8.1 Actual situation

13.6 Training development One should evaluate the progress and development of the training program, basing the evaluation on the principles seen in chapter 3. 13.7 Maintenance indicators As it was mentioned in chapter 10 of this manual, the maintenance indicators are a fundamental part of the development and continuity of the Worlds Class Maintenance program because they will show us the progress and development of the program as well as its success or failure. The results program as predictive documented bases.

of the vibration-monitoring well as the effects of the technologies should be and published on the monthly

In particular, the number of failures found and corrected every month, the financial benefits accumulated in maintenance expenditures and the indicator of the plant's availability should be shown to all administrative and operational representatives.

1. What percentage of corrective, preventive, predictive and proactive maintenance practices are in use today? 2. What predictive technologies are used?

maintenance

3. Are there problems that have frequently reappeared and that could not be resolved? 4. What mechanical and electric problems are most common? 5 What maintenance percentage is related to emergency work orders? 13.8.2 Implemented technologies

predictive

1. What percentage of critical equipment is included in the vibration analysis program? 2. What is the monitoring frequency or interval? 3. Is spectral monitoring analysis program used routinely? 4. What alarm criteria are used? Vibration Analysis ManualPage 115 of 143


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5. Are thermography studies conducted at the plant? 6. What coupler alignment method is used? 13.8.3 Maintenance personnel

4. What is the estimated inventory cost of replacement parts? 5. What is the estimated annual cost of the preventive maintenance program?

1. Who is in charge of the predictive maintenance program? 2. How many members are assigned to the maintenance program? 3. How many persons have received predictive technology training? 4. How many vibration analysis courses are given at the present time?

13.8.4 Maintenance reports 1. Are all the machine failures registered? 2. What information is filed in the repair department? 3. What departments are involved in the maintenance reports? 4. Are the work orders automatically done? 5. What personnel is involved in the work orders? 13.8.5 Maintenance indicators 1. What financial support is offered to the maintenance department? 2. What is the general tendency of the annual maintenance costs? 3. How many production hours were lost because of the equipment failures last year? Vibration Analysis ManualPage 116 of 143


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CHAPTER 14

model. The analyzers CSI have anti-alias filters that eliminate these errors.

Glossary ACCELERATION A measurement unit of force acting upon an object usually measured in G's where a G represents the gravity pull. A sensor used for measuring the acceleration is known as accelerometer. ACOUSTICS Acoustics is the study of machine sounds. The CSI 2115 recorder can measure and analyze the intensity level of a global sound, narrow band spectra and thirds of an octave. ALARM LIMITS Amplitude that defines an alarm condition of the equipment monitored. ALARM STATUS The information about the computer condition that appears on the screen of the analyst for each measurement and which contains the alarm level for this particular point. ALARMS Indicating that characteristics of vibration have changed significantly.

the

ALERT Defined alarm level, calculated by the data management system Master Trend, which indicates that the machine is approaching the failure level. In reports, it is notified as: Alarm "C". ALIAS A happening that results in an erroneous spectral frequency when the frequency signal shown is 0.5 times greater than the

AMPLIFICATION It is a way of increasing the signal amplitude with a desired factor in order to facilitate the signal processing. AMPLITUDE It indicates the force (magnitude expressed in RMS, peak, peak-peak, average, or CD of a measured signal). ANALOGOUS INTEGRATION Converting an acceleration signal to the velocity value, or a velocity signal into distance. The analogous integration is superior to its digital counterpart, because it produces a better estimation of low frequency components in the vibration spectrum, and thus increasing a dynamic range. ANALOGY Converting an acceleration signal to its velocity, or converting a velocity signal into a distance. The analogous integration is superior to the digital method because it can produce a better estimation of low frequency components; besides that, it improves the dynamic range in a vibration spectrum. ANALYSIS PARAMETERS They divide the spectrum by frequency, into bands that are individually observed and analyzed.

AUTO-RANGE It is an automatic adjustment process of the entering signal into the recorder, and it also regulates the amplitude of the recorded signal. This process produces an amplified dynamic range. AVERAGING Vibration Analysis ManualPage 117 of 143


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Recording information about vibration levels, averaged over a number of measurements, to minimize the fluctuation influence produced by aleatory signals (noise). BAND WIDTH Frequency range used to analyze different frequency levels, high and low, and which will record the information. The bandwidth is specified with the maximum and minimum frequency range. BLOCKS Memory space units used in reference to the database. A block is equivalent to 0.5 Kilobytes. BODE DIAGRAM A graphic representation that shows how the amplitude at 1X RPM and its phase change, when the velocity changes in RPM. It is recommended that these values are always related to the starting and stopping of the machines in order to identify the axle resonance and other signal characteristics. BPFI This term is used to identify failures in a bearing component. In this case, it is the ball's (or roller's) passage frequency over a crack or an uneven spot on the inside track of a roller. BSF This term is used to identify failures in the bearing component. In this case, it is the spinning frequency of the ball (or roller) when it moves along the internal or external bearing track. CALIBRATION Thanks to this process the instruments and transducers are reviewed and adjusted periodically to register more precise readings. COEFFICIENTS OF INFLUENCE METHOD

Calculating method, used by the analyst to solve balancing problems. CPM Cycles per minute. It is the same as RPM (revolutions per minute). CREST FACTOR It is the relation between the peak value and the RMS value of a signal: A simple signal of simple frequency has a crest value of 1.414. Aleatory noises have a crest factor of approximately 3. The signals that have high impulse content have a higher crest factor. This factor can be used to check impacts, like those caused by bearing defects. CURSOR An indicator that can be wielded manually and it can be moved on the screen where the spectrum is shown, indicating at each point, where it is positioned, the point's magnitude and frequency values. dB Decibels. It is a relative unit that can be defined in logarithmic notions as dB = 20 log 10 X/X ref. In acoustics, the reference level represents the limit of human perceptions on the sound level, and it is equal to 2 x 10 - 5 newtons per meter squared. DIAGNOSTICS The techniques used to analyze and identify problems in machines. DIGITAL INTEGRATION Converting acceleration into velocity or velocity into distance; first collecting the information and then digitizing the spectrum of each frequency. The digital integration is less recommended than the analogous integration because it produces low frequency components in a spectrum. The digital integration is included in the Master Trend System in order to be Vibration Analysis ManualPage 118 of 143


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compatible with the information registered through the Equipment model 2100. DISTANCE It refers to the distance that an object travels, usually measured in thousandths of an inch or millionth of a meter (micron). The distance is measured with Eddy current sensors representing the real movement of a spinning axle. Sometimes, seismic or piezoelectric sensors are used to integrate the recorded information in units used for distance. In this case, the movement represents the distance relative to the axle, taking as a reference the surrounding frame or chassis where the sensor is placed. EQUIPMENT SIGNATURE A spectrum used as reference, usually equipment’s first registered spectrum. ENTIRE PARAMETERS FOR ANALYSIS A process that divides the spectral frequency into bands which are contemplated and analyzed; these can be grouped in units of six parameters which also include instructions for the analyst about the manner in which one can record information. FFT Fourier fast transformation. A calculation done by computer and it has the purpose of converting the signal from its time mode to the frequency expressed on a diagram. FILTER A contrivance that removes certain signal frequencies while it conserves the rest of the signal. FREQUENCY Number of times an event repeats itself in time units; usually it is expressed in Hertz (Hz) or cycles per minute (CPM).

FUNDAMENTAL FREQUENCY The frequency peak to which the harmonic waves are related. 1X RPM is an example of fundamental frequency. FUNDAMENTAL The primary frequency of the rotation of a machine (1 X RPM), it usually causes the highest energy peak of the spectrum. G's Measurement unit for acceleration; 1G represents the gravity pull at sea level. HANNING A numeric technique used to avoid peaks in spectrum in function of the frequency, avoiding the sprawling due to the phenomenon called "leak". The Hanning window is recommended for the majority of frequency analysis measurements in which the signal is stable. HARMONIC WAVE MARKER A marker with a box or square-like appearance in the spectrum displayed which indicates harmonic peaks of a fundamental peak. HARMONIC WAVES Fundamental frequency multiple HERTZ Frequency in cycles per second. HFD High frequency measurement. The vibration amplitude in G's on a wide band from 5k Hz to 20k Hz or more. INTEGRATOR It offers options for different ways of recording the signal: analogous or digital. See these two previously described points. MEASUREMENT POINTS See the definition of point. MIL'S Vibration Analysis ManualPage 119 of 143


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Measuring unit for distance (thousandths of an inch) MODEM Equipment, that allows communication between the computer server and the recording equipment, using telephone lines. MULTI-PLANE BALANCING A method which balances an element in a machine, and which permits to measure the unbalance in various planes along the axle. The counter-weight measures are added to each plane. The balancing process in a multi-plane, or the opposite of balancing in one plane, is recommended when the machine has various rotational elements, such as: crankshaft, coupler and elements that are connected directly to the axle and cautiously distanced one form anther. NOTES Specific observation that can be obtained from a measurement point of a machine. It includes officially stored information and notes left by the user which have been typed through a computer or hand written. NYQUIST DIAGRAM A polar diagram where amplitude components - peak at 1 X RPM - and its phase component interact in function of the velocity change. The diagram Nyquist is used during the starting and stopping of machines to identify resonance in transmission axles. OUTSIDE OF THE ROUTE An option that permits the recording and storing of the information in measurement points which are not defined on the planned route. OVERLAPPING It is a function that accelerates the information recording of low frequencies. The overlapping range for the CSI 2115 is

from 0 to 80% with the recommendation to apply a 50% value.

PEAK The strongest signal that can be observed in a wave shape, in time mode. For the sinusoidal signals, the peak signal is always 1.414 times the value of the RMS signal. For the no sinusoidal forms, the peak level is often greater than the result that this equation could produce. PEAK-PEAK Difference between the maximum and minimum values of a signal during a given period. For the pure sinusoidal waves, the peak-peak level is twice the peak signal and 2.828 of the RMS value. For the no sinusoidal waves, the peak-peak level is often greater than the result that this equation could produce. PERIOD Time required to complete a cycle of a periodic signal. PHASE The phase of 1 X RPM represents the axle position of a machine expressed in degrees (from 0 to 360) according to the tachometer's pulse, where the highest vibration is appreciated. PLANE Defines one or more revolving elements of a machine that is going to be balanced. Each plane is perpendicular to the line that defines the rotation axle.

POINT Any place on a machine where the information can be recorded. The "measurement point" is an equivalent term. Vibration Analysis ManualPage 120 of 143


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PONDERATION A method to conform frequencies that will be applied to a spectrum based on an answer to a frequency detectable to the human ear. The resulting spectrum represents the intensity of various levels which can be detected by the human ear. PREDICTIVE MAINTENANCE The monitoring technology for periodically monitoring the machines' condition in order to detect failures, probable time of break downs, total failures and to program stoppages in order to repair components, avoiding in such a way excessive costs and production loss. REAL TIME Acquisition of the continuous information, as the spectrum in FFT. RMS The magnitude of a calculated or measured signal, using the mean square root. It is equal to 0.7071 times the peak value of a pure sinusoidal wave. ROUTE One or more machines and their respective measurement points, organized in an efficient sequence for the sake of information recording. RS 232 It is a normal communication, synchronic serial, signal. The cables for connecting computer links and computers or modem equipment are called RS 232. SHOCK TEST A test used to determine the structural resonance of a machine. SIGNAL INTEGRATION MODE It permits the selection of the signal integrating mode: analogous or digital. See integration. SPECTRA

A diagram where the frequency components and their magnitude (amplitude vs. frequency) are shown in a dynamic signal, as a vibration. STATION In the CSI system, it is the grouping of the machines in a plant, with the objective of implementing the predictive maintenance system. All the machines from one specific area can be included or they can be subdivided in routes for the information recording. SUB-HARMONICS Vibration frequencies which are whole fractions of the spinning velocity. For example: 1/2 X RPM, 1/3 X RPM, etc. or another fundamental frequency. TACHOMETER Pulse signal used to measure the spinning velocity of the axle. It can also be used for the acquisition of the dynamic information. TENDENCY ANALYSIS It marks a number of measurement points of a specific parameter vs. time. THIRDS OF AN OCTAVE A method for measuring a signal, contemplating the signal levels in the filters that have a width of 1/3 of an octave. TRANSMISSION RANGE The unit used to indicate the data transmission velocity in a serial connection of a computer system. The model 2115 accepts baud ranges from 300 to 57.6K bauds. TRANSITORY An unstable signal of finite duration. One often refers to it in the starting and stopping of a machine. TRIGGER Vibration Analysis ManualPage 121 of 143


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After receiving a specific signal from the sensor, the trigger makes the recorder start recording information. VELOCITY A measurement of a distance traveled by an object in relation to time. The vibration levels are measured with a seismic sensor. The velocity can also be measured integrating the acceleration signal. VIBRATION PARAMETERS There are six bands of limited frequency which measure vibration signals. In the computer, these parameters are predefined and categorized for each measurement point using the Master Trend data base. They are also known as individual analysis parameters.

VISCOSITY Fluid resistance to cutting effects. It usually decreases when the temperature increases. WAVE SHAPE Analogous or digital representation of a function or signal, represented as amplitude vs. time. WINDOW See the information related to window in "Hanning". XCOM Communications program that permits the computer to transfer routes and data information to and from the analyst.



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CHAPTER 15 Annexes STATIC UNBALANCE PHASE

SPECTRUM

1X radial

ADDITIONAL COMMENTARIES The static unbalance presents vibration levels that are in phase and stable. The vibration amplitude varies according to the spinning velocity; in other words, an increase equivalent to 3 times the spinning velocity will cause an increase of 9 times the vibration level. The vibration of 1X RPM will always be present, and it will dominate the spectrum. This type of unbalance is corrected adding a weight in the plane of the rotor's center of gravity. The rotors that usually present this type of unbalance are narrow, and if the diameter/width relation is greater than 10, the problem will be resolved after a simple static balancing. When this relation is less than 10, it is recommended to make a dynamic balancing in the two planes.

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PHASE

SPECTRUM

1X

Radial and axial

reading

ADDITIONAL COMMENTARIES Par type unbalance presents phase at 180 degrees on the same axle and in the radial direction. The vibration at 1X RPM will always be present, and it will dominate the spectrum. The vibration amplitude will vary according to the spinning velocity. It can cause high axial and radial vibrations. One needs to put weights in both planes to correct it. The 180 degrees difference in the phase will apply to both the vertical and horizontal axles.



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ECCENTRIC ROTOR SPECTRUM

PHASE

1X ventilator

e

Radial reading

+

1X motor +

ADDITIONAL COMMENTARIES The eccentricity occurs when the rotation center is moved from the geographic center of pulleys, gears, bearings, motor rotors, etc. The highest vibration will be at 1X RPM of the eccentric component and in the direction of the imaginary line that unites the central lines of both rotors. The comparative phase reading between the horizontal and vertical axles will be 0 or 180 degrees, indicating both movements in straight lines. When trying to balance eccentric rotors, the vibration is lowered in one of the radial directions but it is increased in the other, depending on the eccentric quantity.



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CANTILEVER FAN PHASE

SPECTRUM

1X Radial and axial reading

ADDITIONAL COMMENTARIES The installed rotors' unbalance in cantilever causes high vibration at 1X RPM in axial and radial directions. The axial readings will be in phase when the radial readings are unstable. These cantilever rotors will usually have both types of unbalance (static and par), each one requiring corrections.



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FLEXIBLE ROTOR PHASE

SPECTRUM

1X Radial reading 2X

The bent axles cause high axial vibration with phase axial readings of 180 degrees between machine supports. The prevailing vibration will be at 1X RPM if the bending is close to the axle's center, and at 2X RPM if the bending occurs at the ends. (Be careful taking axial phases with respect to the sensor's orientation for each axial reading. If one wishes to reverse the direction of the sensor, one should not forget to subtract 180° from the reading). The phase radial readings will show movement "in phase" because the movement that was caused by the bending will occur on both supports. Thus, the amplitudes will be similar on the supports.



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ANGULAR LACK OF ALIGNMENT PHASE

SPECTRUM

1X 2X Radial reading 3X

The angular lack of alignment is characterized by the high axial vibration and differences in phase of 180 degrees from one side of couplers to the other. Typically, high axial vibrations with values of 1X RPM and 2X RPM will be shown. It will not be strange to observe 1X, 2X and 3X components dominate the spectrum. These symptoms could be a problem indicator of a contact between coupler faces. At times, the angular lack of alignment is more critical when the thermal increase at each machine support is not taken into account.



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PARALLEL LACK OF ALIGNMENT PHASE

SPECTRUM

2X 1X

Radial reading 3X

The parallel lack of alignment presents similar symptoms to those of the angular lack of alignment, but with high radial and phase vibration differences of 180 degrees between couplers. The 2X RPM vibration will usually be greater than the one presented at 1X RPM, but its relative magnitude at 1X RPM will be determined by the coupling type and its fabrication. When either of the two types of lack of alignment, angular or parallel, becomes severe, it can generate high amplitudes in the subsequent harmonic waves (4X - 8X) and in the higher harmonic waves, apparently similar to the symptoms of mechanical looseness. The coupler type will be very important in the spectrum's behavior when the lack of alignment is severe. It will be very important to take into account the thermal increase when calculating the lack of alignment value in order to avoid high vibration levels.


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RESONANCE PHASE

SPECTRUM phase

Amplitude

90° 180°

Second critical

The resonance occurs when a forceful frequency, such as unbalance, lack of alignment, etc., coincides with the system's natural frequency, and it can cause substantial amplifications in the vibration levels that can result in premature and even catastrophic failures. The natural rotor frequency can get excited, but usually it originates in the base of the support, foundation, and gearboxes and even in elastic bands. If a rotor is in the resonance state or close to it, it will be almost impossible to realize a balancing due to the great phase changes (90° in resonance, 180° passing the resonance threshold). Sometimes, it will be necessary to change the system's natural frequency. The natural frequencies do not get modified with the operation's velocity change, this characteristic facilitates their identification.


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MECHANIC LOOSENESS

1X Leg base Plate base

Radial reading

base

This type of mechanic looseness is caused by looseness or weakness in the leg area, base plate or machine's foundation. Deteriorated gout, loose base screws or a rickety leg can cause it. A phase analysis will show 180 degrees of approximate difference in the direction between various components that play an important roll in the machine's stability.

2 0. 5

1

Radial reading 3

4X

5X 6X 7X 8X 9X 10X

2X 3X

1.5X

0.5X

1X

This type of machine looseness is caused by loose screws in the strengthening plates and cracks in the frame or supports..

This type of mechanical looseness is usually caused by the inappropriate contact between rotor components causing multiple harmonic waves due to the no linear response of the loose components with respect to the dynamic forces coming from the rotor. It truncates the wave shape. At times, this looseness is caused by an inappropriate contact between an internal bearing track and its axle, excessive play in the strengthening plates, or by an impellent or loose axle fan. The phase is unstable and it can vary a lot from one reading to another, especially if the rotor changes positions on the axle from one start to another. This looseness is highly directional, causing considerable differences in vibration levels with possible increases of 30 degrees if the radial readings are taken near the support. As it can be seen in the spectrum, the looseness will also cause multiple sub-harmonic waves whose value will be at 1/2 or 1/3X RPM (0.5X, 1.5X, 2.5X, etc.)

FRICTION BETWEEN PARTS Vibration Analysis ManualPage 131 of 143


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SPECTRUM

Radial reading 4X res 1.5 X 3X on an 4.5 2.5 ce X 5X X 3.5 X

1X 2X .5 X

ADDITIONAL COMMENTARIES The rotor friction produces similar spectra to those caused by mechanical looseness when the rotating components make contact with stationary parts. The friction can be partial or along the whole surface. It usually generates a series of harmonic frequencies, exciting one or more resonance. Sometimes, harmonic waves are presented (0.5X, 1.5X, 2.5X, etc.), depending on the natural frequency of the rotor. The friction can excite some high frequencies, similar to the noise produced when the chock is forcefully applied against a blackboard. This problem can be serious and last for a short time when an axle rubs against a strengthening plate of a Babbitt, but less serious than the case in which the axle makes contact with a seal, or when an agitator grazes the walls or a tank, or when the dustbin or a coupler makes contact with the axle. Truncated and flattened wave shape


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Code . . .

5X 6X 7X 8X 9X 10X

3X 4X

1X

WEAR AND TEAR AND EXCESSIVE LOOSENESS

2X

FLAT STRENGTHENING PLATE (BABBIT)

The final stages of wear and tear in strengthening plates are normally characterized by a whole series of harmonic waves (up to 20). The flat strengthening plates that cause friction emit high vertical amplitudes in comparison with horizontal readings. The strengthening plates with excessive looseness will have high vibration levels caused by unbalance and residual lack of alignment. These vibration levels would be smaller if the looseness were not excessive.

Radial .42-.48 reading

INSTABILITY CAUSED BY OIL SQUIRTS +

1X

The instability caused by the oil squirts at a frequency between .42 - .48X RPM is at times very severe. It is considered excessive when its amplitude exceeds 50% of the existing clearance in the strengthening plates. The oil squirt is an excited vibration when it causes deviations from the normal operation (attack angle and eccentricity), as one oil squirt may make the axle and the strengthening plate move. The change in oil viscosity, lubricant's pressure and external pre-charge can cause oil squirts.


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OPERATIONS/ MAINTENANCE VIBRATION MANUAL (Nexus A)

Código . . . . .

BALL OR ROLLER BEARINGS ADDITIONAL COMMENTARIES

2X 3X

EXCITEMENT ZON OF NATURAL BEARING FREQ.

natural bearing frequency

120 KCPM

2X3X

30 KCPM

STAGE 2

2X 3X

In this stage, the small bearing defects excite the natural frequency of the bearing components. These natural frequencies are normally in the range of 30.000 to 120,000 CPM. Lateral bands appear above and beneath the natural frequency and they correspond to the failure frequency. The HFD values will be from 0.25 to 0.50 G's.

high frequency vibration at random

In this stage, the bearing failure frequencies appear. As the deterioration progresses, more harmonic failure frequencies appear and the number of lateral bands increases also, in the failure frequencies as well as around the natural bearing frequency. The HFD continue to increase, for example from 0.5 to 1.0 G's. In this stage, the wearing is visible and it can be extended through the whole bearing periphery, especially when there are well defined lateral bands following any harmonic, failing bearing frequency. It is recommended to change the bearings at this stage.

120 KCPM

STAGE 4

1X

STAGE 2

STAGE 3

natural bearing frequency

30 KCPM

2X BPFI

2X 3X

BPFO BPFI

STAGE 3

1X

The initial indications of bearing problems appear in the zone of ultra-frequency, in the range of 20,000 to 60,000 Hz. These frequencies are evaluated by a filter HFD (High Frequency Detection) and they are measured in G's. The value of HFD for this stage will be around 0.25 G's. (This value depends on the machine's spinning velocity as well as on the choice of the measurement points).

STAGE 1

1X

STAGE 1

HFD

1X

FREQUENCY ZONE OF FAILING BEARINGS

STAGE 4 As the bearing sustains major deterioration, the amplitude of 1X RPM changes accordingly. This amplitude increases and makes its harmonic waves increase. The failing bearing frequencies and the natural frequency almost disappear and they are replaced by noise on the spectrum. In this stage, and just before the failure of the bearing, the HFD value goes beyond 3 G's. The bearing's life expectancy is uncertain at this point.



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Code . . .

BALL OR ROLLER BEARINGS (CONT.) The equations for the calculation of the frequencies are: 1. Failure on the internal track (BPFI) BPFI = Nb/2*(1+(Bd/Pd)*cos(τ))*RPM 2. Failure on the external track (BPFO) BPFO = Nb/2*(1-(Bd/Pd)*cos(τ))*RPM 3. Ball or roller failure (BSF) BSF = Pd/2Bd*[1-(Bd/Pd)2*cos(τ)2]*RPM 4. Cage/frame failure (FTF) FTF= 0.5*(1-(Bd/Pd)*cos(τ))*RPM where: Nb = No. of balls or rollers Bd = Ball or roller diameter Pd = Roller diameter pass τ = contact angle


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Code . . .

HYDRAULIC AND AERODYNAMIC FORCES SPECTRUM

PHASE

BPF= No. of blades X spin 1 2

2X BPF

ADDITIONAL COMMENTARIES A. BLADE FREQUENCY PASS The blade frequency pass (BPF) is equal to the number of blades multiplied by the RPM spin. This frequency is inherent to pumps, ventilators and compressors, usually without presenting any problems. However, when there are high amplitudes in BPF and its harmonic waves, these can be generated if the clearance between the blades and the stationary parts is not similar along the whole periphery. On the other hand, the BPF frequency or its harmonic waves can excite the natural system frequencies, causing high vibration levels. Besides, this frequency can have high amplitude if one of the diffusers is detached, or if the rotor is eccentric in relation to the frame. One will observe high frequency BPF when there are obstructions in the tubes or conduits. At random

1X

BPF

1 2

BPF

random high vibration frequency

120

B. FLUID TURBULENCE

C. CAVITATION

The fluid turbulence usually occurs in blowers due to the variations in pressure or air velocity that passes through the ventilator or conduits. A low frequency vibration in the range of 50 to 2,000 RPM will be formed.

The cavitations normally generate random vibrations in the area of high frequency, overlapping at times with the blade passing frequency and its harmonic waves. The problem is usually caused by malfunction in the precision suction. These cavitations can damage seriously the pump components, eroding the impellers. The typical sound of this failure is similar to the one that the gravel would cause passing through the pump.


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Code . . .

GEARBOXES

A. NORMAL SPECTRUM

1X cr ow n

2

GMF = gear frequency GMF = no. of teeth X RPM spin

1x

GM

pin ion

A normal spectrum of a gearbox will show frequencies of 1X and 2X RPM as well as the frequency of the GMF gear. The gear frequency GMF will normally have lateral bands around it and corresponding to the spinning frequency. All the peaks will have low amplitude and there will be no natural frequency excitement. B. TOOTH WEAR

1X cro wn

2

1X pin ion

natural gear frequency

1X

GMF 1X piсуn

C. GEAR UNDER FULL LOAD

1X corona 2X

A clear indication of the gear tooth wear is the excitation of the spinning frequency of the worn out gear. The GMF frequency might or might not change in amplitude; however, the lateral bands will be of greater amplitude when the wearing off is visible. The lateral bands are a major indicator of worn out teeth, even more than the GMF.

The gear frequency is usually very sensitive to the load. High GMF amplitudes do not necessarily indicate a problem, especially if the lateral band amplitudes are maintained low and if the natural gear frequency was not excited. It is recommended to analyze it under full load.


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Code . . .

GEARBOXES (CONT.) D.

ECCENTRICITY AND THE GEAR BACKLASH

1X cro wn

2

1X pin ion

natural gear frequency

GM

The lateral bands slightly high at the gear frequency can be caused by eccentricity, backlash or unparalleled axles, in such a way that one gear modulates the spinning frequency of the other. The spacing of the lateral bands will indicate which gear has problems. When there is an inappropriate backlash, the GMF and the gears natural frequency will get excited; both will have lateral frequencies of 1X RPM. The GMF amplitudes will be reduced when the load on the gears increases only when the backlash is the problem. . E.

LACK OF ALIGNMENT BETWEEN GEARS

1X cro wn

2

1X pin ion

1X

2X

The lack of alignment between gears is almost always excited in the second harmonic wave and greater gear frequencies or GMF, and they usually have lateral bands equivalent to the spinning frequency. At times, they will only show low amplitudes at 1X GMF, but with greater levels at 2X and 1X GMF. It will be important to set the maximum frequency of monitoring for at least 2X GMF if the transducer has the capacity to check these frequencies.

F.

BROKEN OR CRACKED TEETH

1X RPM of a damaged gear tooth

A broken or cracked tooth will generate high amplitudes at 1X RPM in his gear, and also excite the natural gear frequency with lateral bands at the spinning frequency. A better way to observe damaged teeth is the wave shape. The time between impacts corresponds to the spinning frequency of a gear that has one or more broken teeth. The wave amplitudes will be greater. Vibration Analysis Manual Page 138 of 143

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Code . . .

ELECTRIC PROBLEMS SPECTRUM

DIAGRAM

stator

radial reading

stator grooves

rotor

FL=3,600CPM 2X FL

1X 2X

rotor rods ADDITIONAL COMMENTARIES

A. STATOR ECCENTRICITY, INTERFERING LAMINATION AND LOOSE STATOR The stator problems generate high vibration when the frequency of the electric voltage doubles (2XFL), as it can be seen in the diagram's spectrum. The eccentricity of the stator produces a static air gap variable between the rotor and the stator that originated a high unidirectional vibration. A loose leg or an uneven base can cause the stator to become eccentric. A lamination interfering with the stator can heat up the stator, and the thermal change can cause the rotor axle to bend. When the stator is loose, one should suspect lack of sturdiness.

radial reading

B. ECCENTRIC ROTOR (VARIABLE AIR GAP)

Fp

1X

2FL

Fp lateral bands around 2FL L

The eccentric rotors produce a variable rotating air gap between the rotor and the stator that produces pulsing vibration (normally between the frequency of 2FL and the closest harmonic wave to the spinning frequency). In most cases, it will be necessary to take spectra of high resolution and approach or "zoom into" this zone to separate the frequencies. The eccentric rotors generate the frequency of 2FL surrounded by lateral bands equal to the pole passing frequency, or Fp, as well as Fp lateral bands around the rotor spinning frequency. The pole passage frequency could also appear in the spectrum's low frequency area. The most common values for Fp vary from 20 to 120 CPM. FL = electric line frequency Fp = pole passing frequency = FS X P NS = synchronous velocity = 120 X FL/P FS = movement frequency = NS - RPM

P = no. of poles Vibration Analysis Manual Page 139 of 143

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Code . . .

ELECTRIC PROBLEMS (CONT.)

ADDITIONAL COMMENTARIES

Fp lateral bands around 1X, 2X, 3X... C. ROTOR PROBLEMS

1X

Radial reading

2X

3X

RBPF = passage frequency of rotor rods 1X

RBPF 2FL lateral bands around RBPF

2X

Broken or cracked rods, interfering connection rings, rod looseness in the connection rings or interfering lamination will cause a high vibration at 1X RPM hemmed with lateral bands equivalent to the passing pole frequency Fp. Additionally, when there are cracked rods, lateral bands will be formed near the first 4 harmonic spinning frequency waves. When there is a problem with loose rods, a rotor rod (bar) passing frequency RBPF will be created and it will have lateral bands whose value will be equivalent to double frequency (2FL). it is possible that two RBPF harmonic wave bands appear also with lateral bands; in some occasions, the frequency of 2 X RBPF is greater in amplitude than 1X RBPF. The vibration due to electric problems will disappear when the motor energy is cut off.


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Code . . .

PULLEYS AND BANDS SPECTRUM radial reading with bands

x harmonic wave frequency

1X driven pulley

x The band frequency is calculated the following way: band freq. = 3.1416 X RPMpulley X pulley diameter band longitude toothed band freq. = RPMpulley X no. of pulley grooves

1X driving pulley

DIAGRAM

A. DAMAGED, LOOSE AND UNEVEN BANDS The fundamental passage frequency of the bands and their harmonic waves is located in a lower frequency range than any of the two, driven or driving, fundamental pole frequencies, as it can be observed in the diagram spectrum. When they are damaged, loose or uneven, they will cause 3 or 4 harmonic band passage frequencies, occasionally dominating harmonic waves of 2X. The amplitudes are normally unstable and on occasions pulsing with the frequency of either of the two poles. In case of the toothed belts, when there is unevenness between poles or they are worn out, one will observe high amplitudes at the frequency of toothed belts. B. LACK OF ALIGNMENT BETWEEN PULLEYS

1X of driven or driving pulley axial reading

The lack of alignment in pulleys produces high axial vibration levels at 1X RPM in any of the two poles. The amplitude will be greater in the equipment that is less rigid; the amplitude will also depend on the place where the measurement is taken. At times the high axial vibration frequency in a motor will be the ventilator frequency.


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Code . . . axial reading

1X

C. BAND RESONANCE

band resonance

x x

The band resonance can occasionally cause high vibration levels when the natural frequency of the bands coincides with the spinning frequency of either of the two poles. The natural band frequency can be modified changing their tension, or changing their longitude. This natural frequency could be measured with the transducer connected to the support while tensing and releasing one of the bands.



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Code . . .

RHYTHMIC VIBRATION SPECTRUM

DIA

(F 2F1

pulsing vibration

Frequency difference

F1

F2 = rhythmic frequency zoomed spectrum

The minimum vibration occurs when the frequencies are 180° outside of the phase.

The maximum vibration occurs when both frequencies are in phase.

The vibration caused by the rhythmic frequency is the result of two vibration frequencies close to each other; they enter and exit the rhythmic synchrony. The spectrum on the upper part of the diagram shows the pulsing behavior or a vibration peak close to both frequencies. In the zoomed spectrum in the lower part of the diagram, one could observe both vibration frequencies, one close to the other. The difference in frequency between these two vibrations will determine the rhythm with which the vibration levels will move upward or downward. Normally, this rhythmic frequency will not appear in the spectrum because it has very small values that range from 5 to 100 RPM. The maximum vibration values will occur when both frequencies are in phase, and vice-versa, the lowest vibration levels will be obtained when both frequencies are 180° outside of the phase. This type of problems will usually occur when two machines with similar spinning frequency are mounted on the same base and both have a high residual unbalance. The values of the unbalances will add up and subtract themselves, causing rhythmic vibration.


Vibration Analysis Manual Rev0

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