API Recip Compressor Best Practices 0300_060814

Protecting and Managing API-618 Reciprocating Compressors C ompressors

Best Practices

©

2006 Bently Nevada LLC

API-618 Reciprocating Compressor Best Practices

Data Subject to Change without Notice (August 2006)

Proprietary notice – the data contained herein is propri etary to Bently Nevada LLC and shall not be duplicated, used or disclosed in whole or in part for any purpose, other than for which it was furnished, without the express written permission of Bently Nevada LLC.

Table of Contents SECTION 1 -

INTRODUCTION.......................... INTRODUCTION............... ..................... ...................... ....................... ..................... ..................... ....................... ....................... ......................3 ...........3

SECTION 2 -

PROTECTION / MANAGEMENT.............. MANAGEMENT........................ ...................... ....................... ..................... ..................... ....................... .....................4 .........4

SECTION 3 -

TRANSDUCER SELECTION...................... SELECTION................................. ...................... ..................... ..................... ...................... ....................... .....................5 .........5

SECTION 4 -

DRIVERS .................... ............................... ...................... ....................... ...................... ..................... ...................... ....................... ....................... ..................... ..................6 ........6

Electric Motors Motors................................................................ .................................................................................................................................... ...........................................................................................................6 .......................................6 Stator Temperature ........................................................... ................................................................................................................................ ...............................................................................................6 ..........................6 Bearing Temperature......................................................... Temperature ............................................................................................................................. ..............................................................................................7 ..........................7 Bearing Vibration (Rolling Element Bearings) .................................................... .......................................................................................................8 ...................................................8 Reciprocating Internal Combustion Engine..................................................................................................................9 Integral Engine Engine ............................................................... .................................................................................................................................... ...........................................................................................................9 ......................................9 Turbine and and Gearbox Gearbox Driven............................................................................................................ Driven...............................................................................................................................................9 ...................................9 SECTION 5 -

CRANKSHAFT / CRANKCASE.................... CRANKCASE................................ ...................... ..................... ...................... ..................... ....................... ................. 10

® System...................................................................................................................................10 Multi-Event Keyphasor ® Main Journal Journal Bearing.............................................................................................................. Bearing..........................................................................................................................................................11 ............................................11 Temperature......................................................................................................................................................................11 Frame..........................................................................................................................................................................................12 Vibration ............................................................ ................................................................................................................................. ..................................................................................................................12 .............................................12

SECTION 6 -

CROSSHEAD ..................... ............................... ...................... ....................... ...................... ..................... ..................... ....................... ....................... ................... ........ 14

Vibration ............................................................ ................................................................................................................................. ..................................................................................................................14 .............................................14 Shoe Temperature .............................................................. ................................................................................................................................... ............................................................................................16 .......................16 SECTION 7 -

PRESSURE PACKING...................... PACKING................................. ....................... ...................... ..................... ...................... ....................... ....................... ............... .... 17

Case Temperature..........................................................................................................................................................17 Vent Line Temperature ...................................................... .......................................................................................................................... ...........................................................................................18 .......................18 SECTION 8 -

PISTON AND ROD............................ ROD........................................ ...................... ..................... ...................... ..................... ....................... ....................... ............. ... 19

Rod Position.......................................................................................................................................................................19 SECTION 9 -

CYLINDER ..................... ................................ ..................... ...................... ....................... ...................... ..................... ...................... ....................... ...................... ............. 21

Cylinder Pressure Pressure ............................................................... .................................................................................................................................... .............................................................................................21 ........................21 Valve Temperature ............................................................. .................................................................................................................................. ............................................................................................23 .......................23 Discharge Temperature.............................................................. Temperature ................................................................................................................................... .................................................................................2 ............25 5

© 2006 Bently Nevada LLC Page 2 of 25

API618-Reciprocating Compressor Best Practices

Data Subject to Change without notice. August 2006

Section 1 - Introduction This best practices document contains recommendations for the selection and installation of Bently Nevada transducers, monitoring systems, and trending systems on API-618 reciprocating compressors. These recommendations apply to both new machines and existing machines targeted for retrofit installations. API-618 style reciprocating compressors are typically found in refinery and petrochemical applications. The compressors are typically slow speed (less than 600 RPM) and are handling hazardous and flammable gases. Continuous collection, trending and analysis of the cylinder pressure, vibration, rod position, and temperature data using a machinery management system such as System 1® software is strongly recommended. Use of these tools will maximize the ability to diagnose problems and analyze the performance of reciprocating compressors.

2006 Bently Nevada LLC Page 3 of 25 ©



Section 2 - Protection / Management API 618 Guidelines for basic machine protection are typically applied to critical process reciprocating compressors. Machine protection specifics may vary from the API recommendations. The “basic” machine protection found on these machines can also be provided thru the protection / management system described herein for an integrated system approach.

API-618, 4th edition, June 95 ( Table 4 ) Condition High Gas discharge Temp for each Cylinder Low Frame Lube-oil Pressure Low Frame Lube-oil Level

Alarm X X X

Cylinder Lubricator System Failure

X

High Oil-Filter differential Pressure

X

High Frame Vibration

-

High level in Separator Jacket Water System Failure

Shutdown X X

X X

-

Note: X = When the condition occurs, Alarm or Shutdown as required - = When the condition occurs, Alarm or Shutdown is not required

Beyond the standard instrumentation/protection package specified in API-618, these measurements are recommended. Protection Solution – The recommended protection system for reciprocating compressors includes the API-618 protection system with the addition of main bearing temperature, cylinder pressure and crosshead accelerometers. See Cylinder, Crosshead and Crankshaft in the Transducer Selection Section. Management Solution – The recommended management solution for reciprocating compressors includes the recommended protection solution with the addition of System 1® trending and analysis software, temperature monitoring on compressor valves and pressure packing, crosshead shoes (slippers) and piston rod position. Figure 1 shows the placement of each transducer on a reciprocating compressor. Each item is discussed in detail in the Transducer Selection section of the document.




Fully Instrumented Reciprocating Compressor

Section 3 - Transducer Selection The following table summarizes the transducer selection for API-618 reciprocating compressors:

Component

Transducer

Electric Motor

Stator Temperature Bearing Temperature Rolling Element Bearing Vibration

RTD or Thermocouple RTD or Thermocouple Velomitor®

Crankcase

Main Bearing Temperature Crankshaft Position Reference Frame Vibration

RTD or Thermocouple Keyphasor® transducer/ Recip multievent wheel Velomitor®

Crosshead

Machine Vibration Shoe Temperature

Accelerometer RTD or Thermocouple

Pressure Packing

Case Temperature Vent Line Temperature

RTD or Thermocouple RTD or Thermocouple

Piston and Rod

Rod Position

Horizontal and Vertical Proximity Probes

Cylinder

Internal Cylinder Pressure Valve Temperature Discharge Temperature

Pressure Transducer RTD or Thermocouple RTD or Thermocouple


Monitoring Point



Section 4 - Drivers Electric Motors Stator Temperature

Stator winding temperature is typically not a shutdown parameter; however this is subject to NEMA/OEM recommendations or customer preference.

System 3500

Monitor 3500/60 (No recorder output) 3500/61 3500/65 (No recorder output) * - Only supports isolated (non-grounded) thermocouples

Transducer RTD / Thermocouple RTD / Thermocouple RTD / Thermocouple*

Benefits - Electric motor stator winding temperature can indicate problems related to the stator, including unloaded balances between phases, low / improper line voltage, short circuit in windings, and ground in winding. Applications – Can be used on both induction and synchronous motors. Installation – installation includes imbedding either a RTD or thermocouple into each winding. Typically the OEM does this during manufacturing, but motors can be retrofitted. Filtering – 50 or 60Hertz line noise rejection on 3500/60 or 3500/61 Alarm / Shutdown – In the absence of actual engineering data the recommended* initial alarm and danger set points, starting with a maximum ambient of 104ºF (40ºC), are: Insulation Class Alarm Shutdown A 203ºF (95ºC) 221ºF (105ºC) B** 248ºF (120ºC) 266ºF (130ºC) F** 293ºF (145ºC) 311ºF (155ºC) H 338ºF (170ºC) 356ºF (180ºC) *These should be adjusted based on actual operating conditions **Most common classes for industrial duty motors




Bearing Temperature

Bently Nevada strongly recommends that customers use bearing temperature as a shutdown parameter. System 3500

Transducer 3500/60 (No recorder output) RTD / Thermocouple 3500/61 RTD / Thermocouple 3500/65 (No recorder output) RTD / Thermocouple* * - Only supports isolated (non-grounded) thermocouples Monitor

Benefits -Electric motor main bearing temperature can indicate problems related to fluid-film and rolling element bearings, including overload, bearing fatigue or insufficient lubrication. Measuring temperatures at the main bearings and correlating them with other process variables can assist in determining the overall condition of reciprocating compressor drivers. Applications – No known restrictions. Installation - Main bearing caps may be drilled and tapped to accept temperature probes during the manufacturing process. If not done during manufacture, the bearing caps can be removed and drilled to accept the temperature probes. Filtering – 50 or 60Hertz line noise rejection on 3500/60 or 3500/61 Alarm / Shutdown – In the absence of OEM recommendations or engineering data the recommended* initial alarm and danger set points are: Alarm: 180 oF (82ºC) Danger: 200 oF (93ºC) *These should be adjusted based on actual operating conditions




Bearing Vibration (Rolling Element Bearings)

Bently Nevada strongly recommends that customers use bearing vibration as a shutdown parameter. System 3500

Monitor

3500/70 3500/42

Transducer 190501 Velomitor® CT 330500 Velomitor® 190501 Velomitor® CT 330500 Velomitor®

Benefits -Electric motor rolling element bearing vibration monitoring can indicate problems including overload, inner race defects, outer race defects and cage defects. Measuring vibration at the motor bearing(s) and correlating them with bearing temperature and lubricating fluid condition can assist in determining the overall condition of reciprocating compressor driver. System Description – Bearing vibration detection system consists of two components: the Velomitor® Piezo-Velocity Sensor and the 3500/42M four channel monitor. Applications – For machines with rotational speeds below 500 RPM, the Velomitor® CT should be used. For application with rotational speeds greater than or equal to 500 RPM the standard Velomitor® should be applied. Installation – The Velomitor® transducer is mounted to the bearing casing. At a minimum, one should be installed in the horizontal direction. For large motors or critical applications two orthogonal Velomitors® provide early indication of bearing failure.

Bearing caps may be drilled and tapped to accept velocity transducers during the manufacturing process, otherwise the bearing caps can be removed and drilled to accept the Velomitor®. Filtering – Reference Rolling Element Bearing Methodology. Alarm / Shutdown – Reference Rolling Element Bearing Methodology.




Reciprocating Internal Combustion Engine Reference “Reciprocating Internal Combustion Engine” Best Practices. For turbocharger Best Practices, reference the “Turbocharger” Best Practices.

Integral Engine The compressor cylinders, compressor valves, compressor piston, piston rod, crosshead, compressor connecting rod and crankshaft on these machines are covered in these Best Practices. For power cylinder, power piston, power connecting rod and power cylinder valve recommendations reference the “Reciprocating Internal Combustion Engine” Best Practices. For turbocharger Best Practices, reference the “Turbocharger” Best Practices.

Turbine and Gearbox Driven Instrumentation requirements and recommendations for gearboxes applied between turbomachinery and the reciprocating compressor can be found in “Gearbox Monitoring Methodology” document.




Section 5 - Crankshaft / Crankcase

Multi-Event Keyphasor ® ® System System 3500

Monitor

3500/25

Transducer 3300 8mm Proximity probe

The multi-event Keyphasor® system is a special variation of the standard Keyphasor® transducer system that produces a voltage pulse for every 30 degrees of shaft rotation. The signal produced is used by the 3500 compressor monitoring system as an accurate reference of crankshaft position. The multi-event Keyphasor® transducer is typically a proximity probe (recommended for permanent installations in which the probe observes a physical gap). Benefits – Provides a reference signal based on every 30 degrees of crankshaft rotation in addition to a once per turn event to establish a once per turn reference. Without the multi-event wheel, piston ring leaks and valve leaks can be difficult to detect. System Description – The multi-event Keyphasor® system is a special configuration of the standard 3500/25 monitors. Applications – The multi-event Keyphasor® system is required for the cylinder pressure monitor, 3500/77M. The multi-event wheel is strongly recommended to attain the highest accuracy on the cylinder pressure measurements and provide the most accurate pressure-volume (PV) curves Installation – The multi-event wheel is typically mounted to the shaft on the outboard end of the driver within 6-12” (12-25cm) of the bearing. Drilling and tapping of the driver shaft is normally required. The once per turn reference is normally aligned with the top-dead-center position of the #1 cylinder. For those motors with no outboard bearing, a custom multi-event wheel must be fabricated and installed within 6-12” (12-25cm) of the compressor main bearing.

Run-out of the multi-event wheel must be minimized to ensure accurate angular resolution. The probe mounting bracket should be constructed and mounted to minimize relative movement between the probe and the multi-event wheel that would be seen as vibration or run-out. The table below provides angular uncertainty for total indicated run-out (8mm probe) and gap voltage (with the probe at its nearest position). Run-out (Mils Pk-Pk) 5 10 15 20 25

Uncertainty –8V gap (Degrees ) -0.13/+0.03 -0.26/+0.05 -0.42/+0.08 -0.60/+0.10 -0.82/+0.12

Uncertainty –12V gap (Degrees) -0.15/+0.02 -0.34/+0.04 -0.56/+0.06 -0.85/+0.08 -1.29/+0.10

Filtering – N/A Alarm/Shutdown – N/A 2006 Bently Nevada LLC Page 10 of 25 ©



Main Journal Bearing Temperature

Bently Nevada strongly recommends that customers use bearing temperature as a shutdown parameter. System 3500

Monitor 3500/60 (No recorder output) 3500/61 3500/65 (No recorder output)


* - Only supports isolated (non-grounded) thermocouples

Benefits - High crankshaft main bearing temperature can indicate problems related to fluid-film bearings, including overload, bearing fatigue or insufficient lubrication. Measuring temperatures at the main bearing and correlating them with other process variables can assist in determining the overall condition of the compressor. Applications – No known restrictions. Installation - Main bearing caps may be drilled and tapped to accept temperature probe during the manufacturing process. If not during manufacture, the bearing caps can be removed and drilled to accept the temperature probes after machine installation, during an overhaul or retrofit. Filtering – 50 or 60Hertz line noise rejection on 3500/60 or 3500/61. Alarm / Danger – In the absence of OEM recommendations or engineering data the recommended* initial alarm and danger set points are: Alarm: 180 oF (82ºC) Danger: 200 oF (93ºC) *These should be adjusted based on actual operating conditions




Frame

Vibration Bently Nevada strongly recommends that customers use frame vibration as a shutdown parameter. It is a recommended shutdown parameter in API 618. System 3500

Monitor

3500/70M

Transducer 190501 Velomitor® CT2

2 – For Operating Temperatures in Excess of 185°F (85°C), consult sales representative.

The cylinders on balanced-opposed compressors are physically offset, causing moments to be generated on the crankshaft. The pressure forces across the machine can become unbalanced due to process changes, valve unloading, or damaged valve assemblies. These forces are transmitted through the bearing to the frame, resulting in crankcase vibration at one or two times machine running speed. Frequencies 1X to 2X the machine speed occur on reciprocating compressors due to their layout and all whole multiples of running speed due to gas forces. Excessive amplitudes at these frequencies may indicate mechanical or operational problems. Velomitor® piezo-velocity sensors are ideal for detecting machinery problems on reciprocating compressors where rotationrelated vibration is transmitted to the compressor frame. Velomitor® sensors eliminate the crossaxis sensitivity problems inherent to moving coil velocity sensors. At the same time, they have a better signal-to-noise ratio at the low running speed (frequency) of reciprocating machines when compared to standard accelerometers. Benefits -Typical operational problems that the Velomitor® sensor and monitor can detect include: Imbalance due to an unusual pressure differential or inertial imbalance. Looseness in the foundation attachment (such as deteriorating grout or shims). High moments caused by excessive rod load. • • •

System Description - Frame vibration detection system consists of two components: the Velomitor® Piezo-Velocity sensor and the 3500/70M Recip Impulse/Velocity Monitor. The Velomitor® sensor employs an accelerometer with a piezoelectric crystal at its core along with a l ow noise amplifier /integrator that provides an output in velocity units. The result is a small sensor with no moving parts, integrated electronics, and a virtually unlimited lifespan. The transducer provides a vibration signal in velocity units. Applications - The Velomitor® CT transducer is ideally suited for measuring casing vibration on reciprocating compressors with a running speed down to 90 rpm. The monitor should use “peak” readings and should not use the “rms” or “integrate” options since the low frequency response would be affected by these selections. Installation - The best locations to mount Velomitor® transducers are on the crankshaft frame in the horizontal axis between each pair of cylinders in-line with the main bearings. Mounting Velomitor® transducers level with the bearing split line is preferred, as it places them in the direct path of the forces acting on the machine. 2006 Bently Nevada LLC Page 12 of 25 ©



Filtering – When used in a system with accelerometers mounted above the crosshead, the high and low pass filter corners should be set as close as possible to 1/2X and 20X, respectively. When the system does not include accelerometers above the crosshead, the filter corners should be set to the widest possible settings (3Hz to 30 kHz). Alarm / Shutdown – In the absence of OEM recommendations or engineering data the recommended* initial alarm and danger set points are: Alarm: 0.25 in/s peak (6 mm/s peak) Danger: 0.5 in/s peak (12 mm/s peak) *These should be adjusted based on actual operating conditions




Section 6 - Crosshead

Vibration

Although not an API recommended shutdown parameter, Bently Nevada recommends that customers use crosshead vibration as a shutdown parameter. System 3500

Monitor

3500/70M

Transducer 330400 Accelerometer and 37439-01 Mounting Base

Placing accelerometers over each crosshead provides the single best method to detect machinery problems due to impact-type events. Impact-related events characteristically cause free vibrations and are typically due to liquid ingestion into the cylinder or mechanical problems such as looseness in the crosshead and piston assembly. Acceleration can detect impacttype machinery problems better than a velocity measurement due to the high frequency vibrations created by impact events. Under normal conditions, the vibration level should be very small. As impacts occur, the vibration level increases and the waveform will resemble the classic impact ringdown response over each stroke, as shown in the figure. The large increase in amplitude should be readily apparent from looking at an acceleration waveform generated by an impact. Benefits - The benefits of monitoring free vibration using accelerometers include the ability to detect the following mechanical faults: Liquid ingestion into the cylinder. Excessive crosshead clearance. Loose or cracked nuts, bolts or pistons. Excessive clearance in the crosshead pin bushing. In addition to these mechanical faults, the crosshead accelerometer also includes the ability to detect valve opening and valve closing events. • • • •

System Description - The 3500/70M Recip Impulse/Velocity Monitor is a 4-channel monitor that accepts input from seismic transducers, conditions the signal to make various vibration measurements, and compares the conditioned signals with user-programmable alarms. Channel pairs of the 3500/70M can be configured for acceleration transducer inputs. 2006 Bently Nevada LLC Page 14 of 25 ©



Applications - The 330400 Accelerometer transducer is ideally suited for measuring free vibration events on reciprocating compressors. Installation - Install an accelerometer on each cylinder over the crosshead, distance piece or cylinder to detect impact-type events. For best results with a single accelerometer per throw, install the accelerometer directly above the crosshead in the vertical plane. Filtering – When used in conjunction with a case-mounted Velomitor® transducer (see Frame Section) and to protect against only mechanical faults, the filtering should be set between 3 Hertz and 2 kHertz. Although not recommended, the low pass corner setting can be changed to 20 kHertz to include protection for events with high frequency content such as valve failures.

If the accelerometer is the only monitoring or protection system then minimal filtering is recommended. Segmental Banding – Six segmental vibration bands provide protection at discrete intervals during the crankshaft revolution. In the absence of engineering data* initial bands should be configured as Band 1 – 350 degrees start, 20 degrees duration (Trapped debris/liquid ingestion head end) Band 2 – 170 degrees start, 20 degrees duration (Trapped debris/liquid ingestion crank end) Band 3 - 185 degrees start, 25 degrees duration (Loose valve / Loose running gear) Band 4 – 10 degrees start, 25 degrees duration (Loose valve / Loose running gear) Band 5 and 6 – spare, configured per customer request. Alarm / Danger (3Hertz to 2kHertz Filtered) – In the absence of OEM recommendations or engineering data the recommended* initial alarm and danger set points are: Alarm: 1.5 g’s peak Danger: 2.0 g’s peak *These should be adjusted based on actual operating conditions Alarm / Danger (3Hertz to 20kHertz Filtered) – In the absence of OEM recommendations or engineering data the recommended* initial alarm and danger set points are: Alarm: 2.0 g’s peak Danger: 5.0 g’s peak *These should be adjusted based on actual operating conditions




Shoe Temperature Crosshead shoe temperature is typically not a shutdown parameter. System 3500



Benefits – Crosshead shoe (slipper) temperature can indicate problems including overload, fatigue, or insufficient lubrication. Applications – On reciprocating compressors there is an up running and a down running crosshead. The up running side is on the left side of the machine when viewing from driver to driven equipment with the machine turning in the clockwise direction. If the machine were turning in the counter clockwise direction then the up running side would be on the right side of the machine. If only one temperature probe is requested it should be placed on the active side (e.g. top on up running side and bottom on down running side). Installation – An RTD or thermocouple may be mounted either on the bottom or top of the crosshead guide. Precise machining of the crosshead guide is required to make the necessary provisions for the temperature probes. Filtering – 50 or 60Hertz line noise rejection on 3500/60 or 3500/61. Alarm / Danger – In the absence of OEM recommendations or engineering data the recommended* initial alarm and danger set points are: Alarm: 180 oF (82ºC) Danger: 200 oF (93ºC) *These should be adjusted based on actual operating conditions




Section 7 - Pressure Packing

Pressure packing prevents process gases from leaving the cylinder and entering the distance piece and crankcase. With the increase in concern for the release of volatile organic compounds, packing glands incorporating a nitrogen-purged cup have grown in popularity. Case Temperature

Packing case temperature is not typically a shutdown parameter. System 3500



Benefits – Pressure packing temperature can indicate problems related to the packing, including excessive wear, insufficient cooling or insufficient lubrication. Applications – Applies to pressure-packing glands. For those glands not drilled for temperature, the vent line temperature measurement can be applied. Installation – The RTD or thermocouple should be installed as close as possible to the packing. Typically, provisions are made on the packing case flange to insert a temperature probe into the case. Filtering – 50 or 60Hertz line noise rejection on 3500/60 or 3500/61. Alarm / Danger – In the absence of OEM recommendations or engineering data the recommended* initial alarm and danger set points are: Alarm: 180 oF (82ºC) Danger: 200 oF (93ºC) *These should be adjusted based on actual operating conditions




Vent Line Temperature

Vent line temperature is not typically a shutdown parameter. System 3500



Benefits – As the purge packing begins to leak from the atmospheric side, the leaking gas exits through the packing vent line to flare. With the increase in process gas flow, the vent line becomes hotter. For years, operators have used the subjective method of touching the line to see if gas is leaking. Applications – The application of vent line temperature monitoring is well suited for all reciprocating compressor applications. Installation – A RTD or thermocouple may be embedded or affixed on the packing case vent line. It is important to have only one packing case vent line at each monitoring point to assure any leak will cause a temperature change in the monitored vent line. The placement of the temperature probe should be as close to the packing vent discharge as practical. Filtering – 50 or 60Hertz line noise rejection on 3500/60 or 3500/61. Alarm / Danger – In the absence of OEM recommendations or engineering data the recommended* initial alarm and danger set points are: Alarm: 140 oF (60ºC) Danger: 160 oF (71ºC) *These should be adjusted based on actual operating conditions




Section 8 - Piston and Rod Rod Position Bently Nevada does not recommend that customers use rod position as a shut down parameter. System 3500

Monitor

3500/72M

Transducer 3300 11mm X & Y Proximity Probes1

1 – For piston rods with a diameter less than 3.0”, consult sales representative.

The 3500/72M monitor is designed to measure the rod position from the geometric center of the cylinder bore at the pressure packing case. Based on configuration data, a circular acceptance region is defined. When the piston moves too close to the cylinder wall in any direction, as defined by leaving the acceptance region, an alarm or danger signal is generated. In some cases, although not recommended as a Best Practice, the 3500/72M Rod Position Monitor may also be configured with a single probe to provide single rod position. Benefits - The Bently Nevada Rod Position Monitoring System continuously monitors the crosshead looseness, rod bow and rider band condition of each cylinder in a reciprocating compressor. The monitor has the following features: Continuous online indication of maximum magnitude and direction of rod movement along with the crank angle at which the maximum occurs. This information points to the source of movement enabling you to schedule maintenance to replace rider bands or repair the crosshead only when required, maximizing the lifespan. Alert and Danger alarm level indications warn of potential cylinder damage. •

•

System Description - The 3500/72M monitor is a four-channel monitor providing rod position measurements for two piston rods using an X-Y probe pair on each rod. The measurement is primarily a machinery management tool. The monitor provides alarms on rod position and rod position angle using data from the orthogonal probe pairs and position crank angle, peak to peak amplitude, gap, 1X amplitude, 2X amplitude, and Not 1X amplitude measurements for each of the horizontal and vertical probes. Applications – The 3500/72M monitor can be applied to any horizontal, vertical or V-shaped reciprocating compressor greater than 600 horsepower. For compressors less than 600 horsepower, consult sales representative. Installation - X and Y proximity probes must be mounted in an orthogonal arrangement. The probes should be mounted directly on the high-pressure packing gland. For single plane rod position measurements, the preferred probe orientation is in the true vertical. A Keyphasor® sensor is required (see the Crankshaft/Crankcase section).

Monitor configuration requires the following user supplied parameters: Proximity probe pair calibration data, physical mounting location and mounting angles Cylinder bore diameter Cylinder to bottom of piston clearance (rider band effective thickness) Cylinder to top of piston clearance (piston to cylinder effective clearance) • • • •




• • • •

Piston Material Piston rod length and diameter Probe Position Operating temperatures

Filtering – N/A Alarm / Danger - In the absence of OEM recommendations or engineering data the recommended* initial alarm and danger set points are:

Rod Position Alarm and Danger Initial Setpoints* Concentric Rider Bands Eccentric Rider Bands

Position Magnitude Alarm Position Magnitude Danger

(Piston Top Clearance > Piston Bottom Clearance)

(Piston Top Clearance < Piston Bottom Clearance)

(Piston Bottom Clearance) * 0.70 * (Probe Position / Piston Rod Length)

(Piston Top Clearance) * 0.70 * (Probe Position / Piston Rod Length)

(Piston Bottom Clearance) * 0.85 * (Probe Position / Piston Rod Length)

(Piston Top Clearance) * 0.85 * (Probe Position / Piston Rod Length)

Alarm/Danger Time Delay should be set for its maximum value of 3 seconds. *These should be adjusted based on actual operating conditions




Section 9 - Cylinder

Cylinder Pressure

Although not an API-618 recommended shutdown, Bently Nevada strongly recommends that customers use rod reversal as a shut down parameter. System 3500

Monitor

3500/77

Transducer 165855-XX Cylinder Pressure Transducer

The 3500/77M Cylinder Pressure Monitor is a four-channel monitor with provisions for inputs from up to four pressure transducers. Benefits - The most effective method to determine the overall health of a reciprocating gas compressor is through examination of the cylinder pressure profile. The cylinder pressure monitor provides on-line access to the internal pressure for each cylinder on the compressor. This enables continuous monitoring of rod reversal, peak compression rod load, peak tension rod load, cylinder pressures and compression ratios. This provides valuable information on the condition of suction valves, discharge valves, piston rings, packing glands, and crosshead pin.

The difference in calculating the forces for the crosshead pin and the connecting rod is the inertial mass of the crosshead is used to calculate the forces on the crosshead pin. It is not used to calculate the force on the piston rod. The OEM should be consulted in order to decide whether to monitor either crosshead pin forces or piston rod forces. Note: If the piston rod is necked down where it is bolted to the crosshead making it the weakest part of the running gear, then monitoring at the piston rod is be tter. If the crosshead yoke, crosshead pin or small end of the connecting rod is more susceptible to breakage, then monitoring at the crosshead pin is better. Typically, monitoring at the crosshead pin is the chosen point. System Description – Cylinder pressures are monitored through the use of permanently mounted pressure transducers located on each chamber of the cylinder. The cylinder chamber pressure along with crankshaft position is used for both continuous monitoring data and also performance data. Separate alarm and danger set points can be set for each continuous monitored point.

Continuous monitoring data includes the following Discharge pressure Suction pressure Maximum pressure for each crankshaft revolution Minimum pressure for each crankshaft revolution Compression ratio • • • • •




• •

Peak rod load for both compression and tension Number of degrees of rod reversal

With an interface to System 1® software, the following performance data is generated from the cylinder pressure monitor data output: Indicated horsepower Capacity at suction conditions Capacity at discharge conditions Suction horsepower losses Discharge horsepower losses Indicated clearance Flow balance of suction to discharge Median capacity between suction and discharge capacity Adiabatic flow balance between adiabatic discharge and suction Power to median capacity Displaced volume Adiabatic discharge temperature • • • • • • • • • • • •

With an interface to System 1® software, the following software plots are generated from the cylinder pressure monitor data output: Pressure versus displaced volume (P-V Diagram) Log pressure versus log volume (Log P – Log V Diagram) Combined rod load versus crank angle Gas rod load versus crank angle Pressure versus crank angle Pressure versus time • • • • • •

Applications – The 3500/77M monitor is applicable to all reciprocating gas compressors with either single or double acting cylinders in either single or tandem arrangements. Installation – Pressure ports are required on each chamber of the cylinder. Refer to API 618, Section 2.6.4.6 (4th Edition), for cylinder pressure port requirements. Cylinder pressure transducers mount to an isolation valve. Typically, this is a Kiene double block and bleed isolation valve that mounts on the cylinder pressure ports. A multi-event Keyphasor® transducer is strongly recommended (see multievent Keyphasor® system). When retrofitting an existing cylinder without pressure ports, an indicator ported suction valve assembly can be used to provide a cylinder pressure tap. Filtering – N/A Alarm / Danger – In the absence of OEM recommendations or engineering data the recommended* initial alarm and danger set points are: Rod Reversal (reference API paragraph 2.4) Alarm: Less than 25 degrees of rod reversal Danger: Less than 15 degrees of rod reversal *These should be adjusted based on actual operating conditions




Valve Temperature

Valve temperature is not typically a shutdown parameter. System

Monitor 3500 3500/60 (no recorder output) 3500/61 3500/65 (no recorder output) * - Only supports isolated (non-grounded) thermocouples


Suction and discharge valves are typically the highest maintenance items on a reciprocating compressor. Faulty valves can significantly reduce the efficiency of the compressor. The temperature monitor displays the temperatures of the compressor valves and can help manage your valuable reciprocating equipment. Benefits - The benefits of monitoring valve temperature monitor include the following: Detect bad or damaged valves at an early stage. Bad valves can result in reduced capacity, reduced efficiency, and damage to the cylinder liner due to valve parts falling into the cylinder. Determine if gas leakage is occurring between the head and crank ends of the piston due to damaged or worn piston rings. •

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System Description- During normal process conditions, an increase in the gas temperature near a valve is a primary indication of a failing valve. The temperature monitor provides early warning of valve temperature changes and allows the operator to identify the bad valve(s). Applications - By recompressing the same gas, a leaky valve becomes hotter than normal, causing the valve cover plate temperature to increase. Since the normal operating temperature of each valve varies with changes in load, gas stream and ambient temperature, it is necessary to compare the temperatures of similar valves in the same process conditions. Measuring the differential temperature between these valves provides an early and reliable indication of a degrading valve. If a valve is unloaded, however, it may affect the temperature of that individual valve and can cause a wide variation in temperature.

Leaking piston rings will cause the temperature of the entire cylinder to increase through the reworking of gas between each side of the piston. Therefore, detecting changes in absolute valve temperature is also important. If a temperature increase for all valves in the same cylinder is not due to a process change or lubrication problem, it is most likely due to piston ring leakage. Both intake and discharge valves at the head end and crank end will show an increase in temperature due to piston ring leakage. Installation – The thermocouple or RTD should be placed as close to the valve as possible. However, in most installations the temperature probe mounts on the valve cover.

With the new o-ring type valve cover, installation of the probe into the gas passage is possible. This is accomplished by mounting a thermowell directly to the valve cover that enters the gas passage. The thermowell should extend into the gas passage as far as possible allowing placement close to the valve. Under no circumstance should the valve jackbolt be altered in anyway without review and specific recommendations from the OEM. 2006 Bently Nevada LLC Page 23 of 25 ©



Filtering – 50 or 60Hertz line noise rejection on 3500/60 or 3500/61. Indicated Temperature Alarm / Danger – In the absence of OEM recommendations or engineering data the recommended* initial alarm and danger set points are: Alarm: 20 oF (11ºC) above normal suction or discharge temperature Danger: 30 oF (17ºC) above normal suction or discharge temperature *These should be adjusted based on actual operating conditions Temperature Relative to Group Alarm / Danger – In the absence of OEM recommendations or engineering data the recommended* initial alarm and danger set points are: Alarm: 20 oF (11ºC) above other valves in same group Danger: 30 oF (17ºC) above other valves in same group *These should be adjusted based on actual operating conditions




Discharge Temperature

Bently Nevada strongly recommends that customers use discharge temperature as a shutdown parameter. It is a recommended shutdown parameter in API 618. System 3500

Monitor 3500/60 (No recorder output) 3500/61 3500/65 (no recorder output) * - Only supports isolated (non-grounded) thermocouples


Discharge temperature is one of the first parameters used to monitor the condition of reciprocating compressors. Discharge temperature gives a good indication of overall cylinder health. Benefits - Monitoring of discharge temperature can give an indication of worn valves, unloaders, piston rings, inadequate lubrication, excessive compression ratio, or insufficient cooling water. Applications – Should be standard on all reciprocating compressors. Installation – The temperature sensor should be mounted in the discharge line as close as possible to the cylinder. This is typically in the neck of the discharge nozzle. Filtering – 50 or 60Hertz line noise rejection on 3500/60 or 3500/61. Alarm / Danger – In the absence of OEM recommendations or engineering data the recommended* initial alarm and danger set points are: Alarm: 20 oF (11ºC) above normal maximum** Shutdown: 30 oF (17ºC) above normal maximum** *These should be adjusted based on actual operating conditions **Not to exceed OEM recommended operating limits




API Recip Compressor Best Practices 0300_060814

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