Air Jet Manual

Air jet erosion test rig as per ASTM G76

USER MANUAL OF AIR JET EROSION TEST RIG AS PER ASTM G76

By, M/s. Magnum Engineers Peenya, Bangalore-58.

M/s Magnum Engineers, Peenya, Bangalore www.magnumengg.com

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CONTENTS 1. INTRODUCTION

2. TYPES OF EROSION RIGS

3. DESCRIPTION OF THE EQUIPMENT

4. MAJOR PARTS OF AIR JET EROSION TEST RIG

5. TEST PROCEDURE

6. MAINTENANCE & SAFETY

7. PHOTOGRAPHS OF AIRJET EROSION TEST RIG


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PART I GENERAL INFORMATION WARRANTY The equipment is warranty for a period of 12 months from the date of instillation. When the consignment reaches your place, please check the items as per the list provided along with the machine. If there any short or any damage found please send E-mail or inform us over the below telephone number immediately. 1. 080-41170935 2. E-mail: [email protected] SAFETY PRECAUTIONS

The AIR JET EROSION TEST RIG AS PER ASTM G76 is an electro-mechanical Device. Please follow the instructions carefully.

Personnel injury may be resulted by improper operation.

The equipment may be damage by improper operation.

Only our service engineer installs and services the equipment.

Please ensure proper earthing.

Voltage between Earth and Neutral should be less than 5 Volts.

Do not attempt at wire circuitry while power is ON.

Do not attempt to examine the components and signals when the equipment is ON.

Do not attempt to disassemble or modify internal circuitry or wiring.


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INTRODUCTION The solid particle erosion is a form of material degradation caused by the impact of hard particles against a target material, at reasonably high velocities (>10 m/s). Mechanically solid particle erosion is quite different from the other form of erosion like liquid impact erosion and cavitations erosion, since the contact between the contact between the hard particle and the material is only momentary during erosion. It is different from other related wear processes like sliding wear, abrasion, grinding and machining. Solid particle erosion (henceforth referred to as erosion) is immense technological and economic importance as illustrated in the following examples: The performance of aircraft and helicopters operating in dusty environment Industrial gas turbines burning coal as fuel deteriorate both structurally and aerodynamically in the presence of solid particles in the fluid. Bulk particulate matters are transported from one location to another by pneumatically conveying them through pipelines. Erosion of these pipes at the bends and changes in direction is a severe problem especially when the conveying product is abrasive and angular. Definite interrelationship has been established between the maximum depth of penetration and the mass erodes, phase density, and mean particle size and the bends geometry. Erosion is a severe problem in coal gasification and liquefaction plants. Plant failure analysis indicates that two third of the reported failures are material related. Of this one third were due to erosion. Gun barrel undergoes erosion during firing of a round from the barrel, hot gases move down the barrel, behind the accelerating projectile at velocities greater than 500 m/s, sufficiently high to scour the metal ROM the surface. The entrainment of solid particle of combustion unburned propellant and wears debris formed by sliding wear causes erosion of the barrel material. A wide range of equipment’s used in the oil industry and the thermal power plants suffer significant erosion. To develop the erosion resistant materials and coatings for various applications one needs specialized test facilities. In the area of erosion testing the situation is particularly bad since only very recently ASTM (American Society for Testing and Materials) published a standard for solid particle erosion testing procedure. In addition erosion rigs are not being manufactured anywhere in the world on a commercial basis. Therefore, the erosion rigs have to be fabricated locally. The design of erosion rig requires the consideration of a few important aspects; firstly, the actual operating conditions relevant to the system of interest should be characterized. Typically, the following information should be available.


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The velocity and the angle of impact of particles on the component surface. System temperature and pressure Impacting particle size, shape, density, hardness The nature and inertness of the fluid carrying particles The concentration of the particles in the fluid i.e. phases density. In most of the cases the data on impact velocity and the attack angles is hard to come by due to the inaccessibility of the component of interest. In such a situation, the computer modeling of the component and the simulation of the two-phase particle – fluid flow behavior will be necessary to arrive at the reasonable values of velocity and angle. It may be noted that even though the most of the test parameters listed above are easily obtainable, the test rig should be built over a range around these known values of test parameters. Secondly, the effect of various parameters like temperature, impact velocity, and angles, particle related properties on the erosion behavior must be known early on, either through comprehensive literature survey or on the basis of past experience. This is necessary because the erosion rig should simulate closely at least those parameters, which markedly influence the erosion rate. For example it’s well known that the rate of erosion is independent of the impacting particle hardness as long as it’s about twice the hardness of the target material. Therefore if the hardness of the eroding particle is more than twice that of the target material, a more suitable erodent has to be use TYPES OF EROSION RIGS Erosion is simulated in the laboratory by one of the methods. The “sand blast method “, where particles are carried in a stream of air and impacted into a stationary target and the”whirling arm method”, where target is spun through a chamber of particles. On the basis of high accuracy achievable and the design simplicity the present machine is based on sandblast type. A continues flow of dry air through a mixing chamber accelerates the erodent particles up to a high fraction of the air velocity. The particles then exit the nozzle in an erosive jet, where they impact a stationary target enclosed in a separate chamber. The distance of the nozzle and the target can be adjusted using a power screw mechanism to elevate or lower the entire specimen block. The erosion rate is calculated based on the weight loss method and wear mechanism can be studied using SEM. The erosion rigs are also classified based on velocity and temperature capabilities as: (i)High velocity (>10 m/s), room temperature (HVRT) erosion rig. (ii)High Velocity, high temperature (up to 400 C) (HVHT) erosion rig. (iii) Low velocity (<10 m/s), room temperature (LVRT) erosion rig. (iv) Low velocity, high temperature (LVHT) erosion rig


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DESCRIPTION OF THE EQUIPMENT The “Air Jet Erosion Testing Equipment “ designed and fabricated by M/s. Magnum Engineers, Bangalore is the first compact and light - weight erosion testing equipment ever built in India for solid particle erosion testing. The equipment is one of its kinds in terms of testing utilities, the user- friendly features it offers on the one-piece control panel and appeals with its pleasing esthetics. Built according to the ASTM (American Society for Testing and Materials) G-76 standards for erosion testing, the equipment can be used for testing polymers, coatings, steels, organic materials for wear loss due to erosion over a range of impinging velocities, particle sizes, particle flux and attack angles. Erosion, which is a process of wear, may be broadly defined as the progressive loss of material from a solid surface due to mechanical interaction between the surface and a fluid, a multi-component fluid or impinging solid or liquid particles. Specifically in the present machine the mechanical interaction is nothing but a momentary contact of the erosive particle with the specimen, which leads to scouring of the material and consequent loss of the original material. Erosion is an important wear mechanism in industrial applications. Despite the existence of ASTM and DIN standard methods, everyone has their own way of doing erosion tests. ASTM G 76 "Standard Practice for Conducting Erosion Tests by Solid Particle Impingement" in fact acknowledges that the one single laboratory test may not be sufficient to evaluate expected service performance. Actual erosion service can involve a range of particle sizes, velocities, attack angles & environments, all of which influence erosion rate. Key parameters to define and control in an erosion test are as follows: 1. Particle velocity. This is not the same as the air velocity, but is often assumed to be 3.3times the air velocity. 2. Particle mass flow rate 3. Nozzle wear 4. Particle spread from nozzle 5. Size and shape of particle 6. Angle of impact of the particles 7. Properties of the material are being tested.


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One particular feature of the ASTM G76 method is the fact that the very small jet diameter (1.5mm) results in the particles "drilling" into the surface. The standard states that the depth of penetration should not exceed 1 mm. This is a deep hole in any surface and in fact the deeper the penetration, the more the physical state of the erosion jet will change (due to interaction of the particles hitting the surface and rebounding). These very severe test conditions are not appropriate for coatings, for which the test must be designed to determine the wear of the coating, not the substrate material. The present machine serves at milder testing conditions in terms of attainable particle velocities and mass flow rates of the erodent. A related problem of a small nozzle size such as that defined by ASTM is that the nozzle will wear. This result in a change in the shape of the particle stream as it emerges from the nozzle and this will result in variability in the data. ASTM G 76 defines a nozzle of 1.5-mm inner diameter and 50 mm long. This small nozzle size means that there is a large backpressure and the abrasive sand has to be fed under pressure to achieve the required mass flow rates (2 +/- 0.5 g/minute). A pressure of 20 p.s.i. (1.4 bar) at the entry to the nozzle is typically required to give a particle velocity of 30 m/s. The nozzle does not have to be manufactured from Tungsten Carbide; instead they are made from standard seamless drawn type 304 stainless steel tubing. The internal surface finish can be carefully controlled and the cost of replacement nozzles when necessary is very low. The larger nozzle diameter results in a wider spread of particles which are therefore more suited to erosion testing on coatings as well as solid material: there is less of a tendency to "drill" holes in the surface; In addition, there is a much smaller influence of rebounding particles on the impinging jet, resulting in a better controlled erosion process. The larger nozzle size also permits a wider range of particle types to be used in the course of testing, allowing better simulations of real erosion conditions. The mass flow rate is controlled by use of a rotating grooved disc and particles are delivered from the groove to the air stream by way of venturi suction. Mass flow rate is adjusted by controlling the speed of the rotating disc. Particles are fed from a simple hopper under gravity into the groove. The air pressure and length of nozzle determine the velocity of the particles. A wide range of particle velocities is covered 27m/s (corresponding to 81m/s of air velocity) and a feed rate of 0.2 to 200 g/minute.


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Features: 1. Vertical traverse for the sample stage: provides variable height, which influences the size of the eroded area. 2. Different nozzles may be accommodated: provides ability to change the particle plume dimensions and the velocity range 3. Large test chamber with sample mount (typical sample size 75 mm x 25 mm) that can be angled to the flow direction: by tilting the sample stage, the angle of impact of the particles can be changed and this will influence the erosion process. 4. Optional heating system: permits “hot” tests up to 250°C 5. An erodent reservoir capable of storing an additional 3 kg of erodent.


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MAJOR PARTS OF THE AIR JET EROSION TEST RIG. 1. Abrasive storage Hopper (TOP).

2. Abrasive Flow Control Knob.

3. Abrasive Nozzle-Height Adjustment.

4. Vibrator Pad-Pneumatic Type.

5. Pressurized conveyor abrasive flow chamber

6. Specimen holding-heater block, heater, specimen sample, and indexing unit.

7. Double disc assembly-motor, upper disc with slit, lower disc without slit, arrangement to hold.

8. Dust collecting unit (gunny bag).

9. Display panels.

10. Air dryer.


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DISPLAY PANELS: 1. Digital Pressure indicator

2. Digital Preset timer indicator

3. Digital Preset temperature controller

4. Heater on-off switch

5. Pulse meter for rpm indication

6. Panasonic Conveyor speed controller

7. Double disc speed controller

8. Mains ON-OFF switch

9. Vibrator knob (For abrasive hopper)

10. Pressure regulator valve


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Description of Control Panels: Pressure indicator: which indicates the operating pressure of the system? Ex: 1.5bar This can be varied by pressure control knob During test condition once the pressure is set, don’t vary.

Preset time indicator: It is an instrument, which indicates set time for the test. Ex: Hr-Min-Sec

Temperature indicator and controller: It indicates set temperature for the test. It can also set for the required temperature value

Heater switch: It is provided for heater to ON-OFF. Pulse meter-Indicator: this indicates the speed of the double disc motor. Conveyor motor speed controller: It is used to set the conveyor motor for the required speed. It ranges from 4 rpm to 28rpm.

Double disc speed knob: This knob is used to vary or to set the required speed of the double disc motor. Here we can increase or decrease the speed of the double disc and also we can set for the required speed during calibration process. Maximum speed of the motor is 3000rpm. Main ON-OFF switch: this switch is used to ON/OFF the machine.

Double disc ON-OFF switch: this is a separate on-off switch given for Double disc system, which should be used during calibration process

Vibrator knob: this knob controls the flow of air to the vibrator, which is fixed on the sand hopper. This vibrator is of pneumatic type, by increasing or decreasing the flow rate air to the vibrator we can control the vibrating action of the sand hopper. By providing this type of vibrator, sand from hopper will flow freely without any disturbance.

Pressure regulator: pressure regulators are used to regulate the flow of dry air into the system. Required pressure can be achieved by varying the pressure-regulating knob. Before opening the pressure-regulating knob ensure for following. 1. Compressor is switched ON. 2. Compressor OUTPUT connected to dryer INPUT. 3. Dryer OUTPUT connected to test rig INPUT


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Safety Precautions: 1. Do not open the door during test condition 2. High velocity dry air along with abrasive from nozzle is harmful to body. 3. Do not inhale the abrasive dust, it is dangerous to health. 4. As soon as the test time completed, switch off the heater switch. 5. Remove the specimen; allow it to cool for sometime. 6. Use recommended abrasive size. 7. Do not use the sand that as already used for the test. 8. Double disc arrangement must be kept in safe place. 9. Use safety gloves to remove heated sample after the test completes. 10. Use safety goggles while testing is going on.


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Test procedure: 1. Check that all the switches, knobs and valves are in OFF position. 2. Clean the test rig before the test starts. 3. Connect the test rig to 230V 50 Hz supply. 4. Start the compressor. (Ensure pressure regulator valve is closed) 5. Connect outlet of compressor to input of dryer, output of dryer to air inlet provided on backside of the test rig. 6. Switch on the dryer. 7. Switch ON the mains. 8. Place the specimen on the specimen holding block and clamp firmly using the clamping fingers provided. (Before placing clean the specimen and weigh the specimen on the electronic balance to know the initial weight of the specimen). 9. Maintain 10mm distance between specimen surfaces to nozzle tip (ASTM STANDARD) and tilt the specimen holding block for the required angle. 10. Fill the abrasive storage hopper with abrasive. 11. Adjust the sand nozzle for the required height by adjusting the nut (knurled round nut).(gap between abrasive flow nozzle and abrasive feed conveyor 1. Set the conveyor motor for the required speed. 2. calibrate for the abrasive flow rate (gm/min) 3. Switch ON the heater and set the heater for the required temperature.(if the test based on temperature)

4. Set the preset timer for the required test period in HH-MIN-SEC.


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5. Release air to sand vibrator, which starts to vibrate. 6. Close all the doors. 7. Open the pressure-regulating valve for the required operating pressure. 8. Press the cycle start button. 9. Once the test time is completed, air is closed, switch OFF the heater, open the door, and allow the specimen to cool for sometime. 10. Remove the specimen, clean it and reweigh the specimen on electronic balance.(0.1mg) 11. Difference in weight loss can be observed. 12. Once the specimen is removed, close all the valves, knobs and switches. 13. Clean the test rig for every test.


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PROCEDURE FOR DOUBLE DISC METHOD TO FIND PARTICLE VELOCITY

Place the double disc arrangement unit in its position and clamp it firmly by tightening the thumbscrew provided.

Remove the upper disc.

Set the speed of the lower disc to 1500 to 3000 rpm.

Apply the lapping paste on the surface of rotating lower disc; apply light pressure on the disc with scratch pad in order to remove the impressions of last test.

Observe for removal of sand impressions.

Clean the disc with good cloth or tissue paper.

Stop the rotating disc, once again clean well for no mark or impressions.

Place the upper disc on the lower disc, which has got slits on four sides on its circumference.

Mark the reference line on the lower disc with respect to the upper disc slots.

Tighten the disc firmly provided Allen screw.

Switch on the double disc and set the known RPM.

Set the pressure regulator for the required pressure.

Set the test period through pre set timer.

Set the conveyor speed for sand displacement.

If the abrasive not flowing properly, open the pneumatic vibrator for easy flow of sand.

Close all the doors.

Press the cycle start button.

When the test duration completes, turn the pressure regulator, pneumatic vibrator, double disc speed and conveyor speed knob to zero position.

Remove the double disc arrangement from its position; clean the arrangement with good cloth or through acetone.

Remove the upper disc and observe the impressions made by sand particles on lower disc during the test period.

Calculate the particle velocity in m/sec as per the procedure given below.


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Procedure for calculating the particle velocity: Sand impressions

Lower disc

We know that S= R* Ø Where, S= sector length in mm R= radius of the lower disc in mm

S

Ø = angle in radians

Ø R

Particle velocity (Vp) is given by the formulae 2×22÷7×N×R×L

m/sec

60×S

Where, Vp

particle velocity in m/sec

N

speed of the double disc rev/min

R

radius of the lower disc in mm

L

distance traveled by sand particles, or distance between upper disc and lower disc in

mm S

sector length in mm


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Ensure: 1. Proper size abrasive in the abrasive hopper. 2. Ensure that proper size specimen is placed and fixed rigidly. 3. Ensure for compressor is ON and pressure regulator is in OFF condition while starting the compressor. 4. Ensure that the specimen is cleaned and weighed on electronic balance before placing the specimen on specimen holding block. 5. Ensure for proper hold of the double disc assembly by tightening the knob provided on the holding unit during calibration process. 6. Ensure for the diameter of the nozzle. 7. Ensure for test temperature before cycle starts. 8. Ensure for all doors are closed before test starts.


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Maintenance and Safety:

1. Clean the machine for every test. 2. Use moisture free dry abrasive, so that abrasive will flow freely from abrasive flow nozzle. (Heat the abrasive in oven for 10min at 120 degree centigrade.) 3. Keep safely the double disc arrangement when it is not in use because if the slit on the upper disc is damaged, there will be an error in calibrated readings.

4. Polish the lower disc for every test, such a way that the centerline on the disc must be visible. 5. The distance between upper disc and lower disc must be 25mm. 6. Adopt safety procedures while conducting test. 7. While test is going on don’t open the front doors. 8. After the test completes, allow the specimen for 5 minutes for cooling if the test is temperature based.


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PHOTOGRAPHS OF AIR JET EROSION TEST RIG


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AIR JET EROSION TEST RIG AS PER ASTM STANDARD G76


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TOP FRONT PANEL OF AIR JET EROSION TEST RIG

BOTTOM FRONT PANEL OF AIR JET EROSION TEST RIG


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TEST PRESSURE INDICATOR

TEST PERIOD INDICATOR

TEST SET TEMPERATURE INDICATOR


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SPECIMEN HEATING ON/OFF

DOUBLE DISK SPEED INDICATOR

ABRASIVE CONEVYOR SPEED CONTROLLER M/s Magnum Engineers, Peenya, Bangalore www.magnumengg.com

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DOUBLE DISC SPEED VARIABLE KNOB

DOUBLE DISC ON /OFF KNOB

CONTROLLER ON/OFF M/s Magnum Engineers, Peenya, Bangalore www.magnumengg.com

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TEST CYCLE START PUSH BUTTON SWITCH

TEST CYCLE STOP PUSH BUTTON SWITCH

VIBRATOR AIR FLOW CONTROL KNOB


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05

01

06 07

08

02

09 10 03 11

04 12 ABRASIVE FLOW CONEVYOR SYSTEM 01. AIR INLET TO ABRASIVE STORAGE HOPPER 02. SEALING DOOR 03. AIR PRESSURE SENSOR 04. STAND OF DISTANCE FOR ABRASIVE FLOW ADJUSTMENT KNOB 05. ABRASIVE STORAGE HOPPER 06. PNEUMATIC VIBRATOR 07. AIR INLET TO PNEUMATIC VIBRATOR 08. LOCKNUT 09. ABRASIVE FLOW NOZZLE 10. ABRASIVE FLOW CONEVYOR 11. SEALING DOOR CLAMPS 12. AIR AND ABRASIVE COMBUSTION CHAMBER M/s Magnum Engineers, Peenya, Bangalore www.magnumengg.com

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03

02 04 05 06 07 01

08 SPECIMEN HOLDING ARRANGEMENT

01. ANGLE VARIATION KNOB 02. STAND OF DISTANCE ADJUSTMENT 03. X- AXIS MOVEMENT 04. CARBIDE NOZZLE 05. SPECIMEN CLAMPING SCREWS 06. SPECIMEN 07. SPECIMEN HEATER BLOCK 08. Y-AXIS MOVEMENT


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03 02

04

01

05

SPECIMEN AND CLAMPING ARRANGEMENT 01. SPECIMEN CLAMPING FINGERS 02. HEATER BLOCK HOLDER 03. CARBIDE NOZZLE 04. SPECIMEN 05. HEATER BLOCK


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UNIT FOR HOLDING DOUBLE DISK ARRANGEMENT


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DRY AIR TO TEST RIG

AIR INLET FROM COMPRESSOR

AIR DRYER UNIT


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01 02

03 POWER SUPPLY UNIT 01. MAINS ON/OFF 02. POWER CABLE 03. FUSE


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01 05

02

04 03

SPECIMEN HOLDING UNIT

01. SAND NOZZLE 02. SPECIMEN HOLDING CLAMPS 03. CLAMPING SCREWS 04. SPECIMEN 05. SPECIMEN HOLDING BLOCK


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02

04

03

X Y, Z & θ AXIS

01. X-AXIS MOVEMENT 02. Z-AXIS MOVEMENT 03. INDEXING HEAD (0°TO 90° WITH 2° LEAST COUNT) 04. Y-AXIS MOVEMENT


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DOUBLE DISC UNIT HOLDER

Upper disc with slit Lower disc

DOUBLE DISC ARRANGEMENT


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Air Jet Manual

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