Reciprocating Compressor Testing

The reciprocating compressor testing article provides you information about reciprocating compressor mechanical running test and reciprocating compressor thermodynamic performance test procedures. This content is supplementary article for Third Party Inspection for Reciprocating Compressor article.

This content also covers what is named reciprocating compressor factory acceptance test.

Both tests are done separately. The purpose of these tests is to verify the specified mechanical properties and the specified thermodynamic performance data of the compressor.

Reciprocating Compressor Testing - Applicable Standards

The applicable standards for these tests are:

  • API Standard 618; reciprocating Compressor for Petroleum, Chemical and Gas Service Industries
  • ASME PTC 10; Performance Test Code on Compressors and Exhausters
  • BS EN ISO 5167-2; Measurement of fluid flow by means of pressure differential devices inserted in circular cross-section conduits running full - Part 2: Orifice plates
  • BS ISO 5389 Turbo compressors Performance Test Code

Reciprocating Compressor Testing - Mechanical Running Test at manufacturer's shop

The following components are used from Job equipment

  • Compressor main unit
  • Lube oil unit

The following components are used from test stand

  • Motor
  • Pressure gauge
  • Temperature gauge

The following components are not used in the test

  • Suction/Discharge Valves
  • Surge Drum
  • Gas Piping
  • Drum/Piping Support
  • Instrument

The compressor is assembled in test stand in manufacturer's shop. The the cylinder valves would not be installed to perform non-load continuous operation.

The compressor is operated at the specified rotating speed for 4 hours continuously and mechanical stability, temperature, pressure, vibration and noise are checked.

After 4 hours continuous operation the reciprocating compressor needs to be stopped and bearing temperatures to be measured.

Then the reciprocating compressor is diassmbled and strip down inspection is done based the requirement of inspection and test plan.

Measurement items during Mechanical running test

Rotating Speed

The rotating speed is measured by a tachometer every 30 minutes. The measurement value to be an average value of those indicated by the tachometer.

Rotating speed need to be be within of the specified rotating speed.

Oil Temperature

The supplied and discharged oil temperature of crankcase is measured by temperature gauges in the shop lube oil unit every 30 minutes.

The supplied and discharged oil temperature needs to be within specified values.

Oil Pressure

The supplied oil pressure of crankcase (bearings)and discharged oil pressure of lube oil pump are measured by pressure gauges in oil unit every 30 minutes.

The obtained values need to be in within specified values.

Vibration

The vertical and horizontal vibrations of crankcase are measured at two locations by the use of a shop vibration meter. Also, the vibration at cylinder is measured with respect toaxial, horizontal and vertical directions by the use of a shop vibration meter. Vibration measurement needs to be done once during test operation.

The vibration of crankcase (peak to peak) needs to be within specified values.

Noise

The noise is measured at a distance of 1 m from the side of the main unit and four directions by using a shop noise meter. Noise measurement to be done once during test operation.

The obtained noise value need to be within specified value.

Temperature Measurement After Test Operation

The temperature for each of the following bearings just after stopping the 4-hour continuous test operation need to be measured.

  • Temperature of main bearing
  • Temperature of crank pin bearing
  • Temperature of cross head pin

The measured values need to be within specified values.

Lube Oil Console Running Test

After completion of successful oil flushing the lube oil console running test needs to be done. Running test would be performed based on the following conditions for 4 hours, and temperature and pressure shall be measured every 30 minutes.

  • Oil grade as per design
  • Lube oil pressure as per design
  • Lube oil temp as per design
  • Motor speed as per design
  • Start up as per design (generally cold condition)

No leakage must be seen during the test and Pressure drop of filter element shall not exceed a specified value at operating oil temperature. No abnormal sound shall be confirmed during the running test.

Tempered Cooling Water Console Running Test

After completion of successful cooling water flushing the tempered cooling water system running test needs to be done. Running test would be performed based on the following conditions for 4 hours, and temperature and pressure shall be measured every 30 minutes.

  • Fluid as per design (water with inhibitor or etc.)
  • Pressure as per design
  • Temperature as per design
  • Motor speed as per design

No leakage must be seen during the test and no abnormal Pressure drop must be confirmed. No abnormal sound shall be confirmed during the running test.

After checking of the above items at two times, the water pump is changed to another and the same items needs to be checked.

Reciprocating Compressor Testing - Thermodynamic Performance Test Procedure

The reciprocating Compressor thermodynamic performance test is similar to the centrifugal compressor. You may review Centrigugal Compressor Testing for detail test instruction.

Following data need to be extracted from a centrifugal compressor design book, datasheet and operating manual and to be available during the test.

Specified Operating Speeds

  • Normal Operating Spee
  • Minimum Operating Speed
  • Maximum Continuous Speed
  • Trip Speed

Maximum Shaft Vibration

  • At Maximum Continuous Speed
  • At Trip Speed

Lube Oil Data

  • Oil Viscosity Class
  • Oil Inlet Temperature
  • Oil Inlet Pressure
  • Maximum Oil Volume Flow Of Compressor

Shaft Seals

  • Seal Type
  • Seal Medium

Reciprocating Compressor Testing Preparation for Mechanical Running Test

Normally a check list is used for controlling which of items are based design and actual operating condition.

The following components are used from Centrifugal Compressor Test Stand (Not Original)

  • Drive unit (Electric motor)
  • Gear box
  • Coupling (poss. with adapter)
  • Intercooler
  • Oil unit
  • Process gas piping
  • Instruments
  • Vibration monitoring system
  • Data acquisition equipment

The following components are used from centrifugal compressor (original)

  • Coupling (poss. with adapter) X
  • Seal gas panel
  • Instruments
  • Shaft vibration measurement equipment

Note: The coupling and instruments are used from both systems i.e. test stand and original components of compressor

Reciprocating Compressor Testing - Mechanical Running Test

  1. The mechanical running test is done with the following sequence:
  2. The speed increase from standstill up to minimum driver control speed.
  3. Speed increase in steps of approx. 10% of maximum continuous speed up to maximum continuous speed (MCS) under consideration of the lateral natural frequencies.
  4. Continuations of operation until lube oil and bearing temperatures have stabilized.
  5. Speed increases up to trip speed. Test runs for 15 minutes at trip. Babbitt metal temperatures, oil inlet and outlet temperatures and pressures and the overall oil volume flow are measured and recorded once. Shaft vibrations are measured and recorded once at all contact measuring locations.
  6. Speed deceleration to MCS. Test runs for 4 hours at MCS. Babbitt metal temperatures, oil inlet and outlet temperatures and pressures and the overall oil volume flow are measured and recorded in intervals of about 20 minutes. Inlet and outlet temperatures and pressures of the handled fluid are measured and recorded. Shaft vibrations are measured and recorded at all existing measurement points in intervals of about 20 minutes. A vibration spectra analysis is carried out approximately in the middle of the 4 hours test run.
  7. Speed increase up to trip speed.
  8. Speed deceleration to final standstill.

Unfiltered and filtered displacement amplitudes and the corresponding phase angles will be recorded and plotted vs. speed during coast down. Bode plots during coast down.

After completion of the mechanical running test and after sufficient cooling-down the compressor will be checked according to the inspection and test plan.

Reciprocating Compressor Testing - Vibration Measurements

Shaft vibrations and axial displacements are measured. Vibration measurements are carried out with the vendor measuring system. All other necessary instrumentation for vibration analysis needs to be available by centrifugal compressor vendors.

For assessment of the allowable amplitudes of the shaft vibrations according to design the monitoring systems installed in the test stand are used. For visualization and preparing plots a mobile diagnostic system are used.

Run out is determined and recorded. Only these values are binding for the machine. At low speed the shaft vibration monitor only indicates the slow-roll-signal.

If the measured slow-roll-signal values during the test run exceed distinctly the specified run out values, run out are controlled and, if necessary, refurbished after completion of the test run without repeating the test run.

Reciprocating Compressor Testing - Required Data for Thermodynamic Performance Test

Following data need to be extracted from a centrifugal compressor design book, datasheet and operating manual and to be available for calculations.

Operating Conditions

  • Gas Type
  • Mass Flow, Wet

Inlet conditions

  • Pressure
  • Temperature
  • Relative Humidity
  • Inlet Volume, Wet

Discharge Conditions

  • Pressure
  • Temperature

Performance

  • Shaft power at compressor coupling (incl. losses)
  • Compressor speed
  • Polytropic head
  • Polytropic efficiency

Similarly the test medium and related operating parameter need to be identified. N2 normally is used as the test medium. Following also need be specified:

Test Meduim Inlet Condition

  • Pressure
  • Temperature
  • Relative Humidity
  • Gas Constant X Compressibility Factor
  • Inlet Volume Flow, Dry

Test Meduim Discharge Condition

  • Pressure
  • Temperature

Performance

  • Gas Power
  • Compressor Speed

Reciprocating Compressor Testing - Thermodynamic Performance Test Procedure

Before starting the thermodynamic performance test the compressor is operated for a sufficient period of time at the calculated test conditions to demonstrate acceptable mechanical operation and stable values of all measurements.

All instruments are inspected separately and the measured variables in identical measuring planes are compared to each other.

The duration of the test is depending on the time needed to reach steady-state test conditions. This condition is insured by steady-state values of pressures and temperatures.

An automated data acquisition system is used. The data are recorded, processed and displayed online.

Reciprocating Compressor Testing - Measuring and Analysis

Previous to the test all measuring instruments for pressure and temperature are calibrated. On customer's request the calibration can be redone after the test for one instrument each for pressure and temperature at the inlet and discharge port.

The inlet and discharge pressures and temperatures are measured on the basis of the applicable documents.

The mass flow is measured according to BS EN ISO 5167-2

The shaft power will be calculated with the heat balance method.

For the mechanical power losses the design value is used.

The Reynolds Number correction is done in accordance to ICAAMC.

Measuring uncertainty per BS ISO 5389

Related Articles:

TPI Inspection for Reciprocating Compressor, TPI Inspection for Centrifugal Pump, TPIInspection for Gas Turbine, TPI Inspection for Steam Turbine, TPI Inspection for Fan and Blower, TPI Inspection for Centrifugal Compressor, Screw Compressor Testing,Centrifugal Pump Performance Test, Centrifugal Compressor Testing, Fan Mechanical Running test, Fan Performance Test


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