Centrifugal Compressor Testing

The centrifugal compressor testing article provides you with information about the centrifugal compressor mechanical running test and centrifugal compressor thermodynamic performance test. This content also covers what is called the centrifugal compressor factory acceptance test.

This article is a supplementary article for the Third Party Inspection for Centrifugal Compressor.

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.

Centrifugal Compressor Testing - Applicable Standards

The applicable standards for these tests are:

  • API Standard 617; Centrifugal 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

Required Data for Centrifugal Compressor Mechanical Running Test

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 Speed
  • 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

Preparation for Centrifugal Compressor Mechanical Running Test

Normally a check list is used for controlling which all 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

Centrifugal Compressor Testing - Mechanical Running Test

The mechanical running test is done with the following sequence:

  1. The speed increase from standstill up to minimum driver control speed.
  2. Speed increase in steps of approx. 10% of maximum continuous speed up to maximum continuous speed (MCS) under consideration of the lateral natural frequencies.
  3. Continuations of operation until lube oil and bearing temperatures have stabilized.
  4. 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.
  5. 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.
  6. Speed increase up to trip speed.
  7. 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.

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.

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


  • 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


  • Gas Power
  • Compressor Speed

Centrifugal 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.

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

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