Pneumatic Test Procedure

Pneumatic Test Procedure


This document describes the general procedure used for the leak test of piping system requiring this method of leak detection.

Testing Apparatus

Test pump, hose and fittings connections, test medium, a calibrated pressure gauge to monitoring test pressure, pressure recorder may be used to record variable of test pressure, torch flash for visual inspection of leakage, gas detector or soap detergent solution. The pressure gauges and recorder shall be calibrated within 12 months, range of pressure gauge shall not be less than 1.5 times and not more than 4 times.

Safety precautions

Display suitable warnings on the equipment and in the testing areas.

To confirm bolting materials are corrected and met specifications.

Test pump shall constantly attend by experience operator during testing.

Pressure gauges to be monitored by operator during the test.

Test medium

Test medium shall be dried air or nitrogen.

Test package preparation

The test package shall be submitted for approval include a minimum:

  1. A list of all piping spools or equipment,
  2. GA drawings, P&ID drawings or Isometric drawings,
  3. Test pressure,
  4. Test medium,
  5. Pressure gauges, pressure recorder, thermal temperature,
  6. Pressure test certificate sample,
  7. Calibrated certificates,

Preparation and execution

All examinations and stress relieving activities have to complete before testing.

All raised face of flanges and thread end shall be inspected in good condition and make sure no damaged or deformation.

A pressure relief device shall be installed, having a set pressure not higher than the test pressure plus the lesser of 345 kPa (50 psi) or 10% of the test pressure.

All connections by bolting, threading shall be tightened and sealed by its nut.

One pressure gauge shall install at a higher point, other pressure gauge(s) shall install at nearly location for monitoring and control by operator.

Barricade must be limited at the testing area with display signboard with “KEEP AWAY HYDROTEST IN PROGRESS”.

Pneumatic tests will perform by operator under supervision of Supervisor and QC inspector.

The test pressure shall not less than 1.1 times of the design pressure and shall not exceed of the lesser of 1.33 times of the design pressure.

The pressure shall be gradually increased in steps until the test pressure is reached, holding the pressure at each step long enough to equalize piping strains. The pressure shall then be reduced to the design pressure before examining for leakage.

Liquid detergent soap shall be used for leak detection. Application of the solution shall be in a continuous film relatively free from bubbles. Any indication of bubbles shall be investigated for the location of leakage and retest is required

A minimum holding time of test pressure shall at latest 10 minutes or enough time for visual inspection.

Temperature measurement of test medium may be recorded during the test.

The QC inspector shall monitor the testing process and verify that there is no leakage.

Upon completion of the test, test medium shall be drained and unbolt flange joint.

All raised face of flange and thread ends shall be properly protected in good condition.


  1. If test medium was nitrogen, it may be maintained in an internal system approximately 5 psig for internal blanket purpose.
  2. If the flanged joint are connected by non-asbestos gasket, please do not directly spray to gasket, it should be cover the flanged joint by tapes.

Acceptance criteria

Pressure tests are successful if no leaks, no cracks and no deformations found.

If leakage found on products or product welds, their location shall be recorded/marked in drawing and forward the report to QC Engineer for investigation before re-testing.

If leakage found on flanged joints, threaded joints, the pressure shall be reduced to zero and rectify before re-starting test.

No welding shall be performed on the equipment during testing.


The completion of test package includes:

  1. Client’s job number / project number,
  2. Job number,
  3. Duration of hydrostatic test,
  4. Pressure gauge and recorder,
  5. Calibration certificate of instruments,
  6. Date of test,
  7. Tag name or piping spool number,
  8. Test medium,
  9. Test pressure,
  10. Test temperature,
  11. Test results,