Pressure Test Procedure

1. General
Pressure testing shall be carried out in accordance with ASME B31.3, or the premised piping code used in piping specification. The test pressure shall be derived based on the design pressure of the Piping Class, multiplied by the factor as required by the design code. The test pressure for all lines shall be specified in Line List.

Hydrostatic testing shal not take place with system temperature 4°C or less or where the ambient temperature during test falls by 5°C or more, nor during rain or fog unless under suitable cover. Hydrostatic pressure test may however be performed under a lower temperature with a proper frost preventive added to the test water.

The test pressure of Hydraulic system (System No.10) shall be 1.5 x System design pressure/Equipment design pressure instead of Design pressure of piping class.

2. Preperation for Pressure Testing
Upon completion of COMPANY internal testing witness and test accepted by QM, notification for pressure testing shall be submitted to COMPANY for witnessing 24hrs before test. Test package shall be made available at testing area with all reports form and relevant drawings.

Minimum one gauge shall be positioned at the highest point and one recorder to be positioned at the lowest point. Accuracy of pressure gauge shall be at least 1 - 2% at full scale and 1 - 2% for the recorder. The test pressure shall be within 60% of the gauge range (20% from top and 20% from bottom). If there is a deviation of more than 2% between gauge and recorder during test, the test shall be stopped and equipment recalibrated.

Detail design of the test manifold shall be submitted for COMPANY review and approval. 100% NDE (RT, UT & MT) shall be applied and evaluated to ASME B31.3 requirement. Test manifold welds shall be performed by qualified welders.

Testing manifold for which has pressure gauge, ball valves and safety relief valve or equivalent pressure test device shall be installed before the piping system. The test manifolds design pressure shall be equal to or greater than the highest test pressure to be performed. Manufacturing data, drawing and test certificate of manifolds shall besubmitted for COMPANY review and approval. Temperature and pressure gauge and recorders shall be calibrated in accordance with recognized calibration standard and procedure, depending on type and model.

Schematic drawing or test manifold (Equivalent equipment may substitute below schematic configuration)

Unless otherwise noted, all valves are to be through body tested. First block valve for pressure instruments shall be included in the test.

If valves are included in the pressure test, the following applies; ball, plug, slab gate valves and other valves where the cavity pressure may differ from the bore pressure, shall be pressure tested in the half open position. All other valves shall be tested in the fully open position. When check valves are included in pressure test they shall be jacked open or have their internals removed.

Where the test pressure to be applied to the piping is greater than the maximum allowable test pressure for valves, the valves shall be blinded off on the side to be tested, or removed and replaced by dummy spools.

Turbines, pumps, compressors and vessels shall be blinded off prior to pressure testing.

A list shall be prepared for sensitive equipment (i.e. expansion loint, relief valves, inline instruments and etc.) that shall be removed, blocked off or isolated during testing.

Temporary supports shall be installed as necessary to prevent excessive stress on the piping system. Special consideration shall be given to supporting gas piping system and system having spring / counterweight supports, expansion loints or loops. The spring supports or other variable type supports shall be blocked to prevent movement, manufactures recommendation to be obeyed.

All piping joints and welds shall not be insulated until pressure testing is certified as competed. Special section is required to clarify the system with no possibility of pressure testing (Due to open end like as open drain and vent system) that can be full of water visual only.

3. Hydrostatic testing
Upon completion of installation and inspection, piping system shall be pressure tested in accordance with applicable section. Pressure testing shall be conducted in the presence of QM personnel, COMPANY inspector. Pressure testing shall not be allowed during rain unless entire piping system under test is protected from weather. Hydrostatic Pressure shall be 1.5 times the design pressure of the piping class unless noted otherwise in the line list.

The flange gasket used for pressure testing shall be of the same type and grade as that to be used in the final piping installation. The exception shall be approved by the relevant COMPANY engineer. Test fluid shall be filled up to highest part of the piping system and air shall be bled off at the highest point through an open valve or loose flange. Gas or air entrapment in piping under test must be minimized to prevent damage to piping or personnel in the event of unexpected failure.

Unless otherwise specified, static test in which piping is water filled with and leaks examined shall be applicable instead of pressure test for piping and systems operating at atmospheric pressure. All lines such as Relief / Safety valve discharge to atmosphere, vent to atmosphere, open drain, overboardt, open- ended and open to atmosphere shall undertake static leak test.

Instrument take-off piping shall be tested to the outlet side of the piping block valve with the connected piping. The piping block valve shall be fitted with a blind or plug, as required.

Large diameter lines that are grouped together on common suppors shall not be simultaneously hydrostatically tested to prevent overstressing.

The test pump shall be physically disconnected from the system after pressurizing the system and during the pressure test inspection period.

Piping designed for vapour or gas system and subjected to hydrostatic test shall be additionally temporary supported to consider liquid weight.

Pressure gauge and pressure relief valve shall be provided at pump discharge (on test manifold) to check appropriate test pressure of the system and avoid over-pressurizing. The pump shall be maintained constantly during pressurizing by an authorized operator. Additionally pressure gauge and relief valve shall be placed at the system vent to ensure adequate pressure throughout the system and to prevent over pressure to the system. All vents and other connection which serve as vents shall be opened during filling to ensure proper venting of all air or gasses. Before pressurizing, all vents valves shall be closed.

The hydrostatic test pressure shall be increased gradually by 20%, 50% & 100% to reach full test pressure. Each increment shall be held for a period of 10 minutes for stabilization. Mitigation for stabilization step may be approved case by case for practical application between QM and COMPANY representative.

The test pressure shall be maintained for a sufficient length of time to permit visual examination to be made of all surfaces, welds, joints and connections, but not less than 30 minutes. Pressure shall be maintained for 1 hour for piping systems with pressure rating class 600# and above. Care shall be taken to ensure that over pressurizing due to static head does not take place. Air blowing and drying with yard air after hydro test or flushing shall be carried out completely as soon as possible. Pressure test fluid shall not contain suspended solids that may possible plug small lines.

4. Test Medium
For hydrostatic testing, the test medium shall be fresh water unless there is the possible of damage due to freezing or to adverse effect of water on the piping, lining or the process. In that case another suitable non- toxic liquid may be used. If the liquid is flammable, its flash point shall be at least 49°C and consideration shall be given to the environment. If ambient temperature falls below 4°C some time during the entire testing period (until dried system) the test water shall have antifreeze addedd.

5. Pneumatic Testing
Pneumatic testing shall be carried out if a hydrostatic test would damage linings or internal insulation, or contaminate a process which would be hazardous, corrosive or inoperative in the presence of moisture, or would present the danger of brittle fracture due to low metal temperature during the test.

Service Air and Instrument Air can be pneumatically tested.

Pneumatic testing shall be carried out after flushing approved certificate as per each test package. Pneumatic testing shall only take place if the full NDT requirements are fulfilled.

Unless otherwise specified, pneumatic test shall utilize clean compressed air or dry nitrogen as test Medium. If pneumatic test is performed using nitrogen, two bleed valves will be installed, one at the highest point, the other one at the lowest point to prevent trapped expansion of nitrogen gas.

Pneumatic test shall be tested at 1.43 times the design pressure according to the Pressure Directive 97/23/EC. The pneumatic test shall be carried in accordance with the test Isometric. The pressure increment is done gradually on 50% and 10 min stabilization and 70% and 10 min stabilization and full pressure. Pneumatic test pressure shall start at 1.8 bar G. When pneumatic testing at over 1.8 bar G, a preliminary

test shall be made to locate major leaks, then the pressure shall be increased gradually to test pressure. The test compressor shall be physically disconnected from the system after pressurizing and during pneumatic inspection. There shall be at least two certified test pressure gauges for each pneumatic test system.

After full test pressure has been reached and temperature stabilized, all pipe joints shall be inspected with soap solution for leak detection. All welds and flanges are to be exposed during pressure test as per applicable standards.

The specified test pressure shall be kept for one hour. The pressure shall be reduced to the design pressure before examining for leakage.

6. Post Test Requirements
After completion of pressure test, the system shall be depressurized and pressure released gradually in steps.

All vents and drains shall be opened upon completion of testing until all lines in the test loop are fully drained. Vents will be opened first, then drains shall be opened to aviod collapsing of the pipe.

All tested piping system tested with water shall be drained and then blown dry by blowing clean compressed air. Dryness shall be tested with hygrometer.

1. All the piping shall be depressurized after hydro test completed.
2. All piping shall be completely drained of all testing fluid. (water)
3. All the temporary blinds for hydro test shall be removed.
4. After check the all the actions above, following actin to be done under the consideration of piping system.
5. When air jet nozzle is using, after air jet nozzle reaches an end of the test boundary, operator shall supply the dried compressed air and pull the air supply hose with nozzle in order to remove and dry moisture in the piping systems. This activity shall be repeated till complete dry accomplished and in order to ensure the draining of all pocket where the testing fluid may be trapped in the piping system.


In case of difficult to perfect dry only by air blowing, pig can use for drying. Pigging can perform a compete Dry for perpendicular parts of the pipe and even to the parts that are not able to reach. Existing water in the pipe after air blowing shall be dried using pigging method. Sponge Pig can replace drain point and remove the remnants and make a perfect dry.

After loop has been drained, temporary blinds and supports shall be removed and items removed during flushing and testing reinstated. New gaskets shall be installed on all connections that are broken or reassembled after completion of testing. All open ends of the test loop shall be protected from foreign materials by plastic protection caps or plywood.

7. Repair and Retesting
When leaks are identified, the system shall be depressurized before flanges bolts are torqued to stop the leak. Only torque wrench shall be used and not to exceed required torque for bolts. After depressurization the leaking flanges will be reassembled with new gaskets and freshly lubricated bolts and then re-tested after re-flushing of the concetned piece.

After repair of welding joints, NDE shall be carried out and piping system shall be retested.