The Pneumatic Pressure Testing Handbook [Part 2]

Welcome back to our comprehensive guide on pneumatic pressure testing, created in collaboration with Karl Kolmetz. In our previous post, we explored the pressure testing methods, laying the foundation for understanding the principles behind these procedures.

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In this second blog post, we&#;ll dive into the specifics of pipe pneumatic pressure testing standards. You&#;ll learn about the necessary preparations, the importance of accurate reporting and record-keeping, and other crucial details.

Read here the first part of this blog post series about pressure testing methods.

TABLE OF CONTENTS

Pipe Pneumatic Pressure Test Requirements

As we have already reviewed, pneumatic tests are potentially more dangerous than hydrostatic tests because of the higher level of potential energy. Therefore, conducting a pneumatic test instead of a hydrostatic one requires approval from the pressure systems program manager. 

In addition to a justification, a piping schematic is required for the pneumatic pressure test. The image below shows the typical recommended piping schematic for a pneumatic test.

Figure 2. Recommended typical piping schematic for pneumatic testing

Circuit monitoring and checking

For pneumatic testing of circuits, access to the test area should be restricted to personnel directly involved in the procedure, inspection, or monitoring.

The entire circuit should be inspected and tested for leaks during the procedure. If any leaks are found in flanged, threaded, plugged, or welded joints, the system pressure must be released entirely before any rectification work begins. Any individual or supervisor who authorizes or undertakes work on the pressurized system under these conditions will face disciplinary action. 

For flanged joint testing, the flange joints should be hermetically sealed using adhesive paper tape and a pinhole made in the tape to allow for easy leak detection.

The following equipment and components should be excluded from the system and isolated from the test section:

1. Rotating equipment such as pumps, compressors, and turbines.
2. Safety valves rupture discs, flame arrestors, and stream traps.
3. Pressure vessels with sophisticated internals.
4. Equipment and piping lined with refractoriness.
5. Storage tanks.
6. Filters, if filter element(s) is not dismantled.
7. Heat exchangers of which tube sheets and internals have been designed for differential pressure between the tube and shell sides.
8. Instruments such as control valves, pressure gages, level gages, and flow meter (excluding thermocouples).

Exclusions 

The following systems are excluded from the testing requirements of this specification:

1. Any package unit previously tested by the vendor in accordance with the applicable codes.
2. Plumbing systems which are tested in accordance with the applicable plumbing codes.
3. Lines and systems open to the atmosphere, such as drains, vents, open discharge of relief valves, and atmospheric sewers.

Medium

The gas used as the test medium should be nonflammable and nontoxic, such as N2 or inert gas, if not compressed air. 

Nitrogen should be the test medium since it can&#;t enable combustion. Alternatively, clean, dry, oil-free air can also be used. 

Exercise caution when using air in any system that cannot be verified as free of hydrocarbons since this could form an explosive mixture.

Test pressure

The test pressure shall be 110% of the design pressure and according to test pressure. Equipment for testing should be as follows:

• Air Compressor
• Flexible hose
• Calibrated Pressure gauge
• Oil filter
• Temporary piping set
• N2 cylinder, if required
• Safety valve

&#;&#; NOTE:

A safety valve required for pneumatic testing, rapid opening, or pop action of overpressure should be installed and connected with an adequate system of piping not containing a valve that can isolate the tested system.

Blinds for pressure test

1. Plain test blanks shall be used with 3 mm flat gaskets for blanking the flat and raised faces. Provide full face blanks and gaskets for Class 150 connections. However, where permanent operational blinds are installed, they may be used for pressure testing, provided they are rated for the testing pressure.
2. Plate material, extra-length bolts, and gaskets, which are made at the job site, could be used in the testing.
3. Temporary spades and blanks installed for testing purposes shall be designed to withstand the test pressure without distortion. They shall be readily identifiable by painting the handle red.
4. Spare ring joints are required for ring joint flanges as they are to be used only once.

Test Pack Preparation

General

1. The Contractor will prepare a marked-up P&ID (Piping and Instrumentation Diagram) indicating the test limits.
2. From the marked-up P&ID, the Subcontractor will divide the piping into suitable Test Packs. The Subcontractor may revise the size of the packs. Provided that the specification for the limits below is complied with, the Contractor shall be notified of such revisions and will authorize the Subcontractor to proceed if said revisions meet the specifications.

Test pack limits

The Subcontractor shouldn&#;t test through equipment without the Contractor&#;s written approval.

Test pack format

• Pressure test report for piping
• Marked-up P&ID
• Blind checklist
• Welding History Report and Welding Joint Marked ISO Drawing
• NDE report
• PWHT and Hardness test report
• Post-Test Punch List (Contractor + Client)
• Copies of reinforcing pad pressure test certificates (if necessary).

Test Packs must include the latest available revision of each isometric covering the scope of the test.

1. Test limits and highlight lines to be tested.
2. Size (thickness) and location of all test blinds, including those required for instrument connection, e.g., orifice flanges.
3. Identify the location for the connection of the fill and drainage points for the system.
4. Vent points
5. Location and range of pressure gauges to be used. Note that on large piping systems and/or systems with no return valves, more than one gauge may be required.
6. If required, temporary support should also be indicated in the test pack.
7. Any control valve, check valve, safety valve, or other piping accessory that requires removal, turning, or some other action should be highlighted.

Test Packs shall also contain copies of P&ID&#;s marked-up to show at least the following information:

8. Piping Field Test Pack Number
9. Specific Limits of that Test Pack Only
10. Location of Test blinds, Isolation valve, and Temporary piping.

Test pack approvals and distribution

The &#;Original&#; pack should be submitted to the Consultant for review.

Field Revision Request (FRR)

The Contractor&#;s Engineer should check the status of the affected test pack and advise the Subcontractor for test packs where the pneumatic pressure test has been completed. 

The Contractor will over-stamp the original test pack with &#;RETEST.&#; The restamp original will then be returned to the Subcontractor under a memorandum with instructions to carry out the retesting.

Pneumatic Pressure Test Preparations

All testing shall be conducted in accordance with the approved testing procedure and as per the Owner&#;s work permit procedure. Pneumatic tests above a defined pressure (defined by Company Standards) will require a risk review and approval by the Company Safety Department. 

While performing a pneumatic test, the minimum pipe metal temperature should be as listed below to avoid brittle failures:

Nomial Wall ThicknessMinimum TemperatureCarbon steel &#; 38 mm15 °CPost-heat treated ferric alloy steels &#; 25 mm15 °CAustenitic stainless steels &#; 25 mm  12 °CTable 2. The minimum pipe metal temperature

Below are the preparations for a pneumatic pressure test.

1. The safe distance, as identified in the test procedure, shall be indicated by placing appropriate barriers.
2. All staff associated with or conducting a pneumatic pressure test shall be deemed competent by the organization conducting the test.
3. A pre-test safety meeting should be conducted to ensure all personnel on the site who may be exposed know the hazards, mitigations, and emergency response plans.
4. All visual inspections and non-destructive examinations required by the code of construction shall be completed and evaluated as acceptable.
5. All connections shall be inspected pre-test to verify proper assembly and tightness, valve positioning, overpressure protection, and control of the test medium.
6. Testing shall not be conducted if the ambient temperature falls below the above-stated values.
7. All joints, including welds, shall be accessible and left uninstalled, unpainted, and exposed for examination during the test. Joints previously tested in accordance with this specification may be insulated or covered.
8. Before testing
   • Piping systems shall have been thoroughly checked for correctness.
   • All lines, vessels, and equipment shall be checked to ensure that the entire system can be completely drained after testing.
   • Temporary gaskets may be used, but they are not the same as permanent gaskets provided.
     • Such use will not lead to damage to the flange faces.
     • Temporary gaskets are removed immediately after completion of tests.
9. Short pieces of piping that must be removed to permit the installation of a blind or blank shall be tested separately.
10. Lines containing check valves shall have the source of pressure located in the piping upstream of the check valve so that the pressure is applied under the seat. If this is possible, remove or jack open the check valve closure mechanism or remove the check valve completely and provide the necessary spool piece or blinds. 
    A notation shall be included on the Punch List that the check valve flapper has been removed. The Subcontractor shall install a new gasket wherever the check valve bonnet has been disturbed. Where flappers have been removed, valves should be tagged.
11. The test equipment to be used during testing shall have a suitable capacity for the required range of test pressure. The range of pressure gauges to be used shall be with a minimum span of 1.5 times pressure and a maximum span of 2 times test pressure.
12. All pressure gauges need to be calibrated. If gauges have been used previously on other projects or for different purposes, they shall be recalibrated. Validation of gauges and chart recorders shall be for a maximum of 90 days; however, recalibration is required if the calibrated gauge/recorder is damaged or strained.
13. If the specified test duration exceeds 8 hours, a chart recorder must be used to record test pressure.
14. Prior approval must be obtained from the Contractor and Consultant to include vessels or inline equipment in the pressure test circuit.
15. For test pressures exceeding 50 psig, the construction contractor will be required to provide calculations for the stored energy of the system before conducting the test to determine the associated hazards in case of piping rupture.
16. The test assembly shall be provided with the requisite instrumentation to provide a permanent record of the test pressure and metal temperature for the entire test duration. The pressure gauge range shall be such that the test pressure is within the middle second-third of the reading range. 
17. It shall be ensured that the piping connection between the compressed air source and test assembly is safely designed and supported.
18. The test area shall be cleared for safety while bringing the piping system up to test pressure. It may be recommended to conduct the test at night or on weekends when minimum construction or operating personnel are present in the vicinity of the testing area.
19.  Piping within the test limits shall be tied down or firmly secured to prevent uncontrolled pipe movement in the event of rupture or sudden pressure loss.
20. During pneumatic testing, care shall be exercised not to exceed the specified test pressure. A pressure relief device shall be provided, having a set pressure not higher than the test pressure plus a lesser 3.45 bar or 10% of the test pressure. Safety relief valves shall be sized to provide adequate relief capacity from the system being protected.
21. Before soaping the joints, the entire line shall be examined to determine if there is any audible evidence of leakage. If any leaks are found at this time, they shall be marked and repaired after depressurizing the line. The test will be temporarily suspended until the required repair is completed.
22. Bolting shall not be tightened while systems being tested are pressurized.
23. The area around the test assembly, to a minimum distance defined as &#;exclusion zone,&#; shall be cordoned off by red and white barrier tapes. All unauthorized personnel should be away from the exclusion joint before the beginning of the test.

See how TotalShield ensures safety during pressure testing procedures with our enclosures or walk-in chambers. 

Pneumatic Test Procedure

1. Before the test starts, the Supervisor/Tester is to set up the exclusion zone, complete with signs in multiple languages if needed, before pressure is raised on the system. Also, marshals shall be positioned at all exclusion barriers to ensure no personnel enter the exclusion zone.
2. During the pneumatic test, care must be exercised not to exceed the specified design pressure by more than 10% (the maximum test pressure to be marked on the test pressure gauge before pressurizing the system).
3. The test media shall be clean, dry air, or nitrogen. The engineer may propose any other test media as long as it is nonflammable and does not adversely affect the piping system or cause a safety hazard. Oxygen shall never be used as a test media.
4. When pneumatic testing at over 2 kg/cm2, a preliminary check at 2 kg/cm2 shall be made to locate major leaks. The pressure shall be increased gradually by 4 kg/cm2 or 10 percent of the test pressure, whichever is greater.
5. The pneumatic test pressure is required to be increased gradually until it reaches the lower of 25 psi or half the test pressure. Thus, if the design pressure is 100 psi, the required test pressure is 11 0 psi. Since half of this value is 55 psi, the initial pressurization would not exceed 25 psi.
6. A double block and vent valve arrangement shall be included in the pressurizing line to the system being tested. A test pressure gauge shall be downstream of the double block. After each pressure step has been reached, close the block valves and open the vent valve to the atmosphere. If, after 10 minutes, the &#;Step Pressure&#; has held, proceed to the next &#;Step Pressure.&#; If not, examine the entire system for leakage.
7. The pressure shall be held at the design pressure for 5&#;10 minutes before raising it to the test pressure and equalizing the piping strains. At the test, the pressure shall be held for 30 minutes, during which time access within the exclusion zone will be allowed.
8. After 30 minutes, the test pressure shall be reduced to design pressure, at which point access within the exclusion zone will be allowed to the testing team only, and the inspection of the joints shall be undertaken. All flange, threaded, welded joints, and attachments shall be inspected with a proprietary testing solution. The design pressure shall be maintained until inspections of all joints are completed.
9. One common method of testing a flanged joint is to mask it with tape and check for leaks through a pinhole punched in the tape. The pressure shall be maintained at the design pressure for a sufficient length of time to allow all welded, flanged, and threaded joints to be visually inspected. After all the joints have been tested, depressurization will be carried out slowly until the pressure reaches atmospheric.
10. Any leak identified shall be marked with a marker pen, and the system depressurized before any repair or rectification work is undertaken.
11. Depressurization must take place in a controlled manner to avoid cooling due to the refrigeration effect, to equalize pipe strains, and to be cautious about the vented test fluid.
12. The procedure must address the dangers of confined space and the possibility of asphyxiation from a test medium such as nitrogen. This danger is especially high should a leak occur or at the time of depressurization.
13. Upon completion of the inspection, the system shall be depressurized by nominated vent valves, considering any none return valves included within the system.
14. Loosening flanged connections or plugs shall not be used to depressurize. The test system&#;s temperature at the vent point shall also not fall below sub-zero.
15. A Double Block and Bleed (DBB) valve arrangement shall be included in the pressurizing line on the system being tested. A test recording pressure gauge shall be provided downstream of the DBB arrangement. After reaching each pressure step, close the block valves and open the bleeder to the atmosphere. If the &#;Step Pressure&#; is maintained after a five-minute period, proceed to the next &#;Step Pressure&#;; if not, examine the entire system for leakage.
16. All instruments shall be disconnected from the test system before the test starts.

The following table outlines the testing requirements for different types of pressure systems:

Type of SystemTest MediumTest PressureTest ProcedurePressure Vessel (Division 1)1.1 times MAWPASME BPVC-VIII UG99Pressure Vessel (Division 2)1.15 times MAWPASME BPVC-VIII-2Building Services (Pneumatic) For nontoxic fluids, air, vacuum, and nonflammable gasses installed as part of the building (except laboratory and experimental)Nontoxic, nonflammable gasNot exceeding 1.25 times design pressure and not exceeding 150 psig 
Pneumatic testing of plastic pipe or brittle materials not allowedPressure raised by not more than 25% per step. 
10 minutes (minimum) at test pressure.
Pressure may be reduced to design pressure before examining for leaks.
ASME B31.9 ss 937.4Process Piping (Pneumatic) For all gasses and fluidsAir or a nontoxic, nonflammable gas1.1 to 1.33 times the design pressure 
Not exceeding 150 psig without the approval of PSWG 
Pneumatic testing of plastic pipe or brittle materials not allowedFirst leak check performed (smaller of) 0.5 times design pressure and 25 psig 
Raise pressure gradually in steps. 30 minutes (minimum) at test pressure. 
Pressure shall be reduced to design pressure before examining for leaks
ASME B31.3 ss 345.5Pressure Sewer Ejector SystemsAir5 psi15 minutesSewer Lines within building, drainage and storm drainsAir5 psi15 minutesDry Pipe Fire Protection SystemAir40 PSIA hydrostatic test is required in addition to a pneumatic test. 
Pneumatic test for 24 hours with less than 1.5 PSIG pressure loss
NFPA 13 28.2.2.1Fuel GasAir, nitrogen, carbon dioxide, or an inert test gas &#; Never oxygen1.5 times the maximum working pressure, but not less than 10 PSI1/2 hour for every 500 cubic feet of pipe volume (or fraction of) but not less than 15 minutes
NFPA-54 8.1.4Vacuum SystemsAir extractorFor ordinary vacuum systems: Full atmosphere differential. 
For systems not intended to be pumped out to full atmospheric pressure differential: 110% of max allowable external differential pressure, but not more than full atmospheric pressure. 
For vacuum systems within a pressure vessel: 110% of max allowable working pressure differentialASME Section VIITable 3. Test Pressures for New Pressure Vessel and Piping Systems

ASME Pneumatic Pressure Test

It is important to address that a pneumatic test will differ in the ASME pipe code. 

Contact us to discuss your requirements of Pneumatic Test Bench. Our experienced sales team can help you identify the options that best suit your needs.

The ASME B31 Code for Pressure Piping was first introduced in as a comprehensive document for piping design. In , it began to be divided into separate sections to address specific piping systems.

ASME B31.1, or Power Piping Code, provides rules for piping typically found in electric power generating stations, industrial and institutional plants, geothermal heating systems, and central and district heating and cooling systems. This code is critical for power piping professionals as it stipulates the design rules for power generation plants. 

ASME B31.3, or the Process Piping Code, provides rules for piping design for petroleum refineries, onshore and offshore petroleum and natural gas production facilities, chemical, pharmaceutical, textile, paper, ore processing, semiconductor, and cryogenic plants, food and beverage processing facilities, and related processing plants and terminals. This code is known as the Bible for process piping professionals. It dictates the design considerations of process plants. 

ASME B31.5 covers refrigerant, heat transfer components, and secondary coolant piping for temperatures as low as -320 °F (-196 °C), whether erected on the premises or factory assembled.

1. ASME B31.1 Test Power Piping 

The pneumatic test pressure shall be no less than 1.2 times or more than 1.5 times the piping system&#;s design pressure. 

It shall not exceed the maximum allowable test pressure of any non-isolated component. The pressure in the system shall gradually be increased to not more than 1/2 of the test pressure, after which the pressure shall be increased in steps of approximately 1/10 of the test pressure until the required test pressure is reached. 

The pressure shall be continuously maintained for a minimum time of 10 minutes. It shall then be reduced to the lower design pressure or 100 psig [700 kPa (gage)] and held for such time as may be necessary to conduct the examination for leakage. 

Examination for leakage by soap bubble or equivalent method shall be done on all joints and connections. 

2. ASME B31.3 Test Process Piping 

The test pressure shall not be less than 1.1 times the design pressure and shall not exceed the lower of 1.33 times the design pressure or the pressure that would produce a nominal pressure stress or longitudinal stress in excess of 90% of the yield stress of any component at the test temperature. 

The pressure shall be increased until it reaches a gage pressure of the lower of 0.5 times the test pressure or 170 kPa (25 psi), at which time a preliminary check shall be made. 

After that, the pressure shall be gradually increased in steps until the pressure is reached, holding the pressure at each step until the piping strains are equalized. The pressure shall then be reduced to the design pressure before examining for leakage. During the test, a pressure relief device shall be provided, with a set pressure not higher than the test pressure plus the lower 345 kPa (50 psi) or 10% of the test pressure.

3. ASME B31.5 Test Refrigerant Piping

The test pressure should be at least 1.1 and not exceed 1.3 times the design pressure of any component in the system. 

The pressure in the system shall be gradually increased to 0.5 times the test pressure, after which it shall be increased in steps of approximately 1/10 of the test pressure until the required test pressure is reached. 

The test pressure shall be maintained for at least 10 minutes. It may then be reduced to the design pressure, and the examination for leakage may be conducted. During the test, a pressure relief device shall be provided, with a set pressure above the test pressure but low enough to prevent permanent deformation of the system components.

On the table below, you can see the test pressure and procedure for each of these ASME pipe codes.

CodeB31.1B31.3B31.5Test pressureHigher than 1.2x design pressureHigher than 1.1x design pressureHigher than 1.1x design pressureLower than 1.5x design pressureLower than 1.33x design pressureLower than 1.3x design pressure of any component in the systemLower than maximum test pressure of non-isolated componentsLower than pressure that produces stresses in excess of 90% of the yield stressProcedureIncrease the pressure to 1.5 times the test pressureIncrease the pressure until the lower 0.5 times the test pressure or 170kPaIncrease the pressure until the lower 0.5 times the test pressureIncrease in steps of 0.1 times the test pressure until the test pressure is reachedPreliminary leakage checkIncrease in steps of 0.1 times the test pressure until the test pressure is reachedMaintain the test pressure for 10 minIncrease in steps until the test pressure is reached, holding the pressure at each step until the piping strains are equalizedMaintain the test pressure for 10 minReduce the pressure to the lower of the design pressure or 700 kPaReduce the pressure to the design pressureMaintain the pressure during the examinations for leakageReduce the pressure to the design pressureMaintain the pressure during the examinations for leakageMaintain the pressure during the examinations for leakageTable 4. Pneumatic test in different ASME code

Reports and Test Records

At a minimum, the Subcontractor should maintain records of all pressure tests and welding operations, including welder numbers and post-weld heat treatment charts referenced to weld numbers, hardness tests, and certifications.

All records should be submitted and approved by the Contractor and submitted to the Client or Consultant.

For all pressure tests, documentation should be fully traceable during the commissioning period of the tested pipe. It should include, but not be limited to:

• a valid test certificate specifying the date, location, line numbers, test pressure, medium and duration
• a test record chart fully specifying the pressure, temperature, and time relation during the test period

Repairs Before Repeating The Pneumatic Test 

If any leaks are found in a welded, flanged, or threaded joint, the test should be aborted, and the piping system should be depressurized for remedial action. 

If welded joints are found leaking, they shall be repaired using the approved weld repair procedure and subjected to 100% radiography before repeating the pneumatic test. 

Leakage at flanged joints shall be investigated to ensure that the correct flange tightening procedures and bolt torques have been applied. Excessive torquing shouldn&#;t be used to achieve a leak-tight seal at a flanged joint.

Only one more blog post remains in our series! 

Make sure to catch our next blog post for essential insights into safety requirements during pneumatic pressure testing. 

If you need help with your pressure testing procedures, don&#;t hesitate to contact us. Our engineering team will help you find the shielding solution you require.

• Karl Kolmetz

  (Guest Writer)

  Karl Kolmetz is a Senior Managing Director at KLM Technology Group, and the Managing Editor for Engineering Practice Magazine and the Kolmetz Handbook of Process Equipment Design. He has authored more than 160 publications on a variety of subjects for product recovery, distillation simulation, equipment troubleshooting, training, project management, process design, process safety management with a high safety and environmental focus. His research interest focuses on how to apply the fundamentals of engineering to practical applications. Karl is a Certified Practicing Engineer (CPE) from the International Association of Certified Practicing Engineers.

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