The Pneumatic Pressure Testing Handbook [Part 3]: Pneumatic Testing Safety

All good things come to an end, and today is the turn for our Pneumatic Pressure Testing Handbook in collaboration with Karl Kolmetz.

If you’ve followed our blog series, you’ve learned the differences between hydrostatic and pneumatic testing and the requirements for both procedures, including the procedure preparations, ASME pipe codes, test reporting, and more.

This final post will focus on the critical aspects of the pneumatic pressure testing safety requirements, so let’s get to it!

TABLE OF CONTENTS

1. Pressure Testing Safety Guidelines  
2. Roles And Responsibilities
3. General Worksite Safety During Pressure Testing
4. Exclusion Zone
5. Pneumatic Pressure Testing Safety
6. Evaluating and reducing risks of pneumatic pressure testing
7. Testing of Instrumentation Tubing Systems
8. Definitions
9. References

Pressure Testing Safety Guidelines

We have previously highlighted that pneumatic testing is more dangerous than hydrostatic testing. Let’s review the reasons why.  

As it’s well-known, water cannot be compressed like air or gas (Boyles law), so the energy stored in a vessel under hydrostatic pressure is significantly less than in a vessel with air at the same pressure. In contrast, air or gas stores very high potential energy when compressed, which is converted to kinetic energy when a rupture occurs.

In a hydrostatic test, a small leak immediately reduces the gauge pressure, which does not happen when air is the test medium. Leakages are easy to detect, and remedial actions can be taken once minor leaks are detected before total failure occurs. Since the vessel has less potential energy, the damages are mostly limited to nearby area. 

This is not the case in pneumatic tests. Any minor leak path can lead to a rupture and blast within no time, releasing total energy with the impact of a sudden explosion. The time gap between identifying leakage and failure is very small, making it almost impossible to take remedial actions. The damages associated with failure are uncontrollable and huge, so extra precautions should be taken.

Below you can find the general safety guidelines for pneumatic tests:

1. Appointment of Contractor’s Test Controller, who is in attendance and responsible throughout the testing and inspects the welding during the procedure.
2. Appointment of the Subcontractor’s Test Controller, who will be responsible for ensuring safe testing in accordance with the specification.
3. Display of safety warning signs to alert workers in the vicinity of the pressure testing with line identification.
4. Pressure test training and maintenance of a competency register as required by the Contractor Safety Plan.
5. Pressure rating for the test manifold, test equipment, and the required inspection/testing.
6. The air in the subsystem shall be released slowly by opening the valves. The vent valves shall be left open until the pressure in the loop reaches zero.
7. All Contractors and Piping Subcontractors Test Controllers must be cautious when approaching flange joints and listen for escaping air.

When developing the test procedure, assess all procedure-specific hazards that may harm personnel, equipment, or the surroundings in order to prevent or mitigate each hazard. If the detailed test procedures are still in development, use the assessment to first determine which hazardous elements may be eliminated or substituted. 

Once each avoidable hazard is eliminated or substituted, employ engineering controls to neutralize each unavoidable threat at the source before the personnel may be exposed to it. Provide written procedures to manage the remaining hazards and be prepared to train all workers associated with pressure testing to be familiar with those procedures.

A detailed pressure testing section should be included in the Site-Specific Safety Plan (SSSP) for every project involving any pressure testing. This section should specifically include the following:

• A detailed piping and equipment layout 
• Dimensions and locations of all pressure testing equipment, valving, instrumentation, anchors, supports, expansion joints, frac tanks, launchers and receivers, supply and discharge lines
• All key components of the temporary piping systems associated with strength test activities 

Before the testing procedure, safety barriers, fences, signage, and safety zones should also be outlined.

The SSSP should not be generic but specific for the project site and pipeline segment being tested, and all hazards and associated control measures should be identified within it. 

The layout and design of temporary systems and controls used for testing should not be strictly left up to construction personnel but should be reviewed, preferably by an experienced professional engineer and/or a safety professional intimately knowledgeable in calculating piping stresses, dynamic forces, and implementing safety measures to keep both personnel and the public safe.

A test plan outlining a step-by-step sequence of operations should also be prepared before conducting pressure testing.

A Job Safety Analysis (JSA) will be prepared, and on-site safety briefings (tailgates) will be conducted at the beginning of each shift with all affected and involved personnel in the pressure test. These briefings will outline all specific activities to be performed during the shift, associated hazards, and hazard control measures. 

Specific tasks, roles, and responsibilities for each involved crew member and leader will be reviewed and understood by all. Three-way communication will be leveraged to ensure understanding by each crew member during the on-site safety briefings.

Roles And Responsibilities

1. Health and Safety (HS) Responsibilities 
   • Be involved in performing the hazard assessment. 
   • Provide technical support for the interpretation of pressure testing safety guidelines. 
   • Evaluate the effectiveness of the Site-Specific Safety Plan (or equivalent). 
   • Immediately stop and correct any safety-related non-compliant activities. 
2. Employee Responsibilities 
   • Unless they’re part of the testing team, they shouldn’t enter or be present at a pressure testing procedure. 
   • Personnel performing the test should approach the pressured line only when performing their duties. The staff should use safety barriers to protect themselves from the pressurized line and position the testing equipment in a way that minimizes potential hazards. 
   • Review safety requirements of the Site-Specific Safety Plan. 
   • Do not work over or near where pressure testing is being conducted. 
   • Wear the appropriate personal protective equipment (PPE) for the task. Wear hearing protection (which may include double hearing protection) adequate to reduce the noise below 80 decibels. 
   • Attend required training before working on the task. 
   • Report any non-compliant HS activities to a Supervisor. If employees have concerns about the safety at the site, do not enter or otherwise be present at a pressure testing event and report it to the Supervisor. 

General Worksite Safety During Pressure Testing

These are the general safety specifications for pressure testing: 

1. Incorporate general worksite safety precautions and procedures as applicable. 
2. The following are examples of general worksite safety precautions and procedures which may be incorporated into the SSSP:
   • Adequate lighting should be available throughout testing operations. 
   • Safety equipment and supplies should be readily available and should include, but are not limited to:
     • Emergency spill kit
     • Fire extinguisher
     • Ladders
     • Mobile light plants
     • Whip checks
3. Install mats or utilize secured ladders for access to test header valves. When using mat bridges across the excavation, handrails must be installed if elevated 6′ above a lower level. 
4. Provide for and require the installation of devices that mark the limits of the exclusion zone. 
5. Keep unauthorized personnel out of the test area. 
6. Inform all affected site and community personnel of the planned test. 
7. Provide for and require that equipment and materials are arranged to give unobstructed access and egress during testing and in the event of an emergency. 
8. Establish lines of communication between the Owner/Facility, Contractor, and local authorities. 
9. Provide for and require the use of reliable transportation and communication systems during all aspects of the testing event. 

Exclusion Zone 

The exclusion zone is a designated area around the equipment or system under testing, where personnel are not allowed to enter during the test. This safety measure protects people from potential hazards associated with the pressure test.

Here are the considerations that must be taken for the exclusion zone:

1. Precautions should be taken to ensure that people not directly engaged in the testing operations remain out of the test area during the test period. 
2. Provide for and require that signs, barricades, or other protective barriers are placed in a manner and at a distance sufficient to delimit a safe zone to protect personnel and the public from unanticipated pressure release or equipment failure. 
3. For hydrotesting only, a minimum distance of 50 feet should be maintained between the facilities being tested and any person, whether the public or the personnel conducting the test. The safe distance may be increased, and the temperature probe, manifold, and recorders may have to be set back further than 50 feet due to potential projectiles or extreme volume/pressure. 
4. For pneumatic testing, the exclusion zones are significantly larger by orders of magnitude. The responsible engineer must establish the exclusion zone on a case-by-case basis. Factors such as pipe size, test pressure, total test footage, and surrounding structures affect the size of the exclusion zone and must be considered by the engineer to establish the appropriate exclusion zone for each pneumatic test. 
5. In locations with limited space (urban areas), install a K-rail or other appropriate physical barriers around the exposed pipe to protect the public. If this equipment is used in lieu of the established safety perimeter, all facilities within the line of site must be properly protected. 
6. Restrict access to the immediate area involving the pressure test (i.e., test shelter, manifolds, pressure pumps, instruments, etc.) to only those actively engaged in the testing operation. 
7. Set up test equipment outside the safety zone and use a caution ribbon to restrict access around the test equipment. 
8. During pressure testing events, distinct warning signs, such as “DANGER – HIGH-PRESSURE TESTING IN PROGRESS” must be posted at the test site and additional locations identified in the SSSP. 
9. When testing in a populated area, an extensive informative campaign (e.g., warning signs, barricade tape, strobe lights, and/or security guards) may be required to inform and protect the public from hazards associated with testing activities. 
10. Notification 
    • Residents within close proximity of the facility being tested, as well as state and local enforcement agencies, if applicable, should be advised by the Owner/Operator of the testing program and kept informed of the progress, as necessary. 
    • When testing at or above 100% Specified Minimum Yield Strength (SMYS), consider clearing the exclusion zone for the entire length of the pipe being tested. 

Pneumatic Pressure Testing Safety

Pneumatic strength tests present different hazards, the most significant being stored energy. The explosive decompression generates a blast wave and launches projectiles. 

For above-ground ruptures, the shock wave carries the most significant risk. The shock wave could impact surrounding equipment, buildings, and people. For below-ground ruptures, the energy released is translated to the soil surrounding the pipeline, creating a crater (ejecting material). The safety radius should consider damages caused by projectiles by calculating the maximum distance a projectile can be thrown. 

In addition to the requirements previously outlined, the following are supplemental requirements for pneumatic tests: 

1. When critical equipment/piping is near the system being tested, the equipment/piping being tested must be properly anchored/restrained. Anchors are intended to be used in conjunction with restraint systems. Common designs include deadman anchors, clamped-stakes anchors, concrete blocks, and helical anchors. They should be installed and placed based on spacing from engineering calculations or guidelines for the expected forces to be encountered. 
2. Hard piping should be used between the gas source and the injection location. It should be pretested to a minimum of 1.5 times the test pressure. If using flex hoses, do not exceed the maximum velocity per the manufacturer’s recommendation and verify the hose’s condition and pressure rating. 
3. Pressurize at a steady rate. Ensure the sound of gas flowing or equalizing can no longer be heard before continuing to the next step. Note that larger volume systems or higher test pressures require longer pressure equalization times, while shorter, simpler systems require less time. 
4. Soap test all pressurized fittings at 100 psig. Hold leak test pressure for 15 minutes. The Test Supervisor should confirm all soap test locations. 
5. Ensure there is overpressure protection. The set pressure of a pressure relief device should not be more than the greater of (1) the test pressure plus 10 psi, or (2) 105% of the maximum test pressure. The device must be tested before each strength test to ensure it is fit for service. 
6. To contain any projected missiles, above-ground equipment (temporary equipment, temporary piping, etc.) must be physically shielded wherever possible. This can be achieved by using temporary barriers/shielding, including protection between the test controls and the assembly under pressure. 

Learn how TotalShield pressure testing enclosures provide high-impact force protection.

7. The piping should be inspected to determine if the inside surfaces are contaminated with a combustible or flammable material (e.g., iron sulfide, condensate). If found, remove such materials before air testing. 
8. Perform a leak survey before the pneumatic test to identify areas that need repair. 
9. Have a written Safety Plan for securing the exclusion zone for the test duration. Establish roles and responsibilities and ensure communication between all patrols and the incident commander. 
10. Have a written pressurization and depressurization plan. Monitor pressure and temperature at nozzle and on the mainline. 
11. When using nitrogen, ensure the nitrogen supplier has a functional low-temperature shutdown. 
12. Have a written leak and rupture plan. 
13. Create a communication plan to inform the surrounding public of the planned test. 
14. Consider the possibility of crack propagation from a rupture. If possible, perform destructive testing to validate the system’s material properties (i.e., fracture toughness). 
15. Establish an emergency command center before the test. 

Evaluating and Reducing Risks of Pneumatic Pressure Testing

The following are considered essential to minimize the risks of failure and injury during high-pressure pneumatic testing:

1. Pneumatic testing must be conducted by internally experienced, trained, and competent staff.
2. A pre-test safety meeting should be conducted to ensure all personnel present on the site who may be exposed are aware of the hazards, mitigations, and emergency response plan. Develop and deploy a Site-Specific Test Plan, including descriptions of safety procedures and requirements.
3. Comprehensive testing and safety procedures must be formalized, implemented, and available to all personnel involved in the testing activities
4. Test procedures must clearly define the points in time during the test when test personnel are permitted to leave sheltered areas and enter the exclusion zone. As a minimum, the test procedure must clearly indicate: 
   • Purpose 
   • Reference documents 
   • Personnel performance qualifications/training/capabilities
   • Operating method 
   • Test sequence 
   • Applicable pressure test values 
   • Hazards and safety concerns during proof-pressure testing 
   • Safe distance 
   • Remote visual check, if applicable 
   • Evaluation of results 
   • Certification
5. 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 hydrocarbon-free since this could form an explosive mixture.
6. Engineers must provide a comprehensive design review report that includes evidence of the suitability of existing designs under specified testing conditions. Verify that test equipment and materials are rated to withstand the test pressures.
7. Design validation shall be performed under defined testing conditions and ensure all parts of the expansion joints and the entire unit conform to the code construction requirements. Pressure design calculations for both operating and test pressures must be documented and checked for all parts.
8. Materials received must be carefully checked to ensure compliance with material specifications (including a review of all material test reports received). The project must have a suitable Positive Material Identification (PMI) procedure that effectively ensures proper materials in the fabricated Expansion Joint. 
9. For materials whose resistance to brittle fracture at low temperatures has not been enhanced, a test temperature above 60 °F (16 °C) should be used to reduce the risk of brittle fracture during the pneumatic test. Precautions should be taken to prevent gas expansion, temperature drop, and thermal stresses due to temperature gradients.
10. Provision of pressure relief valves sized to handle the maximum output of the pressure source to avoid excessive testing pressure.
11. The gauges shall be positioned in a place that is readable by both the personnel controlling the pressurization and the test administrator. Only certified and calibrated gauges with a dial of a range neither less than 1 nor more than 4 times the test pressure will be used.
12. The use of a Non-Destructive Examination (NDE) must be maximized to ensure the quality of all welded joints in the system. Butt welded joints should be 100% ultrasonically or radiographically tested, and all other welds should be 100% Penetrant Tested. The Expansion Joint fabrication tests (along with any necessary operational records) should be reviewed before testing.
13. If available, carry out the test in a specific isolated test bunker with adequate lighting. 
14. A limited access area and pressure control point should be established for pressure tests where the risk of injury from potential fragments, shockwaves, or other consequences of any pressurized system failure are determined to be unacceptable. Unauthorized personnel should be kept out of the test area. 
15. Calculate the minimum distance from the boundary of this area to the pressurized component. The restricted distance is the distance from the item(s) under testing to which barriers are placed to prohibit access and the distance at which the test is monitored. 
16. Precautions should be taken to see that persons directly or not directly engaged in the testing operations remain out of the test area during the test period. During pressure testing, distinct warning signs, such as “DANGER – HIGH-PRESSURE TESTING IN PROGRESS” must be posted at the test site and additional locations identified in the SSSP.
17. Schedule tests at optimum times to ensure safety. The risk of injury resulting from a test system failure can be dramatically reduced by testing at night or on weekends when fewer personnel are on-site (and possibly off).
18. As no person is allowed in the exclusion area during the proof-pressure test, the test shall be observed and controlled at a safe distance by video cameras and video recording. The cameras will record and provide a clear view of the entire unit during the pressurization, pressure test time, and depressurization.

Testing of Instrumentation Tubing Systems 

Pressure testing of threaded and welded piping presents different hazards than instrumentation systems constructed of tubing and compression fittings. The amount of stored energy in instrumentation tubing systems is generally very low. The primary concerns for the safe distance when testing instrumentation tubing are the “line of fire” and proper anchoring of the test system. 

For instrumentation tubing, the owner shall assess the potential consequences of a failure and identify any required controls and precautions in the test procedure to prevent personnel injury. The owner is responsible for providing competent personnel to oversee the testing. 

The procedure shall include: 

1. Verifying proper anchoring of the tubing and specifying minimum safe distances for the shop and testing personnel. 
2. Addressing line-of-fire hazards for personnel who will be conducting the leak test. 
3. Verification that all fittings were marked, installed, tightened, and gap-checked according to the manufacturer’s installation procedure. 
4. Complete depressurization of the system before adjusting or tightening any joints. If any leaks are detected, all pressurization steps must be repeated after performing any such adjustment to any repair. 
5. Leak-testing of all joints, generally through a bubble test that employs a leak-testing solution to emphasize leaks by producing bubbles. 
6. Care shall be taken to ensure testing personnel stay out of the line of fire of connections being subjected to bubble testing; bubble testing shall follow the recommendations of the bubble solution supplier. 

Typically, the safe distances required for pneumatic tests of instrumentation tubing will be considerably less than the safe distance for threaded or welded systems due to the low risk of potential failure and the low volume of the test piece.

By considering all potential hazards and adhering to these safety protocols, you’ll be on your way to conducting a successful pneumatic test.

For us at TotalShield, safety is our top priority. We hope this blog series has provided you with the insights needed to better understand and perform pressure testing procedures so you can secure a successful testing environment. 

If you need to improve your worksite safety, our Shielding Rooms will protect your personnel and machinery during pressure tests, so don’t hesitate to contact us!

Thank you for following along, we look forward to bringing you more insightful knowledge in the future 🛡️

The Pneumatic Pressure Testing Handbook Glossary & References