Hydrostatic testing a pipeline is a necessary part of the commissioning process during new construction to verify structural integrity and to meet OT requirement for defining a Maximum Operating Pressure. Tests can also re-certify the pipeline after modifications or changes in service. Hydrotests can be used as an alternative or enhancement to In-Line Inspection techniques, especially for crack-like defects.
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Each mainline test has unique challenges that should be planned for prior to executing the test. A few of the primary concerns include water fill without entraining air, temperature stabilization and accurate temperature measurement. Working with an expert testing partner you can trust saves time and money and ensures proper compliance and certification in support of efficient project start up and operation.
Higher testing pressure and higher % SMYS (Specified Minimum Yield Strength) requirements started in the 1960s. ASME B31.1.8 was the first standard to require post-construction testing. Modern tests occur at high % SMYS levels and can employ a “spike” test interval (short time duration) as an assessment of narrow, crack-like defects that may be present.
While Maximum Operating Pressure (MOP) testing has not significantly changed over the past several decades, there have been a few newer applications that have been added to the testing approaches, such as “spike” testing at high % SMYS of the pipe. Precise and detailed planning and thorough documentation of the plan will improve the probably of a successful hydrostatic test. In addition to all the planning, clear communication of expectations and testing requirements is essential for success throughout all phases of the planning and execution of the test.
Working with a third part testing partner is more efficient and cost effective when it comes to proper pipeline certification. To leverage the full benefits of third-party testing, it is important to seek a highly qualified and experienced team who understands your goals.
Specialized Equipment
Pipeline operators often do not own the specialized equipment required for mainline hydrostatic testing, including high flow rate and high-pressure pumps that are used for the displacement of product with water. Many hydrostatic testing evolutions require external resources with equipment and experience to increase the probably of a successful test. A testing partner will have access to modern hydrostatic testing equipment that complies with the U.S. Department of Transportation (DOT) standards and should have experience with implementing testing processes in accordance with DOT requirements.
Engineering Data and Documentation
A successful hydrostatic test will produce the engineering data necessary for the MOP of the pipeline. Successfully completing the hydrostatic test and providing the necessary documentation is essential when the pipeline operations are audited by State or Federal officials. Without a properly conducted hydrostatic test and the documentation to justify the MOP of the pipeline, issues could become a regulator’s audit findings. A good third-party testing partner understands the pitfalls related to poor documentation and incomplete test data records. By managing this process from start to finish with full attention to detail and proper procedure, a third party ensures the continued smooth operation of your project.
Compliance and Certification
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Certifying the results of hydrostatic testing requires support from a qualified individual or team of experts. Independent contractors can attest that the test was completed successfully and will provide the required compliance and engineering reports associated with the test. Repeating a test because of a planning mistake, failure in communication or an issue with the pipeline can be very expensive. Third party certification can prevent the risk, cost and inefficiency of having to shut a pipeline down to repeat a test.
Cost Savings and Operational Efficiencies
A trusted third-party tester can help you focus your internal resources on the larger scope of executing the pipeline project successfully rather than be caught up in the details of properly executing the hydrostatic test. An experienced testing team will be able to make final determinations of a “good” test per ROPI calculations.
Third-party testers also help eliminate the qualification and training costs associated with tasking in-house staff with managing the hydrostatic test and associated recordkeeping. With an independent view of lessons learned and improvement opportunities, an outside testing group can help advance and achieve operational efficiencies for future testing.
Partnering with a third-party hydrostatic testing organization as early as the project planning phase is helpful. A qualified team should review your company’s assets and test plan to ensure that the tests will meet the appropriate standards and codes prior to the hydrostatic test date. Having the testers onsite to examine the details of the test set-up, testing equipment and P-V plot preparation and to witness the test firsthand is essential. After the test has been completed, written documentation, forms and a report ensure all findings are appropriately documented.
As a trusted third-party tester, TRC’s engineers plan, design, QA/QC, witness and certify hydrostatic tests and provide the associated required documentation to support successful pipeline projects. Our pipeline experts leverage ensures our nationwide experience and expertise to meet your specific testing challenges and to provide the best solutions to protect your assets.
We are also skilled in training pipeline operators in the skills necessary to successfully oversee hydrostatic testing, ensuring that your employees know what questions to ask and follow critical steps so that the test is appropriately executed.
For more information about our solutions or to discuss your unique project needs, contact Rodney Vasques at rvasquez@trccompanies.com.
I do this incidentally as a part of my job, so have some familiarity with it.
I've never been able to find good agreement on standards for hydrostatic testing of air compressor tanks, particularly the test pressure to use. For new tanks, I've seen several standards. One approach is to arbitrarily have a standard % test pressure, typically 130%, 167% or 200%. Another is to measure the volume of the vessel before filling, measure it under test pressure, and measure again after decanting. The amount of stretch under pressure, along with the permanent stretch measured after decanting allow mechanical engineers to calculate if the vessel was tested past it's yield strength. Of course, this is too complex for our purposes.
Here's a good standard, in my opinion, for testing. It uses 167% of working pressure as a standard, but requires the vessel to be held there for 30 minutes to give it time to fail. It is the New York City standard for commercial applictions.
FDNY Requirements For Hydrostatic Tank Testing
Hydrostatic tank testing must be completed by a licensed certified tank tester with special equipment designed for the task.
The tank should be tested every five years.
The tank must be tested more often than every five years if there are any visual signs of degradation or damage.
Requirements under the law state that the tank to be tested must be filled with water and pressurized to 167% of the maximum operating pressure listed on the side of the tank.
The tank, including all of the valves and other closures, must hold the pressure test for at least 30 minutes without leaking or bulging.
Details and requirements for hydrostatic testing are covered under OSHA regulations section 180.407.
My thoughts are that this is a good defensible standard. If the pressure is only brought up instantaneously and not held, I think that 200% of working pressure is more appropriate, but also is more likely to fail the tank.
I built a special pump for doing this years ago, I used a constant displacement low volume pump, and a bypass pressure regulator. It runs continuously, and can get hot enough to boil water. I have a small radiator and fan set up on the bypass to cool the water before going back to the input side of the pump. I use it with a measured volume of water, and can measure the leakage rate using the lost volume. That is for piping systems, which are allowed a certain amount of leakage per time.
As an aside, pay no attention to the comments that berate you for not drying out the inside of the tank when done. All air compressors operate at 100% humidity nearly continuously when in operation. That's the nature of compressing and cooling gases that have water vapor in them. The dampness caused by your test is no different than the water that condenses continuously inside the tank when you operate the compressor. That is in fact the reason we periodically hydrostaticaly test tanks; the moisture causes rust inside, reducing the wall thickness and weakening the tank.
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