Hydrostatic testing and the applicable codes such as API 650 and API 620 and tanks in low temperature application such as LPG and LNG.
A common misunderstanding in the market is the purpose of Hydro-Testing or also known as Hydrostatic testing of new built product storage tanks. Many believe that the hydro-test on a new built storage tank is just a leak tight test and others believe that hydro-testing is important to do for settlement measurement. The answer is both are partially correct, and there is more to the story.
This article discusses how hydro testing is not just simply water transfer and when done by experienced specialists a hydrostatic test can be made to suit several types of tank(s) services, testing of components and the elements of a tank that are evaluated when hydro testing is performed completely and properly.
While the majority of Hydrotesting is done on new API-650 fabricated tanks or API-653 recertified tanks there are more and more other tanks being constructed to other codes, such as API-620.
In situations where a tank may be designed to operate at a small internal pressure, which is less than 2.5 PSI (above 2.5 PSI API-620 applies) or when the internal pressure does not exceed the weight of the roof plates and additional test is performed. In this designed for situation, this type of tank must be tested with water 51 mm or 2 inches above the top angle and a vacuum box test of all roof seams / welds is performed. Caution must be used when conducting the following test condition and strict operating test procedures must be followed. The code does allow test some pneumatic test procedures where design pressure exceeds the weight of the roof plates and additional pneumatic test of 1.25 times design pressure can be added. While there are many situations that may dictate this additional testing, this procedure is typically used on tanks having anchor bolts and chairs to test uplift as well avoid deflection of tank shell to bottom over pressurization and bottom deflection. It is not recommended that the cargo be used to hold the tank done as the shell to floor weld joint is still under stress which is not the preferential joint of failure should it occur.
So why all this preparation around why Hydrotesting is critical and not just a water transfer?
As you may already be aware is that NCS Fluid Handling Systems team successfully completed the largest Hydro-Test of an LPG tank in Canada in 2019 and now is on the largest LPG hydrotest in Canada currently. The tank is a part of a new LNG facility under construction in NW BC and is has an inner tank nearly 300′ in diameter and has a hydro test height of 75′ (The Design liquid level is must higher that 75′ overall and closer to 125′ overall). The tank is approximately 1.2MM barrels (190,900m3 – 50,400,000 US gal).
As previously stated, Hydro-testing is the process of filling a storage tank with water, and in some cases pressurizing it to a required test pressure and then verifying that the tank can withstand the pressure. In all cases the tank gets a fully functional operational check and settlement test . This process is an essential step in ensuring that LNG storage tanks meets the designed criteria and all elements of the inner and outer shells and foundation meet construction requirements to hold liquefied natural gas (LNG). NCS Fluid Handling Systems specializes in providing hydro-testing support services for these types of tanks and all others.
The team at NCS is experienced in both water transfer and water treatment operations, which are two integral components of the hydro testing process. The company has expertise in designing systems for transferring large volumes of water into the tanks safely and at required flow rates to meet the applicable design codes. Additionally, NCS Fluid Handling Systems also provide onsite filtration systems capable of treating water to the required levels of quality for hydro-testing purposes. In the case of LPG and LNG where the internal tank materials are suitable for extreme low temperatures, with LNG typically stored at -162°C (-260°F) the materials of construction will have high Nickle and or Chromium that must be protected from contaminates during testing and and cleaned post hydro. The team is experienced in designing water transfer systems to maintain the water temperature for safe testing.
NCS Fluid Handling Systems understands that safety is paramount when it comes to hydro-testing LNG storage tanks. Their team has a proven track record of successful hydro testing operations and their services have been praised by clients from various industries, including oil & gas, marine and chemical engineering. All operations are conducted in compliance with industry regulations and standards, providing customers with peace of mind that their systems are safe and reliable.
In summary, NCS Fluid Handling Systems provides comprehensive support services for hydro-testing LNG storage tanks. Their experienced team excels in both water transfer and treatment processes to ensure that all operations are completed efficiently and safely in accordance with industry regulations.