NCS Fluid Systems API Tanks & Hydro-testing

NCS Fluid Systems Hydrotesting Tanks

NCS Fluid Systems Hydrotesting Tanks

With nearly 40 API 650 and API 653 tank hydrotests performed in the past 2+ years the NCS Fluid Handling Systems crews and project managers ready the equipment for the next round of tanks that will be hydro-tested in 2018 and 2019. This team of hydrotesting specialists have been preparing line routes, crossing agreements and temporary diversion licenses over the past months as part of the first steps of preparation. Pumps, hose reels, API manways, floating inlet suctions, flow meters and much more equipment are being tested and marshalled for deployment over the next couple weeks. Some will be relocated to new yard locations and dispatched as required and other will ship direct from NCS locations to site right away.

But, we are often asked why tank owners perform a Hydrotest and the explanation is in the following summary.

The answer is to perform a fully function operational test using a test medium heavier than the designed for cargo (water is safer than a hydrocarbon product as a test medium if there is a non-complying element detected during testing). This test process is to confirm tank base integrity and settlement is uniform, test tank components such as pontoons on floating roofs, roof drains, roof seals, rolling ladders inside the tank, roundness, leak free and confirmation that the tank will operate as designed. Then turnover documentation is provided to the tank owner so that their application to the appropriate governing authority will allow them to fill the tank with their product.


There are two main codes, one repair code and one standard when it comes to the fabrication of field erected storage tanks; API 650 for new built tanks and API 620 for tanks above 2.5 PSIG but less than 15 PSIG. API 653 for recertified existing tanks and API 12D for standardized production build tanks. API 650 is the most common code for newly erected field build tanks with API 620 picks up where API-650 leaves off with regards to pressure and is the governing standard for the design and large, above ground field-assembled storage tanks that contain petroleum gases or vapors as well as other liquid products.  These storage tanks are designed to operate at 250°F or less with an operating pressure of up to 15 PSI, at which point the ASME codes take over for pressure vessel design. For the most part API 620 Tanks are typically referenced for Liquefied Natural Gas, Liquid Oxygen or other storage of chemicals which require internal design pressures more than those allowed by API 650.

API 653 is specific to existing tanks that have been taken out of service and inspected, required repairs made and depending on the type and degree of repair a Hydro test may be required. API 12D is a standard that is specific to the design and application the tank will operate in, and is the least common in this market. 

When experienced crews are required to perform all services related to a fully operational and functional hydro testing North American customers’ look the NCS Fluid Handling Systems and the skilled team trained to perform all operational checks related to the testing of these tanks.

While some businesses will advertise the filling of a tank or multiple tanks with water as performing the Hydrostatic test, this only contributes to confusing what a fully functional test is. At NCS Fluid Handling Systems we understand the total cost of ownership of these valuable tank assets and the long-term expectations owners have for their continued performance, that is why NCS provides specialized training to all levels of our staff, so that this dedicated team can meet the specialized skills required and enhanced degree of service owners expect for pre-commissioning these value assets. Starting with temporary water diversion licensing, surveying crossing agreements, water analysis (pre-and post test), water fill and transfer, full operational checks of floating roofs, stairs, ancillary components, filtration, iron removal, erosion-controlled water release to source and tank dewatering and drying. As the sole source for any or these required services NCS Fluid Handling Systems understands our clients needs fully, not just one part of a valuable overall service.


American Petroleum Institute (API) 650 was originally released in 1961 and is the international standard for tanks widely used for tanks that are designed to internal pressures of 2.5 PSI or less and store products such as crude oil, gasoline, chemicals and produced water.

The American Petroleum Institute realized that the industry needed a design specification that allowed for regional and global considerations that the API 12 series did not provide. The API-12C specification was, for lack of a better term “pre-engineered and tested” as most of the 12 series tanks are, they are standardized designs based on practical applications or predetermined size and performance parameters. So, from the foundation of API-12C the API-650 became the governing code for petroleum product storage tanks. This standard now provided designers the considerations for varying conditions that globally affect tank design, such as extreme weather variations and material performance, seismic design and zones, wind overturning, internal pressures, varying heights and diameters, material grades and thickness, non-destructive testing as well as hydro testing for all the above conditions and variations.

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