Standards Matter

Standards for Aboveground Tanks Help Store Dangerous Liquids Safely

UL Standards & Engagement
September 21, 2022

Diesel Tank

Why It Matters

Aboveground tanks are a popular choice for storing flammable and combustible liquids due to their low upfront and long-term maintenance costs. They are easier to access than underground tanks, and they also require much less installation work. Often, they are used to store fuels, crude oil, and other liquids, which have the potential to be dangerous, especially when stored in large quantities. 

According to the National Fire Protection Association (NFPA), U.S. fire departments responded to an estimated annual average of 301 fires at outside storage tanks from 2007-2011. Although these types of fires have decreased by 76% since 1980, they still have the potential to cause property damage, injuries, and even death. These fires are often ignited by lightning or industrial equipment, and can be catastrophic — especially if standard product requirements have not been met.

What We’re Doing

UL Standards & Engagement has developed several standards for liquid storage tanks, one of which is UL 142, the Standard for Steel Aboveground Tanks for Flammable and Combustible Liquids. The Standard covers steel primary, secondary, and diked-type atmospheric storage tanks intended for the storage of noncorrosive, stable flammable and combustible liquids with a specific gravity (spg) not exceeding 1.0 in aboveground applications. Tanks covered by the Standard may be fabricated in different shapes (cylindrical, rectangular, obround) and with different orientations (vertical, horizontal), but all must meet the construction, performance, and marking requirements provided by this Standard. 

The performance requirements of UL 142 include numerous tests to verify the integrity of the tanks, including a Tank Leakage Test and Hydrostatic Strength Test. During the Tank Leakage Test, soap suds and air pressure are applied within the tank to detect any leakages. As an alternative, the test can also be conducted by completely filling the tank with water and applying pressure hydrostatically to check for leaks. Similarly, the Hydrostatic Strength Test relies on water and pressure, but in this test, the pressure is gradually applied in increments of 5 psi until the test gauge pressure of 25 psi is attained. At each increment, the pressure is held for two minutes, and the tank must not show any signs of leakage or rupture.

How You Can Help

Our Standards are developed through a consensus-based process, which integrates scientific and testing expertise with input from our Standards Technical Panel (STP) members and stakeholders. STP members represent a variety of interests, including industry, academia, government, retail, and manufacturing. If you are involved in the design, construction, sale, or operation of tanks for flammable and combustible liquids, and you would like to help improve safety in your industry, please submit a proposal or apply to join an STP.