UL 142 – The Industry Standard for Steel Aboveground Tanks for Flammable and Combustible Liquids

You’ve probably heard of the UL 142 standard if you own aboveground fuel storage tanks or if you’re considering large volume aboveground fuel storage tanks to improve fueling logistics in your business or organization.

There’s a lot of engineer and attorney speak packed into UL 142. And guess what? Fuel storage tanks can and often must comply with more than one standard. Add on code compliance requirements, and you might feel overwhelmed.

“The NFPA 30 Flammable and Combustible Liquids Code requires atmospheric tanks to be designed and constructed in accordance with one of several recognized engineering standards, one of which is the UL 142, Standard for Safety for Steel Aboveground Tanks for Flammable and Combustible Liquids,” according to UL. “The International Fire Code in turn requires tanks to be designed, constructed and installed in accordance with NFPA 30.”

Confused? You don’t need to be. Let’s take a look at UL 142 alone. When we break it down into plain language, you can see what’s important and begin to compare standards, like UL 142 vs UL 2085.

What is UL 142 Standard?

The “UL” in UL 142 stands for UL Standards & Engagement, one of three arms of the 129-year-old testing, inspection and certification organization previously known as Underwriters Laboratories but now known simply as UL. The organization works in more than 110 countries to ensure consumer product safety.

(UL certification isn’t limited to products. UL also certifies personnel, facilities, processes and systems to applicable standards and requirements. When a product is “UL LISTED,” it means the product has undergone rigorous UL testing and complies with UL standards.)

The “142” in UL 142 designates which standard. Since UL published its first standard for tin-clad fire doors in 1903, the nonprofit has published 1,700 safety standards.

UL 142 limits potential hazards such as fire, leaks and spills to help ensure the safe storage of flammable and combustible liquids in three kinds of shop-fabricated steel storage tanks:

1. Primary storage tanks
2. Secondary storage tanks (double wall tanks)
3. Diked-type atmospheric storage tanks.

All steel fuel storage tanks must comply with UL 142. The standard does not cover poly tanks or portable tanks intended for mobile fueling (mounted on trailers) or transport (such as shipping containers).

What Are UL 142 Requirements?

UL 142 tank requirements cover construction, performance tests, markings and production line tests, and manufacturing and production tests.

• • Construction. Specifications include UL 142 tank materials, joints, connections, fittings, manholes, fill, drain and gauge openings, and painting. Requirements also include the primary and secondary containment means, supports, etc.
    • Shape. Tanks may be cylindrical, rectangular or round with horizontal and vertical orientations and with or without multiple compartments.
    • Size. Requirements differ by tank shape because stress distributions on round and cylindrical tanks are more uniform than on rectangular tanks. The irregular wall sizes and shapes of rectangular tanks cause irregular stress distribution.

• • Performance tests. Requirements include tank leakage, hydrostatic strength, top loading, buoyancy, hydrostatic load, tank support load, and lift lug tests designed to verify tanks shows no signs of leakage, structural damage or both as a result of these tests. UL 142 requires performance tests on a selected number of samples. For example, UL 142 has minimum requirements for rectangular tank plate thickness regardless of tank size and height. These performance tests ensure walls are thick enough to handle the resulting stresses at different pressures.

• Markings and production line tests. Tanks must include specific markings (see bullets below). In addition, UL 142 tank manufacturers must leak test 100% of the UL LISTED primary and secondary containment tanks they produce.
  • Each aboveground tank that complies with UL 142 requirements must have a permanently affixed UL Listing Mark.
  • The Listing Mark includes the UL symbol, the word “LISTED,” a control number and the name of the tank construction indicated in the manufacturer’s Listings (e.g., Secondary Containment Aboveground Tank, Generator Base Tank, etc.)

What’s Covered?

UL 142 Listing covers basic tank features: all containment spaces and their openings (manways, emergency vents, normal vents, fill/withdraw, gauging, monitoring and other functional openings) with connections (threaded or flanged fittings) and integral tank accessories (ladders, stairs, lifting lugs and heating coils or hot wells).

All primary tank compartments are provided with openings to accommodate filling, withdrawing and inventory control. All secondary tank interstitial spaces are provided with openings for leak detection monitoring.

What’s Not Covered?

UL 142 Listing does not cover external 3rd party equipment or components that are shipped with, attached to or added to tanks. Examples of what’s not covered include hoses, pumps, meters and fuel management systems installed as third-party items to help operate fuel dispensing facilities, motor fuel dispensing at farms and isolated construction sites, and on-demand mobile fueling as quoted in NFPA 30A.

Because UL 142 doesn’t cover certain accessories, it is expected that the authority having jurisdiction (AHJ) — generally a local fire or building inspector — will approve the use and/or installation of these accessories independent of the tank Listing.

Consult your AHJ about specific code requirements outside the scope of UL 142.

Unity UL 142 Tanks

Unity Fuel Solutions makes two types of UL 142 LISTED tanks:

• UL 142 BLOC Tanks
• UL 142 GRANDE Tanks

UL 142 BLOC Tanks

Unity BLOC Tanks are a “cube style” double-walled fuel storage tank with flexible storage and dispensing for diesel, gasoline and lubricant oils.

• Capacity: 264 to 2,642 gallons
• Safety: Primary tank + interstitial space + secondary external tank. Freestanding design allows 360-degree tank viewing and inspection.
• Convenience: Fast and easy transport to site. Modular design requires minimal site preparation. Place-fill-and-pump installation.
• Compliance: UL 142, ULC S601-14

UL 142 GRANDE Tanks

Unity GRANDE tanks are a self-contained aboveground fuel storage tank (AST) and fuel management solution for diesel, gasoline, lubricants and other hydrocarbon liquids.

• Capacity: 2,969 to 28,370 gallons
• Safety: Primary tank + interstitial space + secondary external tank. All aboveground for maximum visibility during monitoring and maintenance.
• Convenience: Fast and easy transport to site. Made to fit ISO container footprints (20, 40 and 48 feet). Requires minimal site preparation. Integrated pump bays.
• Customizable: Standard and add-on compartments for lubricants, coolants, waste oil. Ready-to-use pumps, reels, meters, filtration. Multiple products in same tank footprint. End-mounted security cabinet options: steel or roller shutter doors and internal spillage trays; house pipework; pumps; gauging; alarms and controls.
• Compliance: UL 142, ULC S601-14

More Resources

Information on tanks with UL 142 certification may be found in the Online Certifications Directory.

• The Aboveground Flammable-liquid Tanks (EEEV) product category includes information on the products covered under this category.
• The Special-purpose Tanks (EFVT) product category covers Listed UL 142 aboveground steel tanks that include generator base, work-top, lube oil, waste oil, day/utility and other special-purpose tanks.

Need Help? Ask the Experts

For help in choosing the right UL 142 double walled tank, it makes sense to ask the experts. Unity Fuel Solutions is North America’s leader in double walled storage tanks. For advice on the tank and system that’s right for you, call the Unity team at 800-234-1689.