At most airports fuel for aircraft and ground vehicles is stored in aboveground storage tanks (ASTs). Each State will have their own regulations defining size and number of tanks, locations, setbacks, safety equipment, and specifications for loading and dispensing fuel.
While each state has the right to determine its own regulations, states generally adopt national fire codes and modify them to fit local requirements. The most popular code adopted is the National Fire Protection Association (NFPA) code.
Adhering To Code
The Sections of NFPA regulating aboveground storage tanks are NFPA 30, titled Flammable and Combustible Liquids Code, and NFPA 30A, Automotive and Marine Service Station Code. NFPA 30 primarily deals with fuel tank design and safety, and NFPA 30A deals with fuel handing and safety issues at service stations and marinas.
While NFPA 407 regulates airport fuel systems, many states use NFPA 30A to regulate fueling small aircraft by pilots.
Typically, NFPA 30 and 30A regulate aboveground storage tanks according to three factors:
1.) Type of inflammable or combustible liquid stored;
2.) Location of the tank in relation to property lines, public ways, and buildings on the same property; and
3.) Type of intended use.
The NFPA allows unattended service stations with aboveground tanks provided the tanks are ‘Fire Resistant’. A Fire Resistant Tank is designed and tested by a Nationally Recognized Testing Laboratory (NRTL) to maintain its structural integrity for a period of not less than two hours when exposed to a temperature of 2,000oF, as described in UL 2085, Standard for Insulated Aboveground Tanks for Flammable and Combustible Liquids.
Three UL codes and two SwRI codes relate to ASTs:
UL142 AST: a construction standard for steel tanks; does not require a fire test.
SwRI 97-04 Fire Tested Tank: requires a two hour, 2000oF fire test; primary tank must pass 5 psi air pressure test for one hour. No temperature limits. Optional: Vehicle impact resistance, ballistics resistance.
UL2080 Fire Resistant tank: requires a two hour, 2000oF fire test, temperature limit: 800o F avg., 1000o max. at any one thermocouple. Optional: Vehicle impact resistance, ballistics resistance.
SwRI 93-01 Protected Tank: requires a two hour, 2000oF fire test, temperature limit: 260o F avg., 400o max. at any one thermocouple. Optional: vehicle impact resistance, ballistics resistance.
UL2085 Protected tank: requires a two hour, 2000oF fire test, temperature limit: 260o F avg., 400o F max. at any one thermocouple. Optional: vehicle impact resistance, ballistics resistance.
In most instances, ASTs that comply with the UL142 construction standard and SwRI 97-04/UL2080 fire tests are acceptable for use at airports, in particular for the turnkey, self-service fuel stations that my company specializes in.
The Steel Tank Institute (STI), a trade association representing fabricators of steel construction products and their suppliers, licenses many tank manufacturers to sell their products under the Flameshield ® (UL142, Fire Resistant) and Fireguard ® (UL2085, Protected) trademarks.
While concrete has been a traditional insulator, the significant weight increase this brings has led some tank manufacturers to now offer lightweight thermal insulation that can be 75 percent lighter than concrete, reducing the costs for shipping, installation, and relocation.
But are UL2085-listed tanks worth the additional cost and weight? First, let’s consider the need for the lower temperature limits dictated for UL2085 tanks.
The principal difference between UL2085 and UL2080 fire test criteria is that the former limits the average temperature rise to 260o F average above ambient, with a maximum for any one thermocouple limited to 400o F above ambient.
The SwRI 97-04 Fire Resistant criteria is based on the NFPA definition of a Fire Resistant tank which does not require these temperature limits. As noted by Bob Benedetti, Senior Flammable Liquids Engineer of NFPA, in the Flammable and Combustible Liquids Code Handbook: