Ethanol Compatibility with
Fiberglass UST Systems
Due to state bans on methyl tertiary butyl ether (MTBE), notably in California
and New York, the use of ethanol motor fuel (i.e., a maximum of 10 percent ethyl
alcohol in gasoline) has expanded. However, other states, particularly in the
Midwest, have used ethanol fuel for many years. The market share of ethanol
motor fuel has grown from virtually zero in 1978 to 7 percent in 1986, and is
approaching 100 percent today. Although this represents a significant volume of
ethanol stored and dispensed through the pre-1978 population of underground
storage tanks (USTs), it is comforting to know that fiberglass USTs and piping
that store conventional gasoline or MTBE added gasoline should perform equally
well when handling gasohol.
While it is natural for those of us in the petroleum marketing industry to focus
on UST compatibility with ethanol, the introduction of ethanol into the
marketplace raises many other considerations. First, with vehicle turnover
averaging 20 years or more, there are both old and new automobile fuel handling
systems that must be compatible with oxygenated motor fuels and additives. For
this reason, the U.S. Environmental Protection Agency (EPA) provides consumer
protection by limiting the amount of ethyl alcohol in motor fuel to 10 percent.
If this EPA limit is exceeded, automobile manufacturers will void their
warranties for non-flexible fuel vehicles.
Second, the elastomers in fuel dispensing equipment, other than tanks and
piping, are often more vulnerable to fuel base-stock and additive changes. This
includes Buna-N gaskets and “O” rings, and submerged metals such as aluminum,
copper, and black or cast iron. Thus, for older equipment it is prudent to
consult the manufacturer of dispensers, pumps, monitoring systems, nozzles and
swivels when making changes in stored fuels.
Finally, EPA requires that methanol blends exceeding 5 percent methyl alcohol
meet hazardous substance storage and piping requirements and be secondarily
contained. Thus, all double-wall fiberglass tanks and piping have been
manufactured for storage of 100 percent ethyl and methyl alcohol since 1988 for
piping and 1990 for tanks.
Ethyl alcohol, because of its affinity for water, is not blended into gasoline
until it is loaded into the delivery tank truck. American Petroleum Institute
(API) member companies address the need to control the ethanol blend component
in API Recommended Practice (RP) 1626 that states: “In-truck blending is not
recommended since complete blending may not occur.” Thus, so-called
“splash-blending” ethanol in tank trucks is not recommended since the
ethyl/gasoline components tend to stratify and remain stratified after delivery
to the refueling facility. As a result, the pump may pick up a high
concentration of stratified ethyl alcohol, damage the automobile engine and not
be covered under warranty.
This affinity of ethyl alcohol for water is a strong reason to follow API RP
1621 and remove water from tank bottoms when the water exceeds one inch. While
ethanol can safely absorb 0.5 percent ethyl alcohol into a solution, the water
reduces the motor fuel BTU content and octane rating, again affecting the
consumer. When ethanol absorbs more than 0.5 percent of alcohol, a
“phase-separation” will occur as the alcohol begins to drop out of the gasohol
solution into the water bottom of the tank. This phase-separated alcohol/water
bottom encourages the growth of aerobic bacteria colonies, which are detrimental
to petroleum fuels and certain fuel handling components. Experience has shown
that this is not a problem with fiberglass tanks and piping.
While gasohol entered the marketplace in 1978, UL did not include gasohol and
methanol fuels in material compatibility testing protocol, until later. As a
result, the UL listing for fiberglass tanks and piping included ethanol in 1981
and 1988 respectively (i.e., UL 1316 and UL 971). Thus in 1978, when gasohol was
first introduced, there were some 100,000 fiberglass USTs in conventional
gasoline service before the UL listing process included gasohol in their
compatibility testing protocol. Therefore, the early users of fiberglass tanks
and piping (i.e., major oil companies) and fiberglass tank and pipe
manufacturers conducted independent studies to determine the effect of gasohol
on the fiberglass material used for in-service USTs. It was determined that the
fiberglass components used in pre-1981 tanks and pre-1988 piping were
essentially the same as those subjected to UL compatibility testing and there
was no technical reason to believe that the older USTs were not gasohol
compatible. In 1992, Owens Corning, the manufacturer of the oldest fiberglass
tanks, advised certain major oil companies that some tanks were approaching
30-years-old and the warranties have expired. As a result, the affected
companies conducted surveys of these older tanks, including tanks in alcohol
service (e.g., in the Midwest) and confirmed that the tanks were satisfactory
for continued service. In summary, technical evaluations and historical
experience demonstrate that there is no material or technical reason why
properly installed pre-1988 piping and tanks in conventional or MTBE service
should not perform equally as well when handling 10 percent ethanol blends.
Underground fiberglass piping and fittings installed in service stations have
been compatible with up to 100%-percent ethanol for over 40 years.
Sullivan (Sully) Curran P. E., Executive Director
- 1983 - The September 1983 issue of the Underwriters Laboratories (UL) Gas &
Oil Equipment Directory includes multiple manufacturers with listings for
fiberglass “non-metallic tanks for petroleum products, alcohol’s and
alcohol-gasoline mixtures.” The UL use of the term “alcohol’s and
alcohol-gasoline mixtures” is defined in UL standard 1316 to include fuels with
any level of ethanol or methanol up to and including 100%.
- 1988 - In 1988, UL began listing underground fiberglass piping and tanks for
100% ethanol and methanol.
- 1990 – By 1990, Institute member fiberglass tank manufacturers had modified
their tanks constructions to handle gasoline with any level of ethanol or
methanol up to 100% for all double-wall fiberglass tanks and in some cases
single wall fiberglass tanks.
- 2004 - UL did not include fiberglass piping or tanks in the 2004 suspension
of UL markings for fuel dispensing
devices that reference compatibility with alcohol-blended fuels containing
greater than 15-percent alcohol.
Fiberglass Tank & Pipe Institute
Sullivan D. Curran, P.E., is the Executive Director of the Fiberglass Tank and
- This paper discusses the compatibility of gasoline-alcohol blends with
fiberglass storage tanks and piping systems manufactured by current members of
the Institute, namely Ameron International - Fiberglass Composite Pipe Group,
Containment Solutions Inc., Fiber Glass Systems and Xerxes Corporation. While
this paper includes the Institute’s understanding on products from former
members, it is not an analysis of products by other manufacturers.
- Institute tank company plants may have changed manufacturing specifications
at different times within a given year listed above. In addition, certain tanks
were manufactured according to customer specifications. Thus, tank owners
needing specific production information, will need to provide the manufacturer
with delivery date and delivery location.
- Nothing in this paper alters the given piping or tank manufacturer’s warranty
for the product at the time of sale.
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