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Ethanol and USTs
Certain northeastern and western states are expanding the use of ethanol motor
fuel (i.e. maximum of 10% ethyl alcohol in gasoline) and are joining 50% of the
other states that have, since 1978, added incentives to the federal government
reduction in ethanol motor fuel taxes. From virtually no ethanol in 1978, its
market share grew from 7% in 1986 to 30% today. While this represents a
significant volume of ethanol stored and dispensed through the pre-1978
population of USTs, it is comforting to know that tanks and piping in
conventional or MTBE gasoline service should perform equally as well when
handling ethanol.
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 other considerations. First, with vehicle turnover averaging
every 20+ years, there are both old and new automobile fuel handling systems
that must be compatible with reformulated motor fuels and additives. Thus, the
EPA provides consumer protection by limiting the amount of ethyl alcohol to 10%
and automobile manufacturers will void their warranty if this EPA limit is
exceeded. 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 & “O” rings, and submerged metals such as aluminum,
copper and black or cast iron. Thus, for older equipment it is well to check
with the manufacturer of dispensers, pumps, monitoring systems, nozzles and
swivels. Finally, the EPA requires that methanol blends exceeding 5% methyl
alcohol must meet hazardous substance storage and piping requirements and be
secondarily contained. Thus, double-wall fiberglass tanks and piping
manufactured since 1988 (piping) and 1990 (tanks) are 100% ethyl and methyl
alcohol compatible.
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
member companies address the need to control the ethanol blend component in API
RP 1626 which states: “In-truck blending is not recommended since complete
blending may not occur.” Thus, “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. Thus, the pump may pick up
a high concentration of stratified ethyl alcohol, damage the automobile engine
and not be covered under warranty. Finally, the affinity of ethyl alcohol for
water is reason to follow API RP 1621 practices and remove tank water bottoms
when they exceed one inch. While ethanol can safely absorb 0.5% ethyl alcohol
into solution, the water reduces the motor fuel BTU content and octane rating,
again affecting the consumer. And when alcohol absorbs more than 0.5%, a
“phase-separation” will occur as the alcohol begins to drop out of the gasohol
into the water bottom. This phase-separated alcohol/water bottom encourages the
growth of aerobic bacteria colonies, which are detrimental to petroleum fuels
and certain fuel handling components and should be avoided.
While gasohol entered the marketplace in 1978, Underwriters Laboratories did not
include gasohol and methanol fuels in the 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. Later in 1992, Owens Corning, the manufacturer of the oldest
fiberglass tanks, advised certain major oil companies that tanks were reaching
30-years of age and the warranties were expiring. As a result, the affected
companies conducted surveys of these older tanks, including tanks in alcohol
service (e. g., Midwest) and confirmed that the tanks were satisfactory for
continued service.
Thus, in summary, technical evaluations and historical experience are evidence
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% ethanol blends.
Note: Sullivan D. Curran, Executive Director of the Fiberglass Tank and Pipe
Institute, wrote this paper. The paper discusses the compatibility of
gasoline-alcohol blends with FRP storage tanks and piping systems ONLY
manufactured by members of the Institute. This paper does not address other FRP
manufacturers of FRP products manufactured by others. |
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