Ethanol Compatibility with
Fiberglass UST Systems
E-10 Compatibility
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 for all gasoline motor vehicles excluding nonroad
engines such as consumer products (e.g., property care equipment) or nonroad
vehicles (e.g., marine vessels). 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. Third, 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.
Finally, the fuel systems for nonroad engines and nonroad vehicles were designed
for conventional or MTBE blended gasoline and are typically not compatible with
ethanol blended fuels. Further, the accumulation of water from condensation in
the transportation and storage system is controllable in such gasoline since it
is not absorbed by the fuel and being heavier than the fuel, accumulates on the
tank bottom. American Petroleum Institute (API) Recommended Practice (RP) 1621
Bulk Liquid Stock Control at Retail Outlets recommends the removal of tank water
bottoms for such gasoline when the water exceeds on inch.
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
RP1626 Storing and Handling Ethanol and Gasoline-Ethanol Blends at Distribution
Terminals and Services Stations 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
1626 and remove any water from tank bottoms. E-10 is known to absorb 0.5 percent
water into a solution at room temperature or less when colder, the water reduces
the motor fuel BTU content and octane rating, again affecting the consumer. When
E-10 absorbs more than +/ - 0.5 percent of water, a “phase-separation” will
occur as the alcohol begins to drop out of the gasohol solution into the bottom
of the tank. This phase-separated alcohol/water bottom is oxygen rich and
promotes the growth of aerobic bacteria colonies. Such bacteria colonies are
detrimental to petroleum fuels and will cause Microbial Induced Corrosion (MIC)
in certain fuel handling metallic components. This includes metallic striker
plates that are not encapsulated in a corrosion resistant material such as
fiberglass. In summary, while water removal is a good housekeeping practice and
there is a companion growth of bacteria colonies accompanied by MIC, experience
has shown that this does not have an adverse long term affect on the fiberglass
tank lifespan. 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 E-10 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 E-10
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 E-10 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 expire. 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.
E-85 Compatibility
Fiberglass piping:
Underground fiberglass piping and fittings installed in service stations have
been compatible with up to 100%-percent ethanol for over 40 years.
Fiberglass tanks:
- 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 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.
- 2006 - 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.
Sullivan (Sully) Curran P. E.,
Executive Director
Fiberglass Tank & Pipe Institute
Disclaimers:
- 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.
2/16/09 sdc rev.2/20/09 rev6/22/09 rev6/30/09 rev7/19/09
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