Fiberglass Underground Storage
Tank Success In the USA
Introduction and Scope
Competition between steel and fiberglass tank manufacturers has resulted in
product comparisons and superiority claims in several areas. While tanks
typically are warranted for 10 to 30 years, the owner recognizes that the
liability costs associated with premature failure far exceed the replacement
value of the tank itself. As a result, the probability of success is of
importance to the tank owner.
Often negative claims are biased by reports based on incomplete information and
the reader will need to look at both sides of what is often competing marketing
information. For example, while not identifying the incident date or
circumstances, there is a recent report on limited single-wall fiberglass
tank failures that occurred in certain European countries. This negative
European report is inconsistent with the historical and essentially release-free
success rate of single-wall and 100% release-free success of
double-wall fiberglass underground storage tanks in the USA. Industry in the
USA is known to be innovative and not bound to traditional technologies. Thus,
when fiberglass underground tanks were introduced over 35 years ago (i.e., 1965)
this new product changed the methods by which tanks were manufactured
(Quality-Assurance-Quality-Control known as “QAQC” procedures) and installed.
This paper addresses the success rate of single-wall fiberglass
reinforced plastic (FRP) tanks and the reasons for their successful application
in the USA petroleum storage market.
Methodology to Determine Success Rate of Single-wall FRP Tanks
Study Time Frame - One must decide on a practical time frame over which a
tank’s condition should be evaluated. For example, there is a population of
single-wall fiberglass tanks that have enjoyed leak-free service for 35
years based on when FRP tanks were Underwriters Laboratories labeled in 1965 and
on historical manufacturer warranty records (i.e., the current FRP tank warranty
period in the USA is typically 30 years). However, over 35 years of tank
ownership changes have made it impractical to gather historical maintenance and
product storage data, which is often not available with these changes.
Realistically, a shorter time frame needs to be selected where data are
available to develop a valid study sample.
Data Collection - An ideal study could result from excavating a
statistically significant sample of tanks and evaluating their condition.
However, the excavation of non-leaking tanks and disruption of a customer’s
place of business is not practical.
Another approach could be to tightness test the tank sample to evaluate tank
condition. At least one previous study compared test results with excavated tank
examinations and found that the tanks may be in worse condition than that
demonstrated by testing. [EPA Tank Corrosion Study; EPA 510-K-92-802; November
1988; page 3]. Therefore, relying on tank testing alone would likely indicate
tank failures (i.e., leaks) but would not fully evaluate tank condition and
potential near-term failure conditions.
In summary, reasonable valid data sources would be from non-tank
manufacturer or installer studies of excavated tank condition experience and
tank testing data.
Data Sources
Scope of available studies - Third party contractors and certain major oil
companies conducted underground tank condition studies by examining excavated
tanks. In addition, one contractor researched and analyzed tank tightness tests
to identify the tank condition of failed tanks. These studies are broad in
scope, covering most geographic areas and environmental conditions. In addition,
the study samples cover a significantly large number of single-wall fiberglass
tanks spanning ages up to 14 years. Following is a listing of these studies:
- Service Station Testing,
Inc., San Antonio, Texas report to Midwest Research Institute, dated
September 16, 1987. This report is on a study of 207 single-wall fiberglass
tanks up to 14 years in age that were excavated and examined, primarily in
Austin and San Antonio, Texas. The fiberglass tanks were found to be leak
free.
- Major Oil Company “A” report
on FRP tank leak data. This company had 11,396 single-wall fiberglass tanks
in service at the time of the study. Their leak tracking system indicated
two leaks, both of which were attributed to improper tank installation.
- Major Oil Company “B” report
on FRP tank leak data. This company had 7,410 single-wall fiberglass tanks
in service at the time of the study. Their leak tracking system indicated
two leaks, one of which was attributed to improper tank installation.
- Tank Corrosion Study (EPA
510-K-92-802). This is an EPA field study conducted in Suffolk County, New
York by the Suffolk County Department of Health Services. The report
analyzes observations made on the condition of 500 excavated underground
storage tanks from February 1987 to September 1988. Two of the excavated
tanks were 8 and 10 year old single-wall fiberglass tanks. The tanks were
leak free.
- Service Station Testing,
Inc., San Antonio, Texas report to Midwest Research Institute, dated July
21, 1987. This was a report on the analysis of tank tightness testing
conducted on 1,921 tanks of which 228 were single-wall fiberglass. The tests
were conducted primarily in the Austin and San Antonio areas of Texas and
portions of Colorado over the period of 1981 to 1987. The fiberglass tanks
were found to be leak free.
Single-Wall Fiberglass Tank Data
Summary
Data
Source |
Number of
FRP
Tanks in Study |
Average
Age (Est.) |
Number of
Failures |
|
Tank
|
Installation |
|
1 |
204 |
7 |
0 |
0 |
|
2 |
11,396 |
8 |
0 |
2 |
|
3 |
7,410 |
6 |
1 |
1 |
|
4 |
2 |
9 |
0 |
0 |
|
5 |
228 |
7 |
0 |
0 |
| |
Totals: 19,240 |
8 |
1 |
3 |
| |
|
% of Total |
0.005% |
0.02% |
Single-wall Fiberglass Tank Success
Experience
Impartial tank condition study data show that single-wall fiberglass tanks’:
- Installation success
rate was 99.9896% successful, or successful in 999.9 tanks out of 1,000
installations.
- Non-failure rate (excluding
installation) was 99.995 successful, or successful in 999.95 out of 1,000
installations.
- Total non-failure rate
(including installation problems) was 99.984% successful, or successful in
999.84 out of 1,000 installations.
Reasons for High Success Rate
The historical success rate for the application of fiberglass tanks in the
United States of America (USA) is primarily due to industry requiring high
manufacturing standards/quality, industry installation procedures and installer
training/oversight.
Manufacturing Standards/Quality – Fiberglass underground petroleum
storage tanks are manufactured in an automated process rather than a job-shop
operation. This automated process lends itself to standardized manufacturing and
Quality Control procedures from the time raw materials and components are
received, to interim composite sampling and final product testing. While each
tank manufacturer follows its patented procedures, the product is performance
tested to meet a third party independent laboratory standard Underwriters
Laboratories UL 1316 Standard for Glass-Fiber Reinforced Plastic Underground
Storage Tanks for Petroleum Products, Alcohols and Alcohol-Gasoline Mixtures.
Finally, UL is retained as the Quality Assurance contractor and routinely
inspects the manufacturing facility to ensure that Quality Assurance Quality
Control (QAQC) procedures are followed. Thus, USA fiberglass tanks are quality
manufactured, meet a third party performance standard, follow third party QAQC
procedures and come with a 30-year warranty.
Industry Installation Procedures - While each fiberglass tank
manufacturer publishes detailed installation procedures, the petroleum industry
(American Petroleum Institute) and the tank installer industry (Petroleum
Equipment Institute) also publish and routinely update underground tank
installation standards (API 1516 Installation of Underground Petroleum
Storage Tanks and PEI 100 Recommended Practices for Installation of
Underground Liquid Storage Systems). These installation standards are
codified in the Model Fire and Building Codes by the Authority Having
Jurisdiction (e. g., cities, counties and states) and required by the federal
government (i.e., Environmental Protection Agency). Thus, the proper procedures
for the installation of fiberglass tanks are readily available and mandated in
the USA.
Installer Training/oversight – Both the petroleum industry and fiberglass
tank manufacturers recognized early on that installation contractors required
training to change old detrimental practices. Improper practices (e. g.,
allowing foreign objects in the backfill, supporting tanks on hard objects, poor
backfill compaction) caused many premature steel tank failures. As a result,
beginning in late 1960, oil company personnel and fiberglass tank manufacturers
conducted contractor installation training programs and the record shows that
over 25,000 personnel were trained. In addition, since 1980, this number has
grown considerably as many states required additional installer training and
refresher courses.
Installer oversight has also become an important part of successful tank
installations. Oversight in the USA is required by federal government rules,
state inspectors and fire code jurisdictions. For example, New York City has
historically required on-site fire personnel oversight while a tank is being
installed.
Summary
A year 2000 market study Havill Consultant survey of retail petroleum marketers
showed that 55% of the underground storage tanks in the USA are fiberglass. Most
of this tank population consists of single-wall tanks and the foregoing record
shows that these tanks have performed successfully. Thus, there may be isolated
manufacturing, installation or oversight reasons when a tank failure occurs. The
petroleum industry is best served in the public arena by identifying failure
causes and implementing proven overall QAQC procedures.
10/09/01 |
