Fiberglass Underground Storage Tank Success in the USAAudio version
Publication: Petroleum Equipment & Technology Archive
Issued: November 2001
Author: Curran Sullivan D. , PE
The success of fiberglass tanks is reported by Sullivan “Sully” Curran, Executive of the Fiberglass Tank and Pipe Institute
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 as measured by historical experience 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 was introduced as a new material for the manufacture of underground tanks over 35 years ago (i. e., 1965) this new product changed the methods by which tanks were manufactured, the QA-QC procedures employed and the method of installation. 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 market.
Methodology to Determine Success Rate of Single-wall FRP Tanks
Historical 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. Sufficient data are available for a shorter time period to develop a valid study.
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.