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Fuel Handling Piping Systems

Published by Jack Pittman and Associates on


Fiberglass pipe was first listed by Underwriters Laboratories Inc. (UL) in 1968. The product was a welcome addition to the market due to the corrosion and thread leak problems associated with single-wall steel pipe, the incumbent material.

UL physical requirements for pressure, bending and tensile performance vs. rating have remained virtually unchanged since that time. The “chemical” requirements have changed significantly since the original draft of UL Subject 971, “Standard for Nonmetallic Underground Piping for Flammable Liquids”. The original requirements of the standard allowed no measurable weight change of the product holding a variety of fuels and liquids over a 180 day period. Both of the NOV products, Red Thread IIA and Dualoy 3000/L met this requirement. Another stringent requirement passed by fiberglass pipe was the required strength retention after 270 days of total immersion (open, square-cut pieces of pipe immersed in a battery of fuels and other liquids).

Since the initial authorization to apply the Listing Mark was given, the fuel market has changed, most notably with the use of alcohol in fuel (both ethanol and methanol) and the requirement for secondary containment. Requirements for the piping have changed, also. In 1995, UL relaxed the requirements for fuel permeation (tested in terms of weight loss) and also allowed candidate products to be tested with “single-sided immersion” where the test fuel or liquid was only in contact with the interior surface of the product. With fiberglass pipe already passing the more demanding test criteria, this level of performance was easily demonstrated.

In 2004, after poor field experience with several products, UL “tightened” the requirements on permeation and instituted new criteria for dimensional stability and weight gain, and also increased the percent strength retention requirements. Following the permeation requirements for primary pipe through this chronology reveals the allowable fluid migration through piping to go from zero (from 1968 to 1995) to 4 grams per square meter per day (to 2004) to the current 1 gram per square meter per day.

Put in more practical terms, this equates to a little over 1/20 (one-twentieth) of a gallon per day per 100 ft. of 2-inch pipe. This is down from the 1/5 of a gallon per day per 100 ft. of 2-inch pipe that existed between 1995 and 2004, but is still higher than the “zero” originally allowed.

The 30-year warranty against internal and external corrosion when used for underground transfer of fuels has been proven repeatedly through almost 50 years of unparalleled performance by any other product offered, ever.

Fiber Glass Systems offers piping products for all fuel types, services and product types. For more information view the Fuel Handling brochure.


Categories: Petroleum