T.R. Consulting, Inc.

November 2002 Safety/Environmental Article

Flexible Piping Failures

By: Thomas Schruben – environmentalguy@aol.com

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Once again, tank owners are having trouble underground. And once again, pipes are the source of the trouble. As I write this article, I am reviewing reports of approximately 200 failures in double-walled flexible pipe systems in 11 states. Many of the failures have occurred within four years of installation, and they seem to be increasing in frequency. Some of the failures have been catastrophic, resulting in the release of thousands of gallons of product. Some pipes have only swelled and have not released product. For these reasons, some tank owners, regulators, and state-fund administrators are concerned that flexible-piping systems are not as reliable and long lived as they’d expected. In a flashback to the mid 1980s, the facts are murky and data is scarce, preventing regulators and UST owners from making fully informed decisions. Even the definition of “failure” is the source of many discussions. One person’s cosmetic defect is another’s system failure. However, two conclusions are clear: tank owners need to increase their vigilance for potential failures of flexible piping, and they should be ready to take swift action when failed piping is discovered.

A Brilliant Solution to an Intractable Problem

I’ve had a long history with UST system flexible piping. From its conception, I was excited by the potential for flexible pipe to provide affordable, reliable secondary containment for petroleum products. In the late 1980s, while with U.S. EPA OUST, I participated in some of the initial discussions on the flexible-piping concept. I then encouraged manufacturers to bring the concept to market.

In developing the 1988 UST regulations, we discovered that piping was a major source of leaks and that piping failures caused some of the largest releases. As was discussed in the preamble to the final 1988 technical requirements for UST’s (40 CFR Part 280), EPA believed that while new tanks that were protected from corrosion showed a remarkable reduction in failure rate over unprotected steel tanks, and that adding spill buckets and overfill prevention devices could dramatically reduce the incidence of overfill releases, the failure rate of fiberglass piping did not differ as dramatically from that of unprotected steel piping.

We at EPA were so concerned about the possibility of future catastrophic piping failures that we required two forms of release detection for single-walled, pressurized piping in the 1988 technical standards. Analysis of piping failures showed that many of the failures were related to the joints assembled in the field. In addition, installers told EPA OUST that while double-walled fiberglass piping was available, it was very difficult to install, prone to failure, and too expensive for most UST owners. Double-walled fiberglass piping systems had twice as many joints as single-walled systems, thus EPA was concerned that they would have twice the opportunity for problems.

Flexible piping rolled out like a garden hose. It would eliminate most of the field-fabricated joints and promised easier installation than double-walled fiberglass piping. The few joints that remained would be safely confined to secondary-containment sumps at the tank and under the dispensers. At the time, it seemed to be a brilliant solution to an intractable problem. The product was well received from its first introduction. In 1997, EPA OUST listed seven manufacturers of flexible pipe (Survey of Flexible Piping Systems, March 1997, ICF Incorporated).

Currently, five brands of flexible pipe are available in the US. The 1998 upgrade deadline was a boon for flexible pipe, particularly in states that require secondary containment for piping. The marketers of flexible piping were hard pressed to keep up with orders from owners who were looking for the reliability and security of secondary containment.

Early Troubleshooting

There were some early problems with flex pipe, but the regulators and many tank owners remained confident that the product would prove reliable. While some of the problems were typical manufacturing problems that surface when any new product goes into mass production, some were unique. Over the years, several of the manufacturers have changed the design of their piping in response to product problems, while others have not experienced failures and thus have not changed their design. The March 1997 report from EPA OUST concludes that:

To date, problems with flexible-piping systems have been limited to fungal decay of first generation polyurethane-coated piping. The fungal decay is mostly cosmetic and does not cause product failure, however, one manufacturer (Total Containment) has changed its outer layer construction to polyethylene and is in the process of replacing the polyurethane piping. Most manufacturers are now marketing third and fourth generation products. Problems with these systems have been infrequent, and manufacturers have stood by their products. From an environmental protection standpoint, the performance of this technology to date has been excellent.

Recent Failures

The failure reports that I have received from regulators and the failures that I have investigated for my clients indicate that there are two distinct failure modes, which sometimes operate in tandem:

• The most common failure mode is one where the outer layers of the primary pipe soften, swell, and ultimately split. The pipe often feels sticky and spongy. The swelling can cause the pipe to grow several inches in length. This growth sometimes tears the secondary containment boot at the sump wall and over stresses the shear valve or flexible connector to which it is attached. Swelling can also seal off the interstice of the coaxial pipe against the coupling ferrule, masking a leak in the primary pipe.

• The second mode of failure involves the end fittings of the primary pipe. The swaged fittings sometimes split or loosen, allowing the pipe to slip off the end fitting. This can happen at either end of the pipe run.

These failures are not confined to a single version of flexible pipe or to a single manufacturer. However, the early reports that I have reviewed show more failures with some brands than others and I have no reported failures for some of the brands. The amount of pipe in the ground in total and for each brand is not known so I can not at this point determine if a particular brand of pipe is failing more frequently than another brand. Also, it is not clear whether the failures are the result of installation error, shipping damage, defective manufacture, defective design, fuel incompatibility, other causes, or some combination of causes.

The 11 states with failures that I have reviewed are principally in the South. Several of the regulators and state fund administrators in northern states with whom I have spoken have not been aware of flexible-pipe failures in their states. However, because owners may not be informing regulators of the piping failures that do not result in reportable releases, this apparent North-South geographic distribution may be related more to reporting than actual failure rates.

Because of these open questions, the regulators and state fund administrators that I have talked to are not ready to determine which, if any flexible piping is too unreliable, as the failures may be isolated to a few specific causes that do not affect all flexible piping installations equally. Clearly, more investigation will be needed before we get a full understanding of the failures and their causes.

Risk Management Actions

One aspect of the failures that is clear to regulators and owners alike is that the piping failures are too often compounded by leaks in sumps and failure of the release detection systems. Not only do sump leaks allow the petroleum to discharge to the environment, they can defeat the release detectors because the product does not fill the sump to the trip level of the liquid sensor. In addition, malfunctioning release detection systems have allowed product to overflow the sumps and flow down the street before the failure was discovered.

UST owners, state regulators, and state fund administrators are approaching this problem in different ways around the country. The following risk management actions may be applicable in many situations:

• Inspect the facilities for signs of impending failure. The good news is that many of the impending failures are easily visible if you know what to look for and where to look. Inspect for sticky and deformed pipe in the sumps and for cracked or loose end fittings. Elongated pipe will sometimes kink in the sump or cause misalignment of the piping tees and ells or bending of metallic piping flex connectors. Inspect the secondary jacket of coaxial piping for any signs of swelling or growth of the secondary jacket over the coupling ferrules. On coaxial systems where "test boots" are installed on the ferrules, the boots may appear compressed or swollen as a result of jacket growth. The swaged area of the end fitting sometimes develops a visible crack before failing completely. A large convenience store chain in Florida mounted an aggressive inspection program of their facilities and discovered several cracked swaged fittings in time to prevent total failure.

• Test the secondary containment and release detection system to confirm that it is working properly. As with all pressurized piping, release detection is critical to preventing releases to the environment. Properly functioning secondary containment and rapid response to release alarms has kept a number of flex piping failures from becoming major releases to the environment. Check that sumps are liquid-tight and that sensors and alarms are working.

• Consider adding additional, redundant piping release detection systems to minimize any release that might occur from a failure of the primary pipe. Some owners believe that two heads are better than one. There are a variety of release detection systems that can be used in combination on pressurized piping, including liquid sensors in the sumps, mechanical line-leak detectors and electrical interlocks from the leak detection system to the pumps. While redundant release detection may not be required by regulations for secondarily contained piping, it can be an inexpensive way to prevent a catastrophic release.

• If you find failed or failing flexible piping, take it out of service immediately, investigate and preserve the evidence of the failure so that an effective examination of the failure can be made and we can all gain a better understanding of the causes of the failures. Have an independent expert at the site when removing failed equipment to perform an unbiased inspection. Many state inspectors, insurance adjusters, and installers (not the original installer of the piping), have the experience and the qualifications for this task. Notify the manufacturer and other parties concerned and work closely with them to investigate the causes of the failure. The manufacturers and marketers of flexible piping need to be involved in the investigation if the owner intends to make a warranty claim. Many owners are preserving samples of failed piping for independent testing, and insurance and warranty claims. Document the condition of the system as it is being uncovered and removed with photographs.

The bright spot in this flexible pipe situation is that many of the failures have been discovered and caught by vigilant UST owners and regulators before they resulted in releases to the environment. With further analysis of these failures and improved communication we can gain a clearer understanding of the root causes of these failures and find better ways to manage the risks.

Thomas Schruben is an independent environmental risk management consultant. He assists UST owners and state funds with environmental insurance, claims, and strategic planning. He can be reached at environmentalguy@aol.com.