The high-pressure fire loop system engineer is responsible for maintaining the water supply for fire suppression at the U.S. Department of Energy/National Nuclear Security Administration (NNSA) Pantex Ordnance Plant in the Texas panhandle.
The Pantex Plant, lying 17 miles northeast of Amarillo, in Carson County, is charged with maintaining the safety, security and reliability of the nation’s nuclear weapons stockpile. The facility is managed and operated for the NNSA by BWXT Pantex, a limited liability enterprise of BWX Technologies and Honeywell.
Because of the facility’s mission, that particular engineer becomes a pretty important person. Failures to the piping system carrying water used to extinguish a fire in such a facility are unacceptable.
Over time, though, a pattern of such failures was occurring, said Melvin Suttle, a former high pressure fire loop system engineer at BWXT Pantex who was promoted to manager of the plant’s Maintenance Work Management Department. The plant operates under the highest levels of safety and security, to which a dependable water delivery system is crucial. Yet Suttle was reporting pipe breaks due to corrosion of the cast and ductile iron system - a system first installed in the late 1940s. The 79,000-foot long high-pressure fire loop is a dedicated water distribution system feeding fire suppression systems and fire hydrants. A break in the pipe can seriously compromise the fire suppression system function.
So Suttle decided to change how things were done in the past. He discovered the benefits of smooth wall high-density polyethylene (HDPE) pipe for industrial water applications. In August 2001, he purchased 60 feet of 18-inch diameter pipe - three 20-foot lengths - as a test case for Pantex.
This initial HDPE use was for an extension of the system that required 5,000-gpm capacity and 40 pounds of residual pressure. “We had several design options, however, HDPE offered solutions to all the issues,” Suttle said. “Back then, the product was brand new to us. It’s performing very well. And knowing what I know about HDPE pipe now, I’m sure that we’ll never have to see that 60-foot section of pipe again.”
Today, Pantex has about 3,900 feet of HDPE installed for the high-pressure fire loop. A couple of thousand additional feet of small diameter (2- to 4-inch) pipe is used on the natural gas distribution system but it doesn’t share the safety-class scrutiny of the fire loop and didn’t require qualification. Pantex has a phased plan to replace 50,000 more feet of the fire loop with HDPE pipe - preliminary drawings for the next phase were reviewed in September 2004.
Getting HDPE approval
Suttle expands on the steps and hurdles that were involved to get approvals to change to the HDPE.
“My impression is that HDPE pipe was viewed by some site engineers (both BWXT and the DOE) as low quality material to be used for temporary service,” he said. “I worked with my management to have vendor demonstrations on site. This was no small task due to site security. I also collected all the vendor data I could find using the Internet extensively, conducted visits to municipalities and observed PVC, iron and steel installations, and talked to several installers.”
He said the high-pressure fire loop is termed a “safety-class” system, meaning the configuration of the pipe, valves, pumps, etc., are governed under a management process.
“This configuration management process is defined by our operating permit, known as the Authorization Basis,” Suttle said. “This is a high level agreement between BWXT and the U.S. Department of Energy for operation of the site.
“Any proposed changes to the high-pressure fire loop must be defined, described and proven to meet the operating requirements of the system,” he continued. “This process, known as a design change proposal, is reviewed by numerous groups each with the privilege of challenging the rationale, including the Department of Energy.”
A DOE engineer did object to the use of HDPE pipe before Suttle proved that the material was listed in NFPA 24: Standard for the Installation of Private Fire Service Mains and Their Appurtenances. Suttle reports that the DOE engineer is now fully supportive of using the material.
Broadening the market
Rich Gottwald, president of the Plastics Pipe Institute, reports that municipal and industrial applications for HDPE pipe are trending up.
“We’re seeing other applications taking the lead of the natural gas industry,” Gottwald said. “More than 90% of our country’s natural gas distribution lines are made of polyethylene pipe. What engineers and contractors are realizing is that if PE pipe is safe and reliable enough to carry natural gas, it certainly is also for water.”
System engineers like Suttle are touting the fusion process for HDPE water pipe. When two sections of HDPE pipe are butt fused using heat, the resulting pipe joint actually becomes as strong as the pipe itself. The result is a virtually leak-free system. And because polyethylene is a nonconductor, the material is physically unable to corrode.
Passing environmental test
Using those first 60 feet of HDPE pipe as a test case three years ago convinced Suttle and his colleagues to continue to use the material at BWXT Pantex. The most satisfying part was making the case for HDPE as the environmentally-positive choice, he said, adding that a sticking point with initial designs was a perceived risk of contaminants leaching into the water supply.
HDPE is also ideally suited to horizontal directional drilling installation (HDD), which was an additional job requirement. The original 18-inch HDPE pipe was installed under two railroad tracks, a roadway, and a security corridor using HDD.
“I documented that first project as much as I possibly could,” Suttle said. “I visually inspected every piece of pipe personally and every fused joint to everyone’s satisfaction.”
The result was a system that delivered the required capacity with 46 pounds of residual pressure.
About the Author: Camille Rubeiz, P.E., is engineering director at the Plastic Pipe Institute (PPI). Since its founding in 1950, PPI has been representing companies who are involved in manufacturing polyethylene pipe systems. Contact: (202) 462-9607, [email protected] or www.plasticpipe.org.
