A cutaway view of the Flowserve Mach 1 high-performance plug valve
Click here to enlarge imageThe Flowserve Flow Control Team developed several valve and automation innovations, including a specialized Durco Mach 1 high-performance plug valve, specifically for use in handling radioactive waste slurries at the Hanford Waste Treatment Project in the US state of Washington.
The Hanford site has one of the largest concentrations of radioactive waste in the world where fifty-three million gallons of high-level radioactive waste, 60 percent by volume of the nation’s total, is stored in 177 old and deteriorating underground tanks just seven miles away from the environmentally sensitive Columbia River. An estimated one million gallons of radioactive waste has already leaked from 67 of the facility’s oldest tanks. This waste has been detected in the groundwater that flows to the Columbia, endangering the river habitat and the health of millions of residents who live downstream in Washington and Oregon.
The Department of Energy’s Office of River Protection awarded a contract to Bechtel National, Inc. in December 2000 to design, construct and commission the Hanford waste treatment plant. This is currently the largest US government construction project, which includes three major nuclear facilities: pretreatment, low-activity waste vitrification, and high-level waste vitrification.
In the first part of the waste treatment process, specialized valves were needed for installation in containment vessels called “bulges.” Each bulge is roughly the size of a swimming pool and is designed to contain all pumps, valves and piping required to transfer the radioactive liquid waste slurry from the existing underground storage tanks to the waste pretreatment building for processing.
The pretreatment system combines a filtration process that removes the solids from the waste slurry and an ion-exchange process that then removes the soluble high-level waste from the remaining liquid. Specifications for this part of the project required manual and automated valves that could be operated and repaired from outside the bulge vessel.
Initially, Bechtel favored top-entry style ball valves for the bulges, but the Flowserve team believed that high-performance plug valves would provide a more effective solution.
“Plug valves work better in slurries than ball valves,” said Larry Shields, the senior sales engineer of Flowserve Flow Control. “Plug valves have adjustable positive sealing upstream and downstream and 360 degrees around the top of the plug. By design, plug valves have no cavities where material can collect and/or solidify.”
A team of Flowserve engineers at the company’s Cookeville, Tennessee engineering and manufacturing site along with their sales team in Washington worked closely with Bechtel to design a new plug valve that could be remotely operated and repaired. Bechtel also required the valve’s seat to be constructed of wear- and radiation-resistant material to stand up to the radioactive slurries at Hanford. Fortunately, Flowserve had already designed the Mach 1 with a variety of seat materials, including Ultra-High Molecular Weight Polyethylene (UHMWPE) to meet these severe requirements.
The next challenge was to qualify Flowserve Automax valve automation systems with Bechtel, and to design and build adjustable stainless steel extensions with double universal joints to enable remote operation and repair of the valves from outside the bulge containment vessels. Bechtel required the valves to be welded into the bulge piping at a five-degree angle to promote drainage. Universal joints at the top and at the bottom of the extensions were required to eliminate any side-loading that the five-degree operating angle would create.
Vince Rohrig, automation product manager, worked with Senior Sales Engineer Larry Shields and Stan Piela, special projects engineer, Flowserve Flow Control, to design field-adjustable hardware for manual and automated operation of the bulge valves regardless of their orientation or distance from the top of the bulge vessels.
“Bechtel wanted stem extensions that could adjust to any length they needed, so we had to innovate again,” Shields said. “We came up with a design for the extensions that could work for any valve in any position in the bulge. Vince’s design allowed the extensions to be manufactured as a standard unit that was adjustable to any length during final installation.”
Bechtel liked the stem extension concept Flowserve presented, so a contract for the bulge valves and automation valued in excess of one million US dollars was signed in August 2002. Flowserve received another multi-million dollar order for jumper valves, which calls for fully automated valves to be used within the radioactive areas of the pretreatment building with more severe requirements for radioactive slurry handling as the bulge valves. Robotic devices will operate and repair the jumper valves.
Author's Note
Mark Shaw is the western regional manager for Flowserve's Flow Control Division, Process Group. He joined the company more than 25 years ago after working in the water well drilling and pump business for several years. Email: [email protected].
