Valve innovations aid nuclear slurry pretreatment

Plug valves, stem extensions, and automation enable remote control and repairs in radioactive waste vessels at the Hanford Waste Treatment Project (WTP) in southeast Washington State.

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FIGURE 2: STAINLESS-STEEL STEMS
Stainless-steel Stem Extensions

To isolate and treat highly radioactive slurries in its “bulge” containment vessels, the Handford project needed stem extensions that could adjust to any length, and be operated and repaired remotely, so Flowserve designed extensions that could work for any valve in any position in the bulge.

 

    
Mach 1’s modifications included updates to its cartridge repair and a remotely operable stem extension for removal and replacement of the repair cartridge. However, due to stringent DOE requirements, Bechtel also required Flowserve to prove Mach 1’s valve design and materials capabilities with a working demonstration in a slurry service that would replicate WTP’s site conditions. Bechtel gave Flowserve worst-case specifications for the radioactive slurry, and required a 20-year-equivalent cycle test. Flowserve developed a recipe for the test media’s drilling fluids and bentonite clay additives that matched the size of the solids and their viscosity and weight per Bechtel’s specifications, and built a recirculating test rig to keep the media solids in suspension as required during valve testing. The results satisfied Bechtel’s requirements, and the modified Mach 1 plug valve was added to its list of acceptable valves for the bulge applications.

Automating the Valves
The next challenge was qualifying Flowserve’s Automax valve automation systems with Bechtel, and building adjustable, stainless-steel extensions with double universal joints to enable remote operation and repair of the valves from outside the bulge vessels. Bechtel also required that valves be welded into the bulge piping at a 5º angle to promote drainage. Universal joints at the top and bottom of the extension were required to eliminate any side-loading that the 5º operating angle might create. Shaw and Larry Shields, Flowserve Flow Control’s senior sales engineer, worked with Vince Rohrig, the firm’s automation product manager, and Stan Piela, its special projects engineer, to design field-adjustable hardware for manual and automated operation of the bulge valves, regardless of orientation or distance from the top of the bulge vessels.

“Bechtel wanted stem extensions that could adjust to any length, so we came up with a design for the extensions that could work for any valve in any position in the bulge,” says Shaw. “Vince’s design allowed the extensions to be manufactured as a standard unit that was adjustable to any length during final installation.”

Rohrig adds, “We’ve done a lot of stem extensions, but nothing like these. Not only did the extensions have to telescope, they also had to be designed to take the weight of the stem extension off of the valves. Bechtel also had a variety of torque requirements for these valves, from 500 to 20,000 in.-lb.”

Consequently, Bechtel also qualified Automax pneumatic actuators with Foundation Fieldbus switches after some added Bechtel and DOE requirements were met. A more than $1 million contract for the bulge valves and automation was signed in August 2002 with Flowserve as the exclusive source. So far, Flowserve has worked with one of several bulge manufacturers to complete the first bulge containing 22 valves, and other bulge valve orders are in process.

Later, when Bechtel asked about Flowserve’s capabilities for WTP’s jumper valve portion, the team presented Bechtel with another modified Mach 1 valve with Automax stainless-steel, rack-and-pinion valve automation. These jumper valves had to be fully automated, so they could be used in the pretreatment building with the same requirements for radioactive slurry handling as the bulge valves. Because of the intense radioactivity in the pretreatment building, the jumper valves were to be operated and repaired remotely by robotics. These valves also were specified with radiation-resistant pneumatic actuators, switches, and accessories to be mounted directly on the valve bodies.

Unlike the bulge valves, however, the jumper valves couldn’t be built with stem extensions for pulling the plug and sleeve out of the valve body for repair. The challenge was to develop a “jack nut” feature that would enable remote release and replacement of the plug and sleeve cartridge assembly by a robot.
In addition, design changes were required to modify the actuators and mounting kits, so the actuation packages could be removed for access to the top of the valve for cartridge replacement. Also, space constraints forced Flowserve to propose smaller, stainless-steel Flowserve Worcester Controls rack-and-pinion actuator units, not previously manufactured with stainless-steel materials, in place of larger, standard Automax stainless steel actuators originally proposed.

“The pretreatment building is a huge facility with lots and lots of equipment,” says Shaw. “Everything is installed very close together. It became apparent that we had to build a very compact automation package. Bechtel gave us specific space dimensions that we had to meet. So we had to be flexible in what we were offering to meet requirements.”

Bechtel next wanted proof that the actuators would meet NQA-1 inspection requirements, and that Flowserve would meet promised delivery schedules. After satisfying these requirements, Flowserve received another multi-million dollar order for the automated jumper valves in August 2004.

“We worked very hard to gain Bechtel’s confidence so we could design valve and automation packages that would meet the needs of their applications and facilities,” adds Shields. “We came up with two plug valve designs that were unique. That’s what put us ahead of the competition.”

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