Solenoid valve

Two-way normally open solenoid for nuclear service

In the highly specialized world of nuclear fluid control components, three critical requirements stand out: suitability for service, an outstanding dependability and exceptional performance.
 
^ solenoid valve

Article by Steve Gatcomb
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Valves designed to handle radioactive fluids must meet rigorous design and code requirements to qualify for use. Trying to use or modify an existing design may lead to frustration, multiple re-designs and failure. A fresh, clean-sheet approach addressing the specific application requirements is best served in these applications. Recently, Valcor Engineering’s Nuclear and Power group received a request for the design of a two-way, normally open solenoid valve that could operate in such an application. The engineers went to work and ultimately produced a valve that exceeded the customer’s rigorous expectations.

The application required a two-way, normally open valve that could handle hot, highly radioactive and chemically toxic fluids while submerged in water (to capture any radiation emitting from the process lines and components). The valve had to be completely sealed, with no potential for fugitive emissions during operation, or over time due to degrading elastomeric seals.

Critical criteria

This required an all-welded pressure vessel to contain the process media, and a solenoid operator that was waterproof (IP68). Further, the valve had to continuously function without maintenance for extended periods of time. The valve has to fail in the open position to not jeopardize the critical safety function of the valve or to interrupt the process. A valve failure would put the entire process at risk, requiring the process system to shut down while the failure was addressed.

Valcor Engineering has maintained an ASME N-Stamp certification for over 45 years. This was the critical criteria in the customer’s selection of Valcor to design their valve, as the valve had to be designed and manufactured under the quality assurance program requirements of ASME Section III, and ASME’s B16.34 code. Without this compliance, the valve would not be suitable for this application.

Valcor’s experience in designing valves for nuclear power reactors, waste treatment facilities and laboratories enabled the engineers to rely on an extensive library of existing nuclear valve designs to inform them of the best materials, manufacturing processes, and design features to use in the development of the new valve. After much design and review, a new valve emerged from the engineering department.

Extended cycle life

Controlling radioactive media requires a robust design that can withstand years of service without requiring any maintenance with the ability to function during and after design basis accidents, e.g. earthquakes. The new valve employs an Inconel bellows to enable the solenoid to actuate the valve without concern for corrosive effects to the valve’s magnetic components and premature pressure boundary seal degradation. This design feature eliminates concerns of fugitive emissions, under high process media temperatures. The design of the custom-made bellows also contributes to extended cycle life (measured in decades) to ensure maximum uptime in operation, resulting in extensive operating life. The poppet seals against a metal seat, ensuring exceptional durability through thousands of actuation cycles. The metal seat also ensures exceptional durability. It will not wear out or leak, even if challenged by contamination in the process fluid.

The resulting valve design exceeds the customer’s requirements, is used in many applications throughout the process system. Iterations of this design could also work for applications in refrigeration, API (active pharmaceutical ingredient) production for biotech and pharma manufacturing, as well as many others.
 

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