Physical Flow Testing and CFD Validation to Ensure Performance of Nuclear Industry Check Valves

To ensure end user performance requirements, BNL Industries Inc. undertook a testing and analysis program to evaluate a revised design of its TwinLine Double Door Check Valve.  Alden used test data from an earlier Twinline design, which was collected by Alden in the laboratory in 2003. The existing data was used to validate Computational Fluid Dynamics (CFD) to determine the flow coefficient (Cv) for BNL’s new valve.  The overarching goal of this effort was to see if a new Twinline design would meet the stringent flow coefficient needs of the end customer and, if not, to make design modifications that would improve performance.  The CFD modeling activity was charged with the following objectives:

  1. Validate the CFD methodology and ensure accuracy by simulating the 10 inch BNL TwinLine Double Door Check Valve calibrated at Alden in 2003.
  2. Estimate the flow coefficient for the new TwinLine double door check valve design.
  3. Estimate the impact of an upstream elbow on the flow coefficient for the new TwinLine double door check valve.

The agreement between the validation model and the calibrated valve was better than 5%.  The valves were modeled with gates fully open.  The net valve coefficient for the upgraded Twinline valve was shown to have a 193% increase in efficiency over the previously calibrated valve.  The effect from an ANSI B16.9 long radius elbow located directly upstream was modeled and was found to reduce the net valve coefficient by 38%.Subsequent physical flow testing of the new valve by Alden later in the year showed a lower flow coefficient than the CFD results had predicted, but still sufficiently high for the customer’s application. The team was able to show that the assumption of fully open doors had not been valid, which led to the discrepancy between CFD and experiment for the new valve design.   Further analysis showed that the door opening angle is predictable with CFD, and, in fact, CFD can be used in the future to determine the flow at which the doors will open fully.

A valuable feature of the Twinline design is the ability to limit the door opening with custom stops to match the desired flow, thereby keeping the valve in a stable open position, without vibration, and extending the valve’s life.  This project has shown that CFD can be used to accurately predict the flow rate as a function of door opening, so BNL and Alden plan to work together in the future to leverage the unique design to meet customer demands.

In a follow-on project, Alden performed further CFD analysis to investigate fluid forces and stresses on the Twinline check valve in a scenario in which the check valve is used in a wet steam environment, as opposed to liquid water.  The results highlighted a high stress location that could easily be modified to handle the new application.

BNL’s use of CFD allowed a reduction of risk for the end client by confirming performance before the valve could be manufactured and tested.  The project has highlighted further possibility for inexpensively customizing Twinline valves by application.

Subsequent physical flow testing of the new valve by Alden later in the year showed a lower flow coefficient than the CFD results had predicted, but still sufficiently high for the customer’s application. The team was able to show that the assumption of fully open doors had not been valid, which led to the discrepancy between CFD and experiment for the new valve design.   Further analysis showed that the door opening angle is predictable with CFD, and, in fact, CFD can be used in the future to determine the flow at which the doors will open fully.

A valuable feature of the Twinline design is the ability to limit the door opening with custom stops to match the desired flow, thereby keeping the valve in a stable open position, without vibration, and extending the valve’s life.  This project has shown that CFD can be used to accurately predict the flow rate as a function of door opening, so BNL and Alden plan to work together in the future to leverage the unique design to meet customer demands.

In a follow-on project, Alden performed further CFD analysis to investigate fluid forces and stresses on the Twinline check valve in a scenario in which the check valve is used in a wet steam environment, as opposed to liquid water.  The results highlighted a high stress location that could easily be modified to handle the new application.

BNL’s use of CFD allowed a reduction of risk for the end client by confirming performance before the valve could be manufactured and tested.  The project has highlighted further possibility for inexpensively customizing Twinline valves by application.

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