A manufacturer of compression check-valve was experiencing a high frequency of nuts seizing up during installation and removal for maintenance. Anti-seize pastes and greases couldn’t be used due to in-service contamination.

Major issues included:

  • Sorting and verifying locknuts prior to installation led to an increase in labor costs and resulted in lost material for failed nuts.
  • Using anti-seize pastes and greases wasn’t an option because of potential chemical reactions or contamination that could occur while in service.
  • Customers couldn’t remove the nuts to perform required maintenance. This created increased downtime and high warranty costs for the OEM.

As costs mounted, the OEM searched for a solution to improve installation efficiency and eliminate maintenance issues.


The ESL nut, in stainless steel 304L passivated, was tested on 300 valves. ESL nuts provided:

  • Better locking performance.
  • No seized nuts during installation or maintenance.
  • Increased re-usability.
  • Elimination of warranty claims related to locknuts.

Following customer feedback, the OEM decided to outfit all of its major valves with ESL nuts. Today, nearly 150,000 valves are produced annually using ESL nuts.

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