Q: Why do valves leak?

A: Valves are mechanical devices that rely upon seats and seals to create mechanical barriers to control flow. A variety of seat designs create these barriers. With use over time, these barriers wear out for a variety of reasons (age, abrasion, erosion, chemical attack, embrittlement, fatigue, temperature, etc.). The increased wear contributes to increasing leaks, and increasing leaks lead to failures and hazards. Regardless of the specific cause, aged seats are susceptible to leaking.

Testing a valve’s integrity is an evaluation of current barrier conditions, and may be used to identify a valve that is wearing out prior to failure. As such, annual valve leakage tests are an important aspect of a well-rounded safety inspection program.