Check Valves: Often Forgotten – Till They Cause Catastrophic Damage
Integrity management of piping systems involves functional testing, inspection and maintenance of components which are identified as “safety critical”. Typically, these component types include control valves, isolation valves, pressure relief valves and instrumentation – but exclude check valves. However, recent incidents involving check valve failures have resulted in fatalities, equipment damage and toxic releases. These incidents have highlighted the need to manage check valve functionality and integrity with a risk reduction focus similar to other piping components.
An integrity program should first identify valves in a Process Unit which are defined as “safety critical” and target these for condition monitoring, inspection and functional testing at intervals established by a risk-based process.
The following locations for check valves in a Process facility should be assessed for “safety critical” considerations:
- At the outlets of fired heaters for emergency isolation;
- On major centrifugal pumps and compressors – particularly those with side-feed and side-products where valve failure could permit “back-spinning” of the machine;
- Downstream of high pressure pumps (differential pressure greater than 100 psi) – where the system relies on a single check valve to prevent reversal of flow;
- In floating roof drains (for storage tanks) – where valve failure can permit accumulation of oil on the roof deck;
- In a pressure relief path – to ensure no unusual resistance to flow;
- Valve designs which are drilled for thermal expansion of trapped liquid or for water to provide anti-freeze protection;
- In permanently-piped utility supplies to process equipment – where flow reversal could seriously contaminate offsite supplies or lead to a release;
- In-plant air and chemical injection lines to process units – where flow reversal can have major consequences;
- If an overpressure analysis of the process system has taken credit for prevention of back flow from the high pressure system to a low pressure system.
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