Check valves inspection
Check valves inspection
What sort of minimum inspection should be made once check valves are offered for inspection during shutdown opportunity?
Re: Check valves inspection
API 570 mandates inspection of critical check valves and external inspection, internal inspection and functional test is required to be performed basically to confirm that it protects the backflow.
Re: Check valves inspection
API 570 outlines three primary inspection and testing methodologies to verify the mechanical and operational condition of CCVs:
External Visual Inspections:
Conducted as part of routine external piping circuit inspections. Evaluates the valve body, external hardware, and general condition without dismantling the line. For valves with external shafts, inspectors check the condition of the shaft retainer mechanism and seats.
Internal Visual Inspections:
Typically performed during scheduled plant shutdowns or when the piping is out of service by removing and disassembling the bonnet cover. What inspectors look for internally:Ensuring the flapper moves freely as required without excessive looseness or wear beyond tolerances. Checking the flapper stop to confirm there is no excessive wear that would allow the flapper to move past top-dead-center and jam in an open position (especially critical for vertically mounted valves). Inspecting internal connection hardware (e.g., ensuring flapper nuts are securely locked to bolts—single tack welds, simple lock washers, or single lock nuts are generally inadequate). Verifying that internal shafts cannot work their way out of the valve body. Checking for fouling, internal corrosion, scaling, or missing components. Performing Positive Material Identification (PMI) on alloy check valve internal components to ensure they match material specifications.
In-Line Function / Backflow Testing:
While less common than visual checks, some specialized programs or independent protection layer requirements mandate in-line function testing (backflow simulation). This involves setting up specific piping configurations to test sealing capability and measure reverse flow behavior on the upstream side.
External Visual Inspections:
Conducted as part of routine external piping circuit inspections. Evaluates the valve body, external hardware, and general condition without dismantling the line. For valves with external shafts, inspectors check the condition of the shaft retainer mechanism and seats.
Internal Visual Inspections:
Typically performed during scheduled plant shutdowns or when the piping is out of service by removing and disassembling the bonnet cover. What inspectors look for internally:Ensuring the flapper moves freely as required without excessive looseness or wear beyond tolerances. Checking the flapper stop to confirm there is no excessive wear that would allow the flapper to move past top-dead-center and jam in an open position (especially critical for vertically mounted valves). Inspecting internal connection hardware (e.g., ensuring flapper nuts are securely locked to bolts—single tack welds, simple lock washers, or single lock nuts are generally inadequate). Verifying that internal shafts cannot work their way out of the valve body. Checking for fouling, internal corrosion, scaling, or missing components. Performing Positive Material Identification (PMI) on alloy check valve internal components to ensure they match material specifications.
In-Line Function / Backflow Testing:
While less common than visual checks, some specialized programs or independent protection layer requirements mandate in-line function testing (backflow simulation). This involves setting up specific piping configurations to test sealing capability and measure reverse flow behavior on the upstream side.
Re: Check valves inspection
As per API 570 para 5.13, "Leak checks of CCVs are normally not required but may be considered for special circumstances."