Overpressure Protection with a Closed Valve?
Overpressure Protection with a Closed Valve?
(OP)
Design rules for valves in ASME B16.34, B31.1, Sections VIII, III etc. require analysis of stem retaining structures to ensure that failure does not result in stem ejection from the valve body.
Analysis is not required to ensure suitable margins exist under pressure and seating preload to prevent the valve failing open.
Without this analysis, am I permitted to rely on a single closed valve as the only overpressure protection provided for a low pressure system connected to a high pressure system in accordance with all requirements in ASME VIII Division 1 Appendix M?
Would I be required to block the stem closed with an external, fully analyzed device if the manufacturer was not motivated to provide the factor of safety on the yoke sleeve or stem nut?
Analysis is not required to ensure suitable margins exist under pressure and seating preload to prevent the valve failing open.
Without this analysis, am I permitted to rely on a single closed valve as the only overpressure protection provided for a low pressure system connected to a high pressure system in accordance with all requirements in ASME VIII Division 1 Appendix M?
Would I be required to block the stem closed with an external, fully analyzed device if the manufacturer was not motivated to provide the factor of safety on the yoke sleeve or stem nut?





RE: Overpressure Protection with a Closed Valve?
"stem retaining structures" are not Pressure Relieving Devices.
RE: Overpressure Protection with a Closed Valve?
Most pressurized systems have drains to vented tanks that are isolated by single valves during normal operation. The vents are sized for atmospheric fill rates, not high pressure fill rates. Appendix M permits this arrangement so long as appropriate administrative controls are in effect (locks and blocks).
My question is whether the stems should be blocked if valve failing open is possible.
RE: Overpressure Protection with a Closed Valve?
For safety, think about installing a spectacle-blind on the LP side of that valve.
RE: Overpressure Protection with a Closed Valve?
Safety is exactly the reason for this post...
I'm not sure which question your NOPE answers.
Perhaps you haven't looked closely at the internals of a manual globe or gate valve.
They all have a yoke sleeve or similar stem retention structure to apply seating load via hand torque.
The yoke sleeve is NOT required by code NOT to fail under hand torque and system pressure (believe it or not).
ASME VIII Appendix M does NOT require this assurance for 'stop valves' used for overpressure protection via isolation (no matter what the valve's pressure rating).
There are small diameter 1500lb valves in the market place that will pop open if an operator applies 25 ftlb of torque to the handle.
I think this is a loop-hole in the code - don't you?
Say anything but NOPE!
RE: Overpressure Protection with a Closed Valve?
RE: Overpressure Protection with a Closed Valve?
I agree with the blind flange idea but the reason would be compliance with the intent of ASME VIII DIV 1 APPENDIX M for overpressure protection using an engineered pressure retaining device.
I believe an 'engineered' external stem compression device or block installed on the valve would provide the same assurance and code compliance.
RE: Overpressure Protection with a Closed Valve?
AThe ESCD (External Stem Compression Device) is attached.
RE: Overpressure Protection with a Closed Valve?
RE: Overpressure Protection with a Closed Valve?
RE: Overpressure Protection with a Closed Valve?
RE: Overpressure Protection with a Closed Valve?
If it is not 'uncommon' to provide this additional assurance in industry, isn't that an indication of a loop hole and should it not be a Code requirement following the normal laws of evolution? I have submitted a written inquiry to the ASME Code Committee (attached), but have not received a reply.
RE: Overpressure Protection with a Closed Valve?
Shaft failures under torque levels needed to turn those sometimes frozen valves have long been a problem, as have installing motors with larger torque capacities than what the valve shafts can withstand.
RE: Overpressure Protection with a Closed Valve?
We have had several yoke sleeve failures in our plant coincident with overtorquing and pressure transients. The valves were 3/4"nps 900lb bellow sealed plug valves with aluminum bronze yoke sleeves shaped like a top hat with a very small radius at the 90 degree shoulder, which failed in bending. The Manufacturer actually claimed that the yoke sleeve was 'designed' to fail before disc and seat damage could occur from over torquing. I can't imagine that industry requested this feature.
RE: Overpressure Protection with a Closed Valve?