Installing an Isolation Valve Upstream of a Relief Valve - air receivers

[Dave Plant Engineer]

thread794-58314 The referenced thread seems to (mostly) endorse the use of an isolation valve upstream of a relief valve provided that certain of the ASME Boiler and Pressure Vessel code is satisfied, primarily, that the isolation valve is controlled in the locked open position. If one reads OSHA 29 CFR 1910.169(b)(3)(ii) it specifically prohibits such an installation on an air receiver, altogether. Just putting this out there for anyone who might need the clarification. Thanks.