Gas Fitter Practice Test

Can a shut-off valve be installed upstream of a relief valve to allow for the removal of the relief valve for servicing without having to empty the contents of a tank?

1. No

2. No, unless the tank is less than 1,000 USWG

3. Only if it is installed by a certified propane technician

4. Only with the permission of the propane company

The correct answer is: No

A shut-off valve cannot be installed upstream of a relief valve because doing so would create the potential for a dangerous situation. Relief valves are designed to prevent overpressure conditions by venting excess gas or liquid to the atmosphere when necessary. If a shut-off valve is placed upstream, it could be closed when the relief valve needs to function, compromising the safety mechanism designed to protect the system. In systems involving pressurized vessels, maintaining the integrity of safety features like relief valves is paramount. If a relief valve is serviced with a shut-off valve upstream, there is a risk that pressure could build up uncontrollably in the tank or system, leading to hazardous situations such as tank rupture or catastrophic failure. Other options touch upon specific conditions or certifications but do not align with the fundamental safety principle that mandates the relief valve must always remain functional and uncontested by shut-off mechanisms upstream. Therefore, the definitive answer regarding the installation of a shut-off valve upstream of a relief valve is no.