How to Install a Pressure Vacuum Breaker

Low pressure storage tanks require pressure vacuum relief valves.

Low pressure-rated industrial equipment carries pressure and vacuum ratings. Pumping material into and out of a low pressure storage tank can lead to over-pressuring the vessel or creating a vacuum that can crumple or implode the vessel. A pressure vacuum breaker can be installed that will provide a path for internal pressure to flow or break the vacuum by allowing air into the vessel. These devices are typically mounted on a nozzle on the vessel.

Things You'll Need

• Pressure vacuum relief valve
• Large wrench
• Gasket

Instructions

1. Lock out the low pressure vessel by ceasing process flow, draining any contents and closing all fluid inlet valves to ensure nothing flows into the vessel. This is for safety concerns.

2. Locate a nozzle on the top of the vessel that is not being used. It is possible that the nozzle will have a blind flange or component that seals the vessel. This should be removed using the wrench.

3. Place the pressure vacuum relief valve on top of the nozzle with the gasket between the two. Line up the flange bolt holes. Insert the bolts from the blind flange and add the nuts, tightening them with the wrench. The tank can now be placed back in service. As pressure increases in the vessel, a valve opens to relieve the pressure. Likewise, if a vacuum is formed in the vessel, a valve will open to let in air, thus breaking the vacuum.

References

• All Star Mechanical: Vacuum Relief Valves