If you think about storage tanks, consider how well they need to breathe. That factor is critical to safety. It also has environmental implications.
Storage tanks need to breathe 'in' when liquid is being removed from the tank. If there's no way to safely inhale, there is a chance the tank could implode. This vacuum condition needs to be controlled by allowing outside air to flow into the tank. Tanks also need to breathe 'out' when being filled with liquid. So if there is no safe way to exhale, either the tank could rupture or vapors could escape causing waste and pollution. This over-pressure condition must also be controlled by allowing air (and only air) to safely flow out of the tank. Changes in thermal conditions can also cause fluctuation in tank pressure levels that need to be controlled.
That is why pressure/vacuum vents are so important. These all-in-one devices are commonly called breather valves and have become staples of safety for storage tanks. Husky pressure/vacuum, or P/V, vents utilize three separate valves to control over-pressure and vacuum conditions that arise in storage tanks.
"When installed properly, the Husky Pressure Vacuum (P/V) Vent Valve can manage the positive and negative pressures in storage tanks along with emergency venting. The Husky P/V vent was designed to meet the positive and negative cracking pressures and leak rates set by the latest CARB specification to minimize vapor exposure and emissions," said Tim Schroeder, Husky Product Design Engineer. "The emergency venting feature was added to handle abnormal fuel deliveries."
Husky offers four models of Pressure/Vacuum vents which are suitable for a variety of applications. Information about these products can be found at http://www.husky.com/husky/pressurevacuum-vents/pv-vent-8060/
The company has also prepared a video to demonstrate the recommended installation procedure for its P/V vents. if there are concerns about shipping damage, perform the California Air Resources Board (CARB) TP-201.1E bench test before installing. The bench test steps are also outlined in the video.
Please refer to the installation instructions that came with your Husky P/V Vent if you have any additional questions.