Morrison Bros. Co.
Morrison Bros 748A-3200 AV 3" FNPT Pressure Vacuum Vent - 20.2k SCFH Venting capacity 2.5 P.S.I.
Morrison Bros 748A-3200 AV 3" FNPT Pressure Vacuum Vent - 20.2k SCFH Venting capacity 2.5 P.S.I.
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Pressure vacuum vent designed for installation on top of the vent pipe of an aboveground or underground storage tank. Poppets seal vapors in the tank when pressure is equalized. The vent allows the tank to “breathe” during filling and dispensing operations. This vent must be used in conjunction with an emergency vent. It is recommended that the opening pressure setting is set below that of the emergency vent so the normal vent operates first. Settings are approximate.
NOTE: Normal vents such as pressure vacuum and updraft vents for aboveground storage tanks should be sized according to NFPA 30 (2012) 21.4.3.
Standard Features
Vents outward and upward in compliance with NFPA 30
Tri-polar mounting screws for mounting exhaust hood in any of three positions
Optional dryer connections accommodate the installation of desiccant dryers on vacuum connection
Optional pressure discharge hood facilitates piping pressure relief to desired discharge point
Construction Details
- Body and hood: Aluminum
- Poppets: Brass
- Seats: Passivated aluminum
- Screens: Stainless steel
WARNING: DO NOT FILL OR UNLOAD FUEL FROM A STORAGE TANK UNLESS IT IS CERTAIN THAT THE TANK VENTS WILLOPERATE PROPERLY. Morrison tank vents are designed only for use on shop fabricated atmospheric tanks which have been built and tested in accordance with UL 142, NFPA 30 & 30A, and API 650 and in accordance with all applicable local, state, and federal laws. In normal operation, dust and debris can accumulate in vent openings and block air passages. Certain atmospheric conditions such as a sudden drop in temperature, below freezing temperatures, and freezing rain can cause moisture to enter the vent and freeze which can restrict internal movement of vent mechanisms and block air passages. All storage tank vent air passages must be completely free of restriction and all vent mechanisms must have free movement in order to insure proper operation. Any restriction of airflow can cause excessive pressure or vacuum to build up in the storage tank, which can result in structural damage to the tank, fuel spillage, property damage, fire, injury, and death. Monthly inspection, and immediate inspection during freezing conditions, by someone familiar with the proper operation of storage tank vents, is required to insure venting devices are functioning properly before filling or unloading a tank.