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FIG 748ALT

Pressure-Vacuum Vent for Ag-Chemical

The 748ALT pressure vacuum vent valve is used with aqua-ammonia and ag-chemical products allowing the tank to “breathe” during filling and dispensing operations. Pressure and vacuum poppets seal vapors in the tank when pressure is equalized.

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.

Product Features

Standard Features

​Settings are approximate

Conserves vapors

Tri-polar design for mounting exhaust hood in any of three positions


Construction Details

  • Body and hood: Aluminum
  • Seats and poppets: PTFE coated aluminum
  • Screens: Stainless steel

Product Ordering Instructions

Figure Suffix Size Description Weight (lbs)
748ALT 0100 AV 2” 8oz/sq.in. Pressure Vacuum Vent 5.5
748ALT 0200 AV 2” 16oz/sq.in. Pressure Vacuum Vent 5.5
748ALT 0300 AV 2” 32oz/sq.in. Pressure Vacuum Vent 5.5
748ALT 0800 AV 2” 8oz/sq.in. Pressure Vacuum Vent w/Dryer Connection 6
748ALT 0900 AV 2” 16oz/sq.in. Pressure Vacuum Vent w/Dryer Connection 6
748ALT 1400 AV 2” 8oz/sq.in. Pressure Vacuum Vent w/Pressure Discharge Hood 5
748ALT 1500 AV 2” 16 oz/sq.in. Pressure Vacuum Vent w/Pressure Discharge Hood 5
748ALT 2000 AV 2” 8oz/sq.in. PV Vent w/Dryer w/Pressure Discharge Hood 5.5
748ALT 2100 AV 2” 16 oz/sq.in. PV Vent w/Dryer w/Pressure Discharge Hood 5.5