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FIG 351S & 748A

Flame Arrester/Pressure Vacuum Vent

Flame arresters provide a positive barrier that keeps flames from passing through the pressure vacuum vent line into a storage tank’s vapor space.

WARNING: Do not use with acetylene, carbon disulfide, Ethelene oxide or hydrogen gases. For use with normal hydrocarbon flames such as gasoline in air. Routine inspection is required to ensure airways are clear and free of debris. Blocked airways can cause structural deformation of the tank.

WARNING: DO NOT FILL OR UNLOAD FUEL FROM A STORAGE TANK UNLESS IT IS CERTAIN THAT THE TANK VENTS WILL OPERATE 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. Normal vents such as pressure vacuum and updraft vents for aboveground storage tanks should be sized according to NFPA 30 (2018) 21.4.3

Product Features

Standard Features

When the 351A is combined with a 748A, it combines all the features of the flame arrester and a 748A pressure vacuum vent.


Construction Details

351S

  • Body and cover: Cast iron
  • Arrester Plates: Stainless steel
  • Arrester grid housing: Brass

748A

  • Body and hood: Aluminum
  • Poppets: Brass
  • Seats: Aluminum
  • Screens: 30 mesh stainless steel


Restrictions & Warnings

Do not use with acetylene, carbon disulfide, Ethelene oxide or hydrogen gases. For use with normal hydrocarbon flames such as gasoline in air.

Routine inspection is required to ensure airways are clear and free of debris. Blocked airways can cause structural deformation of the tank.

Product Ordering Instructions

Fig Suffix Size Description Weight
351S 4000 AV 2” This product is being replaced by the 352 Flame Arrester. Please refer to 352 product page. 31
351S 0200 AV 2” 2oz/sq.in. Flame Arrester/748A Pressure Vacuum Vent 42
351S 0300 AV 2” 4oz/sq.in. Flame Arrester/748A Pressure Vacuum Vent 42.5
351S 0400 AV 2” 6oz/sq.in. Flame Arrester/748A Pressure Vacuum Vent 42.75
351S 0500 AV 2” 8oz/sq.in. Flame Arrester/748A Pressure Vacuum Vent 43.5
351SB 0500 AV 2” 8oz/sq.in. Flame Arrester/748A Pressure Vacuum Vent, BSP Threads 43.5
351S 0600 AV 2” 12oz/sq.in. Flame Arrester/748A Pressure Vacuum Vent 44.5
351S 0700 AV 2” 16oz/sq.in. Flame Arrester/748A Pressure Vacuum Vent 45.75
351S 4100 AV 2” 8 oz/sq.in. Flame Arrester/749 Pressure Vacuum Vent 32
748A 0100 AV 2” 2oz/sq.in. Pressure Vacuum Vent 6.75
748A 0200 AV 2” 4oz/sq.in. Pressure Vacuum Vent 7.5
748A 0300 AV 2” 6oz/sq.in. Pressure Vacuum Vent 8.25
748A 0400 AV 2” 8oz/sq.in. Pressure Vacuum Vent 9.25
748A 0500 AV 2” 12oz/sq.in. Pressure Vacuum Vent 10.5
748A 0600 AV 2” 16oz/sq.in. Pressure Vacuum Vent 11
748A 0700 AV 2” 2oz/sq.in. Pressure Vacuum Vent w/Dryer Conn 6.75
748A 0800 AV 2” 4oz/sq.in. Pressure Vacuum Vent w/Dryer Conn 7.5
748A 0900 AV 2” 6oz/sq.in. Pressure Vacuum Vent w/Dryer Conn 8.25
748A 1000 AV 2” 8oz/sq.in. Pressure Vacuum Vent w/Dryer Conn 9.25
748A 1100 AV 2” 12oz/sq.in. Pressure Vacuum Vent w/Dryer Conn 10.5
748A 1200 AV 2” 16oz/sq.in. Pressure Vacuum Vent w/Dryer Conn 11