Open Nav

FIG 922

Combination Vent/Overfill Alarm

The audible alarm whistles when the liquid level in the aboveground storage tank reaches the preset level. The pressure vacuum vent allows the tank to breathe during filling and dispensing operations.

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 (2008) 21.4.3

Product Features

Standard Features

Functions as both a pressure vacuum vent and audible alarm while utilizing a single 2″ or 3″ tank opening. Installs on the top of the vent pipe, generally 12 feet above grade

105 to 120 decibel whistle alarm (measured at a distance of 1 foot with a fill rate of 90 GPM)

Fully mechanical alarm does not require electricity or batteries

The alarm level can be set to activate at any liquid level by adjusting the cable length to the float device

Minimum fill rate of 20 GPM required for alarm to operate


Construction Details

  • Body: Anodized aluminum
  • Screens: Stainless steel
  • Rainguard: Aluminum
  • Seals: FKM
  • Ball: PTFE
  • Float: Stainless steel


Certifications & Listings

Florida DEP EQ 227

Product Ordering Instructions

Figure Suffix Size Description Weight (lbs)
922 0400 AA 2” - 6 oz Combination Vent/Overfill Alarm 8.5
922 0200 AA 2” - 8 oz Combination Vent/Overfill Alarm 8.5
922 0500 AA 3” - 6 oz Combination Vent/Overfill Alarm 6.3
922 0300 AA 3” - 8 oz Combination Vent/Overfill Alarm 6.3
922BSP 0400 AA 2” - 6 oz Combination Vent/Overfill Alarm w/ BSP Female Threads 8.5
922BSP 0200 AA 2” - 8 oz Combination Vent/Overfill Alarm w/ BSP Female Threads 8.5
922BSP 0500 AA 3” - 6 oz Combination Vent/Overfill Alarm w/ BSP Female Threads 6.3
922BSP 0300 AA 3” - 8 oz Combination Vent/Overfill Alarm w/ BSP Female Threads 6.3