Warning: In order for the
Fig. 922 to function properly, all emergency vents, fill connections, tank openings and piping connections must be airtight. Emergency vent should be set at least 2 oz. higher than the Fig. 922.
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
The Fig. 922 Combination Vent/Overfill Alarm is a fully mechanical, high intensity audible alarm that alerts you when your tank is near full while also allowing your tank to breathe during filling and dispensing operations. The unit is equipped with a whistle which incorporates a 2” or 3” full port pressure/vacuum vent. The unit can be set to activate at 90% fill height by adjusting the cable length to the fl oat device. The adjustment tool is provided. The unit attaches to a 2” or 3” N.P.T. pipe mounted on the tank. Minimum fi ll rate for alarm to
operate is 20 GPM.
Note: Not for use on vapor recovery systems.