22 www.morbros.com PRESSURE/ VACUUMVENTS Fig. 748ALT *:6 Fig. 548… brass body and hood. Brass (raised) metal-to-metal seats/poppets. Fig. 548A… aluminum body and hood. Brass (raised) metal-tometal seats/poppets. 2" available with British Pipe Threads. ) *) :* 1. Brass (raised) metal-to-metal seats/poppets. 2. Threaded gauge hatch for manual gauging access. | % = > $ ! < orientation. #* :* ^ 6::' ^ 6 < L @ d M L @ d M L % M L ZM L $ # M & & $ $ & + && ? & & $ $ +&&& 2 & & $ $ "( Pressure/Vacuum Vent For “normal” venting of aboveground storage tanks. Allows tank ! $ discharging operations. Pressure/ vacuum poppets seal vapors in the tank when pressure is equalized. This vent must be used in conjunction with an emergency vent and it is RECOMMENDED that the opening pressure setting is set below that of the emergency vent *:6 1. Aluminum body and hood. 2. Brass poppets. ) *) :* } % = > $ ! < orientation. 2. Optional pressure discharge NPT hood. > ( ^ #* :* ^ 6::' 6 < L ZM L @ d M L @ d M L % M L $ # M ! & & ? $ & + && > & & $ & + && ? & & $ & + && & & $ & + && & & & $& +?&& ? & & && +?&& Size…2" NPT Body and Cap…aluminum * ® coated aluminum Screens…stainless steel ( must specify)…male NPT connection for dryer application … pressure discharge NPT hood *:6 Pressure-Vacuum Vent For Ag-Chemical… vent valve used with aqua-ammonia and ag-chemical products allowing tank to ! $ ^ Poppets seal vapors in the tank when pressure is equalized. Settings are approximate. $> $> ( ^ #* :* ^ 6::' 6 < L ZM L @ d M L @ d M L % M L % M L $ # M ! & & 2 $ && & + && > & & 2 $ $ & + && ? & & > $ $& & + && & & > $ $& & + && & & $ $ & $& +?&& ? & & && $ +?&& 2! & & ? $ $ >2+&&& > & & $ 2 $ >2+&&& ? & & $ $ && >2+&&& & & $ $ $ >2+&&& & & $ $ $ >&+&&& ? & & 22 $ & $& >&+&&& Fig. 748 Pressure/Vacuum Vent With Gauge Hatch… for “normal” venting of aboveground storage tanks. Allows tank to ! $ and discharging operations. Pressure/vacuum poppets seal vapors in the tank when pressure is equalized. This vent must be used in conjunction with an emergency vent and it is RECOMMENDED that the opening pressure setting is set below that of the emergency vent so the normal vent Q @ 548 Series 748 A Series 748 ALT Fig. 548 WARNING…? $ $ $ 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 $ K + $ excessive pressure or vacuum to build up in the storage tank, which can result in structural damage to the tank, fuel spillage, property < < $ +< & + < inspection during freezing conditions, by someone familiar with the proper operation of storage tank vents, is required to insure venting $ + ! $ Normal vents such as pressure vacuum and updraft vents for aboveground storage tanks should be sized according to NFPA 30 (2008) 21.4.3
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