Emergency Vent & Manhole Cover ( Pressure & Vacuum)

The Shand & Jurs Model 94221 Emergency Vent and Manhole Cover provides emergency relief of excessive internal pressure and vacuum beyond that provided by tank breather requirements. This weight loaded vent utilizes Expanda-Seal™ diaphragms which provide tight seals between pallets and seats. Special diaphragm materials are available for vents subjected to severe low temperatures or used on tanks storing heated stock. Corrosion resistant pressure/ vacuum seat is standard. Model 94221 is available in 20" and 24" size to fit a standard API or ANSI flange. Special Flanges are available including DIN. The pallet starts to lift when set pressure is approached. Flow efficiency rises rapidly to approximately 60% of a perfect orifice at 40% excess of the set pressure. At a higher overpressure, the pallet completely clears the manhole and the efficiency approximates 75% . For a standard setting the capacity at 1.4 oz./ sq. in.( 40% overpressure) is approximately 500, 000 SCFH for the 20" size. Pallet construction permits settings from 1.0 oz./ sq. in. for aluminum pallet & 1.3 oz./ sq. in. for S.S. pallet standard to 8 oz./ sq. in. maximum pressure. Vacuum settings are from 1.1 oz./ sq. in. standard to 4.0 oz./ sq. in. maximum. If specifying other than standard vacuum setting, it must be recognized that increased vacuum setting automatically increases the set point of pressure relief.