221P / PV Emergency Access Relief Manhole Cover

These manholes protect against costly tank rupture or implosion by providing emergency venting from abnormal internal pressure or vacuum beyond the capability of the pressure & vacuum relief vent. These versatile devices also provide quick and easy access for tank inspection and maintenance. Model 221 P provides emergency pressure relief only while the 221 PV incorporates an added vacuum relief valve. Both models feature a hinged cover to ensure proper resealing after venting, and a reinforced diaphragm for durability and reduced leakage.