Manhole is a safety emergency ventilation device installed on the top of the storage tank. It is usually used together with fire extinguisher and mechanical breather valve. It can not only avoid accidents caused by sudden overpressure or vacuum in the tank and damage the tank, but also play a role of safety and fire resistance. It is a safety device to protect the storage tank, especially suitable for the dome roof atmospheric pressure tank with materials sealed with nitrogen. The utility model has the advantages of constant pressure discharge, constant pressure suction, flexible opening and closing, safe fire resistance, compact structure, good sealing performance, safety and reliability, etc.
Hg21520-95 specifies the type, basic parameters, dimensions, technical requirements and relevant use regulations of carbon steel and low alloy steel vertical lifting cover with neck flat welding legal person hole. This standard is applicable to the vertical lifting cover with neck flat welding flange manhole with nominal pressure of PN1.0 ~ 1.6Mpa and working temperature limited within the range specified in table 3-2 according to the material category.
