The access manhole is a are often covered with channel, one can from this hole in and out of line, boiler, drain, including telecom, cable TV using elv well, big bridge maintenance in internal channels, etc.

Manhole is installed on top of the tank safety emergency ventilation device, usually with flame damper, using mechanical breather valve, can avoid the accident caused sharp overpressure or vacuum in tank and tank damage and accident, security fire effect, is to protect the safety of tank device, especially suitable for the storage of materials with nitrogen gas cap vault atmospheric tank. It has the advantages of constant pressure discharge, constant pressure suction, open and close, safety and fire resistance, compact structure, good sealing performance and safe and reliable.

The manhole is divided into emergency relief manhole, explosion-proof and fire-breathing manhole, roof manhole, manhole and manhole.

The manhole is usually made of 304,316 L stainless steel or carbon steel.

The manhole of the non-metallic tank is located on the top of the tank. The manhole of the metal tank is located on the bottom of the tank. Most of them are round holes with a diameter of 600mm. The center is 750mm from the bottom plate, which is used for oil tank cleaning or maintenance. The manhole should be used for lighting and ventilation. The capacity of the vertical tank shall be 1~2 personal hole at the time of 5000m3 and 2 personal holes above 5000m3. The installation of manhole shall be the in and out of the oil pipeline are not greater than 90 ° apart. When a manhole is set, it should be placed across the top of the roof of the roof. When set two holes, one is located in the opposite light hole, another should be at least as head of a manhole at 90 °.

The manhole should be located near the right side of the pipeline, and try to make the manhole close to the closed door of the tank, so that the personnel can get in and out, and repair the tank and ventilation.

As the manhole is mounted on the lower body of the tank, the leakage is particularly important. The two flanges are required to ensure their straightness and no drift. Stiffened plates and flanges should be cut on the whole plate without splice. Flange and cover plate are machined with sealing ring, special attention should be paid to protection during construction. Seal with 3mm thick asbestos rubber gasket, do not allow broken. When installing the manhole cover to tighten the bolt, make the diagonal uniform force to prevent the hole cover from deforming.