Definition

Manhole refers to the orifice device used for personnel to enter and exit equipment, containers, pipelines and other closed Spaces. It is a kind of safety and maintenance channel, which is widely used in many fields such as industrial production and municipal engineering. For example, on large oil storage tanks, manholes allow workers to enter the tank for inspection, maintenance and cleaning.

Structural composition

Hole body: This is the main channel part, its shape is generally round or oval. The circular manhole is more uniform in the force, relatively simple to make, and the most widely used. The oval manhole can better adapt to some special installation space requirements.

Manhole cover (or hole cover) : used to close manholes to prevent foreign bodies from entering and personnel from falling accidentally. The materials of manhole covers are diverse, common cast iron, steel, composite materials and so on. Cast iron manhole cover high strength, wear resistance, but relatively heavy; Composite manhole covers are lightweight and corrosion-resistant, but their strength is relatively low. The manhole cover is usually connected to the hole body by hinges or bolts for easy opening and closing.

Sealing device: In order to ensure the tightness of the enclosed space, sealing devices are generally installed around the manhole. For example, in the manholes of some chemical containers, rubber seals are used to prevent internal liquid or gas leakage.

Classification by use

Communication manhole: mainly used for communication pipeline system. Communication manholes are generally arranged along communication pipeline lines to facilitate construction personnel to lay and maintain communication cables. In the underground streets of the city, the communication manhole will appear at a certain distance, and the staff can enter the underground pipeline through the manhole to expand the communication line and repair it.

Chemical container manhole: In chemical production, various reactors, storage tanks and other containers need manholes. These manholes should meet the special requirements of the chemical process, such as corrosion resistance, high temperature resistance, high pressure resistance, etc. For example, the manhole on the high-pressure reactor must be designed and manufactured to withstand the internal high-pressure environment, and to ensure a good seal to prevent leakage of chemical materials.

Power manhole: used for laying and maintaining power cables. In substations, power tunnels and other places, power manholes can provide access for staff to overhaul and connect power cables.

Installation requirements

The installation positions of manholes must be reasonable to facilitate personnel access and device maintenance. On the oil storage tank, the manhole is generally installed on the top or wall of the tank, taking into account the layout and maintenance space of the equipment in the tank.

Ensure good sealing during installation. For manholes with pressure requirements, a pressure test is required after installation to ensure that no leakage occurs within the specified pressure range.

The height of the manhole installation also has certain requirements, such as the manhole on the ground, the top of the manhole cover should be flush with the surrounding ground or slightly higher than the ground to prevent rainwater from flowing into the manhole.