Manhole

A manhole refers to an opening structure used for personnel entry and exit to facilitate installation, maintenance, and safety inspections. It is mainly composed of short tube sections (or short pipes), flanges, and handles on the manhole cover. Considering safety inspections, pressure vessels require a specified number of manholes and their small sizes, see "Inspection Holes." Manhole materials include carbon steel and stainless steel. Manholes are categorized as atmospheric pressure and pressure manholes based on pressure conditions; as round, elliptical, and rectangular manholes based on shape, with rectangular manholes only suitable for atmospheric pressure equipment; and as horizontal and vertical installation manholes based on installation position. The manhole cover fixing methods include rotating covers and lifting covers; the opening speed of manholes includes standard and quick-opening types. Manhole structures and dimensions are generally standardized and can be selected or designed according to relevant manuals.