详情描述

A manhole refers to an opening structure used for personnel entry and exit of equipment for installation, maintenance, and safety inspections. It is mainly composed of short筒节 (or short tube), flanges, and a manhole cover with a handle. For safety inspection considerations, pressure vessels require a specified number of manholes and their small sizes are listed under "inspection holes." Manhole materials include carbon steel and stainless steel. Manholes are categorized by pressure conditions into atmospheric and pressurized manholes; by shape into circular, elliptical, and rectangular manholes, with rectangular manholes suitable only for atmospheric equipment; by installation position into horizontal and vertical installations; and the manhole cover fixing methods include rotating covers and hinged covers. The opening speed of manholes can be either standard or quick-open. Manhole structures and dimensions are generally standardized and can be selected or designed according to relevant manuals.