^ Attribus Innovation (17 January 2019).Environmental Engineering: Environmental Health and Safety for Municipal Infrastructure, Land Use and Planning, and Industry (6, illustrated ed.). Lane was electrocuted after stepping on a metal manhole cover, while walking her dog in New York City. In urban areas, stray voltage issues have become a significant concern for utilities. Hazards caused by stray voltage in manholes Energy absorbing structures to dissipate undesirable flow stream turbulence or velocity.Drop structures from higher elevation flows to lower elevation discharge pipes.Structures that can be integrated into composite manholes include: In these manholes, the entire underground enclosure is constructed of some composite material, in addition to the cover. in Cambridge, UK, and surrounding villages).Ĭomposite ( fiberglass) manholes are commonly used in applications where infiltration, exfiltration, or corrosion by hydrogen sulfide (from sewer gas) are a concern, or where structures need to be factory integrated into a manhole before placement. Manholes can also be found in a triangular shape (e.g. But in the United Kingdom they are nearly always square, or rectangular, in shape, at least at street level. Manholes are usually round, primarily because roundness is the best shape to resist the compression of the earth covers are round because they are easier to manufacture than square or rectangular shapes, they are easier to move by rolling, and they can't fall into the opening. Manholes are usually outfitted with metal, polypropylene, or fiberglass steps installed in the inner side of the wall to allow easy descent into the utility space. Because of legislation restricting acceptable manual handling weights, Europe has seen a move toward lighter-weight composite manhole cover materials, which also have the benefits of greater slip resistance and electrical insulating properties. These covers are traditionally made of metal, but may be constructed from precast concrete, glass reinforced plastic or other composite materials (especially where cover theft is of concern). Manhole closings are protected by a grating or manhole cover, a flat plug designed to prevent accidental or unauthorized access to the manhole. ( July 2019) ( Learn how and when to remove this template message) Unsourced material may be challenged and removed. Please help improve this section by adding citations to reliable sources. These manholes are typically around 450 mm × 450 mm (18 in × 18 in) square. In Australia, manhole also commonly refers to an access hatch used to get access from a room or hallway into the ceiling cavity of a building. In rural and undeveloped areas, services such as telephone and electricity are usually carried on utility poles or even pylons rather than underground. Manholes are generally found in urban areas, in streets and occasionally under sidewalks. The majority of underground services have manholes, including water, sewers, telephone, electricity, storm drains, district heating, and gas. Manholes are often used as an access point for an underground public utility, allowing inspection, maintenance, and system upgrades. PMG manholes in a city street, Perth, Western Australia Manhole being used to access sewer Installation of a fiber-optic manhole in Brooklyn, New York An uncovered manhole in Beirut, LebanonĪ manhole ( utility hole, maintenance hole, or sewer hole) is an opening to a confined space such as a shaft, utility vault, or large vessel. For other uses, see Manhole (disambiguation).
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