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　　 Hygienic manhole What are the features?

　　Hygienic manholes, also known as stainless steel hygienic manholes, meet the specific requirements of various media in the food and biopharmaceutical industries. Types include atmospheric‑pressure models, pressure‑rated models with sight glasses, handwheel‑operated versions, as well as rectangular, elliptical, elliptical models with mirrors, and square designs. Applications: suitable for stainless steel tanks and vessels. Such applications typically require secure access to the interior of large storage tanks and containers. A hygienic inspection manhole is a negative‑pressure type, generally fabricated from stainless steels such as 304, 316, 321, or 316L, with a pressure rating of up to 0.3 MPa.

　　It is typically installed on large tanks and vessels in the dairy, brewing, beverage, pharmaceutical, bioengineering, and other industrial sectors. Because the application often demands high pressure‑bearing capacity, selecting the appropriate stainless‑steel plate thickness for the quick‑opening manhole and ensuring the structural strength and sealing performance of the manhole itself are critical technical considerations. The opening mechanism is designed to be convenient, safe, aesthetically pleasing, and practical. Both the interior and exterior surfaces are usually finished with either mirror polishing or a matte finish, achieving a surface roughness (Ra) of 0.8 µm or better. Quick‑opening manholes are commonly mounted at the bottom or top of storage tanks and are often used in conjunction with fire extinguishers. This not only prevents tank damage and personnel injury in the event of a sudden pressure surge inside the tank or a vacuum emergency caused by an accident, but also provides effective safety and fire‑protection benefits, thereby maximizing tank protection. To prevent leakage, sanitary‑grade manholes are strictly required, and installation must comply with established safety codes and regulations. Manufacturing standards are equally stringent: the mating surfaces of the upper and lower flanges must be perfectly straight and free of any misalignment. During installation, alignment should be carefully coordinated, and bolts tightened evenly to avoid oil leakage resulting from deformation of the cover plate or uneven stress distribution.

　　Sealing rings are typically made of silicone rubber. The outward‑opening manhole cover HT is used on the top or side of pressure vessels and tanks. Manhole covers are manufactured from 304 and 316L stainless steel. Available types include standard pressure‑rated, mirror‑finished pressure‑rated, handwheel‑operated, rectangular, elliptical, mirror‑finished elliptical, handhole, and square designs; dimensions and material specifications can be customized to meet customer requirements. Non‑standard manholes can also be fabricated according to customer‑provided drawings and samples.

　　Manholes are widely used in large tanks and vessels across industries such as dairy, brewing, food, beverage, pharmaceuticals, and bioengineering.

　　In the beverage, dairy, biotechnology, and other food industries, large tanks or vessels are used for extraction during production. These equipment containers demand stringent sealing and pressure‑resistance performance; therefore, manholes are installed to facilitate routine maintenance and to ensure safety and fire‑protection functions. Quick‑opening manholes offer substantial pressure‑bearing capacity, so they should be fabricated from high‑quality, thick stainless steel. For sealing, silicone rubber is typically employed to prevent leaks and ensure reliable, stable operation. Depending on the specific requirements of each industry, quick‑opening manholes come in various types—such as atmospheric‑pressure manholes and sanitary‑grade manholes—and may be round, elliptical, square, or other shapes.

　　 Hygienic manhole As the name suggests, it is designed to meet pressure requirements during operation, with a mirror‑finished surface. Typically, the design pressure ranges from 0.3 MPa to 1.0 MPa, and the working pressure falls within this range. Common dimensions are diameters of 100–800 mm. Process requirements include: an internal and external surface finish of Ra ≤ 0.8 μm, with internal mechanical polishing and electropolishing achieving Ra ≤ 0.2 μm; the exterior surface is finished either by mirror polishing or matte treatment.

　　Styles and dimensions can be customized to meet any project requirement. Hygienic manhole Also known as a quick-opening sanitary manhole, it features a convenient, safe, aesthetically pleasing, and practical opening mechanism. Primarily, it serves as an access device that allows workers to enter and exit storage tanks for operations and maintenance. To meet the requirements for operating pressure and sealing performance, upper and lower flanges should be welded at the joint between the manhole body and the cover, and the corresponding bolts tightened.