News and Information

　　 Hygienic manhole What is it?

　　Hygienic manholes are negative-pressure type, manufactured from SUS304 or 316L stainless steel, and meet the stringent requirements of various process media in the food and biopharmaceutical industries. They are suitable for use in dairy, brewing, food, beverage, pharmaceutical, and bioengineering sectors. These manholes are particularly well-suited for the food, brewing, dairy, and chemical‑processing industries. The pressure vessels also feature a quick‑opening design, offering convenient and safe access while maintaining a practical and aesthetically pleasing appearance.

　　Hygienic open‑type manhole covers, designated as HT, are used on the tops or sides of pressure vessels and tanks. At pressures ranging from 0.05 to 0.5 MPa, these covers are available in materials such as 304 and 316L, with options for atmospheric‑pressure or pressurized designs, featuring sight glasses, handwheels, and configurations including rectangular, elliptical, elliptical with sight glass, handholes, and square shapes. Material specifications can be customized according to customer requirements. Non‑standard manholes can also be fabricated based on customer drawings or samples. These products are typically installed on large‑capacity cans and larger vessels in industries such as dairy, brewing, beverage, pharmaceuticals, and bioengineering. Given the stringent pressure‑bearing demands of their application, the selection of stainless‑steel plate grades and thicknesses, as well as the structural strength and sealing performance of the quick‑opening manhole itself, are critical to this technology.

　　 Hygienic manhole The opening mechanism is characterized by convenience, high safety, and an aesthetically pleasing appearance. Typically, both the inner and outer mirror surfaces are polished or finished with a matte coating, achieving a surface roughness of Ra ≥ 0.8 µm. Quick‑opening manholes are generally installed at the bottom or top of the vessel and are equipped with flame arrestors, among other features. This design not only prevents vacuum‑induced damage to the vessel and potential casualties caused by a sudden pressure rise inside the tank or emergency situations, but also provides excellent fire‑safety protection, thereby maximizing the overall safety of the vessel.

　　In order to prevent Hygienic manhole In the event of a tank leak, the installation of sanitary‑grade manholes must also adhere to stringent requirements, with safety procedures followed step by step. The same applies to production needs. The mating surfaces of the upper and lower flanges must be perfectly flat, with no wobbling or misalignment. When installing quick‑opening manholes, align the center precisely and tighten the bolts evenly to prevent deformation of the cover plate or uneven stress that could lead to oil leakage. During the forming process, stainless steel manholes may accumulate oil residues, burrs, and develop a rough surface or oxide layers. Therefore, prior to surface treatment, it is essential to remove oil, burrs, surface irregularities, and oxides to ensure satisfactory results in subsequent processing steps.

　　Stainless steel manhole extrusion is a plastic-forming process in which pressure is applied to the rear end of a large‑section billet, causing it to undergo plastic deformation as it passes through the die opening. This results in a smaller‑section billet or component that conforms to the cross‑sectional shape of the die. Extrusion is classified into direct extrusion, reverse extrusion, and composite extrusion. Plastic‑processing extrusion is primarily used to produce profiles, tubes, and other shapes, and aluminum profile extrusion has experienced rapid development over the past decade to two decades.

　　The electrode for degreasing the sanitary manhole, corresponding to the stainless steel components, may be made of stainless steel or low‑carbon steel. The electrode area is larger than that of the stainless steel part and primarily serves to conduct electricity and perform burnishing.