News and Information

　　 Hygienic manhole Manufacturers note that, on the surface, stainless steel manhole seals resemble solid circular covers, whereas handhole seals are rectangular covers with relatively lower load‑bearing capacity. In terms of dimensions, although stainless steel manholes come in many varieties, they generally adhere to standard sizes and tend to be comparatively larger; handholes, by contrast, are fewer in number, much smaller in size, and their dimensions and depths are tailored to specific site conditions and requirements. Functionally, stainless steel manholes serve as transit and relay points along the main communication backbone, while handholes act as terminal nodes within the distribution network. From an orientation standpoint, stainless steel manholes can be installed on urban arterial roads, sidewalks, or other locations regardless of direction, whereas handholes are restricted to sidewalks and landscaped medians.

　　Sanitary‑grade manhole manufacturers note that, because stainless steel manholes are located at the bottom of oil tanks, they must withstand substantial liquid pressure. To prevent leaks, stringent installation standards are essential. Sealing grooves are machined into both the flange and the cover plate; care must be taken during installation to protect these features and avoid oil leakage during service. Each time a manhole is removed, clear markings should be made to ensure proper reinstallation and maintain sealing integrity. When tightening the nuts on the manhole cover, apply even torque in opposite diagonal pairs to prevent deformation or uneven stress that could lead to leaks.

　　 Hygienic manhole Manufacturers’ recommendations for selecting stainless steel manholes:

　　1. Once the nominal diameter, standards, and permissible approvals of stainless steel manholes have been understood, you can select a manhole that meets the corresponding requirements.

　　2. Verify the medium, working pressure, and temperature for which the manhole is suitable, or select the appropriate manhole type and material based on the specific operating conditions of the medium.

　　3. Determine the structural configuration: such as circular manholes, elliptical manholes, square manholes, and so on.

　　4. Determine the manhole body material: 304 stainless steel, 316L stainless steel, etc.

　　5. Verify whether the manhole has any special requirements, such as temperature resistance, corrosion resistance, or specific height specifications for the tank section.

　　6. Precautions: When using a manhole, the accompanying sight glass must also be verified to meet requirements regarding the process medium, pressure rating, explosion-proof design, and corrosion resistance.

　　Hygienic manhole The manufacturer’s recommended polishing method for manholes is:

　　1. Magnetic‑abrasive polishing of stainless steel square manholes: According to manufacturers of hygienic‑grade manholes, magnetic‑abrasive polishing employs magnetic abrasives that, under the influence of a magnetic field, form an abrasive brush to grind the workpiece. This method offers high processing efficiency, excellent quality, easily controllable process conditions, and favorable working conditions. With appropriate abrasives, surface roughness can reach Ra 0.1 µm.

　　2. Fluid‑polished stainless steel square manhole: According to manufacturers of hygienic‑grade manholes, fluid polishing achieves surface finishing by using a high‑velocity liquid stream carrying abrasive particles to scour the workpiece surface. Common methods include abrasive jet machining, liquid jet machining, and hydrodynamic grinding. Fluid grinding is driven by hydraulic pressure, causing a liquid medium loaded with abrasive particles to flow rapidly back and forth across the workpiece surface. This medium is typically composed of a special compound—similar to a polymer—that exhibits excellent fluidity at low pressures, mixed with an abrasive; the abrasive may be silicon carbide powder.