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　 　Hygienic manhole The manufacturer shall ensure that manholes are inspected and accepted at every stage of the production process, from receipt of raw materials to shipment of the finished product, in accordance with applicable national and enterprise standards. During and upon completion of equipment fabrication, the seller shall conduct detailed inspections and tests in compliance with relevant standards and drawings, prepare an inspection report, and assume responsibility for the report’s completeness and accuracy. The seller shall guarantee that the manufactured products fully meet the buyer’s on-site installation requirements. The buyer shall notify the seller prior to the factory acceptance of the manholes; the acceptance personnel may, in accordance with the provisions of this Technical Specification, review any documentation related to the product’s manufacture and inspection. Should any quality issues be identified, the seller shall carry out corrective measures until the product complies with the specified quality requirements. The buyer’s acceptance does not constitute a warranty of product conformity; the product must also pass a field‑operation qualification test.

　　Sanitary‑grade manhole manufacturers consider stainless steel manholes to be safety and emergency venting devices installed on the tops of storage tanks, typically used in conjunction with fire extinguishers and mechanical breathing valves. They not only prevent accidents caused by sudden overpressure or vacuum inside the tank but also serve as a means of safe firefighting. These are essential safety devices for protecting storage tanks.

　　Sanitary manhole manufacturers consider stainless steel manholes particularly suitable for use in arched atmospheric tanks equipped with nitrogen‑blanketing systems. They offer advantages such as constant‑pressure venting and suction, flexible opening and closing, fire safety, a compact structure, excellent sealing performance, and reliable operation. Stainless steel manholes are available as prefabricated units, typically with a diameter of 600 mm. The center of the manhole is generally positioned 750 mm above the floor, facilitating easy access for workers during installation, cleaning, and maintenance, as well as ensuring proper ventilation.

　　 Hygienic manhole The manufacturer’s precautions for stainless steel manhole piles are as follows:

　　1. During the construction of bored piles for stainless steel manholes, the clear distance between adjacent pile holes shall not be less than three times the pile diameter. When the spacing is less than three times the pile diameter, the piles must be staggered and excavated in alternating sections.

　　2. At the opening, a fixture shall be installed that extends at least 300 mm above the ground.

　　3. According to sanitary‑grade manhole manufacturers, provided that the diameter of the stainless‑steel manhole shaft is maintained, any irregularities on the shaft wall need not be addressed, and the wall supports must not encroach upon the shaft’s diameter. The retaining concrete does not constitute part of the shaft body and shall not reduce the effective shaft diameter.

　　4. After each excavation section and after the concrete lining has been poured, inspect the verticality and diameter of the pile hole. Ensure that the deviation in verticality does not exceed 0.5% of the pile length, nor more than 200 mm. The lap length between the upper and lower retaining walls shall be no less than 50 mm.

　　5. During shallow-hole loosening blasting of stainless steel manholes, the drilling depth must be carefully controlled to prevent any adverse effects on the formed retaining wall.

　　6. Each section of the retaining wall shall be completed in a single continuous operation.

　　7. According to sanitary‑grade manhole manufacturers, the retaining wall concrete must be thoroughly compacted. If honeycombing or water seepage is detected within the lining, it should be promptly reinforced, sealed, or drained to prevent external water from entering the shaft through the lining and causing accidents.

　　8. Wall concrete shall not be placed when the formwork is submerged by water in the pile holes.