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　 　Quick-opening manhole It is a safety‑emergency venting device installed on oil storage tanks, typically used in conjunction with flame arrestors and mechanical breathing valves. It prevents sudden overpressure inside the tank due to unforeseen circumstances, thereby averting damage to the tank and potential accidents.

　　Quick-opening manholes are commonly used on oil tanks; therefore, it is worthwhile to understand their installation and maintenance. For most users, this is primarily because quick-opening manholes are located at the bottom of the tank, where the stainless steel manhole must withstand substantial liquid pressure. To prevent leaks, extremely stringent quality standards must be applied during the installation of the manhole assembly. It is also important to note that both the flange and the cover plate are machined with sealing grooves; care must be taken during installation to protect these seals and avoid oil leakage during operation. Each time the manhole is disassembled, clear markings should be made to ensure proper alignment upon reinstallation, thus maintaining a tight seal. When tightening the appropriate nuts, apply even torque in a crisscross pattern to prevent deformation of the cover or uneven stress that could lead to leaks. Furthermore, the manhole is typically fabricated by bending pipe—smaller sizes can be formed from a single piece, while larger sizes may require two or three sections. During operation, the top of the quick-opening manhole is subjected to significant stress, so the upper portion must be reinforced with seamless tubing, and welded joints are strictly prohibited. Pipe bending can be performed either cold‑bent or hot‑bent. Today, the company, under a comprehensive quality management system, offers high‑quality products and services at competitive prices, continuously improving them to meet the diverse needs of its customers, while actively strengthening and expanding both domestic and international markets.

　　 Quick-opening manhole Typically, it is installed at two fixed points midway along a pipe section, because as the hot medium flows through the pipeline, temperature changes cause the pipe to expand. This thermal expansion generates horizontal thrust on the fixed supports at both ends. To maintain force equilibrium, the resulting reaction force causes the bellows compensator to compress and deform, thereby counteracting the stresses induced by thermal expansion in the fixed supports. Therefore, it is important to note that, to minimize deformation and stress in quick-opening manholes during operation, the compensator should be pre‑stretched by half of its expected thermal expansion. This ensures proper alignment between the installation position and the operating position of the quick‑opening manhole. As shown in the figure, when the compensator is compressed to half of its compensation capacity (ΔL), the stress within the compensator becomes zero—corresponding to its design (installation) position. When the compensator has fully compensated for the thermal expansion, only half of the total stress is borne by the fixed supports and the compensator itself. Consequently, we recommend performing a pre‑stretch during installation of the quick‑opening manhole; since the pre‑stretch equals ΔL/2, each arm should be pre‑stretched by ΔL/4. We are committed to providing high‑quality products and services to all our new and existing customers—Wanmu is your trusted partner.

　　That concludes our overview of the installation and maintenance of quick-opening manholes on oil tanks. We encourage all users to carefully review the specifications when making their selection. Should you encounter any additional questions during the purchasing process, please feel free to contact our manufacturer; our experts will be happy to provide you with detailed answers.