A detailed explanation of the entire process of installing pressure-sealing equipment for work: from on-site preparation to safe commissioning During the pipeline non-stop maintenance and renovation operations, installing pressure-sealing equipment is a crucial link that connects the previous stage with the subsequent stage - it serves as the endpoint of the preparatory work and the technical foundation for the subsequent opening and sealing operations. The installation process involves multiple professional fields such as welding, mechanical assembly, hydraulic connection, and sealing testing. Any oversight at any point could lead to medium leakage, equipment failure, or even safety accidents. Therefore, comprehensively mastering the steps, key points, and risk control measures for installing pressure-sealing equipment is of great significance for ensuring the safety of pipeline operations. This article will conduct a deep analysis of the entire installation process and provide a practical guide with strong operability for on-site technicians. I. Installation of Pressure Sealing Work Positioning and Core Principles The complete process of pressure-sealing typically involves on-site surveying, scheme design, welding of connection components, installation of the clamp valve and the hole-making machine, hole drilling, insertion of the sealing device, and removal. Among these, the "installation" stage specifically refers to all operations from the completion and inspection of the connection component welding to the readiness of the hole-making machine for debugging and the availability of conditions for hole drilling. The main tasks of this stage include: accurately installing the clamp valve (full-bore gate valve) on the welded flange short section, assembling and fixing the hole-making unit above the clamp valve, connecting the hydraulic power source and control system, and conducting a sealingity test and functional debugging of the entire installed equipment. The installation work follows three core principles: Sealing priority: All flange connection surfaces, valve sealing surfaces, and main shaft sealing devices must achieve zero leakage; otherwise, subsequent pressure-bearing hole drilling will result in a catastrophic accident. 2. High accuracy in alignment: The coaxiality deviation between the spindle of the hole-making machine and the center line of the pipe opening must be kept within an extremely small range; otherwise, it will cause the cutter disc to wear unevenly and the feed to get stuck. 3. Reversibility of operation: Before any formal drilling holes are made, the installed flange valves and other components should be able to safely be closed and removed, in case of an emergency to terminate the operation. Understanding these three principles will help technicians maintain clear judgment standards when performing each step of the installation process. II. Preparations before Installation: Eliminate potential hazards before startup Before officially starting the installation process, several preparatory tasks must be completed to ensure that the on-site conditions, personnel status and equipment condition all meet the requirements for the operation. 2.1 Confirmation of On-site Conditions The flange joints (or split three-way connectors) on the pipeline have been welded, and the welds have passed non-destructive testing. Moreover, the pressure test reports are complete. There is no accumulation of flammable gas within the work area, and the reading of the portable detector is zero or far below the explosion limit. The safety cordon has been set up, and all non-operational personnel have been evacuated. Firefighting equipment and emergency leak-stop tools have been placed at the designated locations. Weather conditions permit (avoid conducting installation work related to high-altitude or welding operations under adverse conditions such as strong winds or thunderstorms). 2.2 Equipment and Tool Inspection · Clamp valve: Check whether there are any sand holes or cracks in the valve body, whether the gate plate operates flexibly, whether the sealing surfaces of the upper and lower flanges are smooth without scratches, and whether the test holes and blow-off holes have intact plug covers. · Drilling machine: Check that the casing, main shaft, feed screw, cutter disc connection key, sealing cover and other components are free from transportation damage; Rotate the main shaft to check the rotational flexibility; The cutter edge of the cutter disc is intact and sharp. · Hydraulic Power StationcIII. Installation of the Clamp Valve: Establishing the First Line of Defense The clamp valve is the crucial connection point between the pipeline and the hole-making machine. The installation quality of this valve directly determines the sealing reliability of the subsequent operations. 3.1 Treatment of Flange Sealing Surfaces Use a copper spatula or wooden scraper to remove the old gasket residue, rust oil and impurities from the flange surface of the flange joint. Wipe it clean with anhydrous alcohol or acetone. Check if there are radial scratches or pits on the flange surface. If there are defects with a depth exceeding 0.5 millimeters, use a grinding tool to repair them. For stainless steel flanges, use a stainless steel-specific brush and neutral cleaning agent. 3.2 Gasket Placement and Centering Select a gasket that matches the nominal pressure rating of the flange (commonly 304 stainless steel wound graphite gasket). Carefully insert the gasket into the locating step of the flange adapter, ensuring that the center of the gasket coincides with the center of the flange and there is no skew. If the gasket has an inner and outer ring, pay attention to facing outward. 3.3 Installation and Positioning of Clamp Valves Use a sling or a special lifting device to lift the clamp valve, and slowly lower it to a position about 20 millimeters above the upper flange surface. Two assistants should observe from two perpendicular directions and adjust the valve position to ensure that the bolt holes on the lower flange of the valve are aligned with the bolt holes of the flange joint. Slowly lower the valve to avoid the displacement of the gasket or the impact on the sealing surface. For large-diameter valves, a guide pin should be used for auxiliary positioning. 3.4 Bolt Tightening The bolts should be tightened in a cross-symmetrical sequence in three rounds: the first round to 30% of the specified torque, the second round to 70%, and the third round to 100%. During the tightening process, a torque wrench should be used, and after each tightening, a line marking should be made on the nut and the flat surface of the flange. After the tightening is completed, use a feeler gauge to check the flange clearance, and the difference in clearance at each point around the circumference should not exceed 0.3 millimeters. Finally, check that the gate of the clamp valve is in the "fully open" position, and the handwheel or the actuator should operate normally. 3.5 Sealing Verification (Low Pressure) Close the clamp valve, and connect compressed air or nitrogen through the test hole on the side of the valve. The pressure should be controlled at 0.5 to 1.0 megapascals.