Pressure-bearing hole-opening equipment: The "minimally invasive surgical knife" for industrial pipelines and an analysis of its intricate internal structureIn the underground urban gas pipeline network, a non-intrusive and uninterrupted "surgical operation" is underway - engineers are operating a sophisticated device to successfully create a new connection point on the continuously supplying pipeline. The entire process flows smoothly and does not affect the normal gas usage of hundreds of thousands of households. This is a daily miracle created by the indispensable pressure-bearing opening technology in modern industrial pipeline renovation and maintenance. The pressure-bearing hole opening technology is hailed as the "minimally invasive surgery" in the field of industrial pipeline networks. Its core value lies in enabling the modification, branching, or repair of pipeline systems without the need to stop the pipeline flow or empty the medium, thereby maximizing the guarantee of production continuity, avoiding resource waste, and eliminating the huge safety risks brought about by traditional hot work operations. The key to achieving this highly challenging operation lies in its execution terminal - the pressure-bearing hole opening equipment. This special equipment integrates precision machinery, hydraulic transmission, and automatic control. The design and manufacturing level of its internal structure directly determines the safety, accuracy, and reliability of the hole opening operation. 01 Equipment Overview: Functions, Principles and Core Technologies Pressure-bearing hole-making equipment, professionally known as "online pipeline hole-making machine", its core task is to safely and tightly complete the cutting process of circular holes on pipelines that are under pressure and have flowing media, thereby creating conditions for subsequent operations such as connecting branch pipes, installing valves or performing sealing. Its basic working principle can be summarized as "sealing isolation, mechanical cutting, and closed recovery" in three steps. The equipment first connects to the pipe fittings (such as saddle-type three-way fittings) welded on the pipeline through a dedicated clamp valve and achieves sealing. Subsequently, the cutting spindle inside the equipment, equipped with a special hole-cutting tool, is driven by hydraulic or electric power to penetrate the pipe wall and complete the cutting process. The cut material blocks (commonly known as "saddle blocks") are firmly held by the center mechanism of the tool and are then withdrawn together with the tool into the isolated cavity (or "cage") connected to it. Finally, close the clamp valve and isolate the equipment from the pipeline. Then, the equipment can be safely disassembled and all the operations can be completed. Throughout the process, the medium inside the pipeline flows normally and the pressure and production remain unaffected. To achieve this principle, it relies on the precise coordination of several core systems within the equipment: the fixture and sealing system that provides stable support and sealing, the power and transmission system that supplies cutting force and feed, the tool system that performs the cutting task, and the control and safety system that ensures the entire process is controllable. 02 One of the deep disassembly of core components: fixtures and sealing system The fixture and sealing system serve as the "connection bridge" and "sealing lock" between the equipment and the pipeline. Their primary task is to establish an absolutely reliable and leak-free rigid working platform. The connection flanges and fixtures form the framework of the system. They are usually made of high-strength alloy steel and are securely locked in place using clamps, chains, or bolts, which are attached to the pre-welded standard pipe fittings (such as "sandwich"-style open three-way fittings) on the pipeline. The design must ensure that the connection points remain immobile under the combined loads of pipeline pressure, cutting counterforce, and equipment weight, providing a reference point for precise cutting. The clamp valve is the most crucial "safety switch" in the system. It is located between the fixture and the main body of the drilling machine, and is usually designed as a gate type or plug type. Before drilling, the valve is opened to provide a passage for the cutting tool; after the drilling is completed, the valve is closed first to completely isolate the pressure in the pipeline from the main body of the equipment, and then the equipment can be disassembled. The valve core and valve seat must have excellent sealing performance and wear resistance to ensure zero leakage even after tens of thousands of opening and closing operations. The multiple-sealing combination serves as an impenetrable "steel wall and iron gate" for preventing leaks. A typical system consists of at least three levels of sealing: the first is the primary sealing of the weld seam between the pipe fitting and the pipeline; the second is the static sealing between the connection surface of the fixture and the pipe fitting; and finally, the most dynamic and crucial part is the main shaft seal that wraps around the cutting spindle to prevent the leakage of the medium along the axis. The main shaft seal typically employs mechanical seals with self-tightening function or specially designed packing casings. It can accommodate both the rotational motion of the main shaft and the axial feed motion. Under a pressure of several tens of megapascals, it firmly locks the medium to one side of the pipeline. 03 Deep Disassembly of Core Components - Part 2: Power and Transmission System The power and transmission system is the "power heart" and "movement nerve" of the equipment, responsible for converting energy into stable and controllable rotational and feed movements of the cutting tool. The power sources can be mainly classified into two categories: hydraulic drive and electric drive. For large-diameter and high-pressure working conditions, hydraulic drive is commonly used. Its advantages include high torque, good overload protection, high volume-power ratio, and the ability to provide stable and powerful cutting force. Electric drive is cleaner and more convenient, and is suitable for small and medium-sized diameters and situations where it is inconvenient to prepare hydraulic sources on-site. Some advanced models use explosion-proof motors and can be directly applied in flammable and explosive hazardous areas such as oil and chemical industries. The core of the transmission mechanism is a hollow main shaft. Inside the main shaft, there are usually rods for grasping and retracting the material blocks at the end of the opening process. The rotational power of the main shaft is directly transmitted through a gearbox or hydraulic motor. The axial feed of the main shaft (i.e., the entry and exit of the cutting tool) is achieved by directly pushing through a precision screw-nut pair or a hydraulic cylinder. The feed control device is the guarantee of accuracy. In manual equipment, the feed of the screw rod is usually adjusted by a handwheel, and the operator controls it by feel. However, on automated equipment, servo motors or proportional hydraulic valves are used for control, enabling precise programming of the preset feed speed and depth. Even the cutting load can be adaptively adjusted to ensure smooth cutting and protect the tool. 04 Deep Disassembly of Core Components - Part 3: Cutting Tools and Cutting System The cutting tools and the cutting system are the "frontline fighters" directly engaged with the pipe wall. Their design determines the efficiency, quality and safety of the hole opening process. The hole-making tool is the heart of the system. Depending on the material of the pipeline (carbon steel, stainless steel, cast iron, PE pipe, etc.) and its wall thickness, the tool has different designs and material options. For carbon steel pipes, high-speed steel or hard alloy blades are commonly used for cutting; for plastic pipes such as polyethylene (PE), special scraping blades are used to prevent material adhesion.