Diagnosis of Common Faults and Systemic Solutions for Pressure Sealing Hole Opening Machines: In-depth Analysis I. Working Principle and Core Structure of Pressure Sealing Hole Opening Machines (1) Working Principle The pressure-sealing hole-making machine is based on the dual technical logic of "mechanical cutting + sealing isolation". It completes the hole-making and sealing process while ensuring the normal flow of the pipeline medium. The core process is as follows: 1. Equipment fixation: Using devices such as flanges and clamps, the equipment is fixed at the location where the pipeline needs to be operated, ensuring mechanical stability under pressure conditions. 2. Sealed cutting: The power system drives the opening tool to rotate, and the sealing pipe fitting (such as a saddle three-way fitting) is used to perform circumferential cutting on the pipe wall. The cutting process is completely enclosed within a sealed chamber, preventing any leakage of the medium. 3. Sealing connection: After the opening is completed, the sealing head (such as a folding rubber cup or a mechanical gate plate) is pushed into the pipeline by the feeding mechanism. The sealing is achieved through the medium pressure or mechanical force, thus completing the connection of the new and old pipelines or isolating the faulty pipe section. (2) Core Structure Composition The equipment is mainly composed of five functional modules: 1. Power System: Provides cutting power, including hydraulic motors (suitable for high-pressure scenarios) and electric motors (suitable for environments with abundant power supply). The key parameters are output torque (typically 200-1000 N·m) and rotational speed (50-200 r/min). 2. Transmission System: Transmits power to the cutting tools, including the gearbox, coupling, and screw nut assembly, ensuring stable torque transmission and feed accuracy (feed error ≤ 0.5mm); 3. Tool System: The core functional component, including the opening tool (made of hard alloy or high-speed steel) and the sealing head (made of rubber/metal composite material). The selection should be based on the pipe material (carbon steel, stainless steel) and the wall thickness (4-20mm). 4. Sealing System: Composed of O-rings, sealing gaskets, and mechanical seals, it ensures the airtightness of the pressure-bearing chamber (with a design pressure typically ranging from 1.6 to 10 MPa). 5. Control System: Integrates pressure monitoring, speed regulation, and feed control functions, including pressure gauges (with 1.5-level accuracy), servo valves, and travel switches, among other components. II. Common Fault Types and Cause Analysis (1) Decrease in cutting efficiency of the tools or abnormal wear of the tools Fault manifestation The cutting time was prolonged by more than 30% compared to normal operating conditions. The cutting edge of the tool became chipped and frayed, and the cutting surface became rough (with a roughness greater than Ra12.5μm). The sealing surface of the plug head was rapidly worn out, resulting in leakage during the pressure test (pressure drop > 0.05 MPa/h). Analysis of Causes The cutting parameters are inappropriate. Excessive rotational speed (for example, for carbon steel pipes, exceeding 150 r/min) causes the cutting tool to overheat and undergo annealing (the upper temperature limit for hard alloy is 800°C; after overheating, the hardness decreases). Excessive feed rate (greater than 0.3mm/r) causes the cutting force to exceed the allowable stress of the cutting tool (the compressive strength of carbide tools ranges from 2000 to 3000 MPa; excessive load can lead to tool breakage). 2. Influence of Medium Characteristics ◦ The solid particle-containing media (such as sand in crude oil, dust in gas) scour the surface of the cutting tool, causing abrasive wear (the wear rate is proportional to the concentration of the particles and the square of the flow velocity); Acidic media (such as those containing H₂S and CO₂) corrode the tool body, resulting in corrosion wear (electrochemical corrosion accelerates material loss). 3. Incorrect selection or installation of cutting tools ◦ The cutting tools were not matched with the pipe material (for example, using high-speed steel tools to cut stainless steel pipes, which would result in insufficient wear resistance); The installation of the cutting tool is eccentric (with radial runout greater than 0.2mm), which causes an imbalance in the cutting force and leads to excessive wear on one side of the cutting edge. (2) Leakage fault of the sealing system Fault manifestation Leaks or spills occur at the connection points of the equipment and pipelines, as well as at the flange surfaces of the cutting chambers, accompanied by an abnormal odor of the medium or abnormal fluctuations in pressure. Visible cracks, hardening or permanent compression deformation (deformation amount > 10%) can be observed on the surface of the sealing piece. Analysis of Causes Sealing components have aged and failed. ◦ The O-ring (typically made of nitrile rubber) undergoes thermal oxidative aging when exposed to high-temperature media (above 80℃), resulting in a decrease in elasticity (the elongation at break is less than 200%). The rubber gasket at the sealing head becomes swollen due to immersion in the medium (such as gasoline, solvents), with a volume expansion rate exceeding 5%, resulting in the failure of the sealing surface to fit properly. 2. Installation process defects The roughness of the flange sealing surface exceeds the standard (greater than Ra6.3μm), or there are scratches (depth greater than 0.5mm), which causes the sealing element to be unable to fill the gap. The pre-tightening torque of the bolts is uneven (with a deviation of more than 15%), resulting in warping of the flange surface (with a flatness deviation of more than 0.3mm/m), and an imbalance in the distribution of sealing stress. 3. Medium pressure shock The sudden water hammer effect (with the pressure peak exceeding the design pressure by 1.3 times) caused the sealing element to experience instantaneous overload and undergo plastic deformation. Under negative pressure conditions (such as when the pipeline is evacuated), the sealing element is subjected to reverse compression due to the pressure difference between the inside and outside, resulting in flanging or tearing. (3) Abnormal shutdown of the power system or insufficient output Fault manifestation