Pressure-sealing Test Usage Guide: A Perfect Combination of Safety Assurance and Precise OperationIn the modern industrial system, the pipeline network is like a network of blood vessels, transporting various media. And the pressure-sealing technology has become the "minimally invasive surgery" method for these pipeline systems, enabling the maintenance, renovation and branching connection of the pipelines without production suspension. This highly technical operation method relies entirely on strict usage testing procedures for its safety. This article will deeply explore the entire process of pressure-sealing usage testing, revealing the safety code behind this key technology. I. Overview of Pressure-Resistant Sealing Technology and Importance of Testing Pressure-sealing technology is a technique that enables the connection of branch pipes or maintenance operations on pipelines without interrupting the flow. This technology is mainly applied in pipeline systems of industries such as petroleum, natural gas, chemical engineering, and water supply, addressing the significant economic losses caused by traditional operations that require pipeline shutdown and purging. The principle of pressure-sealing operation is that when the pipeline is under pressure, a hole is drilled on the pipeline using hydraulic or pneumatic equipment, and then a dedicated sealing device is used to seal or divert the pipeline. The entire process is carried out under the normal operating pressure of the pipeline, just like replacing the tires of a speeding car. The technical difficulty and risk coefficient are extremely high. A typical pressure-sealing failure accident can lead to disastrous consequences. A petrochemical enterprise once suffered from an ineffective sealing device, resulting in crude oil leakage. This not only caused hundreds of millions of yuan in economic losses but also led to environmental pollution and the suspension of production and rectification of the enterprise. A gas company also experienced a gas explosion due to insufficient sealing during operation, causing casualties and the complete interruption of gas supply to the entire urban area. The fundamental causes of these accidents are mostly directly related to insufficient testing. Using tests as a quality assurance step for pressure sealing operations is of paramount importance. A complete testing system consists of three levels: pre-material inspection, mid-process verification, and post-effect confirmation, covering the entire process from equipment entry to operation completion. Statistical data show that pressure sealing operations that strictly follow the testing procedures can reduce the accident rate by over 95%. II. Pre-test Preparation: Equipment Inspection and Condition Assessment Comprehensive preparations are the foundation for a successful test. The preparatory work before conducting a pressure-sealing test includes three main aspects: equipment inspection, condition assessment, and plan formulation. Equipment inspection is the first step. The sealing equipment usually includes main components such as a drilling machine, a sealing device, a hydraulic station, a connection box, and cutting tools. During the inspection, each item needs to be confirmed one by one: the radial runout of the spindle of the drilling machine (should not exceed 0.05mm), the surface finish of the sealing surface of the sealing device (should reach Ra0.8 or above), the rated pressure and flow parameters of the hydraulic station, the sealing performance of the connection box, and the sharpness of the cutting tool's edge. All equipment must have the most recent calibration certificates and maintenance records. Condition assessment is the basis for formulating the test plan. It is necessary to accurately measure the actual outer diameter, wall thickness, ellipticity, etc. of the operation pipeline (using tools such as ultrasonic thickness gauges and π rulers); analyze the composition of the pipeline medium, temperature, and pressure fluctuation range; detect the pipeline material and corrosion condition (if necessary, conduct hardness tests and metallographic analysis); understand the pipeline operation history and surrounding environmental conditions. These data directly affect the determination of the test pressure and the selection of the test method. The formulation of the test plan requires comprehensive consideration of all factors. Key technical parameters such as the test pressure (usually 1.1-1.3 times the pipeline operating pressure), the holding pressure time (not less than 30 minutes), the test medium (generally water or inert gas), the accuracy grade of the measuring instrument (not lower than 1.0 grade), and the qualification standards need to be clearly defined. The plan also needs to include an emergency response plan, specifying the handling procedures and responsible persons for various abnormal situations. Personnel preparation is equally important. All the operators involved in the test must hold valid certificates and possess the necessary qualifications and experience. Before the test, a technical briefing should be conducted to ensure that each operator is clear about the test process, their responsibilities, and emergency measures. If necessary, simulation exercises should be carried out, especially for complex conditions or tests involving new equipment. III. Material and Equipment Testing: Ensuring Hardware Reliability The quality of materials and equipment directly affects the safety of pressure-sealing operations. The testing contents include three aspects: material verification, performance testing and compatibility testing. Material verification is a fundamental test. The hardness of the sealing material for the plug (typically Shore A 70-90), the compression permanent deformation rate (not exceeding 10%), and the tensile strength (not less than 15 MPa) are all key parameters that must match the pipeline medium and operating conditions. For natural gas pipelines, the material's anti-explosion performance needs to be tested; for chemical pipelines, the material's corrosion resistance and swelling properties need to be tested. Each batch of materials must have a material certificate and performance test report. The sealing performance test is a core step. A dedicated test bench is used to simulate the actual working conditions, testing the sealing performance of the sealing head. During the test, the pressure is gradually increased to 1.5 times the rated value and maintained for 30 minutes. The pressure drop should not exceed 1% of the test pressure. At the same time, the contact condition of the sealing surface is checked. It is required that the contact width be uniform and continuous, without breaks or weak links. For bidirectional pressure-bearing sealing heads, the sealing performance of both directions needs to be tested separately. Mechanical performance tests verify the load-bearing capacity of the equipment. The hole-making machine needs to test whether the output torque and thrust meet the requirements (usually the torque is not less than 2000N·m and the thrust is not less than 100kN); the sealing device tests the strength and stiffness of the linkage mechanism; the hydraulic system tests the setting accuracy of the overflow valve (with an error of no more than ±0.5MPa) and the response speed.