Tips for using pipeline stoppage sealing technology: Practical experience for efficient and safe operations IntroductionPipeline non-stop transportation blocking technology is the core process in the field of modern pipeline maintenance and emergency repair. It enables the completion of operations such as rerouting, maintenance, and valve replacement while the pipeline is in normal operation, avoiding huge economic losses and social impacts caused by pipeline shutdowns. However, this technology involves multiple high-risk steps such as drilling holes, blocking, welding, and replacement, and even a slight mistake in operation could lead to safety accidents. Based on practical industry experience and professional literature, this article summarizes practical tips for pipeline non-stop transportation blocking operations, helping frontline operators improve operation efficiency and safety. I. Skills for Preparing Before Assignments 1.1 Detailed Control of On-site Surveying A successful blocking operation begins with thorough on-site investigation. During the reconnaissance stage, there are several details that are easily overlooked but are of crucial importance: Confirmation of weld position: Before conducting the hole opening operation, it is essential to ensure that the straight weld seam of the pipeline does not lie directly above the pipeline. Otherwise, it may affect the quality of the hole opening or even lead to the failure of the hole opening. This detail may seem simple, but it is often caused by negligence and results in serious consequences. Measurement of pipe inclination angle: For pipe sections that are inclined, the angle must be accurately measured to facilitate data calculation and operation control for the perforation and sealing operation with the sealing device. The measurement error of the angle will directly affect the alignment effect of the sealing device. Ensure sufficient space for the distance of the operation: Especially during the construction of large-diameter pipelines, the installation of the clamp valve requires sufficient space. If installed at an angle to the pipeline, it will cause the pipeline to bear a large torsion force, affecting the sealing effect. Experience shows that it is better to dig an extra bit of soil rather than compromise the installation space of the equipment. 1.2 Specification of the Work Pit Setup The layout of the operation pits not only affects operational convenience but also serves as an important guarantee for safety. According to the requirements of GB/T 28055-2011 "Technical Specifications for Pressure-Resistant Sealing of Steel Pipelines", a partition wall must be set up between the hot work pit and the sealing pit to ensure that the hot work operation is carried out in a relatively independent space. This isolation measure can effectively prevent the spread of risks in case of an accident. 1.3 Key Points of Equipment Inspection The equipment inspection should not be carried out merely as a formality. The following details deserve special attention: Verification of the sealing performance of the clamp valve: The clamp valve is the only valve that separates the medium inside the pipe from the external environment. Its sealing effect directly determines the safety of the operation. All valves and connectors must undergo a tightness test before use. U-shaped clasp inspection: The U-shaped clasp at the center of the hole-drilling tool must remain intact and flexible to ensure that the saddle-shaped plate cut off during the hole drilling process can be easily removed, preventing any accidents caused by it falling into the pipeline. Once this small component fails, the consequences would be unimaginable. Nitrogen cylinder group inspection: During the operation, nitrogen replacement must be carried out strictly in accordance with the operating procedures. Inadequate pressure monitoring and incomplete replacement may affect the safety of the operation. The cylinder pressure and pipeline sealing conditions must be confirmed one by one. II. Techniques for the Two-Three Connection Welding Process 2.1 Key Calculations Before Welding Three-way welding is the foundation of the sealing operation. The calculations made before welding directly affect the success or failure of the subsequent processes: Pressure calculation for welding: Measure the actual wall thickness of the pipe at the position of the elbow ring weld seam. Based on the formula for pressure calculation provided by the standard, recalculate and confirm the welding position. This calculation can effectively prevent welding cracks. Wall thickness avoidance principle: Try to avoid areas where the pipeline is deformed or severely corroded for welding. If it is impossible to completely avoid, assess whether depressurization operations are necessary. 2.2 Fine Control of the Welding Process There are numerous techniques to follow in quality control: Straight weld protection: During straight weld welding, shims should be used to protect the pipeline from direct contact with the electric arc. This technique can prevent the electric arc from damaging the base material. Application of the lead guard plate: Add a lead guard plate at both ends and remove it after welding is completed. This prevents arc initiation and termination on the main body of the three-way fitting, which is beneficial for reducing defect occurrence. Although this adds an extra process, it has a significant effect on improving quality. Control of weld angle dimensions: During the welding of circumferential welds, the weld angle dimensions of the angle welds must be strictly controlled in accordance with SY/T 6150-2017 and the welding process requirements. It is necessary to ensure the strength of the weld while minimizing stress concentration. Layering and Delay Detection: For tri-bonded welding, in addition to the standard requirements of layering and 24-hour delay detection, it is also necessary to conduct a delay crack detection 48 hours later based on the on-site conditions. This "double insurance" detection strategy can detect more potential defects. Grounding requirements: After the three-way welding is completed, each three-way pipe must be grounded during the entire opening and sealing process. This safety measure is often overlooked. III. Practical Skills for Hole Drilling Operations 3.1 Preparations Before Making Holes