The sealing performance of stainless steel double external thread extension pipes is its core performance indicator, directly affecting the safety and reliability of the piping system. Improving sealing performance through process optimization requires a comprehensive approach, addressing aspects such as thread machining accuracy, sealing structure design, material selection, surface treatment, assembly processes, and quality inspection to form a systematic solution.
Thread machining accuracy is fundamental to sealing performance. If the threads of stainless steel double external thread extension pipes have deviations in tooth profile, pitch errors, or excessive surface roughness, it will lead to excessive thread clearance during connection, causing leakage. Optimization measures include: using high-precision CNC lathes to machine threads, ensuring that parameters such as tooth profile angle and pitch meet standards; using dedicated thread cutting tools to avoid machining errors caused by tool wear; using cooling lubricant during machining to reduce thread deformation caused by cutting heat; and conducting thread inspection after machining to reject defective products.
Sealing structure design is crucial. Traditional threaded connections rely on the mechanical engagement of the threaded pair to achieve a seal, but stainless steel has high hardness and a high elastic modulus, resulting in small thread deformation and limited sealing effectiveness. Optimization directions include: designing sealing grooves at the thread root and embedding O-rings or metal gaskets to achieve elastic sealing through compression sealing elements; adopting a double-seal structure, adding an end-face seal to the threaded connection for double protection; and designing a self-tightening sealing structure for high-pressure conditions, using medium pressure to compress the sealing surface and improve sealing reliability.
Material selection directly affects sealing performance. Stainless steel double external thread extension pipes require corrosion-resistant, high-strength materials, such as 316L stainless steel, which has a high chromium content, forming a dense oxide film on the surface to effectively resist chloride ion corrosion; nickel stabilizes the oxide film structure and improves pitting resistance. Material purity must also be strictly controlled; excessive impurities reduce material toughness and increase the risk of cracking. Furthermore, the sealing element material must match the pipe material; for example, fluororubber or silicone rubber should be used for O-rings to avoid electrochemical corrosion.
Surface treatment can significantly improve sealing performance. Thread surface roughness is a crucial factor affecting sealing; excessive roughness can scratch the sealing surface, leading to leakage. Optimization measures include: polishing threads after machining to reduce surface roughness; using electrolytic or chemical polishing to form a uniform oxide film on the surface, improving corrosion resistance; and sandblasting the sealing surface to increase surface roughness, improving the adhesion and sealing effect of the sealing element.
The assembly process significantly affects sealing performance. Tightening torque must be controlled during assembly; insufficient torque leads to poor sealing, while excessive torque may damage threads or sealing elements. Optimization measures include: using a torque wrench to ensure torque meets design requirements; cleaning threads and sealing surfaces before assembly to remove oil and impurities to avoid contaminating the sealing element; lubricating the sealing element to reduce frictional resistance and ensure uniform compression; and conducting sealing tests after assembly, such as air pressure or water pressure tests, to promptly identify and address leaks.
Quality inspection is the final checkpoint for ensuring sealing performance. A rigorous quality inspection system must be established to conduct full-process inspections of raw materials, semi-finished products, and finished products. The testing includes: thread parameter testing, such as pitch, thread angle, and surface roughness; sealing performance testing, such as air pressure testing and helium mass spectrometry leak detection; material composition analysis, such as spectral analysis and metallographic testing; and corrosion resistance testing, such as salt spray testing and cyclic corrosion testing. Through comprehensive testing, the sealing performance of the stainless steel double external thread extension pipe is ensured to meet design requirements.
