First, how to overlap square steel pipes
Square steel pipes are widely used, including structural square steel pipes, decorative square steel pipes, building square steel pipes, mechanical square steel pipes, etc. When used, it is usually necessary to overlap multiple square steel pipes together, so how to connect square steel pipes?
1. Compression type: insert the square steel pipe into the pipe mouth of the pipe fitting, tighten it with a nut, and use the spiral force to compress the sleeve of the pipe mouth through the sealing ring to seal and complete the connection of the square steel pipe. Scope of application: DN (nominal diameter) ≤150mm, can be installed openly or concealed.
2. Welding type: perform annular argon arc welding on the usual socket-type pipe fittings and matching, which plays a sealing role and completes the matching connection. Scope of application: Pipes in public buildings and large buildings, DN is 15mm-100mm, DN greater than 100mm is mostly conventional butt welding; indoors can be installed openly or concealed, and outdoors buried.
3. Heat-shrinkable pipe fittings: When connecting square steel pipes, on-site welding can be used. Since the welding points cannot be handled on the construction site, heat-shrinkable pipe fittings are used for supplementary sealing. A rubber welding sleeve is put on the pipe welding point, and then a special cross-linked polyethylene sleeve is put on the outer sleeve. It shrinks under the action of heat to achieve shrinkage sealing. Applicable scope: Pipes with DN below 400mm.
4. Cone thread type: The external thread sleeve and the matching are annularly welded, and the internal thread pipe fittings are connected with a cone pattern to seal and complete the matching connection. Applicable scope: DN is 65mm-100mm, and the pipelines of public buildings and large buildings can be used in harsh environments such as foundation sinking, high temperature, and high pressure.
5. Limit compression type: The square steel pipe adopts a flanging or port welding ring, and the connection method is a flexible or semi-flexible connection. After the rubber sealing ring limit seal is compressed by 20%-30%, it enters the metal sealing groove, and the limit seal is used to protect the sealing element. The joint can be made of copper or carbon steel. The applicable range is DN below 400mm, suitable for harsh environments such as foundation sinking, various high temperatures, and high pressures.
6. Quick-connect flange type: perform annular argon arc welding on the flange and the matching parts, use quick clamps to compress the sealing gasket between the flanges, play a sealing role, and complete the matching connection. The applicable range is DN 15mm-100mm, public buildings, and large buildings.
7. Flexible quick-connect flange: turn the traditional flange into a flexible flange, the square steel pipe port is flanged or welded, the ring mouth is embedded in the groove, and the sealing rubber part is placed in the groove. The limited compression method is used to protect the sealing element. The applicable range is DN below 400mm, which can be used as a buried pipe.
8. Compression type: insert the square steel pipe into the pipe fitting, the two ends of the pipe fitting are protruding U-shaped grooves, with built-in sealing rings, and the socket part is clamped and connected with a special pipe fitting tool. Scope of application: DN ≤ 100mm, can be installed openly or concealed.

Second, what are the precautions for connecting stainless steel square tubes?
1. Whether it is a square steel tube or a rectangular tube, it should be supplied by the supplier in a unified manner. Square steel tubes of different brands and materials should not be connected.
2. When connecting square steel tubes with threaded valves, nozzles, water meters, and other accessories, it is not allowed to thread the square steel tubes but should be transitioned through threaded accessories such as conversion joints.
3. When the buried connection is required, pay attention to the fact that square steel tubes should not be in direct contact with cement, cement mortar, and concrete. Plastic-coated thin-walled welded pipes should be used or anti-corrosion tape should be wrapped around the outer wall of the pipe.
4. When connecting square steel tubes, pay attention to avoid sharp objects colliding with square steel tubes. When using seals for connection, pay attention to avoid oil or other dirt from contaminating the seals.