Joining steel pipes without welding is a practical, efficient, and cost-effective solution, especially suitable for scenarios where welding equipment is unavailable, or on-site welding is not allowed (such as flammable and explosive environments). Below are 4 mainstream and reliable methods, detailed with operation points and application scenarios, which are widely used in industrial, construction, and pipeline projects.
1. Threaded Connection (Most Common & Easy to Operate)
- Threaded connection is the most widely used non-welding method, applicable to small and medium-diameter steel pipes (such as 3 inch steel pipes) and low-to-medium pressure pipelines. It relies on threaded joints to fasten the pipes, with simple operation and easy disassembly for maintenance.
- Operation Points: First, process standard external threads on the end of the steel pipe (using a thread cutting machine or die); then apply thread sealant (such as PTFE tape or thread sealant paste) to the external threads to enhance sealing and prevent leakage; finally, screw the pipe into the threaded fitting (such as a coupling, elbow, or tee) manually or with a wrench, ensuring tight connection without looseness.
- Applicable Scenarios: Water supply and drainage pipelines, gas pipelines, industrial fluid pipelines, and other low-pressure systems. It is especially suitable for 3 inch steel pipes in municipal and small-scale industrial projects.
2. Flange Connection (High Sealing & Suitable for High Pressure)
- Flange connection is a detachable non-welding method, characterized by strong sealing, high pressure resistance, and easy disassembly. It is widely used in large-diameter steel pipes, high-pressure pipelines, and scenarios that require frequent maintenance.
- Operation Points: First, fix the flange to the end of each steel pipe (using bolts or clamping rings, no welding required); then place a gasket (rubber, PTFE, or metal gasket) between the two flanges to ensure sealing; finally, align the flange holes and fasten them with bolts evenly, so that the two flanges fit closely without gaps.
- Applicable Scenarios: High-pressure oil and gas pipelines, chemical pipelines, boiler systems, and large-diameter steel pipe connections (including 3 inch and larger specifications).
3. Compression Fitting Connection (Quick & No Special Tools Needed)
- Compression fitting connection is a fast non-welding method that uses the pressure of the fitting to clamp the steel pipe, achieving tight connection. It does not require professional processing equipment and is suitable for on-site emergency connection or temporary pipeline installation.
- Operation Points: Cut the steel pipe neatly (ensure the end is flat and free of burrs); insert the pipe into the compression fitting until it touches the bottom of the fitting; then tighten the compression nut with a wrench, which will drive the ferrule inside the fitting to compress the pipe wall, forming a sealed and firm connection.
- Applicable Scenarios: Emergency maintenance of pipelines, temporary pipelines, water supply and air compression pipelines, and small-diameter steel pipes (including 3 inch steel pipes) that do not bear ultra-high pressure.
4. Grooved Connection (Efficient & Suitable for Large-Scale Construction)
- Grooved connection (also known as card sleeve connection) is a high-efficiency non-welding method, which is widely used in large-scale construction projects due to its fast installation speed and strong adaptability. It is especially suitable for steel pipes that need to be installed quickly in batches.
- Operation Points: First, process a groove at the end of the steel pipe (using a grooving machine); then put the grooved end of the pipe into the grooved fitting, and place a sealing ring in the groove; finally, clamp the fitting and the pipe with a clamping bolt, so that the sealing ring is tightly attached to the groove, achieving sealing and fixing.
- Applicable Scenarios: Firefighting pipelines, HVAC systems, municipal engineering pipelines, and batch installation of 3 inch and larger steel pipes, which can greatly improve construction efficiency.
Key Notes for Non-Welding Connection
- Ensure the steel pipe end is flat, smooth, and free of burrs, which is the key to ensuring connection tightness and avoiding leakage.
- Choose the appropriate connection method according to the pipe diameter, working pressure, and application scenario (e.g., threaded connection for low pressure, flange connection for high pressure).
- Use high-quality fittings and sealants to avoid connection failure caused by poor quality of accessories.
- After connection, conduct a pressure test to check for leakage, ensuring the safety and stability of the pipeline system.
