Galvanized steel pipe, known for its durability and corrosion resistance, is a popular choice for water supply piping, outdoor applications, and some structural uses. Traditionally, connecting these pipes, especially smaller sizes like those under 2 inches, is done by threading fittings. But what if pipes aren’t threaded or you’re dealing with a non-threaded section of pipe? Fortunately, there are several reliable methods for non-threaded connections.
1. Butt-welding connection
Butt welding is a welding method that brings the end faces of two items together and welds them on the contact surfaces to form a continuous weld, thereby firmly connecting them into a whole.
Advantages of Butt Welding:
- 1. High Strength: the weld area is continuous and smooth, reducing stress concentration, and is suitable for high-load structures.
- 2. Good Sealing: the weld is dense, with excellent air tightness and liquid tightness, suitable for pipelines and pressure vessels.
- 3. High economic: no additional accessories are required, the structure is simple and light.
- 4. Fatigue resistance: When the weld is well formed, the fatigue performance is better than that of fillet welds.
Disadvantages of Butt Welding:
- 1. Bevel required: Precision machining is required, increasing cost and time.
- 2. Assembly required: Precise alignment of the end faces is required to avoid misalignment and uneven gaps.
- 3. High residual stress in welding: This may affect structural stability and require post-weld treatment.
- 4. Non-destructive testing required: Rigorous testing is required, resulting in high costs and technical requirements.
Fluid Tech offers a complete line of welded pipe fittings, whether you require carbon steel or stainless steel. Our customers consistently recognize our high performance, competitive pricing, and fast delivery.
2. Grooved connection
Grooved Connection is a mechanical connection method that quickly connects grooved pipes, fittings, or valves. It is widely used in fire protection, water supply and drainage, HVAC, industrial pipeline, and other systems, especially in situations where rapid installation and dismantling or pipeline expansion and contraction are required.
How to connect:
Grooving: A circular groove of a specified depth and width is formed on the joint end of a pipe, fitting, or valve using a specialized roll groove machine.
Rubber Seal: A specialized rubber seal (usually C- or U-shaped) is placed between the two groove ends to be connected.
Clamp Locking: A two- or three-piece metal clamp (usually made of ductile iron or cast steel) is wrapped around the seal and the outer surface of the groove. Tightening the clamp bolts tightens the clamp, compressing the seal and deforming it radially, allowing it to conform tightly to the pipe wall and groove.
Advantages of Grooved Connections:
- 1. Quick and Easy Installation: No welding or flange alignment is required; simply roll out the groove, place the seal, install the clamp, and tighten the bolts. This is several times faster than traditional methods, reduces labor costs, and requires minimal technical skills.
- 2. No Open Flame: The connection process requires no open flame, making it suitable for flammable environments and fire-prohibited areas.
- 3. Vibration and Noise Reduction: The rubber seal absorbs vibration and noise, improving comfort.
- 4. Easy Maintenance: Disassembly is accomplished by simply loosening the clamp bolts, making it easy to inspect and modify. The clamps and seals are reusable, reducing costs.
- 5. Highly Adaptable: Reliable sealing performance meets standard pressure requirements.
Disadvantages of Grooved Connections:
- 1. Limited pressure capacity: Suitable for low- and medium-pressure systems like 2.0 MPa, not suitable for high-pressure applications.
- 2. Limited high-temperature resistance: Rubber seals have temperature limitations and are not suitable for high or very low temperatures.
- 3. Space requirement: The clamp assembly requires additional space, making it unsuitable for applications with limited space.
- 4. High machining quality requirements: The grooves must be precisely machined, which can affect connection strength and sealing.
- 5. Long-term aging issues: The seals and clamps require regular inspection and maintenance.
- 6. Not suitable for extremely small pipe diameters: Suitable for pipe diameters ≥ DN40.
3. Press the connection
Press connection is a mechanical joining method that uses specialized tools to apply radial pressure to the joint between a metal fitting and a thin-walled metal pipe, causing both the fitting and the pipe to plastic-ally deform simultaneously, creating a tight, sealed connection. Crimping is widely used in thin-walled stainless steel piping systems (such as drinking water, gas, and compressed air piping), particularly in building water supply, home improvement, and food and pharmaceutical industries.
How to connect:
Pre-install seals: Food-grade silicone rubber or EPDM seals are pre-molded into the fitting socket.
Pipe insertion: Insert the cut pipe end vertically into the fitting socket until fully inserted.
Radial press-in: Using the die of a specialized press-in tool (pliers or power tool), apply strong radial pressure at a specific location on the exterior of the fitting.
Plastic deformation and locking:
Pressure causes plastic deformation of the fitting (usually softer, authenticate stainless steel) and the pipe (usually harder, thin-walled stainless steel).
Advantages of compression fittings:
- 1. Quick Installation: Cutting, deburring, marking, inserting, and crimping the pipe complete a single-point connection in seconds. Easy to operate, requiring minimal skill, and achieving higher efficiency than welding and threading, and even faster than grooved connections.
- 2. Reliable Connection: Mechanical locking and sealing ring compression provide dual protection against pullout and rotation. The sealing ring is located inside the socket, offering improved performance and reliability under positive pressure.
- 3. Safe and Environmentally Friendly: No open flames, high temperatures, or welding slag fumes, making it suitable for use in flammable and explosive environments and confined spaces. No harmful gases are generated, making it environmentally friendly and worker-friendly.
- 4. Excellent Hygiene: The smooth inner surface of the joint reduces water flow resistance and prevents scaling. Using food-grade sealing rings, it meets drinking water hygiene standards and is suitable for use in direct drinking water systems, medical gas systems, and food and beverage production lines.
Disadvantages of compression fittings:
- 1. Non-removable: The connection is permanent, requiring cutting and replacement for repair or modification, which is costly.
- 2. Dependence on specialized tools: Requires specialized tools of the correct brand and size, resulting in high purchase and rental costs and requiring regular tool maintenance.
- 3. Strict insertion depth requirements: Under- or over-insertion can affect sealing and strength, and axial pipe movement must be prevented.
- 4. Limited application: Primarily suitable for small and medium-sized pipe diameters from DN15 to DN100, using thin-walled austenitic stainless steel pipe with a wall thickness of 0.6mm to 2.0mm.
No matter how you want to connect your pipes, Fluid Tech can meet your requirements. We provide the accessories and materials that best suit your project site to help you complete your project smoothly.
Want to know more? Contact us now!
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