Pipe and elbow connection types and methods

In the pipeline system, the connection method of pipe and elbow needs to be selected according to the material, pressure, purpose and construction conditions. The following are common connection methods and precautions for elbow fittings:

1. Welding connection

This is one of the most commonly used connection methods, connecting the elbow and the pipe by welding.

Applicable scenarios: systems with high pressure, high temperature or permanent sealing (such as petroleum, chemical, and power pipelines).

Advantages: high strength, firm connection, good sealing, strong pressure resistance, especially suitable for high pressure occasions.

Disadvantages: welding is difficult, requires professional tools and techniques, and is not easy to disassemble after welding, which is not conducive to maintenance.

2. Flange connection

Flange connection is to fix the flange on the elbow and the pipe tightly together by bolts, and add a sealing gasket (rubber, metal winding gasket, etc.) in the middle.
Applicable scenarios: pipelines that need to be frequently disassembled or maintained (such as industrial equipment, large pipeline networks).

Advantages: easy disassembly, good reusability, easy maintenance, suitable for medium and high pressure occasions.
Disadvantages: Flange connection requires more accessories, which increases the cost, and the connection is prone to leakage. High cost and large space.

3. Threaded connection

Applicable to elbows with smaller diameters. The corresponding threads are processed on the elbows and pipes, and then connected using threaded connectors. Wrap raw tape or apply sealant on the external thread of the pipe and the internal thread of the elbow, and tighten it.
Applicable scenarios: water and gas systems with low pressure (≤1.6MPa) and small diameter (DN≤100).

Advantages: Easy operation, easy disassembly, suitable for low pressure occasions.
Disadvantages: The sealing of threaded connection is relatively poor and prone to leakage. Low pressure bearing capacity, long-term use may loosen and leak.

4. Socket connection

The socket connection is to insert one end of the elbow into the socket at the other end and seal it with sealant (such as PVC glue) or sealing pad.
Applicable scenarios: plastic pipes (such as drainage, chemical anti-corrosion systems).

Advantages: easy installation, corrosion resistance, low cost, suitable for some occasions with low pressure and large diameter.

Disadvantages: The sealing may be affected by the quality of installation. Not resistant to high temperature, limited pressure bearing capacity.

5. Clamp connection

Clamp connection is a convenient and fast connection method, which ensures the tight connection between the elbow and the pipe through special clamps and sealing gaskets.

Pressing type: Use special tools to crimp the pipe fittings and pipes, and seal them with O-rings.
Grooved type: After the end of the pipe is grooved, it is connected to the elbow with a clamp.

Applicable scenarios: Thin-walled pipes such as stainless steel pipes and copper pipes (such as water supply and gas systems).

Advantages: Quick connection, no need for professional technology and tools, no need for fire, and good reusability.
Disadvantages: May not withstand extremely high pressure, suitable for low and medium pressure occasions. Special tools are required and pipe materials are limited.

6. Hot melt connection and electric fusion connection

These two connection methods are mainly suitable for plastic pipe systems, such as PPR, PE, etc.
Hot-melt connection is to heat the interface of the pipe and the elbow to melt and connect them together; electric fusion connection is to use electric fusion sleeve to heat and connect the pipe and elbow.

Advantages: high connection strength, good sealing, suitable for occasions requiring high sealing.
Disadvantages: the operation process requires certain skills and experience, and the selection of connection materials is more critical.

7. Quick-release connector (sanitary connection)

Use clamp or quick-release flange connection, rely on silicone gasket to seal.
Applicable scenarios: stainless steel pipes in food and pharmaceutical industries.

Advantages: easy to disassemble and clean, in line with hygiene standards.

Disadvantages: only suitable for low pressure and clean environment.

8. Other connection methods
There are also some special connection methods, such as socket welding connection, adhesive connection, etc. These connection methods are usually used for pipe connections under specific materials or specific working conditions.

Notes:

1. Matching: Make sure that the material, pressure level, and size (such as DN, PN) of the pipe and elbow match.
2. Sealing material: Select gaskets according to the medium (such as PTFE acid and alkali resistance, metal gaskets high temperature resistance).

3. Construction specifications:
Before welding, the grooves need to be cleaned to avoid impurities.
The threaded connection should not be over-tightened to prevent pipe cracking.
The flange bolts need to be tightened diagonally to ensure uniform force.

4. Safety: Avoid hot work in flammable environments and use mechanical connections instead.

Conclusion:

When choosing the connection method of pipes and elbows, it is necessary to make comprehensive considerations based on specific engineering requirements and the use environment. For example, it is necessary to consider factors such as the pressure, temperature, fluid characteristics, working environment, and maintenance requirements of the pipeline system. At the same time, it is also necessary to ensure that the selected connection method complies with relevant standards (such as GB, ASME, ISO) and specifications to ensure the safety and reliability of the pipeline system.

Read more: Material selection and application of pipe elbows or Long radius elbow vs Short radius elbow