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Pipe joints in water supply are major components of plumbing system provided to connect multiple pipes. There are several types of pipe joints, but their selection depends on pipe sizes, material and flow pressure etc.. Pipe joint provided should withstand pressure of each pipe.
Types of Pipe Joints in Plumbing
Different types of pipe joints used in plumbing system are as follows.
- Threaded joint
- Brazed joint
- Soldered joint
- Welded joint (butt welded, socket welded)
- Flanged joint
- Compression joint
- Grooved joint
1. Threaded Joint in Pipe
Threaded joint means, pipes are connected by screwing with the help of threads provided for each pipe. One pipe having internal threads and the other one having threads externally. Cast iron pipes, copper pipes, PVC and G.I pipes are available with threads.
Threaded joints are available from 6mm diameter to 300mm diameter pipes. They are preferable for low temperature areas and low pressure flows. In the areas of high temperature, the joints may expands and leaked due to thermal expansion. Installation of threaded joint is easy but good maintenance required.
2. Brazed Joint in Pipe
Brazing is the process of jointing pipes using molten filler material at above 840oC. Brazing is generally used for joining copper pipes or copper alloy pipes. The filler material majorly consist tin which has great affinity towards copper. But because of its weak property tin is added to other materials like nickel, bismuth, silver and copper.
The melting point of parent metal should be higher than filler metal. Mechanical strength of brazed joint is low compared to other joints. This type of joint is suitable in moderate range of temperature areas.
3. Soldered Joint in Pipe
Soldering is also similar to brazing but the only difference is in case of soldering the filler metal melts at below 840oC. Soldering also used to joint copper and copper alloy pipes. Before proceeding to soldering flux called paste is applied to pipes and fittings to prevent them from oxidation from flame. Here also we require skilled workers for installation.
Soldered joints are suitable for low temperature areas. These are having low mechanical strength as brazed joints.
4. Butt Welded Joint in Pipe
When the pipes are of same diameter butt welding is to done to join the pipes. It is the most common type of welding. Skilled workers are required to install the joint. These joints are generally used for large commercials and industrial piping systems.
Butt weld provides good strength for the joint and it can resist high pressure because of smooth and continuous surface inside the joint. Butt weld joints are expensive, to make it economical sometimes internal weld backing rings are used, which joins the pipe with less amount of filler material. But these rings may fail under heavy stress and cracks are developed.
The joints are fixed and do not opened for maintenance purposes. External smoothing of welded portion will give good appearance to the piping system.
5. Socket Welded Joint in Pipe
Socket welded joints are used wherever there is a high chance of leakage in joints. Pipes are connected as putting one into other as shown below and welded around the joint. Pipes having different diameters are suitable for this type of joint.
If pipes having similar diameter, then required fittings are used. Welding cost is generally lower than butt welding. Fatigue resistance is lower for socket welded joints when compared to butt weld joints. However, socket welded joint give good results when compared with other mechanical joints.
6. Flanged Joint in Pipe
Flanged joints are used for high pressure flows and for large diameter pipes. In general they are used for plain end pipes or threaded pipes. Two flange components are connected by bolts at the pipe joint to prevent leakage.
Generally these are made of cast iron, steel etc. these are having good strength and do not fail against high pressure. Against high temperatures the bolts may fail under creep lost their grip so, fixing of bolts should be done properly while installing. They are also useful for repairing pipelines and maintenance purposes.
7. Compression Joint in Pipe
When the pipes have plain ends they are joined by installing some fittings at their ends then that type of joint is called compression joint. The pipe ends will be fitted with a threaded fittings or couplings hence they are connected.
So, in this case we can connect pipes of different materials and different sizes. But the joints should be properly fitted to resist flow pressure otherwise they may fail and leakage occurs. Compression fittings are available in different materials and selection of fittings may depend upon our requirement.
8. Grooved Joint in Pipe
In case of grooved joint, the pipe ends consist grooved edges which are connected by elastomer seal and then ductile iron made grooved couplings are used as lock for elastomer seal. This grooved couplings are connected by bolts. These joints are easy to install and economical.
Grooved joints will give good resistance against pressure and allows moderate axial movement due to thermal expansion. But, in high temperature Areas elastomer seal may lost its strength and torsional failure occurs. So, these are permitted to moderate temperature areas.
Grooved joints are easily removable so, for maintenance purposes of pipes these joints are preferable.