What is a Pipe Joint?
Pipe joints are integral to any piping system because it is not possible to have a continuous length of pipe for a pipe network. These joints can make or break a pipeline system depending on the resulting durability of the technique used to form the joint.
There are different materials of pipes used in the pipeline industry depending on the need and the type of product that will be conveyed through the pipe.
Types of Pipe Joints in Plumbing
Different types of pipe joints used in plumbing systems are as follows.
#1. Threaded Joint in Pipe.
These joints screw the pipes together by using pipe threads and sealing material like Teflon tape or pipe dope.
Threaded joints come in a range of sizes, from 6mm to 300mm diameter pipes, and are commonly used in low-temperature and low-pressure applications.
However, in high-temperature environments, these joints may expand and lead to leakage caused by thermal expansion. While the installation of threaded joints is straightforward, proper maintenance is essential to ensure their optimal performance.
#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.
Butt welding is done to join the pipes together when the pipes are the same diameter. In other words, both end are connected together right at the end with no overlap.
This is actually the most common type of welding. These piping systems are most commonly used for industrial piping systems as well as commercial.
Butt welded joints in the pipe can withstand high amounts of pressure because of the smooth surface that is inside the joint. These joints cannot be opened for maintenance purposes.
#5. Socket or a coupler joint.
The most common method of joining pipes is by means of a socket or a coupler. A socket is a small piece of pipe thread inside. It screwed on halfway on the thread end of one pipe and the other pipe then screwed in the remaining half of the socket.
In order to prevent leakage, jute or hemp wound around the threads at the end of each pipe. This type of joint is mostly used for pipes carrying water at low pressure and where the overall smallness of size is most essential.
#6. Nipple joint.
In this type of joint, a nipple is a small piece of pipe threaded outside and screwed in the internally threaded end of each pipe. The disadvantage of this joint is that it reduces the area of flow.
#7. Union joint.
In order to disengage pipes joined by a socket, it is necessary to unscrew the pipe from one end. This is sometimes inconvenient when pipes are long. The union joint provides the facility of disengaging the pipes by simply unscrewing a coupler nut.
#8. Spigot and socket joint.
It is chiefly used for pipes that are buried in the earth. Some pipelines are laid straight as far as possible.
One of the important features of this joint is its flexibility as it adapts itself to small changes in level due to the settlement of the earth which takes place due to climate and other conditions.
In this type of joint, the spigot end of one pipe fits into the socket end of the other pipe. The remaining space between the two is filled with a jute rope and a ring of lead. When the lead solidifies, it is caulked in tightly.
#9. Expansion joint
The pipes carrying steam at high pressures are usually joined by means of an expansion joint. This joint is used in steam pipes to take up the expansion and contraction of pipelines due to changes in temperature.
In order to allow for a change in length, steam pipes are not rigidly clamped but supported on rollers. The rollers may be arranged on wall brackets, hangers or floor stands. The expansion bends are useful in a long pipeline.
These pipe bends will spring in either direction and readily accommodate themselves to small movements of the actual pipe ends to which they are attached.
#10. Flanged Joint in Pipe.
It is one of the most widely used pipe joints. A flanged joint may be made with flanges cast integral with the pipes or loose flanges welded or screwed. Two cast-iron pipes with integral flanges at their ends.
The flanges are connected by means of bolts. The flanges have seen standardized for pressures up to 2 N/mm2. The flange faces are machined to ensure the correct alignment of the pipes.
The joint may be made leakproof by placing a gasket of soft material, rubber, or canvass between the flanges. The flanges are made thicker than the pipe walls, for strength.
The pipes may be strengthened for high-pressure duty by increasing the thickness of the pipe for a short length from the flange.
For even high pressure and for large diameters, the flanges are further strengthened by ribs or stiffeners. The ribs are placed between the bolt holes.
#11. 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 requirements.
#12. Grooved Joint in Pipe.
In the case of a grooved joint, the pipe ends have grooved edges that are connected by an elastomer seal. Ductile iron grooved couplings are used to secure the elastomer seal.
These grooved couplings are connected by bolts. These joints are easy to install and economical.
Grooved joints will give good resistance against pressure and allow moderate axial movement due to thermal expansion.
But, in high-temperature Areas, elastomer seal may be 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.
#13. Hydraulic pipe joint
This type of joint has oval flanges and is fastened by means of two bolts. The oval flanges are usually used for small pipes, up to 175 mm in diameter. The flanges are generally cast integral with the pipe ends.
Such joints are used to carry fluid pressure varying from 5 to 14 N/mm2. Such high pressure is found in hydraulic applications like riveting, pressing, lifts, etc. The hydraulic machines used in these installations are pumps, accumulators, intensifiers, etc.