What is 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
The pipes are usually connected to vessels from which they transport the fluid. Since the length of pipes available is limited, therefore various lengths of pipes have to join to suit any particular installation. There are various forms of pipe joints used in practice, but the most common of them are discussed below.
Different types of pipe joints used in plumbing systems are as follows.
1. 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.
2. 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.
3. 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.
4. 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.
5. 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.
6. Flanged joint
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.
7. 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.