Pipe joints are important in any piping system when pipe length is limited. As a result, pipe joints must be used to create a continuous piping network. Moreover, such pipe joints are often the weakest connections in a pipeline system. As a result, the actual functionality of the piping or plumbing system depends greatly on the durability of the technique utilized to create the joint. Depending on the requirements, a piping system may contain many joints or joining methods. As a result, pipe joints are an integral part of any piping or plumbing system. Generally, pipe joints can withstand pipe pressure.
The design and selection of pipe joints can have a significant impact on the initial installation cost. Furthermore, piping joints influence the long-term operation and maintenance costs as well as the performance of the piping system.
There are several aspects to consider while choosing a pipe joint, such as
- Material expenses
- Labor charges for installation
- Required leakage integrity level
- Regular maintenance requirements
- Specific performance criterion
Furthermore, the pipe joint should meet the necessary code requirements.
Types of Pipe Joints
Various types of pipe joints are utilized depending on the application’s needs. They are classified as follows:
A threaded joint is a type of pipe joining in which pipes are joined by screwing into threads in the pipe. One of the pipes includes internal threads, whilst the other has external threads. Threaded piping joints are appropriate for non-critical, low-pressure, low-temperature, low-cost applications such as residential water, fire protection, and industrial cooling or heating systems. Such pipe joints have moderate productivity and are simple to install. Screwed piping joints should not be utilized for vibrating lines because differential thermal expansion can cause leakage.
Threaded pipe joints are commonly used for PVC, CI, copper, and GI pipes, as well as brass or bronze, carbon, and alloy steel pipes. Although threaded joints are available in sizes ranging from 6 mm to 300 mm, cost considerations often limit industrial uses to 80 mm. For residential water and drainage applications, threaded construction is often utilized with galvanized pipes and fittings. When maintenance or the process involves frequent disassembly and reassembly, a screwed piping system is an excellent solution. It should be noted that threaded pipe joints should only be used within the parameters of the regulatory code.
Butt-welded pipe joints are the most prevalent type of pipe joint found in large commercial, residential, and industrial systems. Butt welding requires the services of experienced pipe welders and fitters. Butt-welded pipe joints have exceptional strength and leakage integrity. Because the inside surface of a butt-welded piping system is smooth and continuous, this pipe joining results in a low-pressure drop.
For high temperature-pressure large bore pipe applications, butt-welded pipe joints are the preferable joints. The majority of butt-welded pipe installations are for NPS 2 (DN 50) or above. They result in a smooth pipe surface.
Socket-welded pipe joints are utilized in systems where leaks can be a concern. One pipe is inserted into the other and welded around the joint in socket welded pipe joints. This kind of pipe joint is typically less costly to create than butt-welded joints. The internal crevice, on the other hand, is prone to corrosion. Socket welded pipe joints have higher mechanical strength than other types of pipe joints.
Brazed and Soldered Joints
Brazing and soldering joints are commonly used to join copper and copper-alloy pipe systems. Brazing of steel and aluminum pipe and tube is also done. Both the brazing and soldering joining processes include the addition of molten filler metal, which is drawn into the joint by capillary action. This metal then solidifies, fusing the components. To avoid the melting of the main pipe, the melting point of the pipe material must be higher than the melting point of the specified filler material.
Joints that are brazed or soldered provide excellent leakage integrity and installation productivity. Brazed and soldered joints are commonly used in medical gas and high-purity pneumatic control systems. However, the mechanical strength of these installations is minimal.
The primary distinction between brazed and soldered junctions is that brazing is done with molten filler material at temperatures above 840 °C, whereas soldering is done at much lower temperatures. They are preferred for services requiring moderate pressure and temperature.
Grooved joints are commonly utilized in fire control systems, ambient temperature service water, and low-pressure drainage applications. They are simple to install and disassemble, resulting in decreased labor costs. Two pipes are joined together in this piping joint by creating grooves at the ends of the pipes with the use of sockets or couplings. They typically have good leakage integrity and can withstand some axial misalignment. Under pressure, the grooved structure prevents the joint from splitting.
In high-temperature applications, the use of elastomer seals limits the use of grooved joints. They are also vulnerable to torsional loading.
Compression joints are commonly used to connect plain piping ends that do not have any end preparations. These pipe joints can withstand a limited degree of thermal expansion and angular misalignment. Pipes of various materials can be connected using compression joints. The installation expense is relatively low.
Pipe ends are joined in compression joints using threaded fittings or couplings. To avoid leaks, the joints must be carefully positioned to monitor the flow pressure.
Compression joints are utilized in instrument and control tubing installations and applications where excellent seal integrity and ease of assembly and disassembly are needed.
Flanged connections are widely used in modern pipes and piping systems due to their ease of installation and dismantling. However, they are expensive due to the high cost of the flanges themselves as well as the labor cost for bolting the flanges to the pipe. Flanged joints are commonly utilized in high-pressure and high-temperature applications. They do, however, tend to leak. Flanged pipe joints make it simple to join different pipe materials. To prevent leakage, a gasket is put between the two flanges.
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