The classification of pipe fittings is revealed

There are many ways to classify pipe fittings, just like a huge family, each member has its own unique identity. Below, we will take a deeper look at the classification of pipe fittings from three main aspects: purpose, connection method and material.

1. Classification by purpose

1. Connecting pipe fittings

Connecting pipe fittings are like the "bridge" of the pipeline world, responsible for connecting different pipes together to ensure the integrity of the pipeline system. Common connecting pipe fittings include flanges, unions, pipe clamps, clamps, ferrules, throat clamps, etc.

Among them, flange connection is to fix two pipes or pipe fittings on a flange plate, then add a flange gasket between the two flange plates, and finally tighten the two flange plates with bolts to make them tightly combined. This connection method has good strength and tightness, and is applicable to a wide range of sizes. It can be used on both equipment and pipelines, and is often used in main road connection valves, check valves, water meters, water pumps, etc., as well as pipe sections that need to be frequently disassembled and repaired; pipe clamps are used to connect two pipe sections, with internal threads or sockets, and the operation is relatively simple. It is often used in some occasions where the connection strength requirements are not particularly high.

2. Direction-changing pipe fittings

When the pipeline needs to change direction, it is time for direction-changing pipe fittings to come on stage. Elbows and elbows are the most common direction-changing pipe fittings, which allow the pipeline to turn according to the design requirements to adapt to different spatial layouts and process flows. There are many types of elbows, which can be divided into 45° elbows, 90° elbows and 180° elbows according to the angle. Among them, 90° elbows are widely used in construction and industrial pipelines. For example, drainage pipes in home kitchens and bathrooms often use 90° elbows to achieve pipeline turning. According to the radius of curvature, it can be divided into long radius elbows (R=1.5D) and short radius elbows (R=D). When conveying fluids, long radius elbows can reduce the impact of fluids on the inner wall of the elbow and reduce pressure loss. Therefore, in some pipeline systems with high requirements for fluid transportation, such as oil and natural gas pipelines, long radius elbows are more commonly used.

3. Reducer fittings

In a pipeline system, sometimes it is necessary to connect pipes of different diameters, and reducer fittings play an important role at this time. Reducer fittings, also called reducers, are divided into concentric reducers and eccentric reducers. The center lines of concentric reducers coincide, and are mainly used for reducing the diameter of vertical pipes; the center lines of eccentric reducers do not coincide and one side is straight, and are often used for reducing the diameter of horizontal pipes. It can avoid the formation of air pockets or liquid pockets at the diameter change point, affecting the normal operation of the pipeline. For example, in a heating system, when the pipeline is diverted from the main pipe to the branch pipe, an eccentric reducer is often used to achieve the change in pipe diameter.

4. Branch fittings

If you want to branch the pipeline system, it is necessary to add branch fittings to the pipeline. Tees and crosses are typical branch pipe fittings. Tees can connect three pipes in different directions in a T-shape or Y-shape. When a main pipe needs to branch out a branch pipe, a tee pipe fitting can be used. In the building water supply and drainage system, the branch pipes that supply water from the main pipe to each water point are often connected with tees. Crosses can connect four pipes in different directions in a cross shape. They are often used in some complex pipeline networks, such as the ventilation duct system of large shopping malls or office buildings. Four-way pipe fittings allow ventilation ducts to branch in different directions to meet the ventilation needs of various areas.

5. Sealing pipe fittings

Sealing pipe fittings are the key line of defense to ensure that the pipeline system does not leak. Common sealing pipe fittings include gaskets, raw tape, hemp, flange blind plates, pipe plugs, blind plates, heads, welding plugs, etc. Gaskets are usually placed between two connecting surfaces to play a sealing and buffering role. Gaskets of different materials are suitable for different media and working conditions. For example, rubber gaskets are often used for sealing general media such as water and air, while metal gaskets are suitable for harsh environments such as high temperature, high pressure, and strong corrosion. Raw tape is a common sealing material with good sealing and corrosion resistance. In threaded pipes, it is often wrapped around the threads to enhance the sealing effect. Raw tape is often used in the installation of water pipes in homes.

6. Fixed pipe fittings

In order to ensure that the pipeline remains stable during operation, fixed pipe fittings play an important supporting and fixing role. Clamps, tow hooks, lifting rings, brackets, brackets, pipe clamps, etc. are all fixed pipe fittings. Pipe clamps are one of the most common fixed pipe fittings. They can fix the pipe tightly to the wall, ground or bracket to prevent the pipe from shaking or moving. In building decoration, the installation of water pipes and wire pipes cannot be separated from the fixation of pipe clamps. Brackets and brackets are used to support longer or heavier pipes. According to the weight, diameter and installation environment of the pipe, choose the appropriate bracket and bracket type to ensure the safe operation of the pipeline system. In industrial plants, large steam pipes usually need to be installed with sturdy brackets to withstand their weight and the stress caused by thermal expansion and contraction.

2. Classification by connection method

Welded pipe fittings: Welding connection is one of the most widely used connection methods in pipeline engineering. Welded pipe fittings are connected to pipes by fusion welding or brazing. The advantages of this connection method are that the interface is firm and durable, not easy to leak, the joint strength and tightness are high, and it does not need to be managed frequently after use. It is particularly suitable for long pipelines. However, welded joints are prone to large welding deformation and welding residual stress, which affects the bearing capacity of the joint. At the same time, stress concentration is easy to occur at the junction of the weld and the pipe (heat-affected zone), which has a great impact on the fatigue fracture of the joint. Common welded pipe fittings include elbows, flanges, tees, reducers, and heads. In the pipeline systems of petrochemical, electric power and other industries, welded pipe fittings have been widely used due to the extremely high requirements for the sealing and strength of the pipeline.

Threaded pipe fittings: Threaded connection, also known as threaded connection, connects pipes to pipes and pipes to valves through internal and external threads. This connection method is simple to manufacture and use, reliable connection, easy to use, and has good versatility. It can be assembled and disassembled and reused. It is mainly used for the connection of steel pipes, copper pipes and high-pressure pipes. However, the pressure is low, and the threads are prone to rot and leakage, so they are mostly used for exposed pipes. In home decoration, some water pipes and heating pipes are connected with threaded pipe fittings, which are convenient for installation and maintenance.

Socket fittings: Socket connections are often used for pipe connections of different materials and temporary pipe connections. The principle is to press the pipe to the pipe fitting through the locking nut and the open clamping ring. The sealing surface is short, the installation is convenient and simple, no special tools are required, and it can be disassembled. This connection method is generally suitable for tap water and gas systems with smaller specifications, but the safety factor is relatively low.

Clamp fittings: Groove connection (clamp connection) is a sleeve-type quick connector composed of clamps, rubber sealing rings and fasteners, which is formed by processing annular grooves at pipe joints and other parts. During installation, after the special-shaped rubber sealing rings are put on the adjacent pipe ends, they are connected with spliced clamps. The inner edge of the clamp is in place in the groove and fastened with fasteners to ensure the sealing performance of the pipeline. This connection method has the advantages of not destroying the galvanized layer of the steel pipe, fast construction, good sealing, and easy disassembly. It can be used for pipeline projects such as building water supply, fire protection water supply, and production water supply. In the fire protection pipeline systems of some large buildings, clamp pipe fittings are widely used, which can quickly realize the connection and installation of pipelines and improve construction efficiency.

Socket and spigot pipe fittings: Socket and spigot connections are mainly used for cast iron pipes, ceramic pipes, plastic pipes, etc., and are mainly used in water supply and drainage pipes with low pressure. Socket and spigot connections are divided into mechanical interfaces and non-mechanical interfaces. The mechanical interface uses a pressure flange to connect with the flange on the pipe end, and presses the rubber sealing ring into the gap of the cast iron socket, so that the rubber ring is compressed and tightly adheres to the pipe wall to form a seal; the non-mechanical interface is divided into asbestos cement interfaces, self-stressed cement interfaces, blue lead interfaces, rubber ring interfaces, etc. according to the different fillers. In the water supply and drainage renovation projects of some old communities, socket-type cast iron pipe fittings are often seen. Although they look simple, they can work stably for many years.

Adhesive pipe fittings: Adhesive connection uses adhesive as adhesive filler to bond homogeneous pipes and fittings together to seal. Adhesive connection has the advantages of simple construction and fast curing speed, and is widely used in drainage systems. However, the peel strength, uneven tear strength and impact strength of the bonding layer are low, and the general adhesive has low heat resistance and poor aging resistance. For example, the PVC drainage pipes in the family bathroom are usually connected by adhesive pipe fittings, which are simple to construct and low in cost.

Hot melt pipe fittings: Hot melt connection is mainly used for domestic water pipe connections, such as PPR and PE pipes. This connection method heats and melts the pipe port through a hot melter, and then quickly docks to form a stable connection. Because it has high requirements on the workers' construction process, tools, pipe materials, and construction temperature, it is most widely used in home water supply systems, and has the advantages of firm and durable interfaces and not easy to leak. In home decoration, hot melt connection of PPR pipes is a key technology, and construction personnel need to strictly follow the operating procedures to ensure the quality of the connection.