Types of elbows

The angle mystery of elbows

As a key pipe fitting for changing the direction of pipelines in pipeline systems, elbows have a wealth of knowledge about their angles. The most common elbow angles are 45°, 90° and 180°.

A 45° elbow is like a gentle steering assistant. It can be very useful when the pipeline needs to be turned at a smaller angle. In some scenarios where the direction of the pipeline needs to be fine-tuned so that the pipeline can change direction at a gentler angle, 45° elbows are often used.

For example, in the laying of household gas pipelines, when it is necessary to bypass some obstacles or fine-tune the direction of the pipeline according to the structure of the house, a 45° elbow can complete the task well. It allows the gas pipeline to be flexibly turned in a smaller space, ensuring the smooth delivery of gas, while not having a significant impact on the pressure and flow rate of the pipeline.

The 90° elbow is the most common "star" pipe fitting in pipe connection. It can realize the right-angle change of pipe direction and is widely used in pipe systems in various fields such as water supply and drainage, heating, ventilation and air conditioning. In the water supply and drainage system of buildings, we often see 90° elbows.

For example, the connection from the wash basin drain pipe in the bathroom to the main drainage pipe, or the turning point of the kitchen sink drain pipe, the 90° elbow plays a vital role. It enables the water flow to change direction smoothly and flow into the designated drainage pipe, ensuring the normal discharge of water in daily life.

In the heating system, the 90° elbow can be used to connect the heating pipe and the radiator to ensure that the hot water can flow accurately to each heat dissipation device according to the design requirements to provide warmth for the room.

The 180° elbow is also called "U-shaped elbow" or "return bend". It can realize the 180° turn of the pipe, that is, to completely reverse the flow direction of the pipe. Although it is not as common as 45° and 90° elbows, it plays an irreplaceable role in some special occasions.

In some industrial production, when the fluid needs to be recycled or processed for a specific process, a 180° elbow may be used. For example, in some chemical production processes, the treated liquid needs to be redirected back to the original pipeline or another nearby processing equipment. The 180° elbow can help achieve this goal, allowing the liquid to complete a "turnaround run" in the pipeline to meet the needs of the production process.

In some sewage treatment systems, in order to achieve the recycling treatment of sewage or specific sedimentation and filtration processes, 180° elbows will also be used. It can cleverly change the flow direction of sewage and make the entire treatment process more efficient.

In addition to these common angles, according to the special needs of the project, there are other non-normal angles such as 60° elbows. They play a unique role in the design of some specific pipeline systems and meet the diverse needs of various complex projects.

Rich and diverse types of elbows

The types of elbows are rich and diverse, and can be classified in many ways from different angles.

Classification by material: Common ones include carbon steel elbows, stainless steel elbows, alloy steel elbows, copper elbows, aluminum alloy elbows and plastic elbows (such as PVC, PPR, etc.). Carbon steel elbows are relatively cheap, have good mechanical properties and certain corrosion resistance, and are widely used in general industrial pipelines and water and gas pipelines in construction projects. For example, many common building drainage pipelines use carbon steel elbows.

Stainless steel elbows are favored in industries with high requirements for hygiene and corrosion resistance, such as chemical, food, and medical, due to their excellent corrosion resistance.

In order to ensure the safety and hygiene of food and prevent the pipeline from rusting and contaminating food, stainless steel elbows are used in large quantities in the piping system of food processing plants.

Alloy steel elbows have excellent comprehensive performance and play an important role in the fields of petrochemicals, electricity, etc. under harsh environments such as high temperature and high pressure. For example, alloy steel elbows are used in the connection of high-temperature and high-pressure pipelines in the process of oil refining.

Copper elbows have good thermal conductivity and are often used in heating systems, etc., which can better transfer heat and ensure heating effects.

Aluminum alloy elbows are light in weight and have certain corrosion resistance. They are used in some occasions where weight is required, such as some pipeline systems in the aerospace field.

Plastic elbows are cheap and easy to install. They are widely used in water supply and drainage pipes for home decoration. PPR plastic elbows are commonly used pipe fittings in home decoration.

According to the production method, there are push elbows, pressed elbows, forged elbows, cast elbows, etc. Push elbows are made by a special elbow pusher. With the cooperation of the core mold and the heating device, the blank on the mold moves forward under the push. During the movement, it is heated, expanded and bent.

The elbows produced by this method have the characteristics of beautiful appearance and uniform wall thickness. They are suitable for mass production. It is the main forming method of carbon steel and alloy steel elbows. It is widely used in large-scale industrial pipeline production.

Pressed elbows are formed by directly pressing the tube blank in the mold using a press. It is suitable for single-piece production and low-cost situations. It is mostly used for the manufacture of small batches and thick-walled elbows.

Forged elbows are made by forging process. They have dense structure and good mechanical properties. They are often used in some pipe connections with high strength and quality requirements, such as high-pressure pipe systems.

Cast elbows are formed by pouring liquid metal into a specific mold and cooling and solidifying it. It can produce elbows with complex shapes, but there may be internal defects. It is usually used in some occasions where the precision and performance requirements are not particularly high, such as some ordinary building drainage pipe elbows.

Classification by curvature radius: It can be divided into long radius elbows and short radius elbows. The curvature radius of the long radius elbow is equal to 1.5 times the outer diameter of the pipe (R=1.5D), and the curvature radius of the short radius elbow is equal to the outer diameter of the pipe (R=1.0D).

Long radius elbows can make the flow of fluid smoother in the pipeline system, reduce fluid resistance and scouring and wear on the inner wall of the elbow. It is suitable for pipeline systems with low requirements for fluid resistance and high flow rate, such as large oil pipelines, gas pipelines, etc.

Short radius elbows take up relatively less space and are more suitable for occasions with limited space, such as pipe connections in some narrow areas inside buildings. However, due to their relatively large resistance to fluid, they are not suitable for high-speed fluid transportation.

Classification by pressure level: There are about seventeen types, which are the same as the pipe standards in the United States, such as Sch5s, Sch10s, Sch10, Sch20, Sch30, Sch40s, STD, Sch40, Sch60, Sch80s, XS, Sch80, SCH100, Sch120, Sch140, Sch160, XXS, of which STD and XS are the most commonly used. Elbows of different pressure levels are suitable for pipeline systems in different pressure environments.

In high-pressure pipeline systems, elbows with higher pressure levels are required to ensure the safe operation of pipelines and prevent accidents such as elbow rupture due to excessive pressure; in low-pressure pipeline systems, elbows with lower pressure levels can be selected, which can not only meet the use requirements but also reduce costs.

Classification by shape and use: including groove elbows, ferrule elbows, double-socket elbows, flange elbows, reducing elbows, seat elbows, internal and external thread elbows, stamping elbows, push elbows, socket elbows, butt welding elbows, internal thread elbows, etc.

Groove elbows are connected to pipes through groove connections, which are quick and convenient to install and have good sealing properties. They are often used in fire protection pipes, water supply and drainage pipes and other occasions that require high installation speed and sealing properties.

Ferrule elbows use ferrules for sealing and connection, which are easy to disassemble. They are generally used in some pipeline systems that need to be frequently disassembled and maintained, such as small pipeline equipment in laboratories.

Double-socket elbows are mainly used to connect two pipes, and both ends are connected by socket and spigot, which are often used for the connection of drainage pipes.

Flange elbows are connected to pipes through flanges, with high connection strength, easy to disassemble and repair, and suitable for various large pipeline systems and parts that need to be frequently inspected. Reducing elbows are used to connect two pipes of different diameters to achieve changes in pipe diameters. They are often used at the diameter change point of the pipe system.

The fixed base elbow has a fixed base, which can be used to support and fix the pipe and increase the stability of the pipe system.

The internal and external thread elbows have both internal and external threads, which are convenient for connecting with pipes or equipment with different connection methods. Stamping elbows are made by stamping process, with a higher pressure level, and are often used for pipe connections with higher pressure requirements. As mentioned above, push elbows have good forming quality and production efficiency.

The socket elbow connects the pipe by socket method, which is simple to operate and is widely used in some small pipe projects.

The butt welding elbow is connected to the pipe by butt welding process, with high welding quality, and is suitable for high temperature, high pressure and pipe systems with strict sealing requirements. The internal thread elbow has internal threads, which is convenient for connecting with pipes or equipment with external threads, and is often used in water supply and drainage pipes in home decoration.