What are bellows and how are they used?

Release time:

2022-07-20

The axial force exerted on the bellows is less than the frictional force, ensuring that the connection remains intact and the bellows do not slip. Tightening the bellows with a specialized wrench generates a remarkably strong clamping force. When using bellows, the preload on the connecting components is uniform. This preload creates substantial friction along the mating surfaces, which is why the bellows design is exceptionally simple yet boasts excellent mechanical performance, is readily disassemblable, highly resistant to fatigue, and remains securely fastened even under dynamic loading—making it a truly promising connection method. Such is the principle behind the bellows connection.

　　The axial force exerted on the bellows is less than the frictional force, ensuring that the connection remains intact and the bellows do not slip. When the bellows is tightened using a specialized wrench, it generates an extremely high clamping force. With the use of bellows, the pre-pressure applied to the connecting components remains consistent. This pre-pressure creates substantial friction along the contact surfaces, which is why the bellows design is remarkably simple yet boasts excellent mechanical performance, is easily disassembled, highly resistant to fatigue, and remains securely fastened even under dynamic loading conditions—making it a truly promising connection method. That’s precisely how bellows connections work: they prevent slippage by relying on friction between the contact surfaces. To ensure sufficient friction and enhance the clamping force, we increase the coefficient of friction on the contact surfaces. Now, let’s take a closer look at the different types of bellows and their applications!

What are bellows and how are they used?

　　To achieve the previous clamping force of the bellows by applying a pre-tension to it, the bellows is made of steel. In the connection of bellows, the friction coefficient has a significant impact on the load. Experiments have shown that the friction coefficient is primarily influenced by the material of the parts and the geometry of the contact surfaces. Often, the contact surfaces within the connection area are treated by sandblasting or cleaning with wire brushes to enhance the friction coefficient of these surfaces. Therefore, bellows can be classified into two types: friction-type and pressure-type.

　　Bellows connections are remarkably simple to install, exhibit excellent load-bearing performance, are detachable, resistant to fatigue, and remain secure even under freeze-thaw loads—making them a highly promising connection method. The principle behind bellows connections involves tightening the nuts with a specialized wrench, which exerts a substantial pre-compressive force on the bellows. This pre-compressive force is then transmitted through the plates and nuts to the connected components as well, creating an equivalent pre-compression in those components. Under the influence of this pre-compressive force, relatively high frictional forces develop along the contact surfaces of the connection.

　　When the axial force on the bellows is less than the frictional force, the bellows will not slip or shift, and the connection will remain intact. The connection is maintained by the frictional force between the contact surfaces of the connecting components, which prevents slippage. By increasing the clamping force of the bellows and enhancing the coefficient of friction at the contact surfaces, sufficient frictional resistance can be achieved. Pre-tensioning is applied to the bellows to generate a clamping force between them. The coefficient of friction in the connected bellows has a significant impact on the load-carrying capacity. Since the coefficient of friction depends primarily on the materials and surface textures of the bellows and the connecting components, during installation, it is common practice to clean the contact surfaces of the bellows within the connection area using wire brushes or sandblasting.

　　Bellows are widely used in instrumentation, with their primary application being as the sensing element in pressure gauges, where they convert pressure into displacement and force. Bellows feature thin walls and high sensitivity, and their measurement range spans from tens of pascals to tens of megapascals. One end of the bellows is fixed, while the sealed end remains free; elastic properties are enhanced by the addition of an auxiliary helical spring or reed.

　　When in operation, the internal pressure causes the flexible end to undergo a displacement that is proportional to the pressure along the length of the air tube. As the movable edge shifts, it moves the pointer, directly indicating the magnitude of the pressure. Bellows are often combined with displacement sensors to form pressure sensors that output electrical signals; they are also sometimes used as insulating components. The function of PE bellows is...

　　PE corrugated pipe, also known as a corrugated plastic sleeve made from polyethylene through extrusion molding, gets its name from its ring-shaped corrugated structure both on the inside and outside. It serves to protect cables from damage. This type of pipe features excellent wear resistance and corrosion resistance. Made from PE material specifically for its resistance to corrosion, wear, aging, and its environmentally friendly properties, PE corrugated pipes are commonly used as branch pipes for stormwater and sewage systems.

　　The functions of corrugated pipes made from PP and PA materials.

　　In addition, corrugated pipes made from PP and PA materials offer flame-retardant properties. These corrugated pipes can be extruded from three types of materials—PE, PA, and PP—and effectively prevent mechanical damage such as breakage and fraying of wires and cables. They boast advantages including flexibility, bendability, acid resistance, and wear resistance, thereby providing excellent protection for wire harnesses, wires, and cables. Typically, flame-retardant and cuttable corrugated pipes can be custom-made and are widely used in industries such as mechanical equipment, automatic control systems, automotive, subway systems, and electrical switchgear cabinets.

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