Types of Metallic Expansion Joints & their Uses

 

What are Bellows Metallic Expansion Joints?

Standard bellows have a wide range of engineering applications. Bellows metallic expansion joints are used to compensate for pipe system motions in a variety of industrial piping applications. The bellows metallic joints keep vibrations, expansions, and other variations from harming long-distance pipes.

This article was penned by Ablaze Lining - a popular High Pressure Bellow manufacturer in India explains the many types of bellows metallic expansion joints and their applications.

Custom Expansion Joints:

Metallic expansion joints are elastic vessels that may be compressed or expanded under pressure or in a vacuum. If the bellow's material is not stressed beyond its yield strength, the release of the vacuum or pressure causes the metallic bellow to revert to its original shape. There are four types of metallic expansion joints, which are classified according to the manufacturing technology, utilised.

1.   Convoluted or Formed Bellows:

Deep drawn reworked tubes are used to make formed metal bellows. Various methods, such as hydro-forming, punch forming, cold forming, and roll forming, are used during manufacture. If mass-produced, these bellows can be made from a variety of metallic materials at a reasonable cost. High-pressure stability and capability are provided by formed bellows.

●     What are these bellows used for?

Bellows that have been formed are widely used in petrochemical refineries, boiler plants, cement plants, thermal plants, and steel plants.

 

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2.   Diaphragm or Welded Bellows:

Formed diaphragms that are welded to the bellow's outer and inner diameter create welded convolutions. The breadth of such bellows is determined by the diameter of the stamped diaphragm. The diameters of such bellows are determined by the available stamping equipment, and they typically range from 12 to 300 mm.

 

Concave, convex, cantilever and nested welded bellows are all common forms of diaphragm bellows. These bellows are constructed of titanium, stainless steel, and other high-strength materials.

●     What are these bellows used for?

Accumulators, pressure sensing, rotary shaft seals, mechanical seals, and valve stem seals all require welded or diaphragm bellows.

 

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3.   Machined Bellows:

Machined bellows are created by grinding or twisting forged rings, tubing, and bar stock that have previously been used to create other forms of metal bellows. Machined bellows are typically produced of low modulus, high-strength titanium alloys as well as heat-treatable, high endurance, and high-strength steel. Custom bellows with a high spring rate that can bear pressures of up to 82.73 MPa are known as machined bellows.

●     What are these bellows used for?

These bellows are used in industrial applications where a fast spring rate and a high-pressure thrust are required.

4.   Deposited Bellows:

In order to create the bellows, metal is first deposited on an aluminium mandrel and then dissolved to reveal the bellow. This type of bellows is made using either electrode deposited or chemically deposited techniques. Using one of the two approaches, you can create whatever bellows form you want to. This type of bellow is typically found in diameters from 1.524 to 177.2mm and thicknesses from 0.0762 to 0.0128mm, depending on the manufacturer.

 

In electroplated or electro-deposited bellows, nickel-cobalt alloy or nickel is commonly used. A minimum wall thickness of 0.1524 mm is required for their diameters ranging from 1.6 to 31.75 mm. Small, thin-walled bellows can be made from these materials.

 

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●     What are these bellows used for?

Deposited bellows are widely used in sensors, electrical applications, and other areas where low spring rate functions and ultra-high vacuums are required.

Final Thoughts:

A metallic bellow expansion joint dampens vibrations, expansions, and other movements that could harm pipe systems. The bellows' joints can be made of a variety of materials depending on the purpose and environment. For example, bellows metallic expansion joints used in marine locations should be made of materials that can withstand corrosion from marine salts.