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Bellows in layman terms are simply devices that have concertinaed sides and have the ability to expand or compress as per the necessity. Normally, bellows are used in industries where there is a need to transfer high temperature and pressure fluids that can cause deformations and stress of varying capacities. Bellows can be made from metal, rubber, or even Teflon depending on the requirements.
Metallic bellows are bellows that are made from metals such as stainless steel, or any other metal alloys. Used in metal expansion joints for the safe and convenient functioning of pipelines and ducts, these are extremely tolerant to heat and pressure, and also have excellent corrosion resistance. The metal bellows are manufactured by first forming cylinder from thin sheets, and then creating circumferential convolutions on the surface. These help in providing a compressive and expansive effect on the device thereby helping to withstand extreme conditions.
To make metal expansion joint bellows, metal bellows manufacturers attach the metallic bellows with end fittings, control rods, liners, cover, and other components to form a whole product. The metallic expansion joints are used in various industries and help contain the stress in the system such as axial, lateral, angular, and universal stress, as well as help in controlling the vibrations, thereby protecting the pipeline as well as the surrounding pieces of equipment.
However, the production is not that easy. There are plenty of protocols and regulations to be followed in the manufacturing process, along with mandatory testing to be done as well. At Kwality Products, we use state of the art equipment to manufacture metal bellows. It is done using hydroforming machines, and mechanical expanders. Apart from these, the manufacturing is done in according to the EJMA standards, as well as pertaining to the ASME codes, thereby maintaining excellent product standard and quality.
Metallic bellows are normally called as metal expansion joints bellows interchangeably. Based on the direction of movement restriction, the direction of flow, and other factors, these can be classified into the following.
This type of metal bellows is used to contain the deflections in the longitudinal direction (along the length). In the case of thermal expansion, this joint compresses along the length thereby accommodating the stress.
This bellow expansion joint is used where there is a requirement to constrain angular movements in a single plane. With the help of a hinge, these restrict the deflection in one direction. They are used in systems where there is a change in the direction of flow of the substance.
This is a type of pressure balanced bellow expansion joint and is used in piping systems where there is no room for pressure acting on the piping system and also a directional flow change is present. This absorbs motion in the axial direction.
As the name suggests, this type of bellows is used to constrain all the movements in the lateral (perpendicular to the central axis) direction. Using control rods attached, the lateral expansion joints also control the pressure thrust including full vacuum.
This form of pressure balanced expansion joints is used to constrain axial movements without transferring any load on the pipe system, unlike normal axial joints. By using two bellows in line together and acting in opposite directions to control the pressure inside, this is mainly used in systems where pressure on the system must be avoided at all costs.
The universal bellows joints, also sometimes known as a double bellow expansion joint is made up of 2 bellows attached together by a pipe in between. Due to this design, this can absorb movements that are beyond the capacity of axial expansion joints. These can also restrict deflections in the axial, lateral, and angular directions.
Gimbal expansion bellow joints, also known as angular expansion joints are used to absorb deflections in multiple angular directions. By using multiple hinges or gimbal, these can constrain movement in all the planes.
These are the simplest form of the expansions bellows, this type is basically manufactured as the sole bellow alone as they can be easily welded to the end fitting by any skilled worker. They are used in heat exchangers and can absorb small axial movements.
This type of expansion joints uses tie rods along with the bellows to constrict reaction forces and spring forces by containing them within the bellow itself. These can absorb axial movements, and a certain altered design can also be used to absorb small lateral deflections.
These are simply put, 2 bellows that are joined by a pipe section, and have control rods attached to the flanges. They help in absorbing large amounts of lateral movements in all directions. The control rods also help in absorbing axial reactive forces to an extent.
A double-hinged bellow joint simply uses two hinged bellows attached together by a pipe section along with welded bars to constrain movements in lateral directions as well as absorb the axial pressure thrusts.
This is used in areas where mounting and demounting of valves or other devices in fixed pipelines is difficult. By using expansion joints fitted with restraining screws that bridge the convoluted part. These bellows are also fixed with compression screws for the demounting.
Using metallic bellows in an expansion joint has several benefits. Some of the key features of this are -
Due to the wide variety of applications, the bellows are custom made. As a result, there are various design parameters such as different size, shape, capacity, etc that can be applied to the bellow as per the customer requirements.
With the help of the strong and durable alloys used in the manufacturing, the bellow is designed to withstand high amounts of stress both thermal and mechanical. It can absorb up to temperature rises of 1000 C, and even contain high pressures of PN 100 (Pression Nominal).
Due to their excellent durability, the maintenance cost for the bellows are almost. As a result, using a metal bellow is a well-made investment.
These can be made for use in conveying liquids, gases, or even solids and abrasive media.
