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Universal Expansion Joints

What is the Universal Expansion Joint?

Expansion joints are simply an assembly of bellows with other components to form a product that can contain movements caused by stress, thermal stress, and other seismic activities. They can be classified into multiple types based on their design, functions, and so on. Some of the common types are axial, lateral, hinged, gimbal, universal, elbow pressure balanced expansion joints and so on. Universal expansion joints are one of the most important and most used types of expansion joints.

Universal Expansion Joint suppliers pliant bellows

The reason behind the widespread usage of universal expansion joints is that unlike a lot of the other types, these can contain movements in all 3 directions namely lateral, axial, and angular. Also known as a double bellow expansion joints, these are made with 2 bellows that are connected by a spool or pipe section. Another major advantage of using this over others is that large amounts of lateral deflection can be absorbed with this. If the capacity has to be increased, this can be done by increasing the length of the pipe section connecting the 2 bellows. In certain cases, tier rods may be attached to limit the axial expansion. If 2 tie rods are used, it can take in good lateral and angular expansion. By using more than 2, you can make the expansion joints to contain only lateral expansion.

Features

  • Vibration and oscillation absorptio
  • Low maintenance cost
  • Compact and light
  • Abrasion-resistant
  • Corrosion-resistant
  • Eliminated pressure thrusts

Installation

Since the universal expansion joints are made from thin material, it is extremely necessary to ensure that the are not damaged during the installation. Also, for correct functioning and fitting, it is important to follow correct procedures during the process.
  • Installation process
    • Be careful while handling the product. It is important to ensure that there are no dents, weld splatter, etc on them.

    • The joint is not made to rectify misalignments in the piping system. As a result, you must not use them to do the same. Imposing unnecessary movements to align can reduce the life cycle and capability.

    • If any sleeves, flanges, etc. are required, you must attach them properly.

  • Do's and Don'ts before the test
    • Store in a cool dry place and not exposed to heavy traffic and a damaging environment.

    • While lifting, do not use ropes or rods through the holes. Use proper lugs instead.

    • Install the product in the direction of flow.

    • Do not subject it to heaving torsional forces.

    • Do not use steel wire, mesh, and other abrasive cleaning products on the surface.

    • Before testing, ensure that you remove all the shipping devices and packaging.

    • Align the bolt holes with ones matching on the mounting flange.

    • Do not use cleaning products that contain Chlorides

    • Do not expose the product to more than one and a half times its rated working pressure.

  • Inspection During and After Test
    • Check for any evidence of leakage or loss of pressure.

    • Check for any distortion of the expansion joint hardware, the bellows and other piping components.

    • Check for any possible squirm in the product.

    • If there are any abnormalities during the testing, it must be evaluated by the concerned authority.

  • Periodic Inservice Inspection

    Just like the checks and inspections before installation, it is extremely important to check the product while it is in service to ensure a successful and smooth functioning.

    • Inspect the product to check if it is functioning as planned by the manufacturer, as well as any unwanted vibrations.

    • Periodic inspection must be done. The frequency of this must be decided based on the working conditions.

    • Through these inspections, the product must be checked for any loose components, any deformations, corrosion on the surface, as well as any other damages.

    • If required, the components must be replaced or repaired as decided by the design team.

  • Typical Causes of the universal expansion joint failure
    • Improper handling during shipping

    • Incorrect installation

    • Improper anchoring

    • Corrosion of bellow elements

    • Higher working conditions that what is designed for

    • System fatigue, etc.

  • Installation Misalignment

    Generally, the expansion joints are not made to sort out the misalignments. However, if there are small deflections, you may contact the manufacturer and tell him beforehand.

Applications:

Due to its ability to absorb movements in all directions, there are mainly used in low-pressure environments such as ventilation ducts, exhaust gas systems, fresh air ventilation equipment, etc.

Advantages:

  • Vibration isolation

  • Wide temperature ranges

  • Low maintenance

  • Better performance than other expansion joints

  • Absorbs large degrees of lateral movement.

Frequently Asked Questions

Why do the universal expansion joints need to be tied?

Tie rods in universal expansion joints help in controlling the movement of the expansion joint. By using 2 tie rods, the movements of expansion can be limited to only lateral and angular with no axial movements. If you are using more than 2 rods, this will ensure that only lateral movements can be contained by the product.

Where should I use a universal expansion joint in piping?

Universal expansion joints have the ability to control movements in all the directions. However, the are used in pipelines where the pressure is low. You will also require good guides and fixed points to install this in the piping. Depending on the length of the pipeline, there may be additional guides and fixed points required.

How long should a universal expansion joint be?

The length of the expansion joints depends on a few interconnected factors. First of all, it depends on client requirements. Depending on the diameter of the target pipeline, the pressure, temperature, etc, the length of the bellows are decided. The length of the middle pipe section or spool is determined by the capacity of control required. For containing higher movements, the length must be increased, and vice versa.

How do you decide on the number of tie-rods in a universal expansion joint?

The number of tie rods required for an expansion joint in the piping system is mainly dependent on the amount of pressure thrust the product has to absorb. For low-pressure expansion joints, 2 tie rods are sufficient. However, for high-pressure joints, there may be even four and above.

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