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Rubber Expansion Joints
Definition : A rubber expansion joint is a flexible connector fabricated of natural or synthetic elastomers and fabrics and if necessary, metallic reinforcements to provide stress relief in piping systems due to thermal and mechanical vibration and / or movement. Noteworthy performance features include flexibility and concurrent movements in either single or multiple arch type construction, isolation of vibration and noise resistance to abrasion and chemical erosion.

Type : Single Arch, Multi Arch, Reducer type, Offset type, Sleeve type etc.

Material : Made of natural / synthetic rubber like EPDM, Chloroprene, NBR, Butyl and Chlorobutyl on a strong carcass made of synthetic / cotton fabric with the reinforcement of steel wire, steel ring etc.

Range :

Size From 25mm NB upto 2500mm NB. Rectangular sizes are also available.
Pressure 26 inches Hg of vacuum upto 40 kg. / cm2g.
Temperature Maximum working temperature varies as per the different grades of rubber used.

Functions :

Reduce Vibration
It isolates and reduce vibration caused by equipments. It reduces transmission of vibration and protect the equipment from adverse effect of vibration.

Dampen Sound Transmission
Rubber Expansion joints tends to dampen transmission of sound because of steel-rubber interface of joints and mating flanges.

Compensate Lateral, Tersional and Angular Movement
Rubber Expansion joints compensate for lateral, torsional and angular movements preventing damages and undue downtime of plant operation.

Compensate Axial Movement
Expansion and Contraction movements due to thermal changes or hydraulic surge affects are compensated for with strategically located rubber expansion joints. They acts as helix springs, compensating for axial movements.

Constuction :
A protective, leakproof lining made of synthetic or natural rubber as the service dictates. This is a seamless tube that extends through the bore to the outside edge of the flanges, its purpose is to eliminate the possibility of the materials being penetrated the carcass and weakening the fabric. These tubes can be designed to cover service conditions for chemical petroleum, sewege, gaseous and abrasive material. The extenor surface of the joint is formed from natural or synthetic rubber depending on service requirement.

Fabric Expansion Joints
Non-Metallic (Fabric) Expansion Joints are flexible connectors designed to provide stress relief in ducting system by absorbing movement caused by thermal changes particularly for low pressure applications. They also act as vibration isolators, shock absorbers and in some instances to make up for minor misalignment of adjoining ducting or equipment. For low pressure ducting systems handling gaseous media, which is likely to adversely react with most of the metals, fabric compensators can be optimal solution.

Features :

  • Large movements
  • Low load on anchors
  • Corrosion resistance
  • Sound and vibration eliminator
  • High temperature
  • Lower material cost
  • Lower system design cost
  • Lower replacement cost

However, matal bellows are completely sealed units and can be designed for very high pressure and temperatures in comparison to fabric type where the pressure is limited to 2000 mm WC and they are leak proof as far as practicable.


Range :

Pressure +/- 2000 mm WC
Size 150 mm NB upto 3500 mm NB. For rectangular sizes there is no size limitation.
Temperature Special design can be made upto a maximum temperature of 1100°C
Material Elastomer coated fabric of the top layer and inner layer of insulating fabric with other layering as per the system requirement.
Construction :
Single / Composite layering with various and connections and internal arrangements.
Metallic Expansion Joints
  Bellow Assemblies / Absorbators Introduction :
These are completely sealed units assembled in numerous ways with different types of end fittings as per the specific requirement of customer for various applications such as Axial, Universal, Gimbal, Hinged, Pressure Balance etc. Uni Joints has the right kind of design, engineering and manufacturing facilities as well as capabilities to match the requirements of EIMA. These allow greater control over quality during every phase of production. The device containing one or more bellows used to absorb dimensional changes such as those caused by thermal expansion or contraction of a pipe line, duct or vessel.

  Features :
  • Individual designed to meet the specific requirement of customers.
  • Highly flexible, absorbs axial, lateral and angular movements.
  • Low anchorage leading.
  • General resistant to any climatic condition.
  • Suitable for media temperature from (-) 200°C for cryogenic application and upto 1200°C (with refractory lining).
  • Easy to install, handle, transport and store.
  • Single Ply / Multiply construction.

Range :

  • Material
    Stainless Steel - AISI304, 304L, 316, 316L, 321, Inconel, Manel, Phospher Bronze, Brass, Mild Steel etc.
  • Thickness of Material
    0.2 mm minimum for single ply construction.
  • No. of ply
    Single / Multi.
  • Inside diameter
    50 mm minimum to 2500 mm maximum. For Rectangular & Square bellows, any size. Capacity for other sizes are under development.
  • Pressure range
    From full vacuum to 200 kg / cm2g
  • Temperature range
    From (-) 200°C for cryogenic application to (+) 1200°C (with refractory lining) for high temperature application.
  Construction & Safety :
Bellows are formed by roll forming process under the most exciting process control in house and permits no points of stess concentration. Bellows are employed in piping systems to absorb differential thermal expansion while containing the system pressure. They are being successfully utilised in refineries, chemical plants, fossils and nuclear power system, heating and cooling systems & cryogenic plants. Typical service conditions have pressure ranging from full vacuum to 1000 psig & temperature from - 420°F to 1800°F. Unlike the most commonly used piping components, a bellow is constructed of relatively thin guage of material in order to provide the flexibility needed to absorb mechanical and thermal movement expected in service. This requires design, manufacturing, quality, handling, installation and inspection procedures which recognize the unique nature of the product.

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