A rubber expansion joint is a flexible connector to absorb noise, shock, vibration, physical and thermal energy. It can be made from natural or synthetic elastomers and may be internally reinforced with fabrics for strength and pressure resistance, or externally with metal reinforcement for movement control.
Rubber Expansion Joints are sometimes called “expansion bellows,” “flexible joints,” or “compensators.” They are a critical safety device designed to safely absorb dimensional changes of pipe systems and ducts. These may be heat-induced expansion and contraction, pressure deformations, installation misalignment, building settlement, or vibrations due to reciprocating machinery.
Types of Rubber Expansion Joints
A variety of rubber and abrasion resistant elastomers are available for each type of joint. These include rubber, abrasion-resistant fabric and special purpose polymers that resist chemical attack, oil, sunlight, acid fumes and ozone.
Spherical Joints
The spherical rubber joint is the most common type of rubber expansion joint rubber. It is manufactured with a straight carcass and covers laid up on a straight mandrel that is reversed to make the rubber cover. The tire cord is then bridged between the flanges. The tube and ply are then placed in a steel mold that is machined to the outside shape. The tire cord is then turned back around end cables or rigid end rings, depending on the style of expansion joint.
Unisource Single Sphere Connectors
A single sphere rubber expansion joint is manufactured with a high-quality EPDM rubber tube and cover. A nylon tire cord is then bridging the sphere from flange to flange, allowing small stress motions to be isolated and vibration to be reduced. The sphere’s face-to-face dimension matches that of a spool-type expansion joint, facilitating direct replacement.
Ultra-Sphere Series 301 Connectors
Unisource Style 301 single sphere rubber expansion joints are designed to absorb small stress motions and isolated vibration resulting from mechanical equipment. They are manufactured to meet or exceed the pressure, movement and dimensional ratings of the Rubber Expansion Joint Division, Fluid Sealing Association.
Typical applications for expansion joints involve the reduction of noise and vibration in pump systems. They also act as shock absorbers to minimize trauma in systems handling abrasive slurries, corrosive chemicals or very reactive liquids or gases.
They can also be used to prevent thermal movement of piping system. The excellent chemical resistance of rubber and synthetic elastomers makes these joints ideal for process piping systems.
Other types of rubber expansion joints are available including braided stainless hoses and brazed stainless hoses with a flexible or metal liner. These are useful for minimizing transmission of vibration to other equipment to protect pumps and to minimize the impact of water hammer, pressure surges and earthquake events.
For more information about the different types of expansion joints, visit our page on “Types of Rubber Expansion Joints.”
In general, rubber expansion joints are a safe, cost effective solution to a variety of piping system challenges. However, they can be susceptible to failure if improperly installed or misused. The most common failures of rubber expansion joints are when the joint is used in inappropriate applications and in a way that it is not intended to perform.