Two bellows connected by a common connector or centre piece, is called Universal expansion joint. These are used to absorb large amount of lateral deflections. In addition to this, Universal expansion joints can also compensate other two types of movements viz. axial and angular. Double expansion joint is different from Universal expansion joint.
Advantages
• Simple and robust construction.
• Absorbs large amount of lateral, angular and axial movements..
• Inexpensive.
• Easy to install
• Low maintenance.
Un- Restrained Universal expansion joint
Unrestrained Universal Expansion Joints can absorb large amount of lateral deflections in addition to axial and angular movements. The applications which has large amount of lateral deflection, the length of the centre piece can be increased to accommodate it. Usually Universal expansion joints are provided with control rods to distribute the movement equally between the two bellows. Control rods are not designed to withstand pressure thrust.
Restrained Type Universal expansion joint
It is same as unrestrained type expansion joint, but with addition of tie-rods. These tie rods are designed to withstand the pressure thrust and so the external movement of the expansion joint is constrained even if the pressure thrust is increased. If the expansion joint has to accommodate angular movement, in one plane only two tie rods are provided 180 degree apart. To restrict this angular movement, four tie rods are provided at in interval of 90 degrees, around the circumference of the expansion joint.
