Type: untied universal expansion joint Untied universal expansion joints and pantograph linkages untied universal expansion joint can absorb large amount of lateral deflections in addition to axial and angular movements. Usually these type of 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. tied universal expansion joint Tied universal expansion joint is same as untied universal expansion joints, 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. Angular movement can be accommodated only if two tie rods are provided 180 degree apart. To restrict this angular movement, four tie rods are provided at interval of 90 degrees, around the circumference of the expansion joint. Feature: Absorbs large amounts of lateral deflection Simple and robust construction Eliminates pressure thrust load Low maintenance Application: Universal expansion joints can absorb movements in all directions, and are used in uncritical, low pressure installations like ventilation ducts, exhaust gas systems, fresh air ventilation and process equipment.