Externally Pressurized Metal Bellows

An Externally Pressurized Expansion Joint is an exceptional product for absorbing large amounts of axial movement in long, straight pipe runs. However, it cannot absorb any lateral deflection. This type of expansion joint is one of the safest and most reliable.  The following unique design features are what make this type of expansion joint an appealing option in steam and condensate applications.


This type of expansion joint is designed such that the system pressure is applied to the outside surface of the bellows element. This feature eliminates the problems associated with column squirm that are present in the typical internally pressurized expansion joint. Eliminating column squirm allows a bellows to be manufactured with an almost unlimited number of convolutions thus an almost unlimited axial movement capability.

Maintenance Free

This type of expansion joint provides a completely leak tight and maintenance free expansion joint. This is a distinct improvement over the slip type or packed type joint, which requires periodic lubrication and repacking in order to function properly.

Self-limiting and Guiding

In this type of expansion joint bellows, provides an internal ring that provides bellows protection in the event of over compression of the expansion joint. This ring also provides protection for the bellows from any contact with the inside of the outer shell.

Drain Connection

Standard UIP International, Inc. Externally Pressurized Expansion Joints come with a drain plug on every unit. This provides the customer with the capability to remove any internal dirt, scale, sludge, condensate or any other foreign matter thus reducing the corrosion problems associated with most internally pressurized expansion joint applications.

Safety and No Additional Liner(s)

In this type of expansion joint, bellows is totally enclosed in an outer shell that is designed to contain the pressure of the system. The outer shell protects the bellows from external damage and reduces the chance of damage during shipment and installation. The outer shell also provides a shield/cover in the event of a bellows failure which redirects the media longitudinally along the pipe instead of radially outward and possibly in the direction of personnel. This type of expansion joint is designed with pipe on the movable end of the expansion joint lining the bellows thus eliminating the need to specify any additional liners. With this type of liner design the expansion joint can accommodate a multi-directional/reverse flow.

Technical Data and Drilling Information