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What are the Advantages of Externally Pressured Metal Bellows Expansion Joints?

251225 TestExternally pressurized metal bellows expansion joints are an ideal solution for applications where high-pressure and temperature are met with the need for long axial movements. Axial movements are compression and extension movements along the axis of the media flow. Internally pressurized bellows often succumb to squirm in these types of applications. This type of construction eliminates squirm and allows for much greater movement allowances. The flexible bellow’s element of this construction is encased within the joint and the bellow’s actions are reversed. The extension movements of the pipes are contained in a compression of the bellows and the encasement of the bellows acts as a second line of defense in the event of failure of the bellows keeping the media contained.

Many of these types of expansion joints come with a drain that allow excess to be removed from the system. Pressurized steam systems are a common place you will find these type of expansion joints. Self-draining convolutions of the bellows element make it impossible for media to collect in the convolutions.

Some inherent features of this design include guide rings, full thickness cover, insensitivity to flow direction, and these joints meet EJMA guidelines for safety. The internal guide rings reduce the need for guides and anchors compared to internally pressurized bellows. These expansion joints do not require liners and are easy to insulate. The external casing protects the bellows element making installing easier and less time consuming with no critical surfaces exposed.

Expansion Joint Customization

All of our bellows expansion joints can be custom made for your application.

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  • Written by:

    Jason Pruitt

    Technology & Creative Services Coordinator, Kadant Unaflex

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