Pipe Expansion Joints Key Terms

Understand the ABC's of expansion joints

By Howard Robertson

Pipe expansion joints are essential in the piping and plumbing industry. Pipe expansion joints are also called compensators, as they compensate for the thermal movement. If you want to use pipe expansion joints, you need to understand certain key terms that you will hear from suppliers or manufacturers. This guide explains some of the common terms associated with pipe expansion joints, such as compensators, banded necks, tie rods, expansion loops and pressure-balanced expansion joints.

Pipe expansion joints, or compensators

Pipe expansion joints connect two pipes to allow (or absorb) axial, lateral and angular motions in the piping system. Expansion joints help with noise absorption and vibration or shock reduction.
Try: You can refer to Trelleborg, an engineering company, for explanation about pipe expansion joints. Additionally, Global Spec gives detailed information about the various types of expansion joints.

Bellows expansion joints

The bellows is the flexible element of an expansion joint that consists of one or more convolutions. Thus, bellows expansion joints use bellows to absorb the motion of the pipe.
Try: Flex-Hose provides an explanation of bellows expansion joints.

Double-expansion joints

Double-expansion joints use two bellows, instead of one, to absorb the pipe motion.
Try: Read about double-expansion joints at Piping Technology and Products.

Bands, or banded necks

Bands are attached to bellows (and called banded necks) to increase their thickness and thus strengthen the bellows.
Try: DME, a manufacturer of piping products, has information about banded necks.

Pipe guides

Pipe guides confine the movement of the pipe along its lineal axis. Pipe guides provide total restriction of pipe movement.
Try: U.S. Bellows, a manufacturer of engineered expansion joints, publishes information about pipe guides. You can also visit Flexicraft Industries, a provider of flexible piping solutions, for an explanation of pipe guides.

Pressure-balanced expansion joint

A pressure balanced expansion joint absorbs axial or lateral movements while restraining the pressure force. You can use this type of expansion joint in places where a change of direction occurs in the run of piping.
Try: Visit Sigmaflex Engineering, a manufacturer of piping expansion joints and hoses, for information about pressure-balanced expansion joints.