Main Anchor
A main anchors is one which must withstand the full bellows thrust due to pressure, flow, spring forces and all other piping loads. A main anchor base for connection to the anchor structure can be furnished as an integral part of a single or double expansion joint, if desired. The expansion joint manufacturer must be advised of the magnitude and direction of all forces and moments which will be imposed upon the anchor base, so that it can be adequately designed to suit the specific application.
Intermediate Anchor
An intermediate anchors is one which must withstand the bellows thrust due to flow, spring forces and all other piping loads, but not the thrust due to pressure. An intermediate anchor base for connection to the anchor structure can be furnished as an integral part of a single or double expansion joint, if desired. The expansion joint manufacturer must be advised of the magnitude and direction of all forces and moments which will be imposed upon the anchor base, so that it can be adequately designed to suit the specific application.
Directional Anchor
A directional or sliding anchor is one which is designed to absorb loading in one direction while permitting motion in another. It may be either a main or intermediate anchor, depending on the application involved. When designed for the purpose, a directional anchor may also function as a pipe alignment guide. In the design of a directional anchor, an effort should be made to minimise the friction between its moving or sliding parts, since this will reduce the loading on the piping and equipment and insure proper functioning of the anchor.
Bellows
The flexible membrane in an expansion joint which compensates for the expansion and contraction of pipework in a system. Also known as compensators.
Laminated Bellows
These bellows are made from multiple concentric tubes. their purpose is to provide greater flexibility than a single ply constructed bellows of the same total thickness and give equivalent pressure retaining capacity.
Convolution
The smallest flexible section of a bellows. the total movement of the expansion joint is proportional to the number of convolutions, and the material thickness.
Cuffs
The unconvoluted portions at either end of the bellows.
Effective Area
The area based on the mean diameter of the convolutions, over which the pressure thrust of the expansion joint is generated.
Pipe Alignment Guide
A pipe alignment guide is a from of framework fastened to some rigid part of the installation which permits the pipe to move freely in only one direction, along the axis of the pipe.
Planar
A planar guide is one which permits transverse movement and/or bending of the pipeline in one plane. It is commonly used in applications involving lateral deflection or angular rotation resulting from "L" or "Z" shaped piping configurations.
Gimbal Unit
A unit designed to permit angular rotation in any plane.
Hinged Unit
A unit designed to permit angular displacement in one plane only.
Axial Movement
Extension and compression of the expansion joint in relation to the other end, at right angles to the longitudinal axis of the unit.
Pressure Balanced Unit
An expansion joint designed to absorb axial movement and/or lateral movement while governing the pressure thrust by means of tie bars inter-connecting the flow bellows with an opposed bellows also subjected to line pressure.
Root Rings
Rings of circular section which support the root radius against collapse from internal pressure loading.
Shroud
A metal cover (normally sheet metal) around the convolutions to protect against damage from foreign objects and during installation of the expansion joint.
Sleeve
An internal tube connected at one end of the expansion joint, to allow the fluid or gas a smooth flow through the expansion joint. By minimising the contact of the fluid with the convolutions.
Telescopic Sleeves
Telescopic sleeves comprise two sleeves closely fitted within one another, each being connected at one end and at opposite ends to one another. The ingress of foreign bodies is controlled by the minimal clearance between the sleeves although movement is limited to axial only.
Spring Rate
The force required to move the expansion joint over a certain distance.
Tie Bars
Bars connected to the expansion joint to restrain the operational pressure thrust of the unit while permitting lateral deflection.
Van Stone Ends
Facings formed integrally with the bellows convolutions or welded on after forming. The flanges are captive but free to rotate and when bolted into the pipeline the vanstone ends provide efficient seals.