glossary of terms - PEBIFLEX - the prominent Indian manufacturer of multiply bellows,metallic expansion joints,flexible expansion joints,compensators,flexible bellows,flexible hoses


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Glossary

Expansion control in pipelines, ducting and vessels which carry hot or cold fluids, or which are exposed to the large variations in ambient temperature is a major problem confronting designers.

As the metal temperature increases or decreases, the dimensional change due to thermal expansion or contraction will enduce excessive stresses in the piping, ducting or vessel and large forces will be transmitted to anchors and connected equipment.

For controlling such stresses and bring them to allowable values for the materials used in piping, ducting and vessels, several different methods are available, such as the use of pipebends and expansion loops.

However the most modern designers prefer the use of metallic bellows expansion joints, because they require less space than bends and loops and because their inherent flexibility enables them to absorb movements in more than one direction, thereby permitting greater freedom in design.

Furthermore, expansion joints prove to be more economical than other devices, so their use results in lower initial costs for piping and construction work, operating costs being reduced as well.

DEFINATIONS

BELLOWS

The flexible element of an expansion joint, consisting of one or more convolutions obtained by the hydro-forming or mechanical forming according to the diameter of the shell of a material suitable for the required duty.

Bellows are welded to tube ends or flanges to constitute different models of expansion joint assemblies.

INTERNAL SLEEVE

A device which is also referred to as liner, telescopic sleeve etc; to avoid the head losses or turbulence and streamline the flow through bellows.

It is required if the fluid flowing through the bellows is at very high velocity.

ENDS

The ends of an expansion joint , which may be either equipped with flanges or suitably beveled for welding to adjacent equipment or piping etc.

They are in compliance with applicable standards in force.

ESTIE RODS, HINGES AND ACCESSORI

In a piping system containing Expansion joints, it may be impractical to use main anchors to absorb the pressure thrust.

In such cases the use of expansion joints provided with tie rods, hinges or gimbals can solve the problem.

TYPES OF EXPANSION JOINTS

Bellows which are flexible element of an expansion joint maybe subjected to axial movement , angular movement , lateral deflection or any combination of these movements.

Therefore different types of expansion joints may be required to meet the different duty conditions.

Some of the most common expansion joints being used for different applications are listed below

1] Single axial expansion joint

2] Lateral expansion joint

3] Angular expansion joint

4] Double universal expansion joint

5] Hinged expansion joint

6] Gimbal expansion joint

7] Pressure balanced expansion joint

8] Externally pressurized expansion joints

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