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Piping Flange Fundamentals
Expansion Joints
A less common type of joint is the expansion joint. Expansion joints cater for thermal expansion of a piping system as its
temperature increases. Although expansion joints are usually considered only to cater for expansion, it is important to
realise that they need to cater for the entire temperature range the piping system operates at, during both contraction
(lower temperatures) and expansion (higher temperatures). To do this, they should not be overloaded during
compression (‘squeezing’) or tensile (‘stretching’) loading. There are four main types of expansion joint:
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Rubber bellow
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Metal bellow
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Slip
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Ball
Metal Bellow Expansion Joint
Expansion joints are used if the installation of expansion loops (piping laid in a semi-circular shape) is not practical.
Pipe Expansion Loop
If thermal expansion of the piping system is not catered for, loads will be transferred to stationary supports and equipment,
which may lead them to failing. The problems arising from thermal expansion must be dealt with at the design stage.
Systems that have wide ranging temperature changes e.g. power plant steam systems, are particularly susceptible to
damage arising due to thermal expansion.
Tip - within the piping industry, expansion joints are being phased-out for new piping system designs and many
companies now prohibit their usage. The reason for this phase-out is because environmental factors often cause
expansion joints to malfunction, and they require constant inspection and maintenance (at additional financial cost).
Flange Construction
Flanges are split into two main areas, the ‘blade’, and the ‘hub’.
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The flange blade encompasses the area where the bolts penetrate through the flange and the flange face.
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The flange hub is the area that accommodates the pipe which attaches to the flange.