Expansion Bellows

Expansion Bellows Information:

Pipestock have a range of Flexible Connectors and Expansion Bellows with various types and sizes to choose from. These fittings are designed to protect pipework joints and can save you the cost of damage and pipe system downtime. The fittings allow for the expansion and contraction caused by temperature variations within a pipe system and additionally they are able to isolate pipe systems from pump vibration which could cause damage.

Key Facts:

1.       Expansion Bellows & Flexible Connectors available
2.       Protect pipe systems against temperature variations & vibrations
3.       Available in a range of types & sizes
4.       Working Pressure between 10 – 16 BAR dependent on fitting
5.       EPDM or NBR used dependent on fitting
6.       Sizes in Imperial
7.       Temperature range as low as -20°C
8.       Top temperature variable on different fittings

Installation Guidance:

Although Pipestock always recommend that customers follow the manufacturer’s installation instructions, we have provided some guidelines of Expansion Bellow installation below:

1. Selection of Flexible Connector/Expansion Bellow

Prior to installation check you have selected the correct Flexible Connector for the application, pressure, temperature and media requirements.

2. Inspection

Before installing Flexible Connectors they should be checked for any damage internally and externally paying particular attention to the mating face. Make sure the sealing face is clean and free of debris as this will prevent a reliable seal being formed with the mating flange.

3. Installation

Flexible Connectors should be installed at their natural length. If gaps are being left in the pipework for retro fitting make sure this gap conforms to the exact natural length of the connector. Pipework should be aligned before installation; the connector is not designed to compensate for poorly aligned pipework.

The correct mating flange should always be selected and the sealing face checked for debris and any sharp edges as this could result in damage to the rubber. If faces of mating flanges have a different diameter a sealing gasket should be used to avoid damage to the rubber face. Flange bolts must be fitted with the bolt head nearest the connector to avoid damage to the rubber. Bolts must be tightened in a gradual manner tightening opposite bolts in turn.
NB: Do not over tighten as this will result in leakage. It is prudent to check tighten the bolts after seven days.

4. Anchoring

It is essential that Flexible Connectors are anchored to protect adjacent pipework and plant. Fig 1 shows how to anchor pipework in close installation to pumps. Selection of tied rubber Flexible Connectors should be considered above 100mm when the pressure is greater than 2.5 bar.

5. Maintenance

Many years free of trouble can be achieved with properly installed Flexible Connectors. It is essential they are used within their temperature pressure and media limitations. Periodic inspection of the rubber is advised to check for deterioration and flange bolts checked for correct tightness. The rubber should never be painted as this could damage the rubber and lead to reduced performance and service life.


The Flexible Connectors are made up of a combination of different materials. EPDM and NBR are used, depending on the connector selected, and these are the materials that provide the protection to the pipework.

EPDM (Ethylene Propylene Diene Monomer) is a synthetic rubber used for a variety of applications. In the case of these Flexible Connectors, EPDM is heat, ozone and weather resistant. It has a range of chemical resistance which you can find out more about by calling us. Most of all, EPDM acts as an absorption material for the vibrations caused by pumps and allows for the expansion and contraction of pipework without any damage.

NBR (Nitrile Butadiene Rubber) is also a synthetic rubber, resistant to oil, furl and other chemicals, to find out more call Pipestock now. NBR has a wide temperature range and is particularly resilient, making it a durable material in the Flexible Connectors. As with EPDM, the NBR material absorbs vibrations and allows for expanding and contracting pipework.

Other materials include metals and plastics which are manufactured from high quality raw materials to ensure a good service life in the product. 
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23 April, 2014
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