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What is an inflatable seal?

An inflatable seal may be used to seal, hold, lift, clamp, squeeze or actuate a linkage; and are available in Silicone, Viton®, EPDM and Nitrile in a range of standard profiles.

An inflatable seal can be compared to a bicycle inner tube, which when inflated expands (radially outwards) to fill a void which is contained within the wheel rim (housing) and a tyre (jacket). Once air is let out of the inner tube the tyre runs flat.

When designing an inflatable seal the same mechanical and pneumatic processes will need to be considered during the design. Most inflatable seal solutions will end up using a ‘standard’ profile, however for some applications a totally bespoke design may be necessary.

Every inflatable seal will therefore require a technical design to be carried out, whilst the delivered solution may well be based on a seal profile that has been used and proven many times. The success or failure will depend on all design constraints being known at the start of the design.

Why use an inflatable seal?

  • they only seal when you want them to
  • once pressure is removed the seals retract to their original shape
  • they do not suffer from premature loss of compression set
  • they can be designed to fill larger gaps than conventional seals
  • they will effect a seal or clamp force even when the two faces are non-concentric or misaligned

How do inflatable seals work?

Standard inflatable seal profiles are designed to expand with the introduction of an internal pressure – each profile will ‘grow’ with increasing pressure following a known and predictable progression.

Once the internal pressure is removed the seal retracts back to its original profile – this return occurs because the elastomer retains a ‘memory’ of their original profile.

It is this predictable performance that is used to select a profile to suit a customers application.

The internal pressure is usually applied by using air, although some applications require the use of an alternative gas or even a fluid.

The medium used is usually introduced through the use of a flexible tube connected to the inflatable seal and terminated in a fitting to suit the customers requirement.

Typical seal profiles

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Choice of material

Materials currently available are Silicone, EPDM, Nitrile and Viton®.  These are offered when required with approvals such as compliance with FDA, USDA 3A and USP Class VI.  The following table details the approvals we can currently offer:

Elastomer FDA Compliant FDA Compliant
+ USDA 3-A
FDA Compliant
+ USDA 3-A
+ Metal detectable
FDA Compliant
+ USDA 3-A
+ USP Class VI
Silicone Yes Yes Yes Yes
EPDM Yes Yes Yes Yes
Nitrile Yes No Yes No
Viton® Yes Yes Yes Yes

Note: Not all suppliers of inflatable seals will warrant that the above approvals also apply to the moulded joint.

Our inflatable seals are 100% compliant with the chosen approval – both the profile and moulded joint are made from compliant compound.

Industries that use inflatable seals

There are many industries that will find an inflatable seal a useful sealing solution.  The following industries already utilise inflatable seals: Pharmaceutical, Medical, Food Processing, Transportation, Marine, Chemical processing, Paper processing and Aerospace.

Designing an inflatable seal

Mantek will provide design assistance and make recommendations based on the information an end-user provides.  To assist in making this as thorough as possible we ask that the Mantek Inflatable seal design form be completed as fully as possible.

A copy of this form may be downloaded here.