Rubber bag transformerRubber bag transformer

Rubber bag transformer - STP

The STP rubber bag transformer is used to protect the dielectric oil in power transformers. It is also called a flexible separator or compensation balloon.

The STP inflates and deflates by compensating for the change in volume. It provides separation between air and oil inside the hydraulic conservator. This avoids 

  • oil pollution 
  • condensation 
  • oxidation 
  • hydrolysis

Thus, the system protects the dielectric oil from external contamination.

The flexible separator has a high mechanical strength. In addition, it is impermeable to gases, oils and water. These characteristics make this transformer conservator airbag an efficient compensator for the protection of electrical transformers.

Assembled by hot vulcanization in autoclave, no leakage is possible. We manufacture this product to measure (material, dimensions, flange and fixing brackets). This rubber bag transformer can then have different shapes according to your needs

  • cylindrical,
  • rectangular, 
  • elliptical
  • or even special shapes.

In addition, for the compensation of bolted conservators, there is the MTP rubber flexible membrane.



  • No maintenance
  • Quick and easy installation
  • Dimensions and accessories custom made


  • Oil protection
  • 100% gas/oil/vapour-proof
  • Delivered with conformity certificates


  • Vulcanized flange
  • Resistant to temperature variations
  • Compatible with a wide range of oils

Detailed information

  • Material: high quality coated fabric
  • Manufacturing technique: hot vulcanization in a vacuum autoclave
  • Dimensions: custom made > contact us
  • Inflation: atmospheric pressure
  • Temperature resistance: -50°C to +100°C
  • Material options: compatible with new generation oils
  • Accessories:
    • Flange
    • Fixation lugs

You can not find your dimensions

Our design department employs the best project leaders and designers and will be pleased to develop and create a tailor-made product specially for your unique project.


Composition / Advice

Care during use
Avoid any contact with surfaces that are excessively abrasive or have cutting edges. Never walk on the product.
Maintenance advice
There are no fixed maintenance intervals. To check after prolonged storage or after use.
Storage advice
Store away from light, damp and temperature variations, in its original case.
Inflation advice
Tested at 0.105bar max. for 12 hours / in use at atmospheric pressure.

Standards / regulations

1 year against all manufacturing defects
ISO 9001, ISO 140001, ISO 45001
Product test
Product delivered with its conformity report.


Fact Sheets / Business Guides
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