STP rubber bags are installed to line inside the conservator tank, allowing oil volume variations while protecting the oil from any type of contamination (external corrosive agents, such as air, ozone, nitrogen, humidity, etc…).

STP rubber bags are made out of elastomer-coated fabric, vulcanized at high temperature under vacuum: fabric reinforcement & external coating are designed to provide very high external resistance to oil and internal protection from nitrogen and atmospheric agents including ozone.

PRONAL offers a large range of elastomers to meet specifications (oil type, working temperatures…) and a wide range of shapes and sizes to fit every requirement.

  • Large range of flanges
  • Easy & quick assembly
  • Long service life
  • Maintenance free
  • High mechanical resistance


  • High quality rubber
  • Wide range of working temperatures from - 50 °c to + 120 °c
  • Reliability: maintenance free product
  • No contact between oil & air: no oil pollution, no condensation, no oxidation, no hydrolysis
  • Vulcanized-in flange: no possible leakage !
  • Interior fabric reinforcement at points of contact to avoid punctures
  • Excellent tightness to oil/gases and water vapour
  • Quick-Response manufacturing

Other products for power transformer industry: :

  • Pneumatic lifting bags : used during setting up to the « active part » to lift the coil and allow spacer insertion/adjustment.
  • Flexible tanks : to store oil during commissioning and/or maintenance operations.
Please fill-in the form below:-


Call us at +603 6205 2062 or   CONTACT US
Go Top