Transformer Gaskets and Seals

Transformers are an essential part of the electrical power distribution grid. Transformers perform the function of lowering the voltage supplied to the grid by power producers into voltages that are usable by power consumers. Readily visible in most areas, transformers are often pole-mounted or placed on concrete pads where they supply electrical power to households, industry, and other consumers.

The critical role of transformer gaskets and seals

An essential ingredient present in most transformers is the mineral oil which is used to cool the device and prevent power fluctuations. Should oil leak from the transformer, overheating and catastrophic failure can ensue and the leaking oil may cause environmental damage. To ensure that no oil leaks from the transformer, gaskets and seals are used to safely contain the oil within the transformer housing.

A secondary function of a transformer gasket is to prevent the entry of moisture into the transformer housing. The entry of moisture and humidity into a transformer accelerates the aging and breakdown of the insulating materials used within the transformer, leading to outright failure. Maintaining a weathertight seal through the use of an effective transformer gasket is critical for extending equipment life and preventing costly failures.

A brief history of transformer gaskets and seals

Gaskets and seals made from a blend of nitrile rubber and cork were first used to seal transformers. Because a nitrile-cork seal would lose its compressibility over time as the cork dried out and hardened, these types of seals tended to fail frequently as the seal aged. Although nitrile-cork transformer seals are still sometimes used today, more recently there has been a move away from these types of seals toward those made exclusively from nitrile rubber. By eliminating the cork component, nitrile-only seals exhibit superior resilience and a lower failure rate than seals made from a blend of rubber and cork.

While seals made exclusively from commercial grade nitrile rubber represent an improvement over those made from other inferior materials, they may still deteriorate over time through the swelling that results from exposure to the aggressive silicone-based transformer oils often used today. In addition, as transformer oil ages, acid can accumulate in the oil, making it chemically hostile towards any material with which it comes into contact. Now, Transeal® PREMIUM GRADE Nitrile from American Biltrite provides the best material solution available today for transformer sealing applications.

Transformer gaskets and seals from Transeal® PREMIUM NITRILE rubber

Engineered specifically for use in electrical transformers, Transeal® PREMIUM NITRILE meets or exceeds M409E specifications. Gaskets produced from Transeal® maintain stability and help prevent dangerous transformer explosions and fires.

Gaskets and seals made from Transeal® PREMIUM NITRILE offer the following advantages over those made from commercial grade nitrile:

  • Unrivaled compression set values. 9% represents a typical test result for Transeal® gaskets, compared to 60% for typical commercial grade nitrile.

  • Exceptionally low oil swell. Transeal® PREMIUM NITRILE exhibits a 12% volume change compared to 120% for typical commercial grade nitrile. Silicone-based oils (the most aggressive oils in use today) have little effect on Transeal®.

  • Superior temperature service range. Transeal® PREMIUM NITRILE services temperatures up to 250°F compared to 180°F for commercial grade nitrile. Transeal® gaskets can also be easily removed and replaced in various temperatures.

  • Greater tensile strength. Transeal® PREMIUM NITRILE has a tensile strength of 2400 psi compared to 800 psi for typical commercial grade nitrile. The exceptional tensile strength of Transeal® provides strong resistance to applied loads, system blowouts, or vacuum.

  • Higher elongation. Transeal® PREMIUM NITRILE has an elongation of 500% compared to 350% for commercial grade nitrile.

  • Superior conformability. Transeal® gaskets are recommended when the joint has recesses or expansion limiting grooves – Transeal® is elastic enough to conform to any imperfections on the sealing surfaces.

  • Non-porous. Transeal® PREMIUM NITRILE is not porous, hence it does not require a secondary sealant or paint.

Transeal® PREMIUM NITRILE is an approved material. Transeal® conforms to Hydro Quebec transformer gasket specification SN-14.1. Transeal® is also approved and used by the Tennessee Valley Authority and has been found to be superior when compared to other products. Transeal® is engineered specifically for electrical transformers and meets or exceeds GE and ABB M4094E specifications.

CRG services the needs of OEM’s, power utilities, and maintenance operations by manufacturing and supplying gaskets and seals made from Transeal® PREMIUM NITRILE. These seals are made using the latest CNC production and fabrication technology in our ISO 9001:2015 certified facility. CRG can produce Transeal® transformer gaskets and seals in both large or small order volumes, and our seals are custom-cut to suit almost any transformer design and type.

If you are seeking to improve transformer reliability and prevent costly failures, the CRG sales team will be pleased to review your needs and discuss the advantages of Transeal® PREMIUM NITRILE.

For further information on Transeal® transformer gaskets and seals from CRG, please contact our sales department at