Gasket Sealing Applications

For years you have trusted The Gund Company to supply the best quality transformer insulation materials. Transformer gasket materials are so critical to the life and performance of your transformer; it makes sense to use the best materials for sealing applications as well. Besides the potential for catastrophic failure, improper sealing can lead to oil contamination which can damage insulation materials which can significantly reduce the life of a transformer. Regardless of the transformer, our application engineering expertise can help our customers understand their options for gasket material selection.

Transformers play a critical role in the efficiency and distribution of power to the community.

Including traditional transformer maintenance, regasketing can help maintain the transformer’s dielectric strength, prevent oxygen, nitrogen, and/or moisture leaks, prevent oil contamination, and more…

Regardless of the transformer, our application engineering expertise can help our customers understand their options for gasket material selection.

Oil-Filled Transformer Gasket Sealing Applications
Tap Changer Gaskets Gauge Gasket
Handhole Gasket Pressure Relief Gasket
Manhole Gasket Drain Valve Gasket
Bushing Gasket Feed-Through Gasket
Radiator Valve Gasket Pressure Relay Device Gasket
Tank Gasket Oil Filling Connection Gasket
HV Turret Gasket Valve Gasket
Access Cover Gasket Output Plate Gasket
Header Tube Extension Gasket Tank Cover Gasket

Gasket Types

Regardless of the application, type, or material preference, The Gund Company can assist in designing, material selection, and fabricating services for your needs.

Key Materials for Transformer Gaskets & Seals
Key Properties Nitrile Fluoroelastomer Fluorosilicone
Color Black Brown Blue
Application General Purpose High Temperature Low Temperature
Product Images*
Density (g/cc) 1.225 2.192 1.475
Brittle Point (°C) -35 -20 -60
Tensile Strength (MPa) 13.2 12.1 10.1
Elongation 348% 198% 292%
Compression Set (%) 15% 10% 16%
Operating Temperature (°C) -30 to 100 -20 to 200 -55 to 175
Durometer (Shore A) 70 75 70
Volume Swell (% – 70 hr @100°C) #1 Oil -8 +13 +5
Oil TR-10F (°C) -27.8 -15 -56.3

Additional Materials

Cork & Nitrile (Rubber)

A combination of materials that are molded into sheets or calendared into rolls for fabrication meets customer requirements.


Perfect for gaskets with low to medium torque loads from automotive fluid seals, gearboxes, oil seals, and valve covers. Available in roll or sheets to fit your application.

High-Temperature Fiber

A compressed sheet of synthetic fiber and a Nitrile binder for applications requiring high heat and fluid resistance exhibiting excellent sealability and good creep relaxation.

The Gund Company offers a wide range of insulating gaskets and seals for all your transformer maintenance and gasketing needs. Contact us today with material, application, or quote requests.


The Gund Company is a vertically integrated manufacturer and fabricator of engineered material solutions. Since 1951, we have listened to our customers and learned about the demanding operating environments of their industries. We are AS9100D Certified and ITAR Compliant. Our custom fabricated parts are manufactured according to ISO 9001:2015 certified quality systems.

We understand the challenges of material selection and the demanding operating environment of your application. Our Application Engineering Team takes a consultative approach to understanding your requirements. By relying on our material specialists, our customers gain valuable insight into improving component designs to increase efficiency and functionality while reducing cost. In addition to helping with material selection, we challenge ourselves to optimize production for material yield or fabrication efficiency. As a lean enterprise, we are focused on continuous improvement and finding the most cost-effective, efficient solutions for our customers.

Please contact us today if we can help answer material property questions or provide an application-specific quote. Thank you for the opportunity to earn your business.