Clean the metal surface thoroughly. Remove all moisture, oil and grease, rust, etc. A wire brush and/or solvent may be required.
Take extra care that rust and dirt particles never fall into the transformer. The results could be catastrophic when the transformer is energized.
After rust and scale have been removed, metal surfaces should be coated with Loctite Master gasket No. 518. This material will cure after you bolt up the gasket, so additional glue is not necessary. If the temperature is 50 ºF or more, you can bolt up the gasket immediately.
This material comes in a kit (part No. 22424) with primer, a tube of material, and instructions. If these instructions are followed, the seal will last many years, and the gasket will be easy to remove later, if necessary. If the temperature is under 50 ºF, wait about ½ to 1 hour after applying the material to surfaces before bolting. If you are using cork-nitrile or cork-neoprene, you can also seal gasket surfaces (including the edge of the gasket) with this same material. Loctite makes other sealers that can be used to seal gaskets, such as “Hi-tack.”
GE glyptol No. 1201B-red can also be used to paint gasket and metal surfaces; but it takes more time, and you must be more cautious about temperature. If possible, this work should be done in temperatures above 70 ºF to speed paint curing. Allow the paint to completely dry before applying glue or the new gasket. It is not necessary to remove old glyptol, or other primer, or old glue if the surface is fairly smooth and uniform.
Choose the correct replacement gasket. The main influences on gasket material selection are design of the gasket joint, maximum and minimum operating temperature, type of fluid contained, and internal pressure of the transformer.
Most synthetic rubber compounds, including nitrile (Buna N), contain some carbon, which makes it semiconductive. Take extra care to never drop a gasket or pieces of gasket into a transformer tank. The results could be catastrophic when the transformer is energized.