Which is a better gasket for electrical transformers, black NBR gaskets or Rubber Cork gaskets?
To answer simply, the selection between these two primarily depends on the type of flange where the gasket will be put.
Nitrile Bonded Rubber Cork gaskets: These are used in places where the flanges or mating surfaces are flat in nature. Examples are flat flanges on a tank cover (Curb) of a transformer, flanges of butterfly drain valve connecting the radiator, bushings, oil level gauge, oil conservator cover, etc. The cork granules which are present in such gaskets ensure that internal stress and side flow on compression is the lowest when pressure is applied for tightening of gaskets. This ensures very good performance and long leak-free service life of the gasket material.
NBR Gaskets and cords: These are used in places where the mating surfaces have a recess or a groove to hold the gasket in place. Examples are tank cover (curb) gaskets of large power transformers, bushings with recess for gaskets, O-ring type flanges, etc. The very matter that any solid rubber will follow the principle of maintaining its volume when external pressure is applied, makes this kind of gasket suitable to be used only in grooves to avoid the side flow and disintegration of the gaskets over the long service life.
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