What's the purpose of insulating kit....? (insulating kit is used to avoid cathodic reaction between the different material flanges, But I need some more detail on to this). Is there any direct contact of flange & bolts if we are using insulating kit..?? Also need some more detail on cathodic reaction of flanges....is it really have that much impact...?? as in above ground piping we uses different material flanges sometimes without insulating kit.

Insulating flange kits stops the electrical field that flows through the piping system. This electrical field can cause an aggressive corrosion of the pipe in certain situations, and the use of these flange kits can stop or limit this. Exactly why and how is NOT in my discipline, but you can read up on it at this site: http://www.m-p.com/Flange%20Insulation% ... %20Kit.htm