A flange insulation kit protects a flanged joint from corrosion and ensures the cathodic protection of the pipeline. The working mechanism of flange isolation kits is very simple: they prevent a metal to metal contact among the elements of the flanged connection reducing the corrosion induced by static currents. A flange insulation kit consists of one insulating washer for each nut, one full-length insulating sleeve for each bolt, a 3mm thick insulating gasket (or oval ring), and thick plated steel washers for each nut.
Flange insulation kits are designed to control and prevent the electrolytic corrosion that may impact the flanges and spread on the pipeline, generating a severe impact on its reliability and service life. The insulation components, to have proper dielectric properties, need to be manufactured with appropriate materials, feature chemical stability and low water absorption.
Even if flange insolation kits are rather inexpensive devices, they may have a remarkable impact in extending the service life of the flanges and the connected pipes.
The isolation kits are available for most ASME and API flange sizes, from 1/2 up to 80 inches (and above).
FLANGE INSULATION KIT TYPES
Flange isolation kits are available in four main types, depending on the shape of the gasket element.
TYPE “F” FLANGE INSULATION KIT (RING GASKET)
Type F gaskets (ring type) fit raised and full face flanges (RF). The external diameter of an F type gasket is a bit smaller than the internal diameter of the bolt circle. Special band protectors can be added to the flanged joint to further strengthen the cathodic isolation created by the flange isolation kit (foreign material may accumulate otherwise). Type F gaskets are manufactured from 1/8″ thick fabric based phenolic sheet either without coating or a with a nitrile rubber coating on the two faces. Type F gaskets are also available in non-asbestos fibers with high isolation capacity.
TYPE “E” FLANGE INSULATION KIT (FULL FACE)
Type “E” gaskets (full face type) have an outside diameter matching the OD of the flange. This design helps to keep foreign material outside the flanged joint and protect the isolation properties of the kit. Type E flange insulation kits are available in phenolic, neoprene-faced phenolic, and high-temperature materials.
TYPE “D” FLANGE INSULATION KIT (API RING JOINT GASKET)
Type D gaskets suit the ring joint groove of RTJ flanges (R, RX, and BX). Type D gaskets are available in phenolic grade. This type of gasket is also called “API ring joint”.
TYPE “O” FLANGE INSULATION KIT
Type O Gaskets feature an extra sealing element on both sides of the device, generally, PTFE, Nitrile or Viton Rubber, and are available in both ring and full face design (type E and F). Type O Gaskets are manufactured with phenolic and G-10 materials.
The materials for insulation sleeves are, by default, polyethylene or phenolic.
PROPERTIES OF FLANGE INSULATION KIT MATERIALS
|Gasket Material||Dielectric Strength||Maximum Temperature||Water Absorption|
|Neoprene faced Phenolic||500||175 F||0.45%|
|Plain Phenolic||500||225 F||1.10%|
|Garlock 3400||630||700 F|
|Klinger C4401||300||750 F|
|G10 (NEMA)||UL94 VO||FR||0.01%|
|JM940 Red Devil||2400||700 F|
|Phenolic RTJ Type D||500||225 F||1.00%|
|Sleeve Material||Dielectric Strength||Maximum Temperature||Water Absorption|
|Washers Material||Dielectric Strength||Maximum Temperature||Water Absorption|