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Flange Isolation Kit for Cathodic Protection

A flange isolation kit protects a flanged joint from the corrosion from static currents (by preventing a metal-to-metal contact among flanges, stud bolts, and gaskets). A flange insulation kit consists of one washer for each nut, one full-length insulating sleeve for each bolt, a gasket (type F, E, D, O), and thick plated steel washers for each nut.

WHAT IS A FLANGE ISOLATION KIT?

The purpose of flange isolation kits is to prevent the (electrolytic) corrosion of flanges and flanged joints that static currents present on a piping system may induce.

The gasket isolation kit consists of a special gasket, isolation sleeves for all the stud bolts and nuts, and special washers. These components are manufactured in special materials with proper chemical stability, low water absorption, and dielectric properties.

Even if flange isolation kits are inexpensive accessories, they may extend the service life of pipes and flanged joints. Insulation kits are available up to 24 inches, generally, but higher nominal sizes can be manufactured if needed.

Dielectric flange isolation kits are available for ASME B16.5, B.1647, API flanges of all sizes and classes, from 1/2 up to 80 inches.

FLANGE ISOLATION KIT TYPES

There are four major types of gasket isolation kits, designated as F, E, D, and O. Each type of flange kit fits flanges with specific faces (RF, FF, RTJ).

Flange insulation kit flange insulation kit[/caption]

 

FLANGE KIT TYPE “F” (RING FACE GASKET)

Type F isolation gaskets (ring type) fit raised face flanges (RF). The external diameter of an F type gasket is smaller than the flange face surface.

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 F flange isolation kit
Type F

TYPE “E” FLANGE INSULATION KIT (FULL FACE)

Type “E” gaskets (full face type) have an outside diameter matching the diameter of the flange, i.e. they cover the whole flange surface area.

This design helps to keep foreign material outside the flanged joint and enhances the isolation properties of the kit. Type E flange insulation kits are available in phenolic, neoprene-faced phenolic, and high-temperature materials.

Type E flange isolation kit
Type E

TYPE “D” FLANGE INSULATION KIT (API RING JOINT GASKET)

Type “D” isolation gaskets fit flanges with ring joint face,  as they suit the ring joint groove of RTJ flanges (style R, RX, and BX). Type D gaskets are available in phenolic grade. This type of gasket is also called “API ring joint”.

Type D flange isolation kit
Type D vs. E/F

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.

 

FLANGE ISOLATION KIT MATERIALS

Gasket

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%
Insul-Seal 500 175 F 0.50%
JM940 Red Devil 2400 700 F
Phenolic RTJ Type D 500 225 F 1.00%
Teflon 600 450 F 0.01%

Sleeves

Insulation sleeves for flange insulation kits
Insulation sleeves for flange insulation kits
Sleeve Material Dielectric Strength Maximum Temperature Water Absorption
Phenolic 500 250 F 2.00%
Mylar 4000 350 F 0.22%
NEMA G10 UL94VO FR 0.01%
Minlon 450 300 F 0.90%

Washers

Washers Material Dielectric Strength Maximum Temperature Water Absorption
Phenolic 500 225 F 1.10%
Non-Asb 300 750 F
NEMA G11 UL94VO FR 0.01%
Teflon 600 450 F 0.01%

 

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