Sell with no payment Risks!

Logo Projectmaterials B2B marketplace

Sell with no Payment Risks!

Flange Isolation Kit for Cathodic Protection

Share on whatsapp
Share on telegram
Share on linkedin
Share on email

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.


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.


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]



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” 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” 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 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.




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%


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 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%


4 Responses

  1. Pretty good content,helped me understand what’s in these kits so I can do BOM’s for my projects without worry.Keep up the good work!

  2. I highly suggest consulting a sales person at a manufacturer before specifying these. Avoid Phenolic/Micarta and Minlon at all costs. It will break at some point and render the kit useless. G10 is what is needed at a minimum, which is crosswoven glass reinforced epoxy. Very strong fiberglass 1/8″ thk. Teflon or Viton seal for O&G applications.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Share on whatsapp
Share on telegram
Share on linkedin
Share on email

Searching for something else?


Buy Online!

ANSI Y-Strainers

🚀 Stock Delivery

🇪🇺 EU Origin

💰 Factory Prices

✅  Top Quality

SIZES       ⅜” to 12″
RATINGS 150# · 300# · 600# · 800#
GRADES  Carbon · Stainless
ENDS        Flanged RF · BW · THD · SW