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Gasket Kit for Flange Isolation Joint

A flange isolation gasket kit helps protect the pipeline flanges from corrosion that happens due to galvanic corrosion. The purpose of the flange isolation kits is to prevent the (electrolytic) corrosion of flanged joints and flanges that static currents present on a piping system may induce.

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

Types of Flange Gasket Kit

Here are some types of flange gasket kits:

Flange Kit Type “F” (Ring Face Gasket)

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

You can add special band protectors to the flanged joint that will help to strengthen the cathodic isolation created by the flange isolation kit.

Type F gaskets are manufactured from 1/8” thick fabric-based phenolic sheets either with or without coating or with a nitrile rubber coating on the two faces. The 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) come with an outside diameter that matches the diameter of the flange, i.e., they cover the whole flange surface area.

The design also helps to keep the foreign material outside the flanges joints and enhances the isolation properties of the kit. Type E flange insulation kits come in high-temperature, neoprene-faced phenolic and phenolic materials.

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 a phenolic grade which is called “API ring joint”.

Type “O” Flange Insulation Kit

Type O Gaskets feature an extra sealing element on both sides of the device, usually, Viton Rubber, Nitrile, or PTFE, and are available in both full and ring face design. Type O Gaskets are manufactures with G-10 and phenolic materials.

The materials for insulation sleeves are, by default phenolic or polyethylene.

Installation of gasket kit

Installation of a gasket kit is easier if you know how to do it the right way. Here are a few tips to keep in mind before you go for installation

Check and clean

It is best to remove all the debris and impurities from washers, fasteners, and gaskets. Check all the fasteners (nuts, studs, bolts) and washers to ensure defects like cracks and burns. Always check the flange surfaces, make sure about defects.

Align flanges

Make sure the flanges and bolts’ holes coaxial coincide. The minimum flange gap is 10 mm. Insert the gasket carefully and parallel. Do not use jointing compounds, lubricants, or grease with gasket and flange surface. The compounds can affect the friction between the gasket and the flange can lead to premature joint failure.

Install flange kits

Apply bolt lubricant to the nut and bolt threads and the face of the nut and tighten it. Assemble the steel washer, insulation washer, and insulation sleeve to the bolts by turn (ensure the steel washer is always close to the nut). Insert the bolt holes. Avoid the use of the hammer, as it will damage the sleeves.

Check the alignment of the flange surface and the size of the sleeve if you find installation difficult. Put the insulator washer, steel washer, and nut into bolts on another side of the flange. Tighten all the bolts until the flange meets the gasket.

Do not forget to use the calibrated torque wrench or another tool that has control functions. You can install it following the recommended torque. Tighten the nut always in the symmetrical cross drawing.

Below are 5 steps you need to follow:

Initial tighten all the nuts by hand as you can use a small wrench for big nuts.

Tighten each nut by 30% of recommended torque.

Tighten each nut by 60% of recommended torque.

Tighten each nut by 100% of recommended torque.

Tighten all nuts in a clockwise direction to make sure all the nuts reach the required torque.

Materials for flange isolation gasket kit

  Gasket MaterialDielectric StrengthMaximum TemperatureWater Absorption
  Neoprene faced Phenolic500175 F0.45%
  Plain Phenolic500225 F1.10%
  Garlock 3400630700 F
  Klinger C4401300750 F
  G10 (NEMA)UL94 VOFR0.01%
  Insul-Seal500175 F0.50%
  JM 940 Red Devil2400700 F
  Phenolic RTJ Type D500225 F1.00%
  Teflon600600450 F


From the above classification, it is clear that flange isolation gasket kits are designed to provide complete electrical isolation of a flanged joint. The kits can be made of many different electrical isolation materials from resins, minerals, and rubber because of their isolation properties.

Many brands supply gasket kits for flange isolation joints. If you need assistance to know more about it, contact Texas Flange today and we will get you in touch with the correct suppliers.

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