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Flange Insulating Gasket 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.Flange Insulation kits are designed for electrically insulating the flange and act as an insulator between dissimilar metallic flanges.



Applications of Insulating Gasket Kit are:

They are also used to isolate sections of pipework (dissimilar metals) electrically in the cathodic protection systems. Thus preventing the electrostatic charge flow along the pipelines as they remove the possibility of galvanic cell system creation.


Components of Flange Insulation Kit:

A typical flange insulation kit comprises

  • One central flat or oval section gasket,

  • One insulation sleeve per bolt

  • Two insulating steel washers per bolt

  • Two plated steel washers per bolt.

In order to achieve optimum results it is essential that Flange insulation kits follow certain design criteria. The electrical resistance properties of the components are balanced for the purpose and location in the insulation system. The components are manufactured from insulation materials with high compressive strength and good stability. Insulation kits are generally available till 24 inches, but custom made higher nominal sizes can be produced on the requirement.


Types of Insulating Gasket


Four major types of gasket isolation kits that are are available in the market are F, E, D, & O. Each type of flange kit fits flanges with a specific type of flange faces (RF, FF and RTJ).


Type F 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 E gasket:

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 D 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 O gasket

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 insulation kit installation


1) Check and clean

Remove all the impurities and debris from gasket, fasteners (bolts, studs, nuts) and washers. Check all fasteners (bolts, studs, nuts) and washers, make sure they are free of defects like burrs and cracks. Check the flange surfaces, make sure they are free of defects.


2) Align flanges

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


3) Install flange kits

Apply bolt lubricant to the bolt and nut threads and to the face of nut to be tightened, assembly the steel washer, insulation washer and insulation sleeve to the bolts by turn (make sure the steel washer always close to the nut). Insert the bolts holes. No force used (like hammer), it will damage the sleeves. Please check the alignment of flange surface and size of sleeve if installation it’s difficult. Put insulator washer, steel washer and nut into bolts on another side of flange. Tighten all the bolts until the flange meet the gasket.


4) Install flange kits

Please use calibrated torque wrench or other tool which have control functions. Be installed in accordance with the recommended torque. Tighten the nut always in accordance with the symmetrical cross drawing.

There are 5 steps should be followed:

a) Initial tighten all nuts by hand, the big nut can us small wrench.

b) Tighten each nuts by 30% of recommended torque.

c) Tighten each nuts by 60% of recommended torque.

d) Tighten each nuts by 100% of recommended torque.

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


The content of this article is taken from web open source. The blogs are intended only to give technical knowledge to young engineers. Any engineering calculators, technical equations and write ups are only for reference and educational purpose.


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