Insulating sets comprise of a phenolic laminate or neoprene faced phenolic laminate gasket (Style NCA and NCB only) which is located between the flange sealing faces, phenolic laminate bolt sleeves, two insulating washers per bolt for maximum protection and two plated mild steel washers per bolt. Stainlesssteel washers can be supplied upon request.
Insulating sets are essentially used for pipeline flange corrosion protection, where a seal is required between dissimilar flange materials. The use of dissimilar metallic flanges with a conductive gasket material accompanied with a suitable electrolyte may set up a galvanic cell which will corrode the anodic metal. Insulating sets are also used to electrically isolate flange joints, preventing the flow of electrostatic charge along pipelines.
There are three standard styles of insulating sets available to suit raised face, flat face, and ring grooved flanges, as illustrated below.
It is also recommended that for complete electrical insulation protection that selfadhesive tape is wrapped around the outside diameter of the flange to prevent the ingress of foreign matter.With style NCA and NCB insulatingsets it is imperative that the bore of the gasket is equal to that of the pipe.
This will prevent any foreign matter from accumulating in the annular space between the bore of the gasket and the bore of the pipe thus preventing bridging.
Phenolic laminate provides excellent insulating properties as well as corrosion resistance.
See table for typical properties of 3mm (1/8”) thick phenolic. Other gasket styles such as SICHEM® S11( biaxially modified PTFE and Silica filled ) and non-asbestos sheets may also be suitable.
As standard insulating kits are dimensioned to suit schedule 80 pipe suitable for use on standard and nonstandard flange assemblies up to and inclusive of Class 2500.
Offshore installations, sea water environments, hydrocarbon service, chemical installations, oil refining pipelines requiring galvanic corrosion protection and electrical insulation.
Gasket Material :Sichem S11
Salmarcon identified the need for the isolation gasket set system, offering greater choice in service conditions, no longer restricted by standard isolation sealing technology:
Service Temperature Range:
- Temperature -200°C to + 260°C
Service Pressure Range:
- Upto and including Asme B16.5 2500 lb.
- pH range : – 0 – 14 ( Strong oxidising and reducing agents )
Dielectric strength :
- D149 ASTM 10 Kv/mm
How to tighten the flange bolts
- Clean flanges.
- Insert gasket between flange faces.
- Insert isolating sleeves in bolt holes.
- (If using stud bolts run one nut on one end until end of nut is flush with stud bolt). Place one steel washer and one isolating washer over bolt and insert in bolt hole.
- Fit one isolating washer and one steel washer on protruding bolt end. Hand-tighten the nuts.
- Tighten bolts alternately across the diameter of the flange (see drawing above).
- Always use torque wrench to ensure even tightening.
- Do not overtighten or leakage may occur.
- Ensure that bolts are well lubricated.
- No grease on sealing surfaces
The example shows 24 bolts. With flanges having a different number of bolts you should generally follow the same procedure.
In order to achieve an even distribution of pressure at the flange sealing ring we recommend to tighten the bolts as shown above until the flange faces and the sealing ring are in contact.
If relatively soft and flexible gaskets are used (eg. SICHEM S11) and tightened in a cold condition, the sealing material may relax when the system is put into operation, and the bolts may turn loose.
We therefore recommend to re-tighten the bolts after the operating temperature has been reached – ifpossible without the operating pressure and at ampiente temperature.
In any case the bolts should be checked and re-tightened, if required, after the initial operation and before
bringing the system back from ambiente temperature to the operating temperature.
The Foregoing performance data are intended as guidelines only. Performance suitability for any specific applications should be determined by the user.Variation in temperature, pressure, concentration or mixtures acting synergistically may preclude suggested service use.Material Selection is at the sole risk of the user. Consult with a specialist or Salmarcon for specific applications. Salmarcon ’s responsibilities will be limited to those listed in the Salmarcon standard warranties.
Approvals and certificates
Please contact us for further information about certificates and approvals of our products.