The main functions of the isolation kits are:
- Generate static sealing in the flanged joint.
- To make an electrical isolation in the flanged joint, avoiding the contact between metals of: studs, nuts, washers and flanges.
To make a correct selection of the isolation kits, several aspects and recommendations should be taken into account:
- Verify the working pressure of the pipe line with the technical data sheets of the isolation kits.
- Check the chemical compatibility of the fluid with the packing material used to manufacture the isolation kit.
- Verify the maximum working temperature of all the accessories of the isolation kits, generally the kits work up to 150°C (302°F). For higher temperatures, the technical department should be consulted.
- In low classes, sometimes aramid fiber gaskets are installed. It is important to check dielectric strength and water absorption among others; not all sheet compositions are suitable for use as insulation kits.
- When the pipe line works with RTJ flanges in the joint with high pressures or diameters greater than 4″, it is advisable to use gaskets for critical service RF or FF, the ring joints designed with insulating fibers do not have good mechanical resistance due to their manufacturing process, these cause leaks or electrical passage after a short time.
- When installing insulation kits it is important to increase the length of the standard studs, to the standard length should be added 3/4″ (19 mm), the studs must protrude from the nut at both ends at least 1/3 of the nominal diameter to ensure proper installation. Kits are supplied with additional washers to increase the stud dimension.
- For ASME class 600 flanges and/or diameters greater than 12″, the use of G-10 insulating bushings is recommended. The mechanical strength of this material is superior and prevents the stud from being damaged by friction between the thread and the inside of the flange bores when tightening the stud. Damage to the insulating bushing cuts the electrical insulation, resulting in increased installation costs.
- When using Nema Le washers or a material with low mechanical strength, it is recommended to use an additional aramid washer between the flange and the insulating washer. This will mechanically protect the insulating washer against cracking or breakage due to excessive torque during assembly.
- A non-conductive lubricant should be applied to the threads of the studs and the flange holes where they are to be installed.
- Check that the quantity of accessories of the insulation kits are complete according to the marking on the original packaging. If any element is missing, the kit should not be installed in the flanged joint.