The Real Difference. By Rachel Salisbury A question I get asked a lot, is why cold shrink and how can it benefit me, my installers and my project costs? Is it just a more expensive option with the gimmick of unravelling a core? The answers are simple; there are multiple benefits for cold shrink, both financial and product benefits, it’s well-researched and a tried and tested solution from 3M for cable installations and a must-have in flammable areas of work.
3M cold shrink is made from either EPDM (Ethylene-Propylene-Diene-Monomer) or silicone rubber, that is expanded onto a spiral core. After the cold shrink tube has been placed over the joint or cable end, this inner spiral is pulled out. The insulating tube then contracts to its pre-stretched size and shrinks onto the cable, exerting constant radial pressure for the lifetime of the joint or termination.
Cold shrink products have a 45+ year track record of performing exceptionally well in indoor and outdoor environments, including under harsh conditions. The silicone material conforms well to cable bends, which ensures long term reliability against moisture ingress, or voids within the installation. It is shows excellent performance in the following environments:
ii. Coastal environments
iv. Dusty environments eg. solar power plants, wind farms
v. Vibrations eg. railroad, subway
vi. Underwater environments
vii. Overhead joint applications
Initially heat shrink may provide a good environmental seal obtained with the adhesive and mastics included in the MV termination or joint. However, over time the cable can expand and contract due to temperature changes. During a rise in temperature, a heat shrink material may be able to expand at the same time. But, if the cable contracts due to temperature decreases, either because it returns to its initial temperature or it drops below its initial temperature, a rigid heat shrink material may not shrink with the cable, therefore leaving a void between the cable and the cable accessory. This void can allow moisture and contamination from dust, chemicals, etc. to get into the cable accessory, which may accelerate the likelihood of failure. Long term expansion and contraction of the cable could create cracks and splits in a rigid heat shrink installation.
Tracking is defined as a process that produces localised irreversible deterioration on the surface of an insulator, resulting in the loss of the insulating function by the formation of a conductive path on the surface of the insulator. The cause of tracking is when voltage, moisture and contamination exist together, and it will eventually lead to an electrical failure because it erodes enough of the material so that there is a continuous conductive path from high voltage to ground. When there is a continuous conductive path, there is a short from the high voltage to ground.
Silicone is an excellent track resistant material and is hydrophobic, repelling water and making the insulator self-cleaning which results in a dryer surface and lower leakage currents. 3M outdoor terminations include rain sheds which disrupt any wet leakage paths that occur in industrial environments and also allows the creepage distance of the termination to be much shorter.
UV can damage the material of the termination, which creates cracks where contamination and moisture can be trapped and increase the likelihood of tracking. All 3M Terminations are produced from high performance Silicone, which is designed to be inherently UV resistant. EPDM and Ethylene-vinyl Acetate (EVA) need additives to make them UV resistant, which over time can dissipate and reduce the UV resistance of the material.
The time difference is significant with Heat Shrink taking double the time to install than Cold Shrink.
Other factors to be taken into consideration are delays in days to obtain hot permits, training and the costs of risks, for example: liability of fire, explosion, shutdowns and the associated insurance to cover these.
Multiply up the installations per annum this could provide a real cost saving for companies.
In summary, you get what you pay for, a premium product yet when looking at the total cost of ownership, this product comes out on top. Cold
Shrink – yes, it’s the Real Difference.
Rachel Salisbury has worked as an Application Engineer for 3M in the Electrical Markets Division for 18 years. Rachel advises customers and end-users on applications and specifications for 3M’s range of cable accessories for solutions in rail, construction, oil and gas and the renewables markets.
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