Heat shrink tubing – a complete guide

Heat shrink tubing – a complete guide

Heat shrink tubing is a shrinkable plastic tube that is used to insulate wires, but exactly how is it used? We’ve put together this complete guide to using heat shrink tubing, including how to use it and how to heat it.

What is heat shrink tubing?

Heat shrink tubing is expanded plastic tubing used mainly in electrical work. When heat is applied to the tubing, it shrinks, becoming rigid to provide a protective coating. It can be manufactured from a variety of materials, each of which has different properties and strengths, including synthetic polymers, PVC, and silicone, and is available as single or dual wall tubing. Single wall tubing is the perfect solution for electrical insulation or where protection from abrasion or strain is needed. Dual wall tubing features an adhesive layer inside the tubing which protects against moisture so is suited for corrosion protection or any situation where a firm seal is required. At cableties-online, our heat shrink tubing is manufactured from the synthetic polymer polyolefin which offers excellent resistance to temperature and has an operating range of -40° C to +135° C.

What is heat shrink tubing used for?

Electricians and engineers use heat shrink tubing for electrical insulation, for example when repairing exposed wiring. The tubing also protects against environmental factors such as moisture, dust and chemicals, and it reinforces cables held at tension. Available in a selection of colours, the heat shrink tubing can be used to colour code wires or cabling for easy identification.

What is shrink ratio?

This refers to how much the tubing must shrink to fit the narrowest part of the cable. Where wire or cable size varies, you will need a higher shrink ratio. The shrink ratio is expressed as the inner diameter of tubing before shrinking : the inner diameter after shrinking; a ratio of 2:1 means the tubing will shrink to approximately half its size when heat is applied and a ratio of 3:1 will see the tubing shrink to one third of its original size.  Our single wall polyolefin heat shrink tubing has a shrink ratio of 2:1, suitable for general, all-purpose use. Our adhesive lined tubing has a 3:1 ratio, making it ideal for use as environmental protection sleeves in, for example, the motor and marine industries.

What size heat shrink tubing to buy

As well as taking the shrink ratio of the tubing into consideration, it is important to remember that heat shrink tubing will also reduce in length when heat is applied. This shrinkage is between 5-10% and should be calculated when choosing the length of tubing to buy. If you are unsure of the size of heat shrink tubing needed for the gauge of wire you are using, our staff will be able to help.

How to apply heat shrink tubing

You will need tubing, scissors and a heat gun, and it is also advisable to wear eye protection, gloves and a mask to avoid fumes – if you are working indoors, open windows too. Measure the length of heat shrink tubing required, taking into account the shrinkage in length that will occur and allow an overlap of ¼” to include connectors. Slide the tubing in place, centring between any splices and ensuring an equal overlap on both sides. Apply the heat starting at the middle point and working towards one end before repeating from the middle towards the opposite end – this will stop any air being trapped which could cause bubbles. Do not linger on any area as this will cause brittle or charred tubing.

Heat shrink tubing and electrical supplies from cableties-online

Our 2:1 heat shrink tubing is available in a selection of lengths and colours and we also sell multi-coloured packs of assorted lengths. In addition, we supply 3:1 adhesive lined heat shrink tubing in lengths up to 150m and widths up to 39.1mm, as well as a range of electrical accessories including electrical wire connectors, electrical connector blocks and electrical terminals. Our full range can be seen here.