Heat shrink tubing is a brilliant solution for insulating and protecting wires, cables, connectors and terminations. This tubing is easily fitted within your application and then you simply apply heat to keep it firmly in place. But what can heat shrink tubing be used for and exactly how do you apply it? Here we'll be answering those questions and much more. By the end, you'll have all the info you need to be confident in using heat shrink tubing. Let's get started!
Basics of Heat Shrink Tubing
Heat shrink tubing is an effective solution for repairing, reinforcing, and organising wires, cables, connectors and terminations. Heat shrink sleeving offers effective protection against damage and abrasion. There are many other great advantages too, as it can provide the option of colour coding and bundling your wires and cables.
Heat shrink tubing is particularly useful for outdoor applications where outdoor cables and wiring are exposed to heat from the sun, ultraviolet radiation, and rain. Owing to these factors outdoor cables and wiring have a relatively lower life span, however, you can stretch this lifespan by the addition of a heat shrink tube.
The use of heat shrink tubing is simple and straightforward when using the right tools. Read on to see how it can be done. What Is It Used For? Heat shrink tubes are produced using a two-step process. In the first step, a standard extrusion procedure is applied.
In the second step, the heat shrink tube is expanded and stabilised. To reduce the diameter of the heat shrink tube, users need to apply heat to activate the tubes memory and return it to the original extruded size before expansion.
There are multiple applications of heat shrink tubes, these include:
- Providing electrical insulation
- Protective covering from impact
- Safeguarding from abrasion
- Protective covering from cutting
- Protection from peeling
- Colour coding electrical wires
- Bundling wires together
As you can see, there are many great reasons to use heat shrink tubing. It makes a lot of sense to use the tubing on any wires or cables that may be prone to damage, maintain stability in cable joints and connectors and offer protection against dust and moisture ingress, especially in an electrical application.
How To Use Heat Shrink Tubing
Before we get started, let us look at the tools you will need to use heat shrink tubing. A heat shrink oven/tunnel is the easiest way to apply the tubing but most people won’t have one of these, so you can use a heat gun instead. A heat gun is essential for producing the high temperature needed to melt the shrink tubing. Like any other work involving high heat, you should always use necessary precautions while applying heat shrink tubing.
- Eye Goggles/Safety Eye Glasses
- Face Mask with filter
- Thermal gloves
The eyeglasses will protect you from the heat and any stray fibres/wire etc. The gloves are needed to handle the hot wire and the a filtered face mask is vital to coping with the carbon dioxide fumes. As an added safety measure, try to use the heat gun in a room with sufficient air ventilation.
Choosing the Right Tubing
When you heat the tube, it will start to shrink. To get the best results, you need to know the exact measurement of the shrinkage. The two dimensions that are essential here are the expanded diameter and recovered diameter. Recovered diameter refers to the diameter of the tube after shrinkage. On the other hand, expanded diameter refers to the tube diameter before the shrinkage. As a rule of thumb, you should pick a tube with a smaller recovered diameter than the area you plan on insulating. You will get a tight and secure fit when you follow this rule. It’s an obvious point but the expanded diameter needs to be larger than the area you want to insulate.
In the next step, you will need to cut the shrink tube to the appropriate length. When you are using the correct useable length, it will provide the necessary overlap for existing insulation. It is important to note that the tube will shrink in length by approximately 5%-10% during the shrinking process.
Applying Heat on the Shrink Tube
Now that you know what diameter and length to use for your shrink tube, it is time to place the shrink tube on the area you want to insulate. Ensure the shrink tube covers the entire area you wish to protect. If you want to insulate two separate cables, place the tube in the middle of the wires. Make sure an equal amount of the shrink tube covers both the cables. Allowing for similar overlap will ensure a tight fit. In the next step, you will be using the heat gun.
Before you proceed, check the recommended heating temperature. Depending on the material used to make the shrink tube, the heating temperature will vary quite a lot. You can check the recommended heating temperature from the specification of the shrink tube.
Depending on the length of the cable you are trying to insulate, you need to adopt a different approach for applying heat. If the size of the cable is long, you should start by using heat at the endpoints. Slowly move the heat gun towards the other end of the shrink tube. If possible, rotate the object that needs insulation continuously as you apply heat. Apply the heat over the length and the diameter of the shrink tube.
While using heat, correct your approach so that the shrinkage happens uniformly. Once the shrink tube is completely shrunk down, remove the heat source. Wait a few seconds for the tube to cool down. Only after the shrink has started to cool down, apply physical pressure on it.
If you have done everything right, the shrink tube should fit right into the area you want to insulate.
Different Types (Materials)
There are several types of heat shrink tubing and they all have different uses. Here we take a look at the most common types:
Polyolefin – This is the most common type of heat shrink tubing used. That is generally due to its ability to resist high temperatures but it also has a high level of resistance to chemical contamination. This product can also be adhesive lined (dual wall) for extra moisture protection.
FEP – For any potential chemical spill, FEP acts as a brilliant sealant and is also quite easy to use due to its low shrinking temperature.
PVC – PVC is another very commonly used material for shrink tubing. The smooth surface it provides makes it ideal for bundling and colour-coding wires. Its versatility makes it a good option in many situations. Silicone – Similar to elastomeric, silicone has great flexibility and abrasion resistance. Where it shines is its ability to cope with extreme temperatures. This makes it ideal for sterilisation in medical settings.
PTFE – Also known as Teflon®, PTFE is great for potential chemical contact and low friction. It makes it ideal for wiring that is under constant movement.
Kynar® – In extreme environments, PVDF is the heat shrink tubing of choice. It has incredible flame resistance while also protecting against harsh chemicals and fuels. It’s extremely durable.
Viton® – Viton is another material that has impressive durability against many fuels and oils. It also has impressive flexibility at low temperatures.
Heat Shrink Accessories
While heat shrink tubing in itself is a brilliant solution, there are accessories to go with it that can make it even easier to use. Here we look at the best:
Heat shrink wrap – This is a great alternative to using electrical tape. It allows you to make permanent repairs and will create a tight seal. Just wrap it around the desired area and then apply heat. Heat shrink connectors – The spaces between lengths of heat shrink tubing can be areas of weakness. Heat shrink connectors solve that issue and allow you to safely connect two lengths.
Heat shrink tape – In a similar way to the wrap, this is ideal for small areas which need repair or extra protection. It’s a more effective solution than electrical wire.
How To Pick The Right Size
To determine the diameter size of the cable sleeving, check the product's data sheet. As a rule of thumb, you should use a shrink tube that is around 25% larger than the area you want to cover. Most heat shrink tubes are generally available in three variations of 4:1, 3:1 and 2:1. The shrink ratio means that the tube will shrink 2x, 3x or 4x times its diameter. Other ratios and dimensions are available depending on your requirements.
You'll need to know the inside diameter of the tubing once it has been shrunk. If this is small enough to fit around your wire, then it will be able to form a tight seal. Most manufacturers will have a guide depending on the material used. It’s also worth noting that the length of the tubing will shrink too but this is usually fairly minimal, at up to 10%. It’s important to factor that in when covering your wire.
How to use heat shrink tubing safely
To be fully safe, it's best to use gloves and eye protection. You'll also need a face mask to avoid the fumes. Due to those fumes, you want to apply the heat shrink tubing in a well-ventilated area.
Can you use electrical tape instead of heat shrink tubing? Yes, you can. Electrical tape is great for patching up small areas or as a temporary solution. If you wanted a high level of protection and a more effective and permanent solution, then it would be better to use heat shrink tubing.
Is heat shrink tubing waterproof? Yes, all types of heat shrink tubing are water resistant, however, adhesive lined (dual wall) products are waterproof.
What temperature is needed for heat shrink tubing? This will vary considerably depending on the material you are using. For some materials such as Polyolefin where you’ll only need around 90°C while with PTFE it needs to be around 250°C. It’s best to check before you buy to ensure you have the tools needed.
How heat shrink tubing works
Heat shrink tubing is brilliantly simple. You place the tube over a wire (or wires) that need protection or organising. When heat is applied, the material shrinks in size until it forms a tight seal around the wire and gives it the required protection.
Will heat shrink work if cut? Heat shrink tubing is highly versatile which includes the ability to cut it to any length that you want. While this is true for cutting across it, you shouldn’t cut it lengthwise. This will make it lose integrity and you may not get the seal you need.
Is heat shrink tubing conductive? For most application purposes, heat shrink tubing is not conductive and is used for electrical insulation purposes. There are, however, types of heat shrink tubing that do have a conductive lining if you need it.