How to Use Heat Shrink Tubing

There are four distinct steps to using heat shrink. In this article we also cover aftercare and some FAQs:

1. Selection (the most complex step)
2. Storage
3. Cutting
4. Installation
5. Aftercare
6. Frequently Asked Questions

We take you through these steps in detail to help ensure your project is a success.

1. Selection

1.1 Why use heat shrink?

Heat shrink tubing has many uses:

• As a permanent electrical insulator for wires and components
• To protect from a harsh environment – different types of heat shrink can protect against heat, moisture, fuel, dust and abrasion
• As strain relief where cables might be flexing too much on their own and the heat shrink helps reinforce them
• Cable management – keeping multiple cables tidy
• Labelling:
  • Heat shrink in different colours can be used for colour coding
  • Printed heat shrink can provide useful text-based codes/labels

The needs of the project will help in choosing the type of heat shrink. For example, medical-grade heat shrink will have different specifications from electrical heat shrink required in the next NASA moon mission.

1.2 What is it used on?

The item or items onto which the heat shrink is fitted is called the substrate. Typically this can be wires, cables and components but that’s not the entire list. For example:

• Battery packs held together
• Additional grip for handles (or resurfacing broken handles)
• Rope ends (to prevent fraying)
• Adding insulation to tool handles
• Small repairs (depending on the damage)

1.3 What heat shrink to use:

There are three basic points as a minimum to think of when deciding what heat shrink to use:

1. What will the heat shrink be protecting against?
2. What size is the substrate? The tubing needs to shrink to a tight fit.
3. What size are any obstacles? The tubing might need to be big enough to slide over a connector before it is shrunk into place.

Beyond this, there is the thickness, the material, single or dual wall and the amount of shrinkage.
To help work through this we have an in-depth knowledgebase article on choosing the right heat shrink.

1.4 What colour heat shrink to use:

You have two options when choosing colours:

1. If you are working in an industry that has a standard already in place (such as colours for earth cables) then you should follow that convention. For example, there are standard electronics colour codes.
2. If there aren’t standards already in place then you are free to choose your own.

1.5 What size heat shrink to use:

Getting the size wrong means either the heat shrink can’t be moved into its final location or (when heated) it doesn’t shrink sufficiently to hold itself in place.

You’ll need two dimensions:

1. The largest diameter that the sleeve needs to slide over before it is shrunk (eg the connector size). This is known as the “Expanded” inside diameter of the sleeve.
2. The smallest diameter that the sleeve needs to fit (eg the wire onto which the tube will be shrunk). When the sleeve shrinks it will need to be less than the wire or it will slide about. This is why, for a good fit, the maximum “Recovered*” inside diameter must be less than the smallest diameter it is covering.

We go into this in much more detail in Choosing the right heat shrink.
* Heat shrink is pre-stretched during manufacture. When heat is applied it shrinks or “recovers” back to its original narrow size.

2. Storage: How to store heat shrink

Some heat shrink materials are degraded by UV light. Those that aren’t might still suffer a colour change in their pigments so, to be on the safe side, we recommend storing heat shrink out of direct sunlight and away from a heat source (for obvious reasons).

Physical pressure from other items resting on the stored heat shrink is to be avoided as this could deform the tubing.

Contaminants can also cause problems – store the heat shrink in clean, dry, dust-free environments.

If the heat shrink must meet stringent specifications, the storage requirements become even more important. For example, medical-grade heat shrink is manufactured then double bagged to protect against harmful organisms during storage and transport.

3. Cutting: How do you prepare it before use?

Two key points:

1. Cut the heat shrink without leaving ragged edges as these can split and reduce the heat shrink’s effectiveness. Sharp scissors or knife for small quantities and good quality production tools for commercial quantities. Or have your heat shrink precut.
2. The tubing might also shrink lengthways by a small amount, in which case you’ll need to cut longer than the final length needed. The product specifications will tell you by how much.

4. Installation

4.1 How do you fit heat shrink?

First, move the heat shrink into place. Move it past the widest section (eg a connector) and then into place around the wire(s), cable(s) or component(s) that the heat shrink is to protect.

Silicone lubricant spray is sometimes used to help put the heat shrink in place along a wire if there’s some difficulty. This doesn’t harm the heat shrink, whereas other types of lubricant spray can damage or degrade the heat shrink material.

4.2 How do you heat it?

Apply heat evenly up and down the length of the tubing until it has fully shrunk. Sometimes a more particular approach is needed and you can read about this here in our Knowledgebase article How to heat and shrink heatshrink tubing.

Do remember that the area beyond the heat shrink, such as the surrounding components (and your worktop), will also be heated and might need to be protected.

5. Aftercare – What next, now it is in use?

After installation, inspect (and re-inspect) as part of your standard processes.

6. Frequently Asked Questions

How to use wire shrink wrap

This also answers similar questions such as How to heat shrink wire, How to put heat shrink on wire and How to use heat shrink tubing on wires.
The correct term for the item being covered in heat shrink is “the substrate”. This can be anything that needs a heat shrink covering. In the article above we have used a wire as an example, but we could have used cable, or connector(s) or some other item. The key to success is to get your measurements right.

Example 1: If you intend to fit heat shrink tubing onto a wire that is to be soldered to another wire…

• The heat shrink needs to slide onto one wire successfully (or both wires depending on the joint type)
• It needs to be successfully moved into place to cover the solder joint
• It needs to fit snugly/firmly once shrunk

If that works then you had the measurements correct.

Example 2: If you plan to fit heat shrink tubing to the wire and a connector, then:

• The tubing must be large enough to fit over the connector
• The tubing must shrink snugly/firmly onto the wire

Again, if that works then you had the measurements correct. Connectors are often much large than the diameter of the wire, so this means the shrink ratio is key.
We go into the measurement process in more detail in How to Measure Heat Shrink Tubing.

The temperature of the air from your heat gun is also important – too low and the heat shrink tubing remains unshrunk. Too high and, well … , some damage may occur to the heat shrink tubing and also perhaps anything nearby. You’ll find more detail in How to Heat and Shrink Heatshrink Tubing.

How to melt heat shrink tubing

To get technical for a moment, we are heating the tubing to just above the polymer’s crystalline melting point to make it shrink. What we see though is the tubing diameter start to decrease in size. When this is complete and the tubing has cooled and is no longer shrinking, it should now give good protection to what is beneath the tubing (providing you have purchased the correct tubing for the task).

So you could say you are melting the heat shrink, but only enough to soften it so that it shrinks.

If on the other hand you are literally trying to melt heat shrink tubing into a puddle as if it were made of wax, this is not something we recommend!

What can I use for heat shrink tubing?

Being specialists in this field, our answer is Don’t use anything else but heat shrink tubing. There are so many different heat shrink tubings available that can be at your door in days, for specific or multiple uses. If you are working on cable harnessing then you could use cable wrap.

We also have an option for retro fitting heat shrink after you have made the joint – RPR Wrap Around Heat Shrink for Cable Repair. This typically is needed when someone has carefully completed their work and at that point have realised that the heat shrink is still sitting, unused, on the work area. And it will not fit over the bulkier part of the connector. Darn. RPR Wrap Around to the rescue.

Or it could be that you’ve realised at the start of the task that the size difference between the large connector and thin cable would require a massive Heat Shrink ratio. Again, RPR Wrap Around would be a possible solution.

How to use electrical heat shrink tubing

The article above applies to this FAQ, but with one specific point in the selection process. What will the heat shrink be protecting? General purpose heat shrink is fine for low voltage wiring. We also supply heat shrink suitable for high voltage uses.

If you need assistance, please contact us.

How to apply heat shrink tubing

The article above gives you an overview for this FAQ. But if you are looking for more information, then we recommend reading these articles:

• How to Heat and Shrink Heatshrink Tubing]
• How to Install Heat Shrink Tubing Products