Gamma Electronics Blog

Cold Shrink Tubing – Frequently Asked Questions (FAQ)

by | Jul 8, 2019 | Cable Protection, RF Weatherproofing | 0 comments

Here at Gamma Electronics we get a lot of questions about Cold Shrink tubing, (or sometimes referred to as Cold Shrink Sleeves), which makes sense considering we were the first to develop and make silicone cold shrink popular.  To help better answer and make those answers more accessible we put together the FAQ’s about Cold Shrink below.

What is Cold Shrink?

Cold Shrink is a rubber tube or sleeve that can shrink down many times smaller than its original size, similar to heat shrink tubing.  Unlike heat shrink, cold shrink tubing does not require heat in order to shrink, hence the name “Cold” shrink.  Cold Shrink is made from a rubber material which is held in an expanded state by an inner plastic tube that, when removed, allows the rubber tubing to shrink down in size.

Watch “What is Cold Shrink?”

How Does Cold Shrink Tubing, Shrink?

Cold Shrink Tubing wants to shrink down but it is held in place by an inner, plastic core, that keeps it from doing so.  That plastic core is perforated, with a piece of the tube ready to pull, (we call this piece the rip cord), to make removing it very easy.  As soon as you start to pull the inner core out of the way the tubing immediately shrinks.

A good way to think of Cold Shrink is to go back to some basic science lessons about potential and kinetic energy, using a rubber band as an example.  When you stretch a rubber band it loads up with potential energy.  If you recall potential energy, (in very non-scientific terms), is stored up energy, ready to be used.  The more you stretch the rubber band the more the potential energy in the rubber band increases.  Once you release the rubber band it will shoot across the room, and when it does the potential energy turns into kinetic energy, which simply means energy that is in use.

Cold shrink tubing works very similarly to the rubber band example.  Cold shrink comes with a plastic core that holds the rubber tubing in a state of high potential energy, very much like if you were holding a rubber band in a stretched out, ready-to-fire state.  Once the plastic core is removed from the cold shrink the potential energy turns into kinetic energy, allowing it to immediately shrink into place.

We like to refer to Cold Shrink as being “supercharged,” meaning it has far more potential energy than your typical rubberband.  That supercharged, high potential energy state, allows Gamma Cold Shrink tubing to shrink down to incredibly small sizes as soon as the plastic core is removed.  Once that plastic core is removed, the cold shrink tubing will work its hardest to shrink down to the size it is capable of shrinking down to.

Below is an example of one of our cold shrink models in its “before,” or expanded state, and the “after,” shrunk down state.

SDL-1A-125 Cold Shrink before and after

How Do I Install Cold Shrink?

Cold shrink tubing is incredibly easy to install and can typically be installed in less than a minute.  We made a step-by-step guide for those who are new to cold shrink installation, as well as a short video, (below), where we install cold shrink on an RF coaxial cable/conneciton to make it as clear as possible.

Where Would I Use Cold Shrink Tubing?

One of the most popular uses for cold shrink is on cell phone towers, where it is used to protect electrical cables/connections from water ingress and weather in general.  Cold shrink tubing is also used for various types of cable protection including splicing joints, cable trench applications, and in very confined or dangerous spaces where heat guns and/or blow torches are more difficult to use.  Cold shrink tubing is very popular in the telecommunications market, as well as in the oil, energy, cable television, satellite, and WISP industries.

What is Cold Shrink Made Of?

Cold Shrink is typically manufactured from one of two types of rubber: EPDM or Silicone.  You can easily find cold shrink manufactured from both materials and they both have their perks.  EPDM tends to be more rugged and capable of taking a beating, making it ideal for when the cold shrink is likely to be in contact with other materials, like inside machinery for example.  Silicone on the other hand will shrink down to a much smaller and tighter size than EPDM, and is ideal for applications like cell tower weatherproofing.

We have an entire post dedicated to the differences between EPDM and Silicone Cold Shrink, which you can read here.

What is the Difference Between Silicone and EPDM Cold Shrink?

EPDM, (Ethylene Propylene Diene Terpolymer), is the material that Cold Shrink was originally made of and still has some great uses in industrial applications.  However, EPDM does not have the ability to shrink as far and as tight as silicone cold shrink.  EPDM is compatible with many polar fluids that would adversely affect other elastomers, (i.e. silicone Cold Shrink).  Because of its unique properties, EPDM is most typically used in industrial applications, while silicone cold shrink is what will be used for most tower and RF weatherproofing scenarios.

Learn more about the differences between silicone and EPDM cold shrink here.

What is Shrink Ratio?

Shrink Ratio refers to the size that shrink tubing starts at compared to the size it shrinks down to.  This difference between where the tubing starts versus where it ends up is expressed mathematically in a ratio format.  For example, our SDL-1A-125 cold shrink tubing starts more than 4 times larger than what it ends up shrinking down to.  To make it easy we say it has a 4 to 1 shrink ratio, or 4:1, (technically it is closer to 4.5 to 1).

It is very common to also describe heat shrink tubing by its shrink ratio.  For example, we offer heat shrink tubing in 2 to 1 (2:1), 3 to 1 (3:1), 4 to 1 (4:1), and 6 to 1 (6:1), ratios.  You can see that we categorize our heat shrink tubing by shrink ratio on our heat shrink tubing page.

Most of our silicone cold shrink is around a 4 to 1 (4:1) shrink ratio, although some of our smaller cold shrink models are closer to around 3.5 to 1, (3.5:1).

What is Gamma Cold Shrink Tubing’s Shrink Ratio?

Depending on which model/size cold shrink you are looking at Gamma Gold Shrink tubing typically runs in the range of 4:1 with some of our smaller sizes being 3:1.  To be more accurate our smaller silicone cold shrink tubing is closer to 3.5 to 1 (3.5:1), with our larger sizes being closer to 4.5 to 1, (4.5:1).

Unlike heat shrink tubing which is manufactured in very specific shrink ratios, our cold shrink tubing has been manufactured to match certain cables and/or connections.  Given that, our cold shrink tubing does not have the exact shrink ratios often seen with heat shrink tubing.  You can see all of our different models of silicone cold shrink tubing, including the sizes they start at and shrink down to, on our Silicone Cold Shrink page.

Does All Cold Shrink Tubing Shrink Down to the Same Size?

No.  Different models of cold shrink tubing have different shrink ratios.  Each model of cold shrink tubing shrinks down to a unique size and you will want to make sure that you have the right model that starts large enough to get around your cable, connector, etc., and is still able to shrink down small enough to give you the watertight seal you need.  In our cold shrink sizing chart you can see the cold shrink models that we have tested and that we recommend to match with popular cable and connector combinations.

Below we have images of two of our models of cold shrink, to demonstrate the contrast.  The SDL-1A-125 is larger with a higher shrink ratio, while the SDL-SMA-60 is smaller with a still very impressive 3:1 shrink ratio, (click on the photos to enlarge).

SDL-1A-125 Cold Shrink before and after

Does Cold Shrink Come in Different Sizes?

Yes, absolutely.  In our cold shrink sizing chart, (below), you can see the model of cold shrink we have matched with various cable and connector combinations.  We have tested our cold shrink with these various combinations to ensure that they are watertight, with IP68 rated weather protection.

Each model of cold shrink shown above has been designed for and tested with the connectors and cables shown in the chart.  We test by installing the cold shrink on a cable/connection and then dunking the cold shrink and connection into a water tank more than a meter deep.  After about 45 minutes to an hour we remove the cold shrink/connection from the tank and check for any signs of water getting into the connection.  All of the cold shrink models shown above have passed testing, numerous times, with the cable and connector combinations shown next to them. 

Can You Make Cold Shink in Custom Sizes?

Absolutely.  We have made custom sized cold shrink for varying customers and we can make it in different colors, (including clear).  If you need custom sized cold shrink just reach out to our sales team and they will help figure out the specifics.

How Do I Choose the Right Size Cold Shrink?

There are three things to consider when trying to choose the right cold shrink size, (in no particular order): the starting size, (or pre-shrink size), the length, and the shrunk down size of the cold shrink.

You can start by looking at the largest thing that the cold shrink needs to fit over, (usually the connector).  You need to make sure the cold shrink starting size can fit over that size, plus a little bit of wiggle room for the plastic core of the cold shrink to have enough room to be removed.  If the fit between the cold shrink and the connector, cable, or whatever you’re trying to protect, is too tight, then the inner core won’t be able to be removed and you won’t be able to install the cold shrink.

Next, make sure the cold shrink is long enough to fully cover what you want protected, plus a little extra.  You don’t want the cold shrink tubing to be too short in case you miss the mark ever so slightly.

Lastly, you need to make sure the cold shrink can shrink down small and tight enough to create a water tight seal.  For example, our SDL-1A-125 model shrinks down to 0.4 inches, making it ideal for shrinking onto half inch, (0.5?), cables.  The fact that the SDL-1A-125 will shrink down smaller than 0.5 inches mean you get an even tighter seal with your cold shrink on half inch cables.

If you’re unsure about what size cold shrink tubing you might need feel free to Contact Us, and a member of the Gamma team will gladly help you find the right model for your application.

What’s the Lifespan of Gamma Cold Shrink?

Gamma Cold Shrink is guaranteed to match the lifespan of the cable that it is protecting.

How Do I Remove Cold Shrink Tubing?

Unlike heat shrink tubing, electrical tape, butyl, etc., cold shrink tubing has no adhesive, making it easier to remove than nearly all of those previously mentioned products.  However, cold shrink tubing does shrink down so incredibly small and tight that removing it can still prove difficult, especially if you want to remove the cold shrink without damaging the cable or connection that it’s protecting.

This is the exact reason we designed the Tower Utility Knife, (or TUK).  Unlike a box cutter or scissors the TUK has a guarded blade designed to not cut into a cable or connector while removing cold shrink tubing.

Learn more about the Tower Utility Knife here.

Is Cold Shrink Better than Heat Shrink?

It’s difficult to say that cold shrink is better than heat shrink or vice versa.  The reality is that they have different applications.  What is true is that if you are comparing cold shrink to heat shrink in terms of outdoor cable protection, cold shrink will nearly always be superior.

Heat Shrink is better suited for indoor use and does not offer anywhere near the same level of protection against liquid or dust ingress that you get with Gamma Cold Shrink, Weatherproof Boots, or Slide Locks.  Also, heat shrink is almost always made of thinner material than that which Cold Shrink is made from and is simply less durable.  Additionally, heat shrink products that include adhesive can become problematic in warmer and colder temperatures as the glue can melt in the heat and become brittle and ineffective in the cold.

We recommend Heat Shrink as a form of cable protection and we use it on all of our cables as a strain relief and to avoid any installation issues we install heat shrink on our cables indoors, in a controlled environment.  The majority of the time we do not recommend Heat Shrink to be used outdoors, however there are exceptions for heat shrink products that are specifically designed for some outdoor applications.

Our silicone cold shrink is very capable of shrinking down to some very small sizes, but it still is unable to meet some of the absoutely tiny sizes that heat shrink is oftentimes used to shrink down to.  Many of these tiny applications also don’t require the same level of weather protection that cold shrink provides.

In short, cold shrink and heat shrink both have their purposes and you’re best suited by making sure that you are using the right product in the right application.

What are the Key Benefits of  Cold Shrink Tubing?

There are a lot of great reasons to choose cold shrink tubing but we have identified 7 key benefits that elevate it above the competition:

  1. Incredible Sealing Properties
  2. Fast & Easy Installation
  3. No Special Tools Required for Installation
  4. Cold Shrink is Safer
  5. Longevity
  6. No Adhesive
  7. Quality Control

We go into greater detail about these 7 key benefits in our post, “What is Cold Shrink?”, which you can check out here.

What other questions do you have about Cold Shrink?  Let us know in the comments below!

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