Sizing of Heat Shrink Tubing

Selecting the correct size is the most critical factor in achieving a reliable seal. A common but flawed approach is simply choosing tubing that is twenty to thirty percent larger than the cable. Instead, the selection must account for the supplied diameter (the size before heating) and the recovered diameter (the size after maximum unrestricted shrinkage). As performance is defined by these two states, the correct sizing method involves two simple rules:

• Clearance: The supplied diameter must be large enough to easily slide over the largest part of the connection, such as a bulky cable lug or splice.
• Grip: The recovered diameter must be significantly smaller than the diameter of the smallest underlying cable insulation to ensure the tubing exerts sufficient compressive force to drive the adhesive into all gaps.

Understanding Heat Shrink Ratios

The shrink ratio of any heat shrink tubing indicates the maximum amount the tubing will contract. Common ratios are 2:1, 3:1, and 4:1. A 2:1 ratio means a tube with a 12mm supplied diameter will shrink down to 6mm. Higher shrink ratios (like 3:1 or 4:1) are exceptionally useful in automotive and marine electrical work, as they allow the tubing to clear large terminal ring lugs while still recovering tightly around much thinner wire insulation.

This table has been created to assist in recommending the appropriate sized Heat Shrink to enclose both the swage sleeve and the wire rope for Uncoated Wire Rope
To simplify selection the use of heat shrink on uncoated Wire Rope, the following table gives the

• diameter of uncoated wire rope,
• approximate diameter of a properly crimped or swaged duplex sleeve, and
• recommended  heat shrink sizes by Shrink Ratio.

Notes: 

1. the 2:1 PE is a not recommended (but the cheapest) option. It will not stick as well and requires a MUCH larger range of sizes to even begin to work properly
2. the 3:1 PE Dual Wall is a better choice (but more expensive) and has good adherence with a wider color selection and offers success over a larger range with fewer sizes required.
3. the 4:1 PE Dual Wall is a premium choice (and most expensive) but has excellent adherence and offers success over a larger range with the minimum number of sizes required – but only in BLACK