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Design Calculations And Selection

Busbar SizingCable SizingGeneral TipsCalculations
01
Cable Sizing Guide
02
03
Design And Selection
04
04.1
04.2
Circumference To Lay-Flat
04.3
04.4

Busbar Sizing Guide

Busbar Sizes (mm)
Heatshrink Code
(Low Voltage)
Heatshrink Layflat Size (mm)
Airshrink Code
(Low Voltage)
12 x 1.5 / 12.5 x 3
ATW12.7
20
AS0807
14 x 4
ATW19
30
AS0907
15 x 3
ATW19
30
AS1007
16 x 3
ATW19
30
AS1107
16 x 4
ATW19
30
AS1210
20 x 3 / 20 x 4 / 20 x 6
ATW19
30
AS1410
25 x 3
ATW25.4
40
AS1610
25 x 5 / 25 x 6 / 25 x 6.3
ATW25.4
40
AS1810
30 x 3 / 30 x 6 / 30 x 6.3
ATW38.1
60
AS1910
30 x 10 / 30 x 12 / 31.5 x 6.3
ATW38.1
60
AS2210
40 x 4 / 40 x 6 / 40 x 6.3 / 40 x 10
ATW38.1
60
AS2510
50 x 6 / 50 x 6.3
ATW38.1
60
AS3010
50 x 10 / 50 x 12 / 50 x 16 / 60 x 3 / 60 x 6
ATW50.8
80
AS3510
60 x 10 / 63 x 6 / 63 x 6.3
ATW50.8
80
AS4010
80 x 6 / 80 x 8 / 80 x 10 / 80 x 12
ATW76
120
AS5010
100 x 6 / 100 x 10 / 100 x 12 / 100 x 16
ATW76
120
AS6010
120 x 10 / 120 x 16.5
ATW100
160
AS7010

Cable Sizing Guide

Cable Size (mm2)
Approx. Core 0D (mm) Including Insulation (LV)
Heatshrink Size (ID)
Heatshrink Layflat Size (mm)
0,5
2,1
2,4
3,8
1
2,6
4,8
5
1,5
3,2
4,8
7,5
2,5
3,7
4,8
7,5
4
4,5
6,4
10
6
5,1
6,4
10
10
6
9,5
15
16
6,9
9,5
15
25
9
12,7
20
35
10,8
12,7
20
50
12,6
19
30
70
14,5
19
30
95
16,5
19
30
120
18,5
25,4
40
150
22
25,4
40
185
23,5
25,4
40
240
27
38,1
60
300
30
38,1
60
500
36,5
50,8
80
630
42,8
50,8
80
Selection

General Tips

1
Confirm the OD (Outside Diameter) of the cable/object you need to cover.
2
Decide on the wall thickness you require. Based on the thickness you may need to choose one size up or select a heatshrink with a higher shrink ratio. A standard thin wall heatshrink has a 2 : 1 ratio meaning it will shrink to half its supplied size. (Example: 25.4 mm will shrink to 12.7 mm)
3
All heatshrink sizes are given as the ID (Inside Diameter) and not in mm or lay-flat. Should you not have the ID, refer to the design selection section and see the calculation necessary to determine the ID.
4
When choosing the heatshrink, always allow for at least a 20% shrink and a maximum of 80%, ensuring the product performs according to the specifications.
5
Will the heatshrink be placed onto the cable before or after a lug or ferrule has been crimped into place? If afterwards confirm that the heatshrink size is suitable to fit over the lug/ferrule and if it will still recover to the OD of the cable. If not, a heatshrink with a higher shrink ratio must be selected.
6
Other considerations include:

Application & Shrinking
General Tips

1
Always keep the work area and any cables/applications as clean as possible.
2
When cutting the heatshrink to the required size keep the following in mind:
3
Slide the heatshrink sleeve into place by positioning it centrally over the ferrules I object.
4
What to do before shrinking:
5
Commence shrinking by starting from the middle and working towards the outer ends applying heat circumferentially outwards until the internal sealant (adhesive) has melted, sleeves have a uniform wall thickness and are fully recovered.
6
When shrinking tubing or components with a gas torch, keep the following in mind:
7
Keep the following in mind during the shrinking process:
8
Once shrunk, all tubing should be smooth and free of any wrinkles. Signs of wrinkles indicate incorrect heating and possible air entrapment. For medium voltage (MV) applications, this may lead to failure over time.
9
Allow the heatshrink to cool before applying any mechanical strain or trimming/cutting it to size.
Inside Diameter vs. Layflat
Adhesive Lined
Longitudinal Shrinkage
(Before 100mm)
Longitudinal Shrinkage
(After 95mm)
Handheld Heat Gun
Split When Nicked
Gas Torch Orange/Yellow Tip

Busbar
Calculations

How to calculate/determine the correct size Heatshrink or Airshrink tubing for your busbar dimensions.

1
Looking at the busbar cross-section, sum all four sides, for example, a 50 x 10 busbar will add up to 120 mm.
2
Divide by 3.1415 (π).
3
This result gives the actual OD (outer diameter) of your busbar and thus the min ID (inner diameter) that your Heatshrink needs to shrink down to.
4
Add 10% to this result to allow sufficient clearance. This will ensure that the Heatshrink is easier to install.
Example

Busbar Size: 50 x 10
= (50 + 50 + 10 + 10) / 3.1415
= 120 / 3.1415
= 38.198

Add 10%

= 42.02 mm

This is the most suitable diameter (ID) for your application. Now choose the Heatshrink size that suits this busbar size (50.8).

Lay-Flat To Diameter
Calculations

Heatshrink sizes are stated using the supplied Internal Diameter (ID) of the tube and not the lay-flat (LF) size. If you are not sure of the correct ID you can calculate as follows:

Example

Heatshrink Size: 25.4 mm
LF: 40 mm
‍
10 = (LF x 2) / 3.1415(π)
= (40 x 2) / 3.1415(π)
= 80 / 3.1415(π)
‍
ID = 25.46 mm

Circumference To Lay-Flat
Calculations

Calculate the lay-flat of the tube if you have the diameter (D).

Example

Heatshrink Size: 25.4 mm
‍
C = 3.1415(π) x ID
‍
Circumference (C) is the same as 2 x Layflat (LF)

2LF = 3.1415(π) x ID
2LF = 3.1415(π) x 25.4
2LF = 79.79
LF = 79.79 / 2
‍
LF = 39.9 mm

Imperial To Metric
Calculations

Our heatrshrink is sized in metric (mm) but can sometimes be quoted in inches, use the handy table below for a quick conversion.

Inch
mm
1/32"
0.8
3/64"
1.2
1/16"
1.6
5/64"
2
3/32"
2.4
1/8"
3.2
3/16"
4.8
1/4"
6.4
3/8"
9.5
Inch
mm
1/2"
12.7
5/8"
15.9
3/4"
19.1
1"
25.4
1 1/4"
31.8
1 1/2"
38.1
2"
50.8
3"
76.2
4"
101.6
CONTACT US
office@airshrinksa.co.za
(+27) 11 868 3783