Test methods
Reading a heat shrink datasheet without taking it on trust
Every method cited on this site, the property it measures, and a published figure it belongs to.
A wrap holds on the bench and lets go in a flooded trench at 50 °C. Nothing on the sheet was false. The condition that produced the figure sat in a column nobody read back.
Below is every test method named anywhere on this site, once. Each row carries the method, the property it measures, and a value published against a part you can order. Arrive from a product page, take your row, leave.
Two habits do most of the work. Read the qualifier before the number. Then read the condition, because a good half of what follows moves with temperature.
Mechanical
| Method | What it measures | Published against |
|---|---|---|
| ASTM D638 | Tensile strength and elongation, pulled to break | GTWS pipeline sleeve 22 N/mm² at 550%. Bustape 10.5 N/mm² min at 300% min. Cable repair sleeve 12 N/mm² min at 300% min. Black mastic 0.1 MPa min, red 0.5 MPa min. |
| ASTM D2240 | Indentation hardness on the Shore D scale | GTWS 50 ±5. Bustape 45 ±10. |
| ASTM G14 | Impact resistance of a pipeline coating, by falling weight | GTWS above 15 J. |
| ASTM D1044 | Abrasion resistance, reported as material lost | GTWS 30 mg. |
| ASTM D792 | Density by displacement | Bustape 1.20 ±0.2 g/cm³. Mastic 1.30 ±0.2 black and yellow, 1.20 ±0.2 red. Cable repair sleeve specific gravity 1.4. |
Rows are grouped by method, not by part. Check which part a figure belongs to before it travels into a specification.
Thermal and environmental
| Method | What it measures | Published against |
|---|---|---|
| ASTM D2671, accelerated ageing | Strength and elongation kept after a stated soak in hot air | GTWS after 504 hours at 150 °C: 21 N/mm² at 575%. Bustape after 500 hours at 120 °C: 10 N/mm² min at 250% min. |
| ASTM D2671, low-temperature flexibility | Cracking after a cold soak, then a bend | GTWS none at −15 °C for 4 hours. Bustape none at −40 °C for 4 hours. |
| ASTM D2671, peel strength | Force to pull the adhesive off the substrate, per cm of width | GTWS to steel 100 N/cm at 25 °C, 30 N/cm at 50 °C. To fusion-bonded epoxy 120 and 35. To polyethylene 110 and 30. |
| ASTM D2671, chemical immersion | Elongation kept after 24 hours in the named liquid | GTWS 100% in 10% HCl, 97% in 10% NaOH, 98% in 10% NaCl. |
| ESI 09-11 | Heat shock. Held at temperature, then examined for cracking or flow | Bustape no cracking or flowing at 250 °C for 30 minutes. The cable repair sleeve is published at 250 °C for 4 hours with no method beside it. |
| IEC 216 | Thermal endurance, the basis of a service-temperature claim | Bustape shrinks at 125 °C, continuous −40 °C to +115 °C. Mastic −20 °C to +90 °C, all grades. Cable repair sleeve −55 °C to +125 °C on the outer wall. |
| ASTM D570 | Water taken up by the wall, as a percentage of mass | GTWS 0.5%. Bustape 0.5% max. |
| ASTM E28 | Softening point of a hot-melt adhesive | GTWS adhesive 95 °C. |
ASTM D2671 is not one test. On this page alone it yields an ageing result, a cold-flexibility result, a peel figure and a chemical-immersion figure. A supplier answering "tested to ASTM D2671" has named the book, not the page.
Electrical
| Method | What it measures | Published against |
|---|---|---|
| ASTM D149 | Voltage a millimetre of wall holds before it breaks down | Non-shrinkable HV tape 42 kV/mm. GTWS 36 MV/m. Bustape 22 kV/mm min. Mastic 6 kV/mm min black, 10 red, 15 yellow. |
| ASTM D257 | Volume resistivity of the bulk material | Bustape 1 × 10¹⁴ Ω·cm min. GTWS 1 × 10¹³ Ω·cm. Mastic 1 × 10¹⁰ Ω·cm black, 1 × 10¹⁴ red, 1 × 10⁹ yellow. Non-shrinkable HV tape 1 × 10¹³ Ω·m. |
| ASTM D150 | Dielectric constant, and loss factor with it | Bustape 5 max. Mastic 2 to 3 black, 3 max red, 10 min yellow. Cable repair sleeve 3.0 max. |
| ASTM D2303 | Tracking and erosion on a wetted inclined plane | Bustape no tracking, erosion or flame failure to 3.25 kV for 20 minutes. |
| BS 903 | Physical testing of rubber, used here for the elastomeric tape | Non-shrinkable HV tape 3 MPa at 900% elongation. |
Check the unit before you compare two columns. 36 MV/m and 36 kV/mm are the same figure. Ohm-metres and ohm-centimetres are not, and both appear below.
Application level, where the claim is not a material property
| Reference | What it covers | Published against |
|---|---|---|
| ANSI C37.20.2 | Metal-clad medium-voltage switchgear assemblies | Bustape is stated to meet it for applications up to 36 kV. |
| ISO 21809-3 | Field joint coating on buried and exposed steel pipeline | GTWS cathodic disbondment 3 rad. Worked through on ISO 21809-3, and not repeated here. |
| IP 68 | An ingress class, not a test result | Claimed for the hot-melt seal on the cable repair sleeve. |
| MIL-I-7444 | Fungus resistance, from a military sleeving specification | Cable repair sleeve rated inert. |
| QR series | The manufacturer's own qualification report for one part | Bustape cites Technical Qualification Report QR 1020. |
Nothing here came off a tensile machine. Each row needs its own evidence: a report number, a coating qualification, an agreed depth.
Five things to ask for beside any figure quoted at you
- The temperature
- GTWS peel falls from 100 N/cm to 30 N/cm between 25 °C and 50 °C. Seventy per cent of the bond, inside a trench's own summer range.
- The duration
- 500 hours at 120 °C and 30 minutes at 250 °C are not two versions of one claim. A part can pass either alone.
- The qualifier
- The mastic sheet heads its column typical value, then prints min. and max. inside it, grade by grade.
- The constituent
- A sleeve, a closure patch and an adhesive are three materials under one code. The 95 °C softening point is the adhesive's alone.
- The report number
- Ask for the qualification report by number, as QR 1020 for the tape. A compliance line in a brochure is not a report.
One row names a method that does not measure that property
The non-shrinkable high voltage tape publishes a dielectric loss angle of 0.005 against ASTM D149. ASTM D149 is the breakdown-voltage method. The same manufacturer uses ASTM D150 for the dielectric constant on both the tape and the mastic sheets. Ask which method produced 0.005 before that figure enters a comparison.
Not published — two figures with no method behind them
The mastic sheet gives a 50 Hz loss factor of 0.035 for all three grades and prints a dash where the standard belongs. Ask what was run. IP 68 is the wider gap. It appears on 34 of the manufacturer's 175 published datasheets. None of them prints an immersion depth or a hold time beside it. IEC 60529 leaves both to agreement between maker and user, so the class carries no depth of its own. Get the metres and the minutes in writing.
Figures here that move once the condition changes
Each is a pair. Quoting half of one is how a compliant part reaches the wrong joint.
- GTWS peel to steel is 100 N/cm at 25 °C and 30 N/cm at 50 °C. To fusion-bonded epoxy, 120 N/cm and 35 N/cm.
- Bustape tensile is 10.5 N/mm² as supplied and 10 N/mm² after 500 hours at 120 °C. Elongation over that soak goes 300% to 250%.
- GTWS moves the other way. Elongation reads 550% unaged and 575% after 504 hours at 150 °C, so ageing is not a loss on every axis.
- Mastic dielectric constant reads 3 maximum on red and 10 minimum on yellow. Yellow is the stress-control grade, so the high figure is the point of it.
Where each of these figures is published on this site
A method is explained here once. The parts carry the tables.
- Heat shrink tapeANSI C37.20.2, the 3.25 kV tracking result, the ageing set.
- Pipeline corrosion protection sleevePeel, impact, abrasion and immersion, all GTWS.
- Wraparound cable repair sleeveGMRS sizes, and a printed table belonging to another part.
- Mastic tapeThree grades, three columns, the qualifier changing between them.
- Non-shrinkable HV insulation tapeThe BS 903 values and the ohm-metre column.
- ISO 21809-3The one reference above worked through in full.