Two face setsTJ-26
100mm Wide Vice Action Grips
Wide vice-action jaws hold the two sides of the cut across their full width. Rubber slips by creeping rather than jumping, so grip area matters more than clamping pressure alone.
SpecificationsTesting standard
ISO 505
Conveyor belts — Method for the determination of the tear propagation resistance of textile conveyor belts
Written and technically reviewed by Dak System Inc. engineeringLast reviewed
ISO 505 cuts an initial tear in a textile conveyor belt and then measures the force needed to make that tear run. It is aimed squarely at longitudinal ripping — the failure that takes a whole belt out of service — and it is run either on the full belt thickness or on the carcass alone. The current edition is ISO 505:2025, superseding ISO 505:2017.
At a glance
- Test type
- Tear — a cut or nick is forced to grow
- Published by
- ISO
- Edition
- ISO 505:2025
- Material
- Conveyor & transmission belts
- Runs on
- Series 7200 and Series 9000
What the test does
A test piece is cut from a textile conveyor belt and an initial tear is made in it. The two sides of the cut are clamped in the machine and pulled apart at a given speed, so the existing tear is forced to run. The force required to keep it running is what the method measures.
The test piece may be full thickness, covers included, or the carcass alone. Those two variants answer different questions and are not interchangeable: full thickness tells you what the belt as built will do, carcass only isolates the fabric.
What it measures, and why it matters
Longitudinal ripping is the most expensive single failure mode on a bulk-handling conveyor. A tramp iron bar, a broken idler or a sharp lump of ore punches through the belt, and once a tear has started the belt tension drives it along the belt for tens or hundreds of metres. The belt is not repaired; it is replaced, and the plant is stopped while it happens.
This method is explicitly aimed at that risk. Its scope names installations where there is a risk of longitudinal tearing, and the number it produces is used to select a belt construction for a conveyor whose duty makes ripping likely — a primary crusher discharge, a run-of-mine transfer, anything where the material can be sharp and large.
What it does not measure is puncture resistance. Making the initial tear is part of the method; whether the belt would have been torn in the first place is a separate question, and one this test deliberately sets aside.
Specimen, and the cut that starts it
Two decisions have to be recorded before anything is pulled: full thickness or carcass only, and which direction the specimen was cut in. Neither is recoverable afterwards.
- Material
- Textile conveyor belt
- Variants
- Full thickness, or carcass onlyThey answer different questions. Full thickness describes the belt as built; carcass only isolates the fabric.
- Initial tear
- Cut to the geometry the standard specifies
- Direction
- Recorded, and normally tested in bothA belt tears very differently along its length than across it.
- Conditioning
- In the standard atmosphere for conveyor belt testing
- Cut the starter tear with a fresh blade
- DakA blunt blade tears rather than cuts and blunts the crack tip. The recorded force goes up and the belt looks better than it is.
The scope of the method is installations where there is a risk of longitudinal tearing. It measures how hard it is to keep a tear running — not how hard it is to start one. Puncture resistance is a separate property and this test says nothing about it.
Rate, and the travel it needs
- Loading
- A tensile pull at a given speed, propagating the initial tear
- Rate
- As specified in the standard; not publicly quotable
- Reported
- The force required to propagate the tear
- Allow enough stroke
- DakThe tear has to run far enough for the force to settle. A short-stroke frame forces a restart, and a restart is an artefact in the middle of the record.
What the result means
Tear propagation resistance—
The force required to keep the initial tear running
Reported as a force, with the variant and the specimen direction against it.
Why longitudinal ripping is the target—
Belt tension drives a started tear along the belt
A tramp bar, a broken idler or a sharp lump starts it; the conveyor then does the rest, for tens or hundreds of metres. The belt is replaced, not repaired.
Full thickness against carcass only—
Covers contribute, and the two figures are not interchangeable
Quoting one against a specification written for the other is a common and expensive mismatch.
How the test runs
- 01Take specimens from across the belt width, in both directions.
- 02Prepare full-thickness or carcass-only specimens as the specification requires.
- 03Cut the initial tear to the specified geometry with a fresh blade.
- 04Condition in the standard atmosphere.
- 05Clamp the two sides of the cut in the grips.
- 06Pull at the specified speed so the tear propagates.
- 07Record the force through the propagation.
- 08Report the propagation force with the variant and the direction.
Grips and fixtures for this method
Self-identifying
Load Cells
A cell sized for the specimen. Tear propagation forces sit far below the belt rated strength, and a cell chosen for the frame flattens the trace the method depends on.
SpecificationsWhat the report has to contain
- Reference to ISO 505 and the edition
- Belt construction, ply count and cover thicknesses
- Whether the specimen was full thickness or carcass only
- Specimen direction relative to belt travel
- Where across the belt width the specimens were taken
- Initial tear geometry
- Conditioning atmosphere
- Test speed
- Propagation force for each specimen
- Mean and the number of specimens
What the machine must be capable of
Tear propagation forces on textile belting are modest by belting standards but the travel is long, because the tear has to be allowed to run. A frame of 5 to 50 kN with a load cell sized for the specimen, a long stroke, and continuous logging over the whole propagation is the requirement. Force accuracy to ISO 7500-1 Class 1 is normal.
Grips must hold a rubber-faced strip without slipping. Vice-action jaws with a gripping face are the usual choice, and jaw width has to suit the specimen. As with all belt peel and tear work, resolution at the bottom of the load cell range matters far more than headline capacity, because a cell chosen for the frame turns a detailed trace into a flat line.
No extensometer is needed; the reported quantity is a force, and the strain of the belt is not part of it.
What goes wrong in practice
Slippage in the grips is the standard failure, and on rubber it shows as a creeping specimen rather than a sudden jump. Too short a propagation length gives a force averaged over too little tearing to mean anything. An initial cut made with a worn blade blunts the tip and inflates the result. And reporting a figure without saying whether it was full thickness or carcass only, and in which direction the specimen was cut, makes it uninterpretable later.
Tear propagation against the other belt failure tests
| Tear propagation (ISO 505) | Full-thickness tensile (ISO 283) | Adhesion (ISO 252) | |
|---|---|---|---|
| Starts from | A cut already in the belt | An intact specimen | A separated interface |
| Failure driven by | Crack running under tension | Fibre breakage | Bond separation |
| Predicts | Longitudinal ripping | Rated belt strength | Delamination |
| Direction matters | Strongly | Yes | Less so |
| Force required | Low to moderate | High | Low |
A belt selected on rated strength alone can still be the wrong belt for a crusher discharge. Tear propagation is the property that governs whether a sharp lump costs a repair or a replacement.
Questions we are asked about this test
What is ISO 505?
ISO 505 is the international method for the tear propagation resistance of textile conveyor belts. An initial tear is cut into a specimen, the two sides of the cut are pulled apart at a specified speed, and the force required to make the tear run is recorded. The specimen may be full thickness or carcass only. The current edition is ISO 505:2025, superseding ISO 505:2017; the 1982 edition, titled for the carcass alone, is withdrawn.
Why does tear propagation matter so much on a conveyor?
Because longitudinal ripping is the most expensive single belt failure. A tramp bar, a broken idler or a sharp lump punches the belt, and belt tension then drives that tear along the belt for tens or hundreds of metres. The belt is not repaired, it is replaced, and the plant stops while that happens. The standard scope names installations where there is a risk of longitudinal tearing, which is exactly this case.
Does it measure puncture resistance?
No, and the distinction matters. Making the initial tear is part of the specimen preparation, so the method deliberately sets aside the question of whether the belt would have been cut in the first place. It measures only how hard it is to keep a tear running once one exists. A belt can be hard to puncture and easy to rip, or the reverse.
What is the difference between the full-thickness and carcass-only results?
Full thickness includes the covers and describes the belt as built; carcass only strips them away and isolates the fabric. Covers contribute real resistance, so the two figures differ and are not interchangeable. Quoting a carcass-only result against a specification written for full thickness, or the reverse, is a common mismatch and one that is invisible unless the report says which was run.
Why does specimen direction have to be recorded?
Because a woven carcass is strongly anisotropic. A tear running along the warp meets a different structure from one running across it, and the two forces can differ substantially. Specimens are normally taken in both directions, and a propagation force reported without its direction cannot be interpreted or compared afterwards.
What machine does it need?
A modest-capacity frame with a long stroke and continuous logging. Propagation forces are well below the belt rated strength, so a 5 to 50 kN frame with a load cell sized for the specimen and force accuracy to ISO 7500-1 Class 1 is right. The travel is the constraint people miss: the tear has to run far enough for the force to settle, and a frame that runs out of stroke forces a restart in the middle of the record.
How should specimens be sampled from the belt?
Across the width, and in both directions. Cover thickness and carcass construction are not uniform from edge to centre, and a set of specimens taken from one edge describes that edge rather than the belt. The same discipline applies to the other belting methods, and it is the difference between a result that represents production and one that represents a convenient offcut.
Running ISO 505 on the Series 7200 and Series 9000
Dak verifies against whichever standard the method names, and where a class applies our frames sit a class tighter than it asks.
| The method asks for | Dak supplies | |
|---|---|---|
| Capacity | Low to moderate — well below the rated tensile strength of the same belt | Load cells from 1 kg to 60 ton on the Series 7200, and 0.5 to 100 kN on the Series 9000 |
| Force accuracy | ISO 7500-1 Class 1 | ISO 7500-1 Class 0.5 — a class tighter than the method asks |
| Gripping | Vice-action grips holding the two sides of the initial cut | Our vice-action grips, built to the specimen |
| Environment | Standard atmosphere for conveyor belt testing | 3009 series chambers, −150 °C to +400 °C — temperature only |
This page describes the method as practised. The governing text is the current edition from the issuing body. Tell us what you are testing and we will answer with the machine, the fixture and a quotation.