Testing standard
Conveyor belts — Determination of strength of mechanical fastenings for textile conveyor belts — Static test method
Written and technically reviewed by Dak System Inc. engineeringLast reviewed
ISO 1120 joins two lengths of textile conveyor belt with the mechanical fastener under test and pulls the joint apart statically until it fails. The standard states its own purpose plainly: to eliminate fastenings of insufficient static strength. It does not cover vulcanised joints, and it is not valid for light conveyor belts. The current edition is ISO 1120:2025.
Two lengths of belt are joined with the mechanical fastener under test, the assembly is clamped in the machine by its two free ends, and it is pulled apart statically until the joint fails. The maximum force is the static strength of that fastening. The method covers both fastener types in common use: those employing a connecting rod through the hinge and those that do not.
It does not cover vulcanised joints, and it is neither applicable nor valid for light conveyor belts as described in ISO 21183-1.
A conveyor belt joined with mechanical fasteners is only as strong as the joint, and the joint is always weaker than the belt. Fastener manufacturers publish a holding strength for each series against belt rating, and the plant engineer chooses a fastener from that table. This test is what puts a number behind the table.
The standard is unusually plain about its own purpose: the test exists to eliminate mechanical fastenings of insufficient static strength. It is a screening test, not a service-life prediction. A joint that passes will still fatigue under repeated passage over pulleys, and nothing in a static pull tells you how long it will last — only whether it should be considered at all.
Failure mode is the second half of the result. A joint can fail by the fastener plate tearing, by the rod pulling out of the hinge loops, or by the fastener tearing through the belt carcass. The last of those is a belt problem rather than a fastener problem and points at the wrong fastener series having been chosen for that carcass.
Everything that makes a field joint good or bad is built into the specimen before the machine is switched on. That is the method, and it is also its weak point.
The maximum force the joint carried before failure
Compared against the belt rating to see what fraction of the belt strength the fastener returns. It is always a fraction.
Plate tears, rod pulls out, or fastener tears through the carcass
The third is a selection error rather than a product fault, and it is the one the force alone will not tell you about.
Pass means fit to consider; it does not mean fit for the duty
The standard says as much: the purpose is to eliminate fastenings of insufficient static strength.
Grips that slip at high load on a compliant belt end do not announce themselves. The trace becomes shallow and rounded rather than showing an obvious jump, and the reported strength is low. Check the belt ends for jaw witness marks after every test.
Wide hydraulic jaws with enough clamping force to hold a compliant, rubber-faced belt end at high load. This is the one method in the belting cluster where clamping force, not resolution, is the binding requirement.
Specifications
For narrower specimens and lower-rated belts, a wide vice-action face takes the full belt end. Check for jaw witness marks after each test — slippage on rubber creeps rather than jumps and does not show in the trace.
SpecificationsThis is the highest-force method in the belting group. A fastened joint on a heavy textile belt can carry tens to low hundreds of kilonewtons, so frame capacity is a real constraint rather than an afterthought, and the specimen is wide. A frame with wide grips and generous daylight is needed — the joint plus free length either side is a long specimen.
Grips have to hold a wide rubber-faced belt end without slipping at high load, which in practice means large hydraulic or heavy vice-action jaws with a gripping face and enough clamping force to hold a compliant material. Force accuracy to ISO 7500-1 Class 1 is the normal requirement. No extensometer is needed; the result is a force.
Where a belt width or fastener series exceeds a standard frame, specimen width can sometimes be reduced by agreement — a decision to record, not to make silently, because a narrowed specimen is not directly comparable.
Joints made to a different standard of workmanship than the field job dominate. Grips that slip at high load on a compliant belt end are the mechanical fault, and they usually show as a shallow, rounded force trace rather than an obvious slip. Insufficient free length lets the grip constrain the belt near the fastener and stiffen the joint. And a result recorded without the failure mode cannot distinguish a weak fastener from a belt carcass that the fastener was never suited to.
Both join a belt. They are chosen for different reasons and only one of them is covered by this method.
| Mechanical fastening | Vulcanised splice | |
|---|---|---|
| Covered by | ISO 1120 | ISO 8094 for steel cord splice adhesion |
| Strength returned | A fraction of belt rating | Close to belt rating |
| Fitted | In minutes, on site, with hand tools | In hours, with a press and heat |
| Repairable | Yes, quickly | Only by re-splicing |
| Fails by | Plate tear, rod pull-out, carcass tear-through | Cord pull-through, cover separation |
A fastener is chosen because a splice cannot be made or cannot be afforded in downtime, not because it is as strong. Comparing the two on strength alone misses the decision that was actually being made.
ISO 1120 is the international static test method for the strength of a mechanical fastening in a textile conveyor belt. Two belt ends are joined with the fastener under test and pulled apart until the joint fails. It covers fasteners that use a connecting rod through the hinge and those that do not. The current edition is ISO 1120:2025, which narrowed the title to textile conveyor belts; it supersedes ISO 1120:2012.
The standard states its own purpose unusually plainly: to eliminate mechanical fastenings of insufficient static strength. It is a screening test. A fastener that passes is fit to be considered for a duty; the test says nothing about how long it will last under repeated passage over pulleys, which is how fastened joints normally fail.
No. Vulcanised joints are explicitly outside the scope, and so are light conveyor belts as described in ISO 21183-1. For steel cord belts, which are spliced rather than fastened, ISO 8094 covers splice joint adhesion and ISO 7623 the cord-to-coating bond that the splice depends on.
Because it says whose problem it is. A fastener plate that tears, or a rod that pulls out of the hinge loops, points at the fastener. A fastener that tears through the belt carcass points at the wrong fastener series having been chosen for that belt — a selection error, not a product fault. The peak force alone cannot distinguish the two, and the report is much less useful without it.
Because the specimen is the belt itself, at full width, and a fastened joint on a heavy textile belt can carry tens to low hundreds of kilonewtons. The other belting methods peel, tear or strip and need only a few hundred newtons to a few kilonewtons. Here frame capacity, grip width and daylight are genuine constraints rather than afterthoughts.
Sometimes, by agreement between the parties — but it is a decision to record in the report, not one to make silently. A narrowed specimen changes how load distributes across the fastener row and is not directly comparable with a full-width result. Where narrowing is not acceptable, the specimen needs a frame sized for it.
A specimen joint made to a higher standard of workmanship than the field job. Every variable that decides whether a fastened joint holds — end squareness, fastener spacing, rivet setting, tool condition — is built into the specimen before the machine is switched on. A laboratory joint assembled unhurriedly on a clean bench can pass comfortably while the same fastener, fitted underground in a hurry, does not.
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 | High for this group — tens to low hundreds of kN on a heavy textile belt at full width | 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 | Wide hydraulic or heavy vice-action grips holding two rubber-faced belt ends | Our self-tightening serrated wedge grips, with V-jaws for round specimens or 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.
