Testing standard
IS 2266
Steel Wire Ropes for General Engineering Purpose — Specification
Written and technically reviewed by Dak System Inc. engineeringLast reviewed
IS 2266 is the Indian Standard specification for steel wire ropes used in general engineering. Its acceptance rests on a breaking load test: a length of rope is terminated at both ends in sockets and pulled to destruction, and the measured breaking load must meet the minimum the standard tabulates for that construction, diameter and wire grade.
At a glance
- Test type
- Tensile — the specimen is pulled apart
- Published by
- IS
- Edition
- 2019
- Material
- Metals, alloys & welds
- Runs on
- Series 7200 and Series 9000
What the test does
A sample of rope is cut with both sides of each cut served so the strands cannot unlay, and both ends are terminated in resin or white-metal sockets poured around the splayed and cleaned wires. Once the sockets have fully cured, the sample is fitted to the testing machine through those terminations, with a free length between them of at least about thirty rope diameters. Any prestressing the standard requires is applied to remove constructional stretch, and the sample is then loaded slowly and steadily to destruction. The maximum force reached is compared with the minimum breaking load the standard tabulates for that diameter, construction and wire grade.
What it measures, and why it matters
The result is the rope's actual breaking load, and the acceptance decision that follows from it. Wire rope is used where failure has consequences — lifting, cranes, hoists, lifts, winches, structural and marine applications — and the standard's tabulated minimum breaking loads are what every working load limit in those applications is ultimately derived from. The test also verifies the whole manufacturing chain at once: wire quality, lay length, core condition and closing tension all show up in the rope's ability to reach its tabulated strength, in a way that testing individual wires cannot capture.
Sample and termination
Wire rope cannot be gripped. The termination is the hardest part of the test, and a bad one destroys the sample without producing a result.
- Free length
- At least about 30 times the rope diameter between terminationsShort enough to fit the machine, long enough that the rope is not restrained by the sockets over its whole length.
- Terminations
- Resin or white-metal socketsThey must develop the rope's full strength. Anything that draws or slips has tested the termination.
- Sample condition
- As manufactured, not straightened or reworked
- Cut ends
- Served or seized before cuttingAn unserved rope end unlays immediately, and the sample is then a different construction from the rope.
- Lubrication
- Left as suppliedRope lubricant affects how the strands move against one another under load; degreasing a sample changes what is being measured.
- Record where the first wire breaks
- Position along the free lengthDakBreaks clustered at a socket point to the termination rather than the rope.
- Allow full cure on resin sockets
- Before pullingDakA resin socket pulled early draws under load, and the sample is wasted.
A test in which the rope drew out of its socket has produced no breaking load at all. It cannot be reported as a low result — the sample is void and must be re-terminated and repeated.
Loading
- Rate
- Slow and steady, approaching the breaking load without shock
- Prestressing
- Where the standard requires itA new rope beds in as the strands settle, and prestressing removes that constructional stretch before any measurement.
- Breaking load
- The maximum force reached
- Expect a cascade, not a single break
- Wires fail progressivelyDakLoad transfers to neighbouring wires as each fails, so the trace steps down. The peak is the breaking load.
Calculations
The maximum force reached before the rope fails, in kN
Compared directly against the minimum breaking load the standard tabulates for that diameter, construction and wire tensile grade.
Tabulated in the standard by diameter, construction and wire grade
A specification value the rope must meet or exceed. It is not a working load.
WLL = MBL / factor of safety
The factor is set by the application's own code — lifting, cranes and passenger lifts all use different ones. It is never chosen by the testing laboratory.
How the test runs
- 01Cut a sample of the required free length, serving the rope each side of every cut.
- 02Prepare both ends and fit resin or white-metal sockets.
- 03Allow the sockets to cure or set fully.
- 04Measure the rope diameter at several points and positions.
- 05Fit the sample to the machine through the socket connections.
- 06Check the rope hangs straight, with no twist introduced by the fitting.
- 07Apply any prestressing the standard requires.
- 08Load slowly and steadily, recording force.
- 09Continue to complete failure of the rope.
- 10Record the maximum force reached.
- 11Examine the failure — position, and whether any socket drew.
- 12Void and repeat any sample that failed at a termination.
What the report has to contain
- Reference to IS 2266 and the edition
- Rope identification — nominal diameter, construction, core type, wire tensile grade and finish
- Manufacturer and reference or batch number
- Measured rope diameter
- Free length between terminations and the termination type used
- Any prestressing applied
- Maximum force reached
- The tabulated minimum breaking load for that rope, and whether the sample met it
- Position and nature of the failure
- Any sample voided for termination draw
What the machine must be capable of
Very high force and, just as importantly, the stroke and daylight to accommodate a sample thirty diameters long plus two sockets. Capacities from tens of kilonewtons to well over a thousand are needed depending on rope size, with force measurement to Class 1. The connection to the machine is through socket adaptors rather than grips, and those adaptors must allow the rope to hang straight without introducing twist — a rope pulled with a turn in it distributes load unevenly between strands. Because the failure is energetic, guarding is a practical requirement rather than a formality.
What goes wrong in practice
Termination failure is the dominant problem and the most misreported. A rope that draws out of its socket has produced no breaking load at all, yet it is easy to record the peak force reached as though it were a result — which understates the rope and can wrongly reject a compliant batch. The usual causes are pulling a resin socket before it has fully cured, or splaying and cleaning the wires inadequately before pouring. Beyond that, unserved cuts allow the sample to unlay, twist introduced during fitting loads the strands unevenly, and degreasing changes the internal friction that governs load sharing.
Rope breaking load or aggregate wire strength
| Rope breaking load | Aggregate strength of the wires | |
|---|---|---|
| What is tested | The whole rope, terminated | Individual wires, tested separately and summed |
| Accounts for helix losses | Yes | No |
| Typical relationship | Lower | Higher — by the spinning loss |
| Used for | Acceptance against the standard | Wire quality control |
The two are not the same number, and the difference — the spinning loss — is real. Wires laid in a helix do not all reach their individual breaking strength together, so summing wire strengths always overstates the rope. Acceptance is against the rope test.
Questions we are asked about this test
What is IS 2266?
It is the Indian Standard specification for steel wire ropes for general engineering purposes. It defines rope constructions, diameters, wire tensile grades and core types, and tabulates a minimum breaking load for each combination. Acceptance rests on a destructive breaking load test carried out on a socketed sample of the rope.
Why can't wire rope be gripped in ordinary jaws?
Because a rope is a bundle of helically laid wires that will simply unlay or be crushed by a flat or wedge grip. Clamping hard enough to hold it damages the wires at the jaw and the sample fails there; clamping less lets the strands draw. The answer is a socketed termination — resin or white metal poured around the splayed rope end — which grips every wire individually and develops the rope's full strength.
What happens if the rope pulls out of the socket?
The test is void and must be repeated with a fresh sample. It has not produced a low breaking load; it has produced no breaking load, because what failed was the termination. Reporting a socket draw as a rope result understates the rope and can wrongly reject a compliant batch. The usual causes are a resin socket pulled before it had fully cured, or inadequate splaying and cleaning of the wires before pouring.
Is the minimum breaking load a working load?
No, and the distinction matters. The minimum breaking load is the force at which the rope is expected to fail — a specification value for acceptance. The working load limit is that figure divided by a factor of safety set by the application's own code, and the factors differ substantially between general lifting, cranes and passenger lifts. A testing laboratory reports against the minimum breaking load and never sets the factor.
Why is the measured rope strength lower than the sum of its wires?
Because the wires are laid in a helix rather than lying parallel to the rope axis. Each wire is slightly inclined to the direction of pull, so it contributes less than its full axial strength, and the wires do not all reach their individual breaking loads at the same moment. That difference is the spinning loss, and it is why acceptance is against a rope test rather than an arithmetic sum of wire tests.
Should the rope be degreased before testing?
No. The lubricant is part of the rope as supplied and it affects how the strands and wires move against one another under load. Degreasing a sample changes the internal friction and therefore the way load distributes between wires, so it is not testing the product that was delivered. The sample is tested as manufactured.
Why does the trace step down instead of dropping at once?
Because a rope fails as a cascade rather than a single event. The most highly loaded wires break first, their load transfers to neighbours, those break in turn, and the process runs through the construction over a short interval. The peak of that trace is the breaking load. A sample that drops instantly and cleanly is more likely to have failed at a termination than in the rope.
Running IS 2266 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 | High — from tens of kilonewtons on small ropes to well over 1000 kN on large constructions | Load cells from 1 kg to 60 ton on the Series 7200, and 0.5 to 100 kN on the Series 9000 |
| Force accuracy | IS 1828-1 / ISO 7500-1 Class 1 | ISO 7500-1 Class 0.5 — a class tighter than the method asks |
| Gripping | Rope terminations — resin or white-metal sockets — rather than grips; the termination must develop the rope's full strength | Wedge, vice-action, pneumatic and hydraulic grips, built to the specimen |
| Environment | Ambient laboratory conditions | 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.