IS 2266 Steel Wire Rope Specification and Breaking Load Testing

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 to destruction: up to 80 per cent of the tabulated minimum breaking force may be applied quickly, after which the force is applied slowly, at approximately 10 MPa per second. 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

IS 2266 refers its general requirements to IS 6594, whose Annex B carries the breaking-force method and its loading rule. The rate is a stress rate, so it has to be converted to a force rate for the rope in hand.

First 80 % of the minimum breaking force

May be applied quicklyIS 6594:2018, Annex B-4.1. Nothing is being measured yet, so this part of the pull only has to be smooth.

The remaining force

Approximately 10 MPa per secondA stress rate over the rope's metallic cross-sectional area, not over the circle its nominal diameter describes.

As a force rate, 16 mm rope

About 1 kN/sDakWorked from roughly 100 mm² of steel in a six-strand 16 mm rope. The last fifth of the pull then takes something like half a minute. Recompute it from the metallic area of the construction actually being tested.

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.

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. IS 2266 names no machine specification of its own; the breaking-force test devolves to IS 6594. It also needs controllable slow loading at the top of its range: the rate is set as a stress rate of about 10 MPa/s over the rope's metallic cross-sectional area, which on a 16 mm rope of a common six-strand construction — roughly 100 mm² of steel in a 201 mm² circle — works out at about 1 kN/s, so the last fifth of the pull takes something like half a minute. 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.

How the test runs

1. 01Cut a sample of the required free length, serving the rope each side of every cut.
2. 02Prepare both ends and fit resin or white-metal sockets.
3. 03Allow the sockets to cure or set fully.
4. 04Measure the rope diameter at several points and positions.
5. 05Fit the sample to the machine through the socket connections.
6. 06Check the rope hangs straight, with no twist introduced by the fitting.
7. 07Apply any prestressing the standard requires.
8. 08Apply the first 80 % of the minimum breaking force quickly, then the remainder at about 10 MPa/s over the metallic area — roughly 1 kN/s on a 16 mm rope — recording force throughout.
9. 09Continue to complete failure of the rope.
10. 10Record the maximum force reached.
11. 11Examine the failure — position, and whether any socket drew.
12. 12Void and repeat any sample that failed at a termination.

Calculations

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 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.