Crane Wire Rope Specification: Size, Construction, Grade and Discard Limits

Thirty-eight of the 68 pick and carry cranes listed on DesiMachines publish a hoist rope size, and every one says the same thing: 13 mm. The diameter is the easy part. A full crane wire rope specification carries six more items beside it, and getting any of them wrong is what ends a rope early.

Those six are the construction, the grade, the core, the lay, the coating and the length. Indian Standard IS 2266 : 2002 requires all seven to be printed on the tag supplied with the rope, which makes that tag the cheapest safety document on the machine. This guide explains each item, what the crane standards ask of a rope, and the point at which one has to come off.

What does a crane wire rope specification include?

The tag on the coil or reel has to carry the size, construction, rope grade, lay, core, coating and length, plus the reel number and your order number. That list is clause 12.1 of IS 2266 : 2002, and read backwards it is also the order you have to place.

The measurement convention catches people out. A rope caliper sits across the crowns, so a reading taken in the valleys says the rope is thinner than it is. Lay matters on a free hook: a Lang’s lay rope wears better over sheaves but wants to spin, so hoist ropes are usually ordinary lay.

What do 6×19 and 6×36 mean on a wire rope?

The first number counts the strands, the second counts the wires in each strand. A 6×19 rope has six strands of nineteen wires, so 114 wires in all. A 6×36 has the same six strands with 36 thinner wires in each, so 216.

That difference decides how the rope behaves. Few thick wires shrug off grit and rubbing but resist bending. Many thin wires bend easily over small sheaves and wear through faster on a dusty site. A hoist rope bends over its sheaves, the grooved pulleys at the boom tip and inside the hook block, thousands of times a day. So the flexible constructions dominate.

The scope of IS 2266 : 2002 says its ropes are for use in cranes, excavators and other general engineering purposes. These are the constructions from that list a crane hoist rope is normally drawn from.

Notice where 6 x 36 SW starts. The standard’s smallest size for that construction is 13 mm, exactly the size the Indian pick and carry fleet runs. The last row matters too: the TIL PIXEF 215 and the TIL MOBILOAD 315 both specify a non-spin rope, and non-spin means one of these multi-layer constructions rather than a plain six strand rope.

Which rope grade and which core does a crane need?

Grade is the tensile strength of the wire in megapascals, and IS 2266 recognises 1570, 1770 and 1960. A higher grade carries more load at the same diameter, which matters because the diameter is fixed by the drum and sheaves and cannot simply be increased. Breaking force is published in kilonewtons; the tonne-force figure beside it is the same number divided by 9.81.

Grade 1960 buys roughly a quarter more strength than 1570 at the same 13 mm. That is real, and it is also why grade is not a free upgrade. Higher grade wire is harder, and harder wire is less forgiving of a worn sheave groove. Match the grade the crane was supplied with unless the maker says otherwise.

The core is what the strands are laid around, and it holds them in position and holds lubricant. A fibre core, marked CF, is natural or synthetic fibre to IS 1804. A steel core, marked CWR, is a small rope in its own right and carries load: the table shows it adding about seven per cent to the breaking force, and it resists crushing where several layers of rope wind on top of each other. A fibre core is more elastic and holds more grease. The two are not interchangeable across the whole range either, since IS 2266 stops the steel core version of 6 x 19 M at 40 mm while the fibre core version runs to 52 mm.

What size hoist rope do Indian pick and carry cranes use?

Thirteen millimetres, on every machine that publishes a figure. The 68 cranes on the books are all pick and carry machines, the type the trade calls a hydra or a Farana, and this is what their hoist specifications state.

The useful thing in that table is the thing that does not change. A 12 tonne Escorts HYDRA 12 and a 25 tonne machine run the same 13 mm rope. What changes with capacity is the number of falls, meaning how many lines of rope run between the boom tip and the hook block. The Escorts HYDRA 14 states six falls on a 12 tonne winch; the Indo Power 30FNX states eight.

Rope length appears on only two of the 68, so plan around that gap. Measure the rope off the machine before ordering, or ask the dealer for the figure against your model and boom length. How the winch, the falls and the hook block work together as a mechanism is set out in hydra and Farana crane parts explained, and the machines themselves are in the pick and carry crane range.

How much can one line of rope lift?

You do not calculate it from scratch. Read the minimum breaking force out of the IS 2266 table for your diameter, construction, grade and core, then divide by a factor of safety. IS 4573 : 2020, the Indian standard for power driven mobile cranes, sets that factor in clause 11.2.1: not less than 4.0 in service for running ropes and for standing ropes passing over pulleys, and 3.0 for a straight standing rope. Clause 11.2.2 allows 3.0 and 2.5 during erection.

Work it through on the 13 mm rope above. A grade 1770 rope with a steel core breaks at no less than 99 kN. Divided by 4.0, one line is good for about 24.8 kN, or roughly 2.5 tonne-force. Clause 11.3 then says that where a load hangs on more than one part of rope, the tension in each part is taken as equal, so four lines come to about 10 tonnes and six to about 15. Those are the winch capacities the specifications publish, which is a sanity check rather than a coincidence.

Three cautions go with that arithmetic, and they matter more than the sum. The specifications do not state the construction, grade or core of the rope fitted, so the figure above is what a 13 mm grade 1770 steel core rope gives, not a measurement of your machine; the rope’s own tag is the authority. The hook block has weight of its own, and it comes off whatever the rope can hold, along with the sling and shackle below it. And rope capacity is not lifting capacity: what the crane may lift at a given radius and boom length is set by the load chart and nothing else. Reading one is covered in how to read a crane load chart, which also lists what gets deducted on site. Never justify a lift with rope arithmetic.

One easily missed figure sits in the same clause. Clause 11.1.1 of IS 4573 requires every splice, socket, thimble and rope anchorage to hold at least 90 per cent of the rope’s own minimum breaking strength. The end fitting is part of the rope, so a hand made termination of unknown strength quietly throws away the factor of safety you just worked out.

Why do the drum and sheaves decide how long a rope lasts?

Because a rope almost never fails in a straight pull. It fails from being bent, and the tighter the bend the sooner. IS 4573 : 2020 puts numbers on the geometry as multiples of the rope diameter d, which for 13 mm work out like this.

Two of those rows have a consequence you can see. A groove worn narrow or gone sharp stops cradling the rope and starts cutting it, so a rope that keeps failing early is often telling you about the sheave rather than about itself. And the dead turns rule explains a feature both TIL cranes list: a third wrap warning, which tells the operator before the rope pays out past the last safe turns on the drum. An anchorage is not designed to hold a load by itself. The related cut-outs and limit switches are explained in crane safety devices, safe load indicators and limit switches.

Clause 11.5 adds the one thing you can control without a spanner: reverse bends are to be avoided as far as possible. A rope bent one way over the boom head and the other way over a second sheave fatigues far faster than one bent the same way throughout. Lubrication matters as well. A rope is greased when it is made, load squeezes that grease out and monsoon rain washes it away, so ask the supplier what dressing penetrates the strands on the rope you bought. Grease points elsewhere on the machine are in greasing a construction machine.

When should a crane wire rope be replaced?

The moment one whole strand breaks, immediately and without discussion. That is the plainest line in IS 3973 : 1984, the Indian code of practice for the selection, installation and maintenance of wire ropes. The rest of its discard section is counting.

The counting rule works on broken wires. Table 6 of that standard sets the number of visible wire ruptures at which a rope is ready for discarding, and it needs two inputs: how many load bearing wires the outer strands carry, and whether the rope is ordinary lay or Lang’s lay. Counts are taken over two reference lengths, 6d and 30d, which on a 13 mm rope means 78 mm and 390 mm.

Find your row from the construction. A 6 x 19 rope carries about 114 wires, so it sits in the 101 to 120 row: five breaks within 78 mm, or ten within 390 mm, and that rope is finished. A 6 x 36 carries about 216 and sits in the 201 to 220 row, at nine and eighteen. Two notes from the standard change those numbers. Filler wires do not count as load bearing, and for constructions with specially thick outer wires, which the standard names as the Seale types, the discard figures drop by two rows. A nest of breaks in one place means discard whatever the count says.

Broken wires are not the only test. Clause 8.2 says no rope should stay in service once the strength lost to wear or corrosion approaches one sixth, or 16 per cent, of the original; once the loss from fatigue, corrosion fatigue, embrittlement or broken wires of any kind approaches one tenth; once the outer wires have lost about a third of their depth; or once the outer wires are loose and displaced. A rope that has taken a severe overwind, overload or shock load comes off unless the affected length can be cut out, and so does any rope that leaves doubt about its safety.

Then there are the shapes, which the standard treats as discard conditions in their own right and which a gloved hand and a slow winch-down will find:

• Cage formation, the bird cage bulge where outer strands lift away from the core
• Loop formation, where wires stand out of the rope like hairpins
• Kinks, flattenings from crushing, and curling from a loaded rope dragged over an edge
• Constrictions, short lengths of reduced diameter, which hide near the end fitting
• Core collapse, where a bent rope stops being round

A hoist rope is not a sling, and their discard rules differ. The broken wire limits for a wire rope sling, with the colour code and capacity of the webbing slings most Indian sites use, are in lifting belt colour code and sling types. Check what the rope runs through as well: a worn hook throat or a hook that no longer swivels freely is its own discard condition, covered in crane hook types, parts and when to replace a hook.

IS 3973 also prints an inspection card in its Appendix C, worth copying onto one sheet per rope. It records the rope’s diameter, construction, lay, core, breaking load and working load, the date it went into service, the measured diameter at each check, and the date and reason for discarding. Two minutes a month on that sheet turns a rope change from a guess into a decision. The wider inspection discipline, including who may operate a crane, is in crane safety rules, checks and operator training.

How do you order the right replacement rope?

Give the supplier all seven items from the tag, not the diameter alone. On a pick and carry crane that reads close to: 13 mm, 6 x 36 SW, grade 1770, steel core, right hand ordinary lay, bright, 80 metres. Then add the two things the tag does not carry.

First, the end termination. Say how the drum end and the hook end are to be finished, and remember clause 11.1.1 of IS 4573: whatever that fitting is, it must hold at least 90 per cent of the rope’s minimum breaking strength. Second, the test certificate. Clause 11.2 of IS 2266 sets the sampling plan for a lot at 100 per cent dimensional checking plus one breaking force test, so a certificate traceable to your reel exists and is worth asking for. Take the old rope’s details off its own tag or the machine’s manual before it goes to scrap, because rebuilding a specification from a worn rope is guesswork.

If you are weighing up a machine rather than a rope, the differences between the pick and carry types are set out in pick and carry cranes in India, and the full range with specifications is in the crane listings. Components and consumables across machine types are indexed in the parts and running costs guide, and the rest of this series sits under the crane guide.

Read next: crane load charts for what the crane may lift, and hydra crane brakes for the other system that holds a load in the air.

Standards cited above: IS 4573 : 2020, Power Driven Mobile Cranes and IS 2266 : 2002, Steel Wire Ropes for General Engineering Purposes. The discard criteria are from IS 3973 : 1984, Code of practice for the selection, installation and maintenance of wire ropes.

Machine figures quoted above are taken from our listings at the time of writing, in October 2026. Prices, specifications and features are indicative, vary by variant, location and date, and should always be confirmed with the official OEM or authorised dealer before any purchase decision. DesiMachines is not liable for decisions taken on the basis of information that may have changed after publication.