Wire Ropes
Introduction
Wire ropes which are often used by cranes. It consists of several strands of metal wire that are twisted into a helix to form a composite rope known as a wire rope.
Thumb Rule: Safe Working Load (SWL) of Manila rope (new rope) square for the rope diameter in mm gives safe working load in KG [D2 mm = SWL (Kg)].
Rope Size Square (Diameter)
12 mm 12X12 144 Kgs
16 mm 16X16 256 Kgs
24 mm 24X24 576
Kgs
Steel Wire Ropes:
These are commonly used in the industry. Ropes made of natural fibers; silica ropes have a limited use. Steel wire ropes find usage in lifting tackle, rope ways, in lifts, cranes and handling lifting operation.
Thumb rule for wire rope is D2X8. One rope lay of a size strand rope each strand have 37 wires. Rope is 6 X 37 = 222 wire in total.
Wire ropes are 8, 10, 12, 16, 25, 50 mm in diameters. If a wire rope is 10 mm, then can lift:
D2X8 = 10 X 10
X 8 = 800 Kg Where, D is Diameter.
In a wire rope, there are 6 strands and each strands have 37 wires so the total wires in a wire rope are, 37 X 6 = 222 wires
Manila ropes are plastic ropes, and its formula is D2, therefore:
10X10=100 Kgs.
1) Handling of steel wire rope should be proper so that neither kink develop nor un-twisting of strands occurs.
2) Bending action on the rope must be avoided especially reverse bending that will induce fatigue in the materials.
3) Through inspection must be carried out at regular interval. So that any over knot or the rope under distress must be immediately remove.
4) Maintenance of steel wire rope must be done regularly.
5) Wire rope must be inspected once in six months by a competent person and recorded in the register.
Wire Rope Inspection
1) Rope on the drum.
2) Pick up point of the load.
3) Rope through pulley.
4) Rope through blocks.
5) Rope attachments.
Defects in Wire Ropes
1. Broken Wire: In all strands in a length to 8 diameters 10% of the wire damages shall be replaced.
2. Wear: It must be replaced if the diameter reduced by more than 15% from normal diameter.
3. Corrosion: It is more dangerous than wear.
4. Bird caging: Due to slipping of strands they open up. Also caused by end of rope being allowed to rotate.
5. Kinks: Caused by faulty handling.
Chains: Chains are used for slings, hoists, marine uses, etc. made from wrought iron and free from mixture of iron scrap or steel and in lap fine welded and safe practice in the use of chain requires that the no load should be even raised with kink twist, knot or twist in the chain. Inspection of all hoisting chains should be performed regularly and frequently.
Lifting Procedure: While initiation of lifting material must lift at 1 ft of height for check the status of material then lift till 6 ft, if the material and steering control found normal then transportation should commence as per instructions.
“Safe Degree Angle” have all details about angle of hook in a chart mentioned everything which is required.