The following Instructions and Warnings combine to provide guidance on Product Safety and are intended for use by those already having a working knowledge of wire ropes, as well as the new user. They should be read, followed and passed on to others.
Failure to read, understand and follow these instructions could result in harmful and damaging consequences.
1. Rope Selection Criteria
Ensure that the correct type of wire rope is selected for the equipment by referring to the OEM’s instruction manual or other relevant documents. If in doubt contact Bridon for guidance.
1.1 Rope Strength
If necessary, refer to the appropriate Regulations and application standards and calculate the maximum force to which the rope will be subjected. The calculation may take into account the mass to be lifted or moved, any shock loading, effects of high speed, acceleration, any sudden starts or stops, the frequency of operation and sheave bearing friction. By applying the relevant design factor and, where applicable, the efficiency of the rope termination, the required minimum breaking load or force of the rope will be determined, the values of which are available from the relevant National or International standards or specific Product Data literature. If in doubt ask for advice from Bridon.
1.2 Bending fatigue
The size and number of sheaves in the system will influence the performance of the rope.
Wire rope which bends around sheaves, rollers or drums will deteriorate through ‘bending fatigue.’ Reverse bending and high speed will accelerate the process. Therefore, under such conditions select a rope with high bending fatigue resistance. Refer to Product Data Information, and if in doubt ask for advice.
1.3 Abrasion
Wire rope which is subject to abrasion will become progressively weaker as a result of:
Externally - dragging it through an overburden, sand or other abrasive materials and passing around a sheave, roller or drum.
Internally - being loaded or bent.
Abrasion weakens the rope by removing metal from both the inner and outer wires. Therefore, a rope with large outer wires should normally be selected.
1.4 Vibration
Vibration in wire rope will cause deterioration. This may become apparent in the form of wire fractures where the vibration is absorbed. These fractures may be internal only and will not be visually identified.
1.5 Distortion
Wire rope can be distorted due to high pressure against a sheave, improperly sized grooves or as a result of multi-layer spooling on a drum. Rope with a steel core is more resistant to crushing and distortion.
1.6 Corrosion
Rope with a large number of small wires is more susceptible to corrosion than a rope with a small number of large wires. Therefore, if corrosion is expected to have a significant effect on rope performance. The rope may have to be lubricated frequently in service, or a galvanized rope may be selected.
1.7 Cabling
‘Cabling’ of rope reeving due to block rotation can occur if the rope is incorrectly selected. Applications involving high lifts are particularly vulnerable to this condition, therefore, ropes specifically designed to resist rotation need to be selected.
1.8 Fixing of Rope Ends
Ropes which have high rotation characteristics must not be selected unless both ends of the rope are fixed, or the load is guided and unable to rotate.
1.9 Connecting Ropes
If it is necessary to connect one rope to another (in series) it is essential that they have the required strength, are of the same type, and both have the same lay direction (i.e., connect ‘right’ lay to ‘right’ lay).
Failure to heed this warning could result in catastrophic failure particularly at a termination which is capable of being pulled apart (i.e., splice) due to unlaying.
1.10 Rope Length
Rope length and difference in length between two or more ropes used in a set may be a critical factor and must be considered along with rope selection.
Wire rope will elongate under load. Other factors such as temperature, rope rotation, and internal wear will also affect. These factors should also be considered during rope selection.