The use of cranes and lifting equipment remains an integral part of our daily life, enabling the efficient transportation of materials, development of our communities and the provision of our energy. Ever increasing demands are being placed upon wire ropes, crane and load sizes are increasing, environmental factors are becoming more varied, and a greater number of operations are happening offshore and in coastal environments. While the design of wire rope is highly efficient for lifting, hoisting, and supporting structures within a crane, it can however be susceptible to damage from fatigue-failure, external abrasion, corrosion, shock loading and mechanical damage. Wire rope accounts for a significant investment in crane costs, while with a lack of maintenance and awareness they can also become a critical point of failure. Ropes can operate under constant stresses, undergoing repeated elongation and contraction while being exposed to debris, environmental factors, and operator misuse. For this reason, it is imperative that regular checks are performed to assess rope condition, identify issues early and to monitor the condition of auxiliary support structures, such as reeves, drums, etc.
In this blog post, we discuss the dangers of not maintaining wire ropes, the essential daily checks to be performed and best practices for maintaining a safe and reliable wire rope.
The Dangers of not properly maintaining crane wire ropes
The failure of a wire rope can have catastrophic consequences, be it interrupted operations, property damage, injuries and even fatalities. However, with greater awareness, regular inspections and maintenance, these catastrophic failures can be avoided.
- Corrosion causing strand breaks can be one of the most difficult failure modes to identify as it typically occurs from within. Pitting on the surface of individual strands will give some indication, while a change to rope diameter gives an indication of the core structure. Inappropriate or poor lubrication can hasten a corrosion failure, while little or no lubrication will offer limited protection, wax-based build lubricants (used during the rope manufacture) can entrain corrosion elements within the rope and increase the rate of failure.
- External abrasion failures occur through irregular contact with sheaves, drums and potentially other protruding parts of the crane structure. Misalignment and poorly grooved drums and sheaves can hasten this failure mode.
- Fatigue-failure is likely to result from the repetitive bending over sheaves and drums, where repeated, elongation and contraction results in metal-to-metal contact and subsequent wire failure. This is often visible on the outer wires in section that frequently move over the sheaves. When a wire break appears, more will follow!
- Shock loading can expose wire rope to forces double the static load and while cranes are designed to take a load gradually and steadily, this cannot always be avoided.
Daily inspections are used to identify issues before becoming critical, allowing you to address them promptly.
Essential daily checks for crane wire ropes
Some of the essential daily checks to be performed by the crane operator include:
- Visual inspection (certain areas require greater attention).
- Check for deformations: Check the wire rope for any signs of deformations, including birdcages, kinks, or twists. These deformations can cause the wire rope to weaken and fail, so it’s essential to address them immediately.
- Checking for abrasions: Look for any signs of abrasion on the wire rope, particularly wire breaks in the most frequently stressed rope zone. Abrasions can be caused by contact with other objects, and they can weaken the wire rope, making it more susceptible to failure.
- Checking for corrosion: Check for any signs of corrosion on the wire rope. Corrosion weakens the wire rope, making it more likely to fail.
- Checking for proper tensioning: Proper tensioning of the wire rope is critical to prevent it from slipping or coming off the sheave. Check that the wire rope is correctly tensioned, and if necessary, adjust it.
- Checking for proper lubrication and the amount visible on the rope surface: Proper lubrication is essential for the safe operation of crane wire ropes. Check that the wire rope is adequately lubricated, and if necessary, apply lubricant to any areas that need it.
- Is the reeving correct.
Best practices for maintaining a safe and reliable crane wire rope
In addition to daily checks, several best practices to follow for maintaining safe and reliable crane wire rope, including:
- Conducting regular inspections: In addition to daily inspections, a competent person should conduct regular more thorough inspections to identify issues before they become critical. These can be monthly or quarterly depending on load, frequency of use and environmental factors.
- Measure rope diameter with suitable equipment at various strategic locations, you should also be aware of the installation diameter.
- Measure rope lay length.
- Measure groove diameter and depth of supporting equipment.
- Address issues promptly: If you identify an issue with the wire rope, address it immediately. Don’t delay repairs or maintenance, as this could increase the risk of failure.
- Selection of the appropriate build lubricant and subsequent relubrication to boost performance.
- Providing appropriate training: Ensure that anyone operating the crane or works with the wire rope is properly trained on how to inspect and maintain it.
- Keeping detailed records: Keeping detailed records of all inspections, repairs, and maintenance performed on the wire rope.
- Following the manufacturer’s guidelines.
While a high-functioning rope lubricant cannot prevent all failure modes, it can act to protect against the main ones and significantly extend rope life. Ensure your lubricant has a suitable corrosion inhibitor present. Look for tests ASTM B117.
While fourball wear scar (IP 239) gives an indication of both external abrasion and fatigue-failure, protection while fourball weld load (IP 239) will indicate performance against shock loading.
Question what build lubricant is being used during manufacture; frequently this is selected for ease of application and not the performance offered to the end user. Request information on the above tests for comparison and remember wax-based ‘lubricants’ can actually have a negative impact on rope life. Lubricant retention is also critical (ASTM D4049). Therefore, ensure either your advised build lubricant or selected dressing lubricant (boosting protection) remains on the rope for prolonged performance.
Wire ropes are critical components of cranes and other lifting equipment. Failure to maintain them properly can have severe consequences. Regular maintenance and daily inspections are essential to prevent wire rope failure. Following the essential daily checks and best practices outlined in this blog post, can maintain a safe and reliable wire rope, minimising the risk of accidents, injuries and property damage.