Unfortunately, hoist wire ropes do fail. And when they do, the incidents are dangerous and can have very serious consequences. Since July 2013, the Australian Government has been notified of 46 events involving injury or the risk of serious injury by objects falling from a crane. There are preventative measures in place that hoist operators can take to reduce risk and improve the safety of their operations. These are the main causes of hoist failure and how to troubleshoot them.
Before Commencing Overhead Crane Operations
Before commencing any industrial operation involving the use of an overhead crane, you should obtain the following:
- Written verification from the crane manufacturer that the type of rope can be used in conjunction with the tower crane.
- An inspection of the steel wire from a third party company which holds a National Association of Testing Authorities accreditation.
Causes of Hoist Failure
A wire rope hoist requires careful selection, installation as well as maintenance. If these processes are done incorrectly, the lifespan of the rope will be significantly shorter. This is because of the way hoists operate. When wire rope is used in hoisting applications, the rope is required to bend around the drum and sheave. This movement causes friction and as a result, requires proper lubrication to allow the rope to operate effectively. Common causes of wire rope hoist failure include:
- Core Protrusion
- Corrosion (ie. improper lubrication or by operating in a coastal environment)
- Fatigue (ie. operating beyond the hoist’s operational cycle)
- Tension (ie. overloading of rope)
Routine inspections performed by a qualified inspector are essential to identify the above risks of failure. If the condition of the rope indicates any sign of potential failure, the rope can be replaced before the failure occurs.
Troubleshooting Hoist Wire Rope Failures
Failure by Abrasion
Wire rope can break when it has been damaged by contact with the hoist drums or sheaves or has struck an external object. The abrasion of hoist wire ropes is externally visible and can be identified by thinned wire.
Troubleshooting Abrasion Damage
- Improperly grooved sheaves and drums
- Frozen sheaves or rollers
- Improper fleet angle
- Improper sheave rotation
- Incorrect rope size
Failure by Core Protrusion
Core protrusion can be caused by improper installation or shock loading. Wire rope core protrusion refers to when the core slips and protrudes from the rope, caused when the outer strands shorten in length. This is risky as it creates an uneven distribution of load to the strands and can reduce the lifespan of the rope.
Troubleshooting Core Protrusion
- Twists in the rope during installation
- Improper seizing techniques
- Shock loading
Failure by Corrosion
Corrosion of wire rope can be internal or external and is typically caused by improper lubrication or environmental factors such as salt concentration in coastal air. This can be identified by surface oxidation (ie. rust), heavy pitting or presence of corroded matter (red dust). Corrosion can be incredibly dangerous and steps should be taken to discard the rope if corrosion is severe.
Troubleshooting Rope Corrosion
- Poor lubrication
- Improper storage
- Environmental damage
Failure by Fatigue
Wire rope fatigue occurs when individual wires lose their ability to bend. This is typically caused by the conditions which the rope operates, including any factor that restricts the movement of wires (ie. direct contact with the sheave). While all wire ropes are subject to fatigue, the severity may be accelerated by abrasion, kinking or nicking damage.
- Undersized sheaves
- Misaligned sheaves
- Improper sheave maintenance
- Tight grooves
- Lack of lubrication
Failure by Tension
Tension is caused by shock loading or overloading the wire rope. Ropes subject to a high amount of tension fatigue have a tendency to fail from the inside out. This damage is caused by overloading or shock even if the weight being lifted is less than the rope’s capacity.
- Change of load balance
- Unstable load
- Rapid load reduction
- Sudden changes in speed while lifting and lowering
Recommendations to Avoid Hoist Failure
Hoist failure can almost always be avoided if the operators are well-trained in risk management procedures. Here’s what we recommend:
- Perform frequent inspections
- Always document inspection and maintenance records
- Have load test certificates available
- Ensure warning and safety labels are available
- Identify field hazards and reduce them prior to or during tasks
- Listen for and assess unusual sounds
Contact Winch Hire Australia for Your Next Project
Winch Hire Australia has remained industry leaders for over twenty years due to our experience, quality of service and commitment to safety. We provide a range of hoists available for hire and also the technical support needed to ensure your project succeeds. Part of our after-sales service includes offering quality assured spare parts with quick delivery and also upgrading your hoisting equipment as required.
If you have any questions regarding hoist failure or would like to hire equipment for your next project, please don’t hesitate to get in touch.