What would happen if one of the four hoists used to suspend the clock had a load brake fail? Would the clock come down on the players?
If a load brake fails the wire rope will free-wheel allowing that portion of the clock to lower if more than one hoist is used. When it stops, it would probably shock load the hoist causing other components to be overloaded and fail also. If the hoist did not have any other failures, then the off balance load will change the tension on the wire ropes still suspending the load.
The lifting gear could be overloaded causing the wire rope to fail, dropping another portion of the clock if, say, four hoists are used. This could keep happening until all the hoists fail and the clock comes down to the ground. If only one hoist is used then the load could free wheel down to the ground after the first failure.
Death trap: Electronic display clocks are heavy, yet they are usually suspended with overhead hoists alone, without safety lines or fail safe mechanisms
What would cause the load brake to fail?
Primarily a lack of maintenance and inspection. Oil leaking into the brake compartment due to a dried up seal could cause a load brake to fail. Hoists located near the roof are usually warm due to the fact that hot air rises. This environment causes the viscosity of oil to change allowing it to leak out of the gearbox and into the brake compartment, especially if there is a dried up seal.
Humidity can cause corrosion to non-lubricated components that are critical to carry the weight of the load. Wire ropes are the most common component to be affected by corrosion. Bearings tend to get flat spots if they are not working and corrosion can cause the bearings to seize if not lubricated according to the manufacturer’s specifications.
Shock loading the hoists during clock maintenance could also cause a failure, while brittle brake linings can fail due to age and condition.
What can be done to prevent the clock from falling in the event of mechanical failure?
It is feasible to use the hoists to raise and lower the clock whenever necessary. Once the clock is at its required height the weight needs to be relieved from the hoists. Securing the clock can be done by locking the clock to a frame mounted to the building designed and engineered to support the clock safely.
Why do builders ignore manufacturers’ recommendations, specifications, information and warnings?
Manufacturers provide as much information as possible to ensure their product is used properly and for the purpose it was designed for. Manufacturers cannot guarantee that a hoist will be able to support the load at all times and in all situations. That is why you will find a section in the owner’s manual invariably entitled “do’s and don’ts”. One of the don’ts is often “never allow anyone to walk or stand under a suspended load”. Hoists are designed to raise and lower loads on a regular basis, not designed to suspend loads for a long period of time. You see the problem with the electronic display clocks in question.
Would a hazard assessment have prevented this practice from occurring?
Yes, but only if the person performing the hazard assessment has the knowledge and experience to recognise the hazard.
Who should first notice a potentially hazardous situation?
Crane inspectors, crane technicians, safety consultants, structural and mechanical engineers.
In summary, a building owner should provide documented evidence of competent operator training as well as inspection and maintenance reports of the hoists, in this case to the owner of the sports team, to ensure the safety of the clock. When it comes to non-standard rigging there needs to be someone qualified, knowledgeable, experienced and confident to control the lift, often referred to as the lift director.
The same goes when you build a garage; you must have an engineered drawing or an approved plan before a building permit is issued. There needs to be a control in place to ensure all safety and building standards are met.
Lifting a load around people is a critical lift and requires a formal plan from a lift director or a professional engineer. Get an engineer’s stamp of approval and remove your liability from the situation.
Lisa Olver
To respond or put questions to Lisa Olver or co-author Judy Mellott please contact Hoist editor Richard Howes at rhowes@wilmington.co.uk, or get in touch directly at: All Canadian Training Institute inc. (ACTI), 100 10405 178 street Edmonton, Alberta, Canada T5S 1R5. Mellott can also be reached at judy.mellott@telusplanet.net.
