Wishbone bale bars - Failure of lifting bars on waste compaction containers
HSE investigated the failure of a wishbone bale bar (also known as a hook bar) and subsequently issued this safety advice on 25 June 2007. This feature can be found on compactors, containers and similar equipment designed to be hoisted onto hook-loader vehicles.
Wishbone bale bars
These bale bars are butt welded to the steel plates of the container. It is a single jointing interface. If the weld fails, there can be sudden and catastrophic failure of the lifting operation.
While wishbone bale bars are NOT inherently unsafe, they are a safety-critical component and should be adequately maintained.
Other designs of bale bars
Designs that conform to the Container Handling Equipment Manufacturers Association (CHEM) Technical Standard TS8 will not fail in a similar manner.
With bale bars manufactured to the CHEM standard, the bar passes through openings in the surrounding side plates and is welded to both inner and outer faces of the supporting plates. Failure of a weld still allows support of the bale bar through the side plate.
Advice for manufacturers
When designing and manufacturing containers fitted with the wishbone bale bar, you should ensure that they are fit for their intended purpose. You should also consider the following:
- installing additional safeguards; or
- stipulating regular inspections of the wishbone bale bar. (The time period between inspections should be based on calculations of the anticipated loads, stresses and strains, corrosion, deterioration and safety factors used in the design process.) The methods of inspection should also be stipulated, for example NDT testing methods.
Advice for importers, hirers and suppliers
Importers, hirers and suppliers of equipment with the wishbone bale bar should clarify the purpose for which the equipment was designed with the manufacturer – this must be reflected in the maintenance instructions. You must then pass this information on to customers so that they only use the equipment for its intended purpose.
Advice for users
You are responsible for maintenance of work equipment. Where equipment is on hire, you should clarify the contractual arrangements for maintenance. Details of the service life should be given to you.
Any maintenance and inspection regime should be based on the manufacturers' recommendations – you are advised to approach them for this information. You will still need to carry out a risk assessment, taking into account the intensity of use, operating environment and variety of operations.
Depending upon the manufacturers' recommendations, maintenance may involve more detailed testing of components (eg non-destructive testing) instead of placing sole reliance on a visual inspection.
Advice for those handling container units
You must carry out a visual check on the balebar before attempting to lift the unit. This should be carried out regardless of configuration. Pre-use checks by the transporter driver are not a substitute for maintenance.
Stating the laden weight of the compaction skip or container
The laden weight of the container (or combined compaction skip and container) should be clearly stated to ensure that the balebar (which is considered to be part of the load being lifted), welds, sideplates and other components are correctly engineered.
Manufacturers, suppliers and users should be aware of the laden weight of containers and ensure that the equipment has been designed for its intended use and that it is maintained accordingly.
Container units should not be overloaded and lifting equipment should be capable of lifting the maximum stated laden weight of the container.