16. Use of other mobile plant as a mobile crane21
16.1 Rated capacity of other mobile plant
16.2 Load chart
16.3 Lifting points on earthmoving plant
16.4 Quick-hitches
16.5 Controlled lowering devices
16.6 Competency of operators
Other mobile plant may be used as a mobile crane to lift or lower freely suspended loads (i.e. the load is not pinned to the boom or on tines, but is hanging from the boom by means of a chain or rope). Other mobile plant that is sometimes used in this way includes backhoes, front-end loaders, excavators and telescopic handlers (also known as 'load-alls' and 'tool carriers').
It is important to note that when other mobile plant is used as a mobile crane, the level of safety provided by the lifting set-up should be at least equal to that when a mobile crane is used.
16.1 Rated capacity of other mobile plant
The rated capacity of other mobile plant is the maximum mass that may be handled at the maximum lift point radius, or reach, for each lift point, without the strength and stability requirements being exceeded. When determining the allowable load to be lifted, the mass of any attachments, such as buckets or quick-hitch, must be deducted, unless the rated capacity chart allows otherwise.
To ensure the stability of the mobile plant, the rated capacity of the plant must not be greater than:
- 75% of tipping load in the stationary mode;
- 66% of tipping load in the pick-and-carry mode; or
- 50% of tipping for articulated wheel loaders and tool carriers.
16.2 Load chart
The load chart for the mobile plant should identify each lift point location, and the corresponding rated capacity for each position. The appropriate load chart should be fixed inside the operator's cab and show the following information:
- manufacturer's name and model;
- boom and dipper arm identification and length, particularly where different boom configurations may be used;
- track width, where this is variable;
- deductions for attachments, such as bucket or quick-hitch devices, so that the net allowable load to be lifted can be determined; and
- one of the following:
- the rated load at the least stable position; or
- where variable load rating is provided for, means to clearly determine the load position in accordance with the rated capacity chart.
16.3 Lifting points on earthmoving plant
Lifting attachments on earthmoving plant are sometimes supplied by the plant manufacturer. If this is not the case, the attachments should be designed by an engineer. Lifting attachments often consist of a welded assembly that fits onto the end of the dipper arm when the bucket is removed. All lifting points on earthmoving plant must form a closed eye, to which a load rated shackle may be attached. Figures 7 and 8 provide an example of a lifting attachment with a closed eye.
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Figure 7 and Figure 8 - Lifting attachment with a closed eye on excavator
A static strength test at 200% of the rated capacity of each lift point must be carried out. The lift points should not show any permanent deformation after testing. The test may be performed with the component dismantled from the machine—this should be done if application of the test load could result in damage to the earthmoving plant.
Hooks should not be used on the dipper arm or other attachments of earthmoving plant, because the load may become unintentionally disengaged as the arm rotates. This can even occur when the hook is fitted with a latch, because the latch may be damaged (e.g. with a mobile crane, the hook hangs vertical, with an excavator, the lifting point rotates).
When lifting lugs are welded to attachments or other parts of the earthmoving plant, the material specifications for the two different components are to be compatible for welding, and the appropriate welding procedures must be followed.
The attachment of lifting lugs to buckets is strongly discouraged for the following reasons:
- Application of the lifted load to the outside of the bucket can load the pins and linkages in a way other than the designer intended.
- It is easier for the operator to unintentionally overload the plant by not allowing for the dead weight of the bucket or because the bucket has earth stuck to the inside.
- The lifting chain or sling can be damaged when a bucket is fitted because it may pass over the front edge of the bucket.
- Lifting lugs on buckets may be damaged when the bucket is used for digging activities.
16.4 Quick-hitches
A quick-hitch is a latching device that enables attachments on earthmoving plant to be rapidly connected to the dipper arm of the plant. While the device saves time and effort, a number of fatalities have occurred in Australia when excavator attachments have fallen off the quick-hitch due to loss of hydraulic pressure.
Locking pins are generally used on quick-hitches to ensure the attachment is correctly engaged and remains locked in position on the dipper arm. All quick-hitch devices should be fitted with a locking pin unless the following can be ensured:
- A system is provided to ensure the quick-hitch device is fully engaged on the bucket or other attachment. Note: the system must not rely on the operator carrying out a visual check on the quick-hitch attachment from the operator's cabin.
- Where the quick-hitch latching device relies on stored energy (e.g. hydraulic fluid pressure or a spring) to be activated, the latching device must be designed so that it remains engaged in the event of failure of the source of stored energy (e.g. drop in hydraulic pressure or spring breakage).
- Any factors that will affect the reliability of the latching device are listed in the quick-hitch manufacturer's instruction manual. This includes the need to ensure any contaminants in the hydraulic fluid do not exceed limits as specified by the manufacturer of the pilot-operated check valve, or other equivalent device. Evidence to demonstrate these conditions are being complied with must be provided and kept with the earthmoving plant (e.g. in the plant's logbook).
16.5 Controlled lowering devices
Burst protection must be fitted to the boom and dipper arm (where attached) hydraulics of all mobile plant used as a crane, regardless of the rated capacity of the plant. This protection prevents the boom or dipper arm falling to the ground in an uncontrolled manner, due to failure of a hydraulic hose or another part of the hydraulics system. Burst protection may consist of controlled lowering devices or pilot-operated check valves that sense a differential in hydraulic pressure and lock the boom in position.
Refer to ISO 8643 : Earthmoving machinery – Hydraulic excavator and backhoe loader boom-lowering control device – Requirements and tests (non-Queensland Government link) for information on the design of controlled lowering devices.
16.6 Competency of operators
All operators of mobile plant must receive training in the use of the particular equipment they are required to operate. When the mobile plant is used as a mobile crane, the operator of the mobile plant may require additional training and competencies. In some circumstances, the operator of the mobile plant may also need to hold the appropriate mobile crane certificate of competency.
Since 1996, the 'LE' type national excavator certificate for excavator operators includes basic competencies for earthmoving equipment used as a mobile crane. Where an excavator operator holds an older type of earthmoving equipment certificate, the operator should also hold a slewing mobile crane certificate.
21. Refer to AS 1418.8 : Cranes, hoists and winches – Special purpose appliances (non-Queensland Government link) for further information on the requirements for earthmoving equipment.
Last updated 21 August 2008