Unloading onto a surface that is not level is the main cause of dump trucks of all types tipping over.
A RISING TREND of accidents with dump trucks around the world has encouraged various national construction organizations to issue general advice about safe use of these machines. This is fully supported by the manufacturers, many of whom encourage customers to undergo training.
The main danger is of the truck tipping over when it is in the active raised position, and the advice applies to dumpers of all types--rigid road-going trucks, semi-trailers, off-road articulated dump trucks (ADTs) and even small site dumpers and appropriately-equipped pick-up trucks and trailers.
The risk comes from the centre of gravity of the loaded dumper or combination being raised beyond a safe level and outside the dimensions of the frame when the load area or 'box' is being prepared for tipping. This situation can arise silently and unexpectedly, especially if the operator has no idea of the weight of material he is handling. And this dangerous condition is particularly likely to be reached if the to-be-dumped material sticks to the top of the load-carrying container.
The problem gets much worse if the dumper is not on a stable level surface when the box is raised, when material flows out unevenly or the rear wheels do not settle evenly as the load is transferred and reduced. These conditions are exacerbated if the suspension system of the dump truck is in poor condition (especially if one side is worse than the other), if the hydraulic lifting cylinder(s) are not working smoothly and properly or if the tire pressures are not matched equally side for side.
To prevent some of these problems developing dump truck load areas should always be emptied out overnight and, if possible, hosed down to prevent sticking of material, too. All mechanical damage that prevents free movement of material in the box should be repaired as soon as it is noticed.
Safe loads
When filling up a dump truck without an onboard load-checking and warning system the operator should always be shown clearly what is an acceptable safe limit for the material being conveyed; remember that wet sand is much heavier than dry, for example. With big machines especially always try to ensure that the box is trimmed side to side as it is loaded so that the weight is continually distributed as evenly as possible.
Pressure should never be put on to the operator or loader to exceed the safe limit; it costs far less to make more delivery trips than to pay for all the costs that a dump truck tip-over will produce--including machine and construction site downtime.
Operators of small multi-purpose dumpers--those based on roadworthy pick-up trucks, for example--often choose to fit load-area liners to their vehicles or tipping trailers. Not only do these keep the machines clean and ready to handle the next job but they can help the material to flow out smoothly and therefore safely, too. These liners can be supplied to fit most of the bigger machines. Many contractors fabricate their own or carry suitable plastic sheeting for use when needed.
When the dump truck driver arrives at the dumping site he should know what he is looking for in terms of a safe area to unload; this is not a job for an unskilled operator. The hand-braked vehicle should be on level ground that is evenly compacted so that the wheels on one side do not sink in. This is especially important if a worked-over landfill site is being used. Inspect the unloading area by walking over it first, especially for voids. Landfill sites are notorious for these.
Unlock the tailgate
Always make sure that the tailgate fastening mechanism is fully unlocked before starting to raise the tipping body; failure to do this could both damage the mechanism and destabilize the tipper. It is common to spread the unloaded material out by driving the vehicle forward with the body raised; this is fine as long as the complete length of straight run is clear. It should be reasonably level too.
It is obvious from the above that maintenance of the dump truck is critical to the safety of the dumping operation. Apart from the points already mentioned operators should make sure that all tire pressures are checked every day, with particular care being taken that they are equal on both sides of the dumper. In the same way the suspension system should be inspected regularly for both adequate performance under load, and for matching from side to side. So should the hydraulic pressure system that operates the box-raising mechanism, with particular attention being paid to the condition of the operating cylinder or cylinders.
Keep the tipper body itself in good clean mechanical condition with all physical damage put right before the machine is put away for the night. Major repairs should be entrusted to a competent welder.
Operating one of these machines is a skilled job which needs both common sense and training as the extent of the risk (and its unseen increase as the box is raised) is not always obvious. And, as with all other types of earthmoving equipment, tired operators are the ones who are most likely to make mistakes.
Experience shows that it is not just the operator of the dump truck who is at risk, however. Other site personnel can get in the way so those working on foot should be warned to keep away both from the dumping site and from the route to it.
Skilled operators also know to make sure they are not required to unload when another earthmoving vehicle is parked or operating alongside as a tipping dumper can cause serious damage to one of these--and to its operation.
2007 Alain Charles Publishing Ltd.
A RISING TREND of accidents with dump trucks around the world has encouraged various national construction organizations to issue general advice about safe use of these machines. This is fully supported by the manufacturers, many of whom encourage customers to undergo training.
The main danger is of the truck tipping over when it is in the active raised position, and the advice applies to dumpers of all types--rigid road-going trucks, semi-trailers, off-road articulated dump trucks (ADTs) and even small site dumpers and appropriately-equipped pick-up trucks and trailers.
The risk comes from the centre of gravity of the loaded dumper or combination being raised beyond a safe level and outside the dimensions of the frame when the load area or 'box' is being prepared for tipping. This situation can arise silently and unexpectedly, especially if the operator has no idea of the weight of material he is handling. And this dangerous condition is particularly likely to be reached if the to-be-dumped material sticks to the top of the load-carrying container.
The problem gets much worse if the dumper is not on a stable level surface when the box is raised, when material flows out unevenly or the rear wheels do not settle evenly as the load is transferred and reduced. These conditions are exacerbated if the suspension system of the dump truck is in poor condition (especially if one side is worse than the other), if the hydraulic lifting cylinder(s) are not working smoothly and properly or if the tire pressures are not matched equally side for side.
To prevent some of these problems developing dump truck load areas should always be emptied out overnight and, if possible, hosed down to prevent sticking of material, too. All mechanical damage that prevents free movement of material in the box should be repaired as soon as it is noticed.
Safe loads
When filling up a dump truck without an onboard load-checking and warning system the operator should always be shown clearly what is an acceptable safe limit for the material being conveyed; remember that wet sand is much heavier than dry, for example. With big machines especially always try to ensure that the box is trimmed side to side as it is loaded so that the weight is continually distributed as evenly as possible.
Pressure should never be put on to the operator or loader to exceed the safe limit; it costs far less to make more delivery trips than to pay for all the costs that a dump truck tip-over will produce--including machine and construction site downtime.
Operators of small multi-purpose dumpers--those based on roadworthy pick-up trucks, for example--often choose to fit load-area liners to their vehicles or tipping trailers. Not only do these keep the machines clean and ready to handle the next job but they can help the material to flow out smoothly and therefore safely, too. These liners can be supplied to fit most of the bigger machines. Many contractors fabricate their own or carry suitable plastic sheeting for use when needed.
When the dump truck driver arrives at the dumping site he should know what he is looking for in terms of a safe area to unload; this is not a job for an unskilled operator. The hand-braked vehicle should be on level ground that is evenly compacted so that the wheels on one side do not sink in. This is especially important if a worked-over landfill site is being used. Inspect the unloading area by walking over it first, especially for voids. Landfill sites are notorious for these.
Unlock the tailgate
Always make sure that the tailgate fastening mechanism is fully unlocked before starting to raise the tipping body; failure to do this could both damage the mechanism and destabilize the tipper. It is common to spread the unloaded material out by driving the vehicle forward with the body raised; this is fine as long as the complete length of straight run is clear. It should be reasonably level too.
It is obvious from the above that maintenance of the dump truck is critical to the safety of the dumping operation. Apart from the points already mentioned operators should make sure that all tire pressures are checked every day, with particular care being taken that they are equal on both sides of the dumper. In the same way the suspension system should be inspected regularly for both adequate performance under load, and for matching from side to side. So should the hydraulic pressure system that operates the box-raising mechanism, with particular attention being paid to the condition of the operating cylinder or cylinders.
Keep the tipper body itself in good clean mechanical condition with all physical damage put right before the machine is put away for the night. Major repairs should be entrusted to a competent welder.
Operating one of these machines is a skilled job which needs both common sense and training as the extent of the risk (and its unseen increase as the box is raised) is not always obvious. And, as with all other types of earthmoving equipment, tired operators are the ones who are most likely to make mistakes.
Experience shows that it is not just the operator of the dump truck who is at risk, however. Other site personnel can get in the way so those working on foot should be warned to keep away both from the dumping site and from the route to it.
Skilled operators also know to make sure they are not required to unload when another earthmoving vehicle is parked or operating alongside as a tipping dumper can cause serious damage to one of these--and to its operation.
2007 Alain Charles Publishing Ltd.
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