Manual and mechanical handling hazards and control
10.5 Types of mechanical handling and lifting equipment
There are four elements to mechanical handling, each of which can present hazards. These are handling equipment, the load, the workplace and the employees involved.
The mechanical handling equipment must be capable of lifting and/or moving the load. It must be fault-free, well maintained and inspected on a regular basis. The hazards related to such equipment include collisions between people and the equipment and personal injury from being trapped in moving parts of the equipment (such as belt and screw conveyors).
The load should be prepared for transportation in such a way as to minimize the possibility of accidents.
The hazards will be related to the nature of the load (e.g.
substances which are fl ammable or hazardous to health) or the security and stability of the load (e.g. collapse of bales or incorrectly stacked pallets).
The workplace should be designed so that, whenever possible, workers and the load are kept apart.
If, for example, an overhead crane is to be used, then people should be segregated away or barred from the path of the load.
The employees and others and any other people who are to use the equipment must be properly trained and competent in its safe use.
10.5.1 Conveyors and elevators
Conveyors transport loads along a given level which may not be completely horizontal, whereas elevators move loads from one level or fl oor to another.
There are three common forms of conveyor – belt, roller and screw conveyors. The most common hazards and preventative measures are:
➤ the in-running nip, where a hand is trapped between the rotating rollers and the belt. Protection from this hazard can be provided by nip guards and trip devices
➤ entanglement with the power drive requiring the fi tting of fi xed guards and the restriction of loose clothing which could become caught in the drive
➤ loads falling from the conveyor. This can be avoided by edge guards and barriers
➤ impact against overhead systems. Protection against this hazard may be given by the use of bump caps, warning signs and restricted access
➤ contact hazards prevented by the removal of sharp edges, conveyor edge protection and restricted access
➤ manual handling hazards
➤ noise and vibration hazards.
Screw conveyors, often used to move very viscous sub- stances, must be provided with either fi xed guards or covers to prevent accidental access. People should be prohibited from riding on belt conveyors and emergency trip wires or stop buttons must be fi tted and be oper- ational at all times.
Elevators are used to transport goods between fl oors, such as the transportation of building bricks to upper storeys during the construction of a building or the transportation of grain sacks into the loft of a barn.
Guards should be fi tted at either end of the elevator and around the power drive. The most common hazard is injury due to loads falling from elevators. There are also
Ch10-H8503.indd 149
Ch10-H8503.indd 149 7/27/07 4:24:37 PM7/27/07 4:24:37 PM
150
potential manual handling problems at both the feed and discharge ends of the elevator.
10.5.2 Fork lift trucks
The most common form of mobile handling equipment is the fork lift truck (Figures 9.6 and 10.10). It comes from the group of vehicles, known as lift trucks, and can be used in factories, on construction sites and on farms. The term fork lift truck is normally applied to the counterbalanced lift truck, where the load on the forks is counterbalanced by the weight of the vehicle over the rear wheels. The reach truck is designed to operate in narrower aisles in warehouses and enables the load to be retracted within the wheelbase. The very narrow aisle (VNA) truck does not turn within the aisle to deposit or
retrieve a load. It is often guided by guides or rails on the fl oor. Other forms of lift truck include the pallet truck and the pallet stacker truck, both of which may be pedes- trian or rider controlled.
There are many hazards associated with the use of fork lift trucks. These include:
➤ overturning – manoeuvring at too high a speed (par- ticularly cornering), wheels hitting an obstruction such as a kerb, sudden braking, poor tyre condition leading to skidding, driving forwards down a ramp, movement of the load, insecure, excessive or uneven loading, incorrect tilt or driving along a ramp
➤ overloading – exceeding the rated capacity of the machine
Figure 10.8 Conveyor systems: (a) Roller conveyor (these may have powered and free running rollers); (b) An overhead conveyor handling wheels. Other designs of overhead conveyor are useful for transferring components and garments between workstations, in for example manufacture of machines or clothing: (c) A slat conveyor in use in the food industry.
(c)
(a) (b)
Ch10-H8503.indd 150
Ch10-H8503.indd 150 7/27/07 4:24:37 PM7/27/07 4:24:37 PM
Manual and mechanical handling hazards and control
151
➤ collisions – particularly with warehouse racking which can lead to a collapse of the whole racking system
➤ silent operation of the electrically powered fork lift truck – can make pedestrians unaware of its presence
➤ uneven road surface – can cause the vehicle to overturn and/or cause musculoskeletal problems for the driver
➤ overhead obstructions – a particular problem for inexperienced drivers
➤ loss of load – shrink wrapping or sheeting will reduce this hazard
➤ inadequate maintenance leading to mechanical failure
➤ use as a work platform
➤ speeding – strict enforcement of speed limits is essential
➤ poor vision around the load
➤ pedestrians – particularly when pedestrians and vehicles use the same roadways. Warning signs, indicating the presence of fork lift trucks, should be posted at regular intervals
➤ dangerous stacking or de-stacking technique – this can destabilize a complete racking column
➤ carrying passengers – this should be a disciplinary offence
➤ battery charging – presents an explosion and fi re risk
➤ fi re – often caused by poor maintenance resulting in fuel leakages or engine/motor burn-out, or through using a fork lift truck in areas where fl ammable liquids or gases are used and stored
➤ lack of driver training.
If fork lift trucks are to be used outside, visibility and lighting, weather conditions and the movement of other vehicles become additional hazards.
There are also the following physical hazards:
➤ noise – caused by poor silencing of the power unit
➤ exhaust fumes – should only be a problem when the maintenance regime is poor
➤ vibrations – often caused by a rough road surface or wide expansion joints. Badly infl ated tyres will exacer - bate this problem
➤ manual handling – resulting from manoeuvring the load by hand or lifting batteries or gas cylinders
➤ ergonomic – musculoskeletal injuries caused by soft tyres and/or undulating road surface or holes or cracks in the road surface (e.g. expansion joints).
Regular and documented maintenance by competent mechanics is essential. However, the driver should under- take the following checks at the beginning of each shift:
➤ condition of tyres and correct tyre pressures
➤ effectiveness of all brakes
➤ audible reversing horn and light working properly Figure 10.9 A brick elevator.
Figure 10.10 Reach truck designed so that the load retracts within the wheelbase to save space.
Ch10-H8503.indd 151
Ch10-H8503.indd 151 7/27/07 4:24:38 PM7/27/07 4:24:38 PM
152
➤ lights, if fi tted, working correctly
➤ mirrors, if fi tted, in good working order and properly set
➤ secure and properly adjusted seat
➤ correct fl uid levels, when appropriate
➤ fully charged batteries, when appropriate
➤ correct working of all lifting and tilting systems.
A more detailed inspection should be undertaken by a competent person within the organization on a weekly basis to include the mast and the steering gear. Driver training is essential and should be given by a competent trainer. The training session must include the site rules covering items such as the fork lift truck driver code of practice for the organization, speed limits, stacking pro- cedures and reversing rules. Refresher training should be provided at regular intervals and a detailed record kept of all training received. Table 10.1 illustrates some key requirements of fork lift truck drivers and the points listed should be included in most codes of practice.
Finally, care must be taken with the selection of drivers, including relevant health checks and previous experience. Drivers should be at least 18 years of age
and their fi tness to drive should be reassessed at three- yearly intervals.
10.5.3 Other forms of lifting equipment
The other types of lifting equipment to be considered are cranes (mobile overhead and jib), lifts and hoists and lift- ing tackle.
Cranes may be either a jib crane or an overhead gantry travelling crane. The safety requirements are similar for each type. All cranes need to be properly designed, constructed, installed and maintained. They must also be operated in accordance with a safe system of work.
They should only be driven by authorized persons who are fi t and trained. Each crane is issued with a certifi cate by its manufacturer giving details of the safe working load (SWL). The safe working load must never be exceeded and should be marked on the crane structure. If the safe working load is variable, as with a jib crane (the safe working load decreases as the operating radius increases), a safe working load indicator should be fi tted.
Care should be taken to avoid sudden shock loading since this will impose very high stresses to the crane structure. It is also very important that the load is properly shackled and all eyebolts tightened. Safe slinging should be included in any training programme. All controls should be clearly marked and be of the ‘hold to run’ type.
Large cranes, which incorporate a driving cab, often work in conjunction with a banksman who will direct the lifting operation from the ground. It is important that banksmen are trained so that they understand recognized crane signals.
The basic principles for the safe operation of cranes are as follows. For all cranes, the driver must:
➤ undertake a brief inspection of the crane and asso- ciated lifting tackle each time before it is used
➤ ensure that loads are not left suspended when the crane is not in use
➤ before a lift is made, ensure that nobody can be struck by the crane or the load
➤ ensure that loads are never carried over people
➤ ensure good visibility and communications
➤ lift loads vertically – cranes must not be used to drag a load
➤ travel with the load as close to the ground as possible
➤ switch off power to the crane when it is left unattended.
For mobile jib cranes, the following points should be considered:
➤ each lift must be properly planned, with the max- imum load and radius of operation known
Drivers must:
• drive at a suitable speed to suit road conditions and visibility
• use the horn when necessary (at blind corners and doorways)
• always be aware of pedestrians and other vehicles
• take special care when reversing (do not rely on mirrors)
• take special care when handling loads which restrict visibility
• travel with the forks (or other equipment fi tted to the mast) lowered
• use the prescribed lanes
• obey the speed limits
• take special care on wet and uneven surfaces
• use the handbrake, tilt and other controls correctly
• take special care on ramps
• always leave the truck in a state which is safe and discourages unauthorized use (brake on, motor off, forks down, key out)
Drivers must not:
• operate in conditions in which it is not possible to drive and handle loads safely (e.g. partially blocked aisles)
• travel with the forks raised
• use the forks to raise or lower persons unless a purpose- built working cage is used
• carry passengers
• park in an unsafe place (e.g. obstructing emergency exits)
• turn round on ramps
• drive into areas where the truck would cause a hazard (fl ammable substance store)
• allow unauthorized use.
Table 10.1 Safe driving of lift trucks
Ch10-H8503.indd 152
Ch10-H8503.indd 152 7/27/07 4:24:40 PM7/27/07 4:24:40 PM
Manual and mechanical handling hazards and control
153
➤ overhead obstructions or hazards must be identifi ed, it may be necessary to protect the crane from over- head power lines by using goal posts and bunting to mark the safe headroom
➤ the ground on which the crane is to stand should be assessed for its load-bearing capacity
➤ if fi tted, outriggers should be used.
The principal reasons for crane failure, including loss of load, are:
➤ overloading
➤ poor slinging of load
➤ insecure or unbalanced load
➤ loss of load
➤ overturning
➤ collision with another structure or overhead power lines
➤ foundation failure
➤ structural failure of the crane
➤ operator error
➤ lack of maintenance and/or regular inspections.
During lifting operations using cranes, it must be ensured that:
➤ the driver has good visibility
➤ there are no pedestrians below the load by using barriers, if necessary
➤ an audible warning is given prior to the lifting operation.
If lifting takes place in windy conditions, tag lines may need to be attached to the load to control its movement.
A lift or hoist incorporates a platform or cage and is restricted in its movement by guides. Hoists are generally used in industrial settings (e.g. construc- tion sites and garages), whereas lifts are normally used inside buildings. Lifts and hoists may be designed to carry passengers and/or goods alone. They should be of sound mechan ical construction and have interlocking doors or gates, which must be completely closed before the lift or hoist moves. Passenger carrying lifts must be fi tted with an automatic braking system to prevent overrunning, at least two suspension ropes, each capable alone of supporting the maximum working load and a safety device which could support the lift in the event of suspension rope failure. Maintenance procedures must be rigorous, recorded and only undertaken by competent persons. It is very important that a safe system of work is employed during maintenance operations to protect others, such as members of the public, from falling down the lift shaft and other hazards.
Other items of lifting tackle, usually used with cranes, include chain slings and hooks, wire and fi bre rope slings, eyebolts and shackles. Special care should be taken when slings are used to ensure that the load is properly secured and balanced. Lifting hooks should be checked for signs of wear and any distortion of the hook.
Shackles and eyebolts must be correctly tightened.
Slings should always be checked for any damage before they are used and only competent people should use
Figure 10.11 Manoeuvring a yacht using a large overhead travelling gantry and slings in a marina.
Ch10-H8503.indd 153
Ch10-H8503.indd 153 7/27/07 4:24:41 PM7/27/07 4:24:41 PM
154
them. Training and instruction in the use of lifting tackle is essential and should include regular inspections of the tackle, in addition to the mandatory thorough examin- ations. Finally, care should be taken when these items are being stored between use.