2. Materials handling

Materials handling is performed by almost every worker in industry, either as a full-time job or as part of other work. It is often done by hand, though increasingly there is some mechanical help. As a rule, many tons of materials are moved for each ton of product produced.

In many industries, materials could not be processed at a reasonable cost if it were not for efficient handling and transportation of materials. Efficient materials handling is therefore an important element of productivity. There are, however, many possible sources of inefficiency, including strenuous or awkward ways of lifting, carrying or transporting materials; arrangements for feeding materials to machines which are inconvenient and time-consuming; unnecessarily long routes for moving materials; and lack of appropriate tools or handling aids.

Handling of materials accounts for a considerable proportion of occupational injuries. These injuries occur in almost every work area, not merely in stockrooms or warehouses. Common injuries include strains, sprains, bruises and fractures and the largest number of injuries occur to fingers, hands and feet. They are primarily caused by unsafe work practices, such as carrying too heavy a load, incorrect gripping, improper lifting or failure to observe proper hand or foot clearance. Lack of personal protective equipment, especially helmets, gloves and footwear, also accounts for many injuries.

In practice, easy, efficient and safe ways of handling and transporting materials go together. Many of the most effective improvements are simple and low in cost. For example, minor changes in layout or work methods can often reduce awkward or strenuous motions in moving materials or products. Special handling aids such as the correct size of boxes, adequate holding devices or jigs, hooks, hand trucks or carts can often sharply reduce time and effort. The layout of passageways and machines can be changed to improve work flow. Mechanical devices such as convey lines can be introduced. Machine feeding methods can be made more convenient, for example, by using magazines. Even with no new equipment at all, methods of lifting and carrying can be improved.

In the majority of the examples shown in this section, the cost incurred in carrying out the solutions is remarkably low. The cost in a few other cases depends on the types of mechanical aids introduced. The solutions are often easily apparent once there has been a careful examination of the ways materials are being moved.

Case 11: A simple wooden cart

In a furniture manufacturing enterprise in the Philippines which employed 35 workers, several workers had to interrupt their work every 15 minutes or so to get more materials. Because these materials were transported in bulk by hand, some materials were dropped on the floor. This affected the quality of the products. Though the supplies were located only about 15 metres from the workplace, the time spent going back and forth was surprisingly long if measured from the moment work stopped until it restarted, and multiplied by 30 or more times a day. Moreover, workers complained of fatigue in their arms.

The solution was to construct a simple wooden cart. No direct cost was incurred because surplus wood and other available materials were used. The estimated cost of the surplus wood was only about US$ 8. Indirect costs included the carpenters time, but this was also minimal. The cart could move enough materials to last each worker for an hour. One worker was assigned to supply materials as part of his general duties.

Figure 27: Use of home-made wooden carts which can be brought near each workstation.

The manager of the enterprise found that he had saved far more than the cost of the cart. The enterprise experienced a considerable increase in productivity. This, of course, was not entirely due to this one improvement in materials handling, but it made a contribution, not least because the workers stopped complaining of fatigue. Cracking and chipping of wood materials was reduced by about 90 per cent.

This example shows at least two important points. First, the improvement was neither costly nor difficult to design and construct. Second, the solution could have been easily ignored because, after all, the workers were not going very far for supplies. The observant manager noticed that more time was being lost than a casual look might suggest, and he listened to the complaints of his workers.

Case 12: A special cart for heavy loads

Moving heavy materials not only consumes a lot of effort, but often leads to accidents which damage material and may injure workers. In a company manufacturing bricks in India, this led to the design of a special cart for transporting the bricks on metal plates to the drying chambers. The factory, which employed 500 workers, was large enough to have a person who could design the cart after having consulted an ergonomist.

Figure 28: A cart with an iron plate for carrying bricks.

The cart was made from bicycle parts and iron angles from the factory workshop. The cost was bout US$ 100, including the time for design and construction. Maintenance costs were about US$ 10 a year.

By using the cart, workers were able to carry the bricks more quickly and with much less physical effort. Their productivity increased by about 15 per cent. In addition, damage to bricks during handling was reduced. Savings outweighed the cost of the cart. While the extent to which the physical effort of the workers was reduced could not be accurately assessed, they clearly benefitted appreciably.

A similar example was reported from Pakistan. In an engineering factory employing 100 workers, two push-carts were introduced for transporting finished products to the warehouse. Each cart cost US$ 100. The direct cost of US$ 200 seemed justifiable as absence due to injuries was much reduced among the transport workers.

Figure 29: Side view of the cart in use. Note the low position of the iron plate being carried.

Figure 30: A worker placing bricks on the iron plate.

In developing countries, there is often unnecessary physical exertion due to manual moving of heavy materials. Even when cost is an overriding consideration, carts and other mechanical aids constructed from local materials often pay for themselves by raising productivity and preventing damage to materials. The cost of potential injuries to workers should also be kept in mind.

Case 13: Improvements in carrying raw materials

In the raw materials unit of a household goods production complex in Thailand, there were complaints of back pains among those who were carrying and lifting 50 kilogram sacks of raw materials before dumping them into a hopper. To prevent back strain and reduce inefficiency, the safety officer and the plant manager discussed the problem and explored various possible solutions.

Together with some changes in work methods, a cart was designed and constructed and the slope of the floor improved. Small adjustments were necessary after a few trials. The cart was then used to carry the raw materials to the place where the sacks were dumped into the hopper. The direct cost was approximately US$ 740 for constructing the cart and improving the slope of the floor.

The workers welcomed the change, saying that the job became much easier. There were no more complaints of back pains after the improvement.

Figure 31: A new load carrying cart.

Case 14: Improving a shovel

The standard shovel requires continuous bending of the back to lift the materials handled. In a construction firm in Calcutta in India which employed about 25 workers as shovellers, there were complaints of backache and fatigue. By adding an additional handle near the base of the shovel, it was possible to significantly reduce the bending of workers' backs. Moreover, the distance the materials could be thrown increased by at least 25 per cent. Productivity also increased by 25 per cent. At the same time, complaints of backache and fatigue were reduced.

The cost of the improvement, made with local materials, was only about US$ 2 per shovel. However, this does not include the work of two ergonomists.

Figure 32: A worker using the old shovel. Notice his stooped posture.

The new shovel illustrates a number of interesting principles. It minimises back-bending postures and gives the worker greater leverage. The length of the new handle is adjustable to allow for the different size of workers. Above all, this example shows that even the most common Cools can be improved. Very often, a standard tool is provided to the worker without much thought on how it is to be used or whether there is a better alternative.

Figure 33: A worker using the modified shovel.

Case 15: Use of an appropriate lever

Lifting of heavy items is quite often done manually. In addition to the heavy weight of these items, they are usually difficult to lift due to the varying shapes and sizes. This was the case for the placement of wheels on axles in a truck manufacturing plant in Indonesia. Each wheel, together with tyre, weighed 50 kilograms and had to be lifted 50-75 cm. A tiring stooped posture was required.

Figure 34: Original working posture for lifting a wheel and tyre.

A spade-like device with two prongs was designed by the workers and introduced. It was nearly one metre long. Each wheel was first leaned against the axle and then lifted by this two-pronged device, which worked like a lever. After the wheel was properly installed onto the axle, the device was released. Because of the leverage, the force required was only 12.5 kilograms, or only one quarter of the weight of the wheel and tyre.

Figure 35: A lifting device designed by workers.

Figure 36: Use of the lifting device.

The cost for making the spade-like device was almost nil, as scraps were used and modified to form the device. The workers no longer felt the wheel lifting to be a heavy job.

Case 16: Improved methods of lifting

In a warehouse and packaging complex in Singapore with about 250 workers, there was a high incidence of backache and backstrain. In a few instances, slipped intervertebral discs occurred.

Data on causes of sick leave, worker injuries and complaints showed a relationship to the lifting and carrying of goods. The safety officer, personnel officer and general practitioner servicing the enterprise then drew up a programme to train the workers on the right methods of handling loads. Before the start of the training programme, the workers and line supervisors were consulted as to how and when the training should be conducted and their views were taken into account. It was decided to give half an hour's training to successive groups of approximately a dozen workers at a time. The safety officer and personnel officer served as instructors.

This training consisted of:

(a) a slide show on the anatomy of the back and lines of force when lifting and carrying;

(b) a talk on correct methods of lifting;

(c) a demonstration by either the instructors or volunteers on how to lift and carry various objects of different shapes and sizes either by one person alone or with others. The proper lifting method consisted of the following:

1. a good, firm grip
2. a straight back
3. proper position of the feet
4. the chin well tucked in
5. the arms kept as close to body as possible
6. proper co-ordination if lifting is done by two or more persons.

After the training, the safety officer frequently went around the worksite to observe if the workers really applied the techniques. The incidence of backaches and strains was reduced significantly over an observation period of twelve months following the completion of training for all the workers.

Direct costs were minimal, involving only expenditure of US$ 20-30 for the preparation of photographic slides and photocopying of notes for distribution to the workers. Indirect costs included workers' time off their work during the training and the time of the instructors. These costs were minimal compared to the total wage bill. Although no exact figures were available, it was estimated that the reduction of sick leave and the increase of efficiency made the solution well worthwhile.

Figure 37: The proper method of lifting step by step.

While this exercise was a success, it should be remembered that such short training courses require repetition. Not only do new workers need to be trained, but all the workers probably require refresher training at least once a year. It is also important to note that line supervisors have an important role to make sure their workers really use their newly-acquired knowledge at all times.

Case 17: Use of a pneumatic device

Awkward postures associated with the handling of materials and products can cause inefficiency, discomfort and muscle strain. Simple mechanical means are quite often an effective solution. This was experienced in a pressure vessel manufacturing plant in Thailand. Workers at the plant's leak test unit complained of discomfort and backstrain from bent postures required to push pressure vessels down into water for the leak test. The plant manager consulted engineers in the maintenance department and workers of the test unit on ways to eliminate the awkward postures.

Figure 38: A worker showing the original method of pushing down a pressure vessel in the water for a leak test.

The engineers came up with the idea of using a pneumatic cylinder to control the iron arms that held the vessels during testing. A pneumatic cylinder was installed at a cost of approximately US$ 75. The labour costs were not included as the work was done by the maintenance department.

Figure 39: The pneumatic cylinder used to push down the vessel.

Work efficiency improved and the handling of pressure vessels at the testing tub became much easier. There were no more complaints of work discomfort and back strain.

Case 18: Improved movement of materials to an assembly workshop

Materials handling costs were an appreciable part of the total production costs in a factory in India producing automobile parts. The section where the maximum amount of materials handling was done was selected for a layout study. This led to improved routes of access from stores to assembly workshops.

The original routes were circuitous. Automobile chassis, body and engine components were brought to the factory in 3.6 × 1.8 metre containers, each of which weighed as much as four tons. A mechanical hoist was used to pick up the containers from a bonded godown (warehouse), bring them to the factory entrance and place them on rollers on the floor. The containers then were manually pushed 30 metres along the rough and uneven ground to an open yard. They were opened there. After some components were carried to the main store, the remainder were stacked on trolleys which were pushed to the main assembly workshop about 75 metres away. Engine parts were taken on trolleys to the engine assembly line about 135 metres away. These long distances were due to the fact that there was only a circuitous route to the assembly lines.

Figure 40: Original transport routes.

Figure 41: The new time-saving transport route.

To improve handling, a sloped pathway was laid from the bonded godown to the unpacking section. Then the components for the main assembly workshop were carried by trolleys on a ramp directly connecting it with the unpacking yard. The engine parts were also taken directly to the engine assembly area. The transport distance was reduced to about one-third in both cases. In the case of transport to the engine assembly area, eight minutes could be saved per trip. Job hazards were also reduced.

Expenses of about US$ 1,000 were incurred to provide a sloped pathway from the bonded godown to the unpacking section, to make openings in the retaining wall and to provide a sloped ramp and a road along the wall. In addition to reduced handling time, the elimination of congestion and hazards were intangible savings for the company.