Movement of Workers in the working area

1. Movement of Workers in the working area Chapter 9

2. There are many types of activity where workers move at irregular intervals between a number of points in the working area, with or without material. • This situation occurs very often in industry and business. In manufacturing operations, it occurs when: • bulk material is being supplied to or removed from continuous process, and is stored around the process; • an operator is looking after two or more machines; • manual workers are delivering materials to or removing work from a series of machines or workplaces. Outside manufacturing operations, examples are: • in stores and shops where a variety of materials are being removed from or put away into racks or bins; • in restaurant and canteen kitchens during the preparation of meals; • in laboratories where routine tests are carried out at frequent intervals.

3. The string diagram • The string diagram is a scale plan or model on which a thread is used to trace and measure the path of workers, material or equipment during a specified sequence of events • The string diagram is a special form of flow diagram, in which a string or thread is used to measure distance. It is necessary that the string diagram be drawn correctly to scale. • The string diagram is started in exactly the same way as all other method studies: by recording all the relevant facts from direct observation. • A string diagram can be used to plot the movements of materials, and, especially when a work study person wants to find out easily just how far the materials travel.

5. Example of a string diagram: Storing tiles after inspection RECORD • In this operational example, tiles are unloaded from kiln trucks on to the bench, where they are inspected. After inspection they are placed on platforms according to size and type. • The loaded platforms are taken on hand-lift trucks to the bins where the tiles are stored until they are required for glazing. Using a string diagram to find out whether the arrangement was in fact the one involving the least transport.

6. EXAMINE critically • A study of the diagram shows at once that the most frequent movement is the 10 x 10 and 15 x 15 rows of bins. Tiles are constantly being withdrawn for glazing. DEVELOP the new layout • The first step in developing the new layout is to locate the bins containing the most handled tiles as near as possible to the inspection bench and those containing “special feature” tiles as far away as possible. The distances covered were reduced from 520 to 340 meters, a saving of 35 per cent.

7. Worker - type flow process chart • Flow process chart — Worker type • Flow process chart — Material type • Flow process chart — Equipment type A worker-type flow process chart is a flow process chart which records what the worker does. • Service and maintenance work, laboratory procedure and much of the work of supervisors and executives can be recorded on this type of charts. • The charting procedure used in compiling a worker-type flow process chart is almost exactly the same as that used on material-type flow process charts. • The definition of the worker-type chart is that it records what the worker does. The definitions of the other two flow process charts, however, state that they record (material type) how material is handled or treated, and (equipment type) how the equipment is used.

8. Example of a worker-type flow process chart: Serving dinners in a hospital ward RECORD • Figure 37 shows the layout of a hospital ward containing 17 beds. When dinners were served by the original method, the nurse in charge of the ward fetched a large tray bearing the first course, together with the plates for the patients, from the kitchen. • The food was usually contained in three dishes, two of which held vegetables and the third the main dish. The nurse placed the tray on the table marked “Serving table” in the diagram. • She set the large dishes out on the table, served one plate with meat and vegetables and carried it to bed 1. She returned to the serving table and repeated the operation for the remaining 16 beds. • She then repeated the complete operation, replacing the plates emptied by the patients with plates containing their portions of the second course and returning the used plates to the serving table, where she stacked them. • Finally she made a tour of the ward, collecting up the empty plates from the second course, and carried everything on the tray back to the kitchen. • The operation has been recorded in part on the flow process chart in figure 38 but only enough has been shown to demonstrate to you the method of recording, which it will be seen is very similar to that used for material-type flow process charts, bearing in mind that it is a person and not a product that is being followed.

10. EXAMINE critically • A critical examination of the flow process chart in combination with the diagram suggests that there is considerable room for improvement. • The first “Why?” which may come to mind is: “Why does the nurse serve and carry only one plate at a time? How many could she carry?” • The answer is almost certainly: “At least two.” If she carried two plates at a time, the distance she would have to walk would be almost halved. • One of the first questions asked would almost certainly be: “Why is the serving table there, in the middle of the ward?” followed, after one or two other questions: “Why should it stand motionless? Why can it not move round? Why not a trolley?” This leads straight to the solution which was adopted. DEVELOP the new method • It will be seen from the broken line in the diagram (representing the revised path of movement of the nurse when provided with a trolley) and from the flow process chart that the final solution involves the nurse serving and carrying two plates at a time (which also saves a small amount of serving time). • The result, as will be seen from the process chart, is a reduction of over 54 per cent in the total distance walked in serving and clearing away the dinners.