Plant operation14.1 Introduction:1.

Plant operation

14.1 Introduction:

1. Process layout

In process layout, similar manufacturing processes (cutting, drilling, wiring, etc.) are located together to improve utilisation. Different products may require different processes so material flow patterns can be complex.

An example is machining parts for aircraft engines. Some processes (such as heat treatment) need specialist support (e.g. fume extraction), while other processes (e.g. machining centres) need technical support from machine setters/operators. So the factory will be arranged with heat treatment together in one location and machining centres in another. Different products will follow different routes around the factory.

2. Cell layout

In cell layout, the materials and information entering the operation are pre-selected to move to one part of the operation (or cell) in which all the machines to process these resources are located. After being processed in the cell, the part-finished products may go on to another cell. In effect the cell layout brings some order to the complexity of flow that characterises process layout.

An example is specialist computer component manufacture. The processing and assembly of some types of computer components may need a dedicated cell for manufacturing parts to the quality requirements of a particular customer.

3. Product layout

Product layout involves locating the machines and equipment so that each product follows a pre-arranged route through a series of processes. The products flow along a line of processes, which is clear, predictable and relatively easy to control.

An example is automobile assembly, where almost all variants of the same model require the same sequence of processes.

Another is paper making. Although different types of paper can be manufactured, all types have the same processing requirements. First the wood chips are combined with chemicals, water and steam in the ‘cooking’ process to form pulp. The pulp is then put together through a cleaning process before being refined to help the fibres lock together. The mixing process combines the refined pulp with more water, fillers, chemicals and dyes, after which it is spread on a fine flexible wire or plastic mesh. This is shaken from side to side as it moves along to lock the fibres into the sheet of paper and to drain away the water. The press rollers squeeze more water out of the paper and press the fibres closer together. The drying process continues to reduce the water content in the paper before finally it is wound onto large reels.

It makes sense then to locate these processes in the order that they are required (cooking, then cleaning, then mixing, spreading, shaking, squeezing, drying and winding) and to let materials flow through them in a predictable manner.