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Having finalised the Concept Analysis and Scope Development phases, the next stage is to carry out a detailed engineering design for the proposed plant. The Engineering Design phase is the point at which specific equipment makes and models are selected, detailed drawings prepared for installation purposes and purchase orders are raised to buy the necessary equipment.
Many significant decisions are made during this stage including the optimum brand and model for a specific application, the layout or orientation of different equipment and space for access to individual equipment both for operations and maintenance.
It is at this stage that the final design takes shape and design decisions are ‘locked in’. After this stage it becomes extremely difficult to make changes to the design without significant additional cost being incurred.
Equipment make and model
Equipment brands and models are often decided by adhering to the organisations purchasing policy which may stipulate which brands are acceptable and even the model to be used. This is an important consideration as the established population of a specific brand or model of equipment on site helps to ensure manufacturers support as well as optimise spare parts holdings by sharing the cost of spares and equipment across a number of similar equipment.
Project teams sometimes purchase different brands and sizes of equipment to that already on site either because they are familiar with particular makes or because the alternatives have a lower up front cost and this helps keep the project budget under control. This can be a short-sighted policy as the new, unfamiliar equipment brings with it additional costs for training and spares which can outweigh the savings made on the purchase price.
A counter argument is the need to keep up-to-date technology on site to ensure support from manufacturers and to take advantage of any technological improvements that may have been made since existing models were installed.
Plant layout issues
The layout or spatial organisation of the different pieces of equipment that make up the new plant is an important consideration as two competing aims are at play. On the one hand it is necessary to minimise traveling time for operations staff as they carry out their normal duties and to reduce the cost of land taken up by the plant. This is especially important in older plants as the site becomes congested and additional land may not be available to use or purchase. On the other hand, sufficient space must be provided between individual machines to allow safe and efficient access for operators and maintenance staff carrying out their normal duties.
Operations staff usually have a lower space requirement than maintenance staff as access to equipment will, in most cases be on foot and therefore a normal walkways will meet their needs for access.
Maintenance staff often require sufficient access to be able to use small cranes and scaffolding etc. around individual equipment and this can increase the space required around individual machines. Only by careful analysis of the operations and maintenance requirements of each machine can the access needs be identified and optimised.
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