Fault repair-

On the other hand, is undertaken whenever a fault which shuts down the system occurs. This can upset schedules of operations.

Preventive maintainance-

It is carried out on a fixed schedule that is arrived at by sound technical considerations.

Designing for Maintainance-

All products, whether big or small need maintainance. It may be the replacement of an electric fuse, or servicing of an automobile or even the overhauling of an aircraft jet engine. Servicing of automobiles and aircrafts is basically preventive maintainance. Its purpose is to inspect the components, change the lubricants , tighten the nuts and bolts which may have loosened because of vibration in use, and correction of minor failures which, if not corrected, may lead to catastrophic failures.

Designing for Use-

A short or too tall a person is always made to feel that he is abnormal. Many products are designed for just the average person, with no thought for the fact that fully 50 percent are below that normal and another 50 percent above it. If only a margin for adjustment was provided, a lot more person would be happier. Many products inconvenience even a normal person. A person has to be a contortion artist to slip in and out from behind the steering wheel of most automobiles. Common household scissors threaten permanent cramps in fingers and palms.
A designer will do well to remember that the product he develops is to be used by people. A well-designed product is one that can be used by people more comfortably, more safely and with more efficiently. It is the product that should be fitted to the person, rather than the other way round. Designing for use essentially consists of ensuring that the points of conflict between machine and men be rounded out in favour of men.

Designing for Shipping, Handling and Installing-

Whether a large piece of equipment or a small consumer item, it needs to be shipped from the factory to the user. It must be packed so as to withstand the conditions encountered in transit. These include the rough handling that a package invariably receives at the time of loading or unloading, the vibration and shock encountered during transit, and the adverse humidity and temperature conditions in transit. We should provide suitable reinforced lifting hooks if the equipment is heavy. Rollers and castors may be installed on some heavy equipment. It may be advantageous to design the frangile parts of an assembly so that they can be packed and assembled on site.

Designing for Production-

As soon we start giving a physical shape to an abstract concept, we must start considering the question of how it will be produced. Designing the structure of a tall building must be accompanied by considerations of how it is going to be erected. If the building is more than a few stories high, we cannot use ground based cranes for work on the higher levels. A design is worthless if it calls for higher accuracies than can be obtained with the machines available to the producer. A good designer always asks himself the question-
• Can this is made with the available machines and skills?
Every method of manufacture has certain strong and certain weak points. A good design utilizes the strong points of the available manufacturing methods.

Example of Designing for Function-

Consider a power plant engineer charged with designing a cooling tower for water used for cooling the plant. The designer decides, based on a preliminary evaluation, on a wet-type counter-flow forced-convention tower. For this he have to calculate how much heat is needed to be removed per hour. He would then provide for that much water must evaporate per hour. He would then provide for that much evaporation by designing the proper height and cross-section of the tower, the dimensions of the wet-pack, and the optimum shape and size of the fill material. For this he needs knowledge of diffusive and convective mass transfer . he will also require knowledge of thermodynamics and heat-transfer processes. He will also calculate the size and power of the blower or fans require for obtaining the desired rate of air flow.