Design for usage: Safety and reliability

Safety

Perhaps the most critical feature of any product is safety. If a product causes harm to people, animals or the environment, it will be deemed a failure and it could potentially drag its makers into costly lawsuits. Therefore, designers must design products that are always safe to operate, even when subjected to unusual operating conditions. Good designers envisage what the product will go through at each and every stage of its life and plan for even the rarest of situations.

Safety is by far the most important and critical requirement of any engineering product. This includes safe operation as well as safe storage, transport, and disposal. Designs that compromise safety can cause injury or even death to people, or could result in environmental pollution. The extent of the harm can range from a wounded finger to the death of millions of people. History is full of cases of catastrophic failure of machines and plants. For example, in 1986 the Chernobyl nuclear power plant in the former Soviet Union suffered a meltdown that caused explosions and the release of radiation into the surrounding environment, resulting in the death and injury of many people and the evacuation of an entire city, which is still abandoned until today.

If a product causes harm to individuals or the environment, the people responsible for it can be prosecuted and be liable to fines and even imprisonment.

Examples

• For all kinds of products, designers must make sure that there are no sharp or protruding edges, surfaces in contact with people are not slippery, too hot or too cold.
• Effluence and radiation must be within acceptable and legal limits.
• Moving parts that can cause injury are covered or inaccessible.
• High voltage electrical equipment must be isolated properly.
• Equipment must be protected against high pressure, as well as overload or short circuit.

Protection against improper use

Furthermore, all products should be designed to protect the user against improper or careless use. The term foolproof operation is sometimes used to describe the extent to which designers can go in order to make sure that their products cannot fail or cause danger to people, even if used in the wrong way.

Reliability

Today, all engineering products are expected to perform their intended functions for a long period of time without having faults, failures, or breakdowns. As a result of continuous evolutionary design and constant improvement of materials and manufacturing processes, many engineering products have today reached a high level of maturity that allows them to work without any problems for the entire lifetime of the product.

For example, most high quality electronic gadgets such as computers, TVs, and smartphones can last so long that their technology becomes out of date before developing any failures. As more and more companies are competing for market share of products, one of the main features through which they are trying to promote their products is reliability.

In the context of engineering design, reliability involves two things.

First, the product should repeatedly perform all of its functions to the same level of performance and accuracy. For example, a reliable measuring device should always give the same reading when used to measure the same amount multiple times. Clearly, a device that gives different measurements for the same amount is not reliable.

Second, the product should not develop a fault, fail, or breakdown for a minimum period of time determined by the nature of the product. For example, almost all modern cars come with a minimum of three years guarantee because their manufacturers trust that their cars will not develop any problems during this period.

Next steps

In the next step, you will learn about the final ‘usage’ element in design: economic operation.