Every machine, building and piece of infrastructure is intended to function correctly within a certain range of factors. Weight, temperature, pressure, vibration, quality of contstruction, durability of materials, and climate factors all affect safety. Most buildings and equipment are engineered to ensure that the ability to respond to extreme changes in any of these factors far exceeds the failure point. Engineers are expected to adapt building plans to account for various failure scenarios such as overloads, deliberate destruction or weather.
Geography
Buildings in flood plains, earthquake zones and tornado paths are engineered to withstand the most likely strength, duration and depth of each event. Flood plain maps will typically depict the average annual, ten year, twenty five year and hundred year high water marks. Machinery such as pumping stations and water treatment plants are typically located above the expected twenty five year high water mark, and may even be located above the expected hundred year high water mark. Buildings in flood zones are often required to be built on stilts, piling or platforms above the twenty five year high water mark. Earthquake zone engineering allows the building to bend and sway within a certain tolerance, without compromising structural integrity. The ability to bend and sway, even though it is usually slight enough to be unnoticeable, prevents cracking and collapse. Tornado zone planning includes creation of hallways and corridors which can be used as shelters. It also includes accounting for excessive load limits both from wind and from debris piled on roofs.
Types
Another term for margin of safety is tolerance. This refers to the range of conditions within which the building or machine will operate without breakage or failure. Triple redundancy is a term used in maritime, military and space applications. Each system has two additional, complete copies of itself in case of failure. Testing is a third term used in relation to margin of safety. Playground equipment, toys, child car safety seats, elevators, boats and exercise equipment are tested to a rating beyond their expected use. For example, a toy intended to be used by children 65 pounds and under will typically be tested to 300 or even 500 pounds. Elevators are tested to between 2000 and 5000 pounds. Overweight switches can stop the elevator if the weight limit is reached. Regularly operating a piece of equipment at either extreme of the margin of safety is not recommended.
Considerations
Margin of safety is not intended to remove all risk, but to minimize potential damage to property and prevent loss of life. Failure to observe safety recommendations, calibrate equipment, maintain warning systems and safety features, and address concerns about signs of potential failure of systems can make a company liable for any damage or loss of life incurred.
Buildings and equipment which have been engineered to withstand extremes, allow people to live and work in confidence. Engineering to increase tolerance for one factor may cause problems in other factors. For this reason, designs are often tested as computer simulations before being used in real world applications.
Effects
Build in margins of safety to lower risk. Insurance costs are reduced, lawsuits are prevented and injury or loss of life is minimized. Engineers brainstorm potential failures to protect public safety while contributing to the creative process of research and development. Each version of the product beyond the prototype is then progressively safer.
Significance
Price is affected by built in margins of safety. The demand for stronger, more flexible, more durable building materials drives price upward, while the increase in safety drives insurance costs, legal awards and emergency medical care downward. It is important to analyze the costs of making anything safer versus the benefits in order to ensure that a given application is financially sound while adequately protecting public safety.
Tags: high water, year high, year high water, five year, high water mark, loss life