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• It is natural for a machine to have hazardous parts/functions/flows.


• If the risk (probability) of comming in contact is high we call this danger


• Typical hazards include,

- pinch points

- crushing

- collision with moving objects

- falling from heights

- slippery surfaces

- explossion

- electric shock

- temperature/fire

- toxicity

- physical strain


• When possible it is best to eliminate hazards. If this is not possible we want to reduce the risk of access (hence danger).


• OSHA (Occupational Safety and Health Administration) regulates workplace procedures.


• Danger can be reduced by,

- signs

- safegaurds (e.g. barriers)

- policies and procedures

- worker training

- special protective equipment (e.g. earplugs)


• Typical additions to machines include,

- barrier gaurds - physical blocks to separate operators and equipment. Interlocks are used to disable the machine when the barrier is open.

- passive safety devices - for example seat belts

- active safety devices - these include

- hand pull-backs

- dead-man controls

- presence sensing devices

- maintenance safety devices - these additions (and procedures) ensure that the machine is still safe, even though the normal safety equipment is disabled.

- warnings - large warning signs, buzzers, status lights, etc. are used to promote awareness.


• Note: It is important to place safety considerations at the top of the design priorities. It is so obvious that it is quite often assumed.



9.2.1 Environment


• Environmental considerations are a natural consideration of the design process and can be considered an extension of safety.


• design factors that will impact the environment include,

- discharges/waste (gas, liquids, solids) from production processes

- energy/fuel utilization in production

- aging of the product - decay, inert, toxic, etc.

- energy/fuel efficiency in use


• There are a wide variety of laws, agencies and organizations that influence manufacturing and consumer products,

OSHA (Occupational Safety and Health Administration)

EPA (Environment Protection Agency)

NIOSH (National Institute for Occupational Safety & Health)

UL (Underwriters Laboratory)

CSA (Canadian Safety Association)



9.2.2 MIL-STD 882B - System Safety Program Requirements


• This standard addresses the likelyhood and acceptability of hazards.


• The basic tables are,







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