Chapter 2.3
Protective Measures
When faced with a hazard, machine designers must find a safety measure that is safe, functional, efficient, and affordable. It may seem like "squaring a circle," but success comes from focusing on two main targets: practicality and safety.
To achieve this, there are two things you should do
1: Follow an 'ALARP' approach
Effort should be 'As Low As Reasonably Possible.'
Apply this to all of the aspects above, except the first. Machine safety is primarily about maximum risk reduction. Functionality, efficiency and cost are secondary. If you get the priorities up side down, it will result in unsafe machinery. Never compromise safety just to save cost or increase efficiency.
2: Do not violate the three basic rules of machine safety
1. Guarding - put the lion in a cage – lock the hazard in (or people out)
If there is a hazard from a moving part, hot surfaces, or electric discharge by contact, never allow people to contact the hazard involuntarily.
That is:
- Do not allow hazardous moving parts to run openly.
- Do not allow hot surfaces and live parts to be touchable.
2. Monitoring and interlocking - put the lion to sleep with an anaesthetic shot, before it can reach the person.
If you cannot follow the first rule, monitor the time interval in which people could contact the hazard source.
End the hazard before the person can come in contact with it:
- Use sensors Use sensors such as light barriers, laser scanners, contact mats etc/ and the control system to monitor the presence of people or hazards (or both)
- Stop a moving part when detecting an approaching person or hazard (or both)
3. Manual control - make the person “tame” or remote control the lion
If you can not follow the first or the second rule, make the person agree to being exposed to the hazard. Where ever possible ensure that the person can end the hazard in time.
That is:
- Make the person press one or two buttons to start and uphold a hazardous movement or situation.
- Place the button(s) outside the hazard area or at a safe distance, if possible. (Two buttons: two-hand control or start button plus enabling.)
- Reduce the speed of movements so the person can still react and let go of the button(s).
