Many injuries are caused when operators intervene in a process, for example to make an adjustment or clear a blockage or during maintenance. This is because interventions for a process malfunction are not likely to be as well planned as for a more controlled intervention such as for planned maintenance. The chances of an incident occurring will therefore increase.
With safeguarding, the basic principle is that dangerous moving parts of the machinery and operators must be kept separate until equipment is in a safe condition.
Separation may be achieved by using various approaches, for example:
- Perimeter fencing with interlocked access to the plant, with no internal access to adjacent danger zones.
- Close guarding of individual machines using locking devices, fixed fences, trip devices, photo-electric safety systems etc.
Answers to the following questions should be considered when assessing if safety precautions are adequate:
- Is distance safeguarding of a section of the line ('a cell') more practicable than close guarding?
- In which areas can the need for frequent access be predicted?
- Will the person in the danger area be in sole control of the risk?
- Have all the failure modes been identified?
- What special maintenance requirements are in use, eg wander leads, permit-to-work systems, power isolation/lock-off procedures?
When looking at the hierarchy methodology for safety precautions safe electrical isolation procedures should always be the first option. This should be prioritised before consideration is given to the options detailed in BS EN 1037:1995 + A.1:2008 Safety of machinery – prevention of unexpected start-up or other standards or methods to prevent unexpected start-up.
Safe electrical isolation means that there needs to be not only a way for electrical energy to be switched off but also that there are suitable precautions available to ensure that it remains switched off. Inadvertent reconnection must be prevented - for example by breaking the 3-phase by mechanical means and also having a locking-off facility.
Further details of cutting off the supply and isolation are given in the Memorandum of guidance on the Electricity at Work Regulations 1989 (HSR25).