Posted By Martin Taylor Recently we have seen a number of small assembly machines supplied with 2 handed start controls as a safeguard for the operator as opposed to interlocked guards or light beams. Personnaly I am not keen on this type of system as I always see a risk to bystanders although the operator is protected What are your opinions on using this method and does anybody have guidelines as to how to select between the various types of operator safeguarding. As always all comments and opinions welcome thanks everybody Martin

Posted By Steve Holliday Martin, In my previous position I came across this and “hold-to-run” controls frequently used on pieces of machinery. As you correctly state, when using this type of guard the operator is safeguarded but not others who may enter the danger zone. If you can get a copy of BS PD 5304 - Safe Use of Machinery (2000), there is some guidance in here in a couple of places (6.3 is one but I cannot find the others for looking). In summary this type of control is the last on the recommended hierarchy and should only be considered where there is no likelihood of bystanders. I have been extremely unpopular raising this on a couple of occasions with machinery designers who are happy to state BS’s in their Declaration of Conformity but have not fully read them or hope you have not! Hope this helps Steve

Posted By Martin Taylor thanks for the feedback and additional information everybody - any further views on guidance for 2 handed start operation very welcome Martin

Posted By Stuart Porter You could argue that there is a health and safety risk on the welder machine (or other similar application) when two people work at it. I would say that this is a 'residual risk' and would be dealt with by warning and informing. eg 'Danger Warning - only one person to work at this machine at any one time'. To also help protect 3rd party persons, barriers or guards could be placed to restrict access, although this is not always necessary or practical. On the spot welders example again, operators may have access to all round the machine, although the danger area is within the operators field of view, this may be acceptable if there is a suitable warning about single operator use. Plus operator training should advise him/her not to use the machine if other persons are present. As far as light curtains go, I would tend to use a light curtain if the machine had a longer or more complicated cycle where we would not want to hold in a 2-hand start for the duration of processing. Light curtains may well do the job, but they may also be an over specification if another method is suitable. A bit like using a four by four for doing the school run. 2 hand start circuits are not a bottom of the pile option, most are designed for applications in risk category 3 and 4 (BSEN954-1). A propriatory 2-hand start safety relay only activates if the two buttons are pressed simultaneuosly and held in, and releasing either button kills the power (to the dangerous device). They must be hard-wired to kill the power and errors in software logic must have no effect on the ability to power down the dangerous device.