Machine Safety: Does adding a hard guard always make your machine safer?
Machine guarding is sometimes approached with the methodology that says lets first add a hard guard to protect the operator from the hazard. Does this always mitigate the hazard, reduce the hazard to an acceptable level, or achieve “safe enough”?
In my opinion this approach only works some of the time. More often, it not only doesn’t solve the problem but it also adds another hazard.
The required practice today begins with a risk assessment per the local jurisdiction or safety standard governing your application or machine. Having said that, adding the hard guard may have been an appropriate next step, however, it’s only the next step. The safety standard will also say that having added the hard guard you will need to update your risk assessment. One of the driving reasons for this step is to hopefully identify any new hazards created by the addition of the hard guard. Reference; Annex G, Risk Scoring Matrix System, ANSI B11, 2008, below.
For example, I’ve seen machines that occasionally require an operator to almost work “in” the machine to clear a temporary jam which would otherwise result in lost production or extensive downtime. To reduce the “very likely to occur” hazard of the operator getting caught by the machine and the resulting “catastrophic” potential injury, a hard guard has been added to the machine. But, all too often I’ve seen where this guard has created another hazard if this guard has to automatically open and close to eject a completed product. The updated risk assessment requirement should document this new hazard and mitigation steps should follow. The new guard may protect the operator while the guard is in the closed position, however, what could happen if the operator gets caught by the machine while the guard is open. It seems to me that the operator is still exposed to the catastrophic hazard of the machine and the new hazard of the guard closing. The operator is certainly better protected by the closed guard but potentially in greater harm’s way because of the new hazard.
So, is the machine safer?
This example suggests the importance of the risk assessment process as a “living” document and the best practice to continually look for machine safety hazards. Adding a hard guard is not always the best answer! And, often it’s recommended to go through this exercise prior to making any changes to the machine because the decision might be made to choose a different machine guarding solution.
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