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Bypassing Safely

 

Quite often the question is asked "How do we gain access into a machine to make adjustments, clear jams, perform maintenance etc., while the machine is running, and do it safely?”. Usually people just turn the safety system off (bypass) which is unacceptable by law.

Frequently, a simple key switch is used to just bypass a safety gate. The problem with this solution is that the key can be left in the switch and the machine will run with the safety gate open all the time, which is unsafe. The key itself may not be safe and, anyway, it depends on human behaviour, thus it is an "administrative control”, which is near the bottom of the hierarchy of risk control. A tongue switch on a safety gate could be bypassed simply by using a spare tongue, carried in an operator’s pocket (a very common problem)!

Risk must be reduced so far as is reasonably practicable via engineering means prior to the implementation of administrative controls according to the legally enforceable risk control hierarchy.

The Victorian OH&S (Plant) Regulations 1995, R. 305 "Designer’s duties in relation to specific control of risk requirements associated with guarding” states that:”

  • If a designer of plant uses guarding as a measure to control risk the designer must ensure that the guarding is-
    • Designed to make by-passing or disabling of the guarding, whether deliberately or by accident, as difficult as is reasonably possible;”

The same applies to employers as per regulation 706.

The same clauses can also be found in the regulations for other states in Australia.

So when there's no alternative other than to bypass safety gates or other safety systems, the AS4024.1-2006 Safety of Machinery offers the following guidelines*:

Part AS4024-1501-2006: Design of safety related parts of control systems – General principles for design. Table 1 refers to 6.10 of AS4024-1501-2006 (Manual suspension of safety functions) and to

AS4024.1202-2006: General principles – Technical principles section 5.11.11: selection of control and operating modes.
Section 5.11.10: Control mode for setting, teaching, process changeover, fault finding, cleaning or maintenance refers to
"….safety of the operator shall be achieved by using a specific control mode which simultaneously –

  • disables all other control modes
  • permits operation of the hazardous elements only by continuous action of an enabling device, a hold-to-run control device or a two-hand control device; and
  • permits operation of the hazardous elements only in reduced risk conditions (e.g. reduced speed, reduced power/forces, step by step operation, e.g. with a limited movement control device.”

So, it should never be necessary to put lives on the line simply to adjust machinery or clear jams. You don't need to break the law either. There are no exceptions under the OHS Act – even during a breakdown you must eliminate the risk, or if it is not practicable to eliminate it, reduce the risk so far as is practicable – so "it's only for a few minutes" short-cuts are not an option. Depending on administration alone is also not acceptable if we can further reduce risk via engineering.

As an example, Pilz has the PIT js two-hand enabling control (see above) which allows your staff to get the job done with the protection of the safety system. In conjunction with the safety system, the PIT js two-hand enabling control keeps both of the user's hands on the controls and away from hazards while plant operates in the low risk mode of your choice - "safe slow speed” or "limited inch”, for example.

In fact, the options are many. You might choose to have the safety system set up so that the machine can be enabled while the safety gate you are accessing can be opened, in conjunction with the two-hand enabler, however any other gate opened at the same time will shut the process down.

For more information on safe bypassing, please contact us.

(*please read all the relevant sections of AS4024.1-2006 Safety of Machinery in full).