Good practices aside, what are we required to provide at each operating station?...
Under the European Machinery Directive: EN 60204 - Health and safety requirements in machine design and manufacture can be derived, in part, as the following...
The operator should be able to make sure easily that all hazard areas are free of bystanders. Otherwise, the control system must be designed and built so that starting is not possible, unless the hazard area is empty. If neither of these is possible, an audible and/or visual warning should be used before start-up. Then, the person in danger should have enough time to leave the area or stop the process. If necessary, there should be remote-control devices in one or multiple predetermined areas (for example, near a hazard zone) If more than one control zone exists, the control system must be built so that if one of them is being used, the others become disabled, except switch off and emergency stop features. In case there are two or more control zones, they all must be equipped with all the necessary control devices and means that prevent errors and dangerous situations...
...Stop requirements: All machines or machine parts in a system should be designed and constructed so that the stopping devices, including the emergency switch-off devices, stop the relevant machine and any other connected machine if their ongoing operation might be dangerous.
Standard stop procedure: Each machine must have a control device that enables safe and complete shut down. All operating areas must include a stopping device to switch off the entire machine or its moving parts, depending on the nature of the hazard, so that this machine is safe. The machine stopping function must take priority over start-up...
So, under EU Machinery Directives, the requirements of the Standards appear fairly clear. You must provide a Stop function at each operating station.
As we know, many of the localized Standards are globally harmonized (IEC) with other localized Standards. With that in mind, let's look at the equivalent Standards to EN 60204 (IEC 60204) applied in North America, namely NFPA 79...
9.2.5.3 Stop.
9.2.5.3.1 Each machine shall be equipped with a Category 0 stop.
9.2.5.3.2 Category 0, Category 1, and/or Category 2 stops shall be provided where indicated by an analysis of the risk assessment and the functional requirements of the machine. Category 0 and Category 1 stops shall be operational regardless of operating modes, and Category 0 shall take priority. Stop function shall operate by de-energizing that relevant circuit and shall override related start functions.
9.2.7.2.3 Means shall be provided so that the machine shall only be controlled from operator control stations in one or more predetermined zones or locations.
9.2.7.3 Stop Function.
9.2.7.3.1 Operator control stations shall include a separate and clearly identifiable means to initiate the stop function of the machine or of all the motions that causes a hazardous condition. The actuating means to initiate this stop function shall not be marked or labeled as an emergency stop device, even though the stop function initiated on the machine results in an emergency stop function.
9.2.7.5 Use of More Than One Operator Control Station.
Where a machine has more than one operator control station, measures shall be taken to ensure that only one control station shall be enabled at a given time. Indication of which operator control station is in control of the machine shall be provided at locations where necessary for the safety requirements of the machine.
Exception: A stop command from any one of the control stations shall be effective where necessary for the safety requirements of the machine.
By my interpretation, the harmonized IEC 60204 / NFPA 79 9.2... Standards both, unambiguously, deem it necessary to provide a Stop function at all operating control stations.
On the flip side, and for further clarification - all operating control stations must also include a Start function. In case it thought, "Can I just provide a Stop button control station with no Start?" For that, either full controls must be provided or a single Emergency Stop button station should be used instead.
Regards,
George
