Redundancy is a design approach used to improve the reliability of a system. It is accomplished by exceeding normal minimal requirements for a system or process. This can mean duplication of critical components, exceeding the minimal requirements of a component, or implementation of multiple separate components.
Duplicating control circuits and components means that if one component or circuit fails, the other, redundant unit will still be able to assure machine shut-down.
Redundancy can also mean placing several steps between personnel and access to the machine. Workers that must pass through a variety of safety doors, light curtains, and restricted access areas are less likely to place themselves in danger.
Clear Operating Indicators are well-positioned, immediately recognizable signals that indicate machine operation. Can and should include a combination of lights and alarms that work together to communicate whether machines are on or off. Common setups include green, red and yellow lights to indicate on, off and standby, and buzzers or horns that signal any changes between different operating states.
Visual indicators can signal to personnel when it is safe to enter the machine space, how far they are permitted to enter, and when they must exit to prevent a full shutdown.
These indicators must be adequately placed so that personnel can see and/or hear them from any point in the machine’s vicinity to reduce the possibility for error.
Integrating relays and switches into smart control systems is the most effective way to cover all of your bases.
Modern relays are able to monitor every part of a safety application: safety gates, light barriers, two-hand controls, pressure sensitive mats, muting, standstill, speed and more. With the right relays, these different safety devices and systems can be linked together to meet redundancy goals.
2 green buttons for starting safetyOpening a safety door can send a signal to the machine, the operator, and the visual or audible signalers to inform personnel that the machine is going into standby for maintenance. This can protect the maintenance technician from any unplanned startup.
Hitting an e-stop is a last resort option when other safety implementations have failed. You typically want to avoid using it but it is a necessary feature in any machine.
The reason for having multiple emergency stops is to provide redundancy, of course, but to also make sure that personnel have several options to choose from so that they can get to an e-stop button as quickly and as safely as possible.
If the machine is segregated from its environment, e-stops should be placed both inside and out of the machine critical area. Placement at access points and operating stations is highly recommended as well.
Tying it all together are procedures put in place that restrict machine access to necessary personnel. This can be accomplished with equipment and training.
Coded switches on a safety door, for example, only work when the correct code is sent from the actuator to the switch. This prevents manipulation and unauthorized access. Unauthorized access can also be prevented by proper lockout/tagout procedures.
Proper lockout/tagout (LOTO) practices and procedures outline specific action and procedures for addressing and controlling hazardous energy during servicing and maintenance of machines and equipment. Only workers who are trained and authorized to lockout machines or equipment can perform service and maintenance operations.
For network-integrated equipment and operations, password protection is recommended.