In the world of automation controls, there are a variety of devices and methods that are used as safety measures to assist a manufacturing facility in providing a safe environment for operators and associated personnel. Here is a list, with pictures, of many safety devices currently available.
1. E-stops – Provides an emergency stop push button (typically red) that may be pushed if an operator senses danger or needs to immediately halt a machine’s operations. It needs to be reset to restart operations, often requiring a reset button to also be pushed.
2. Light curtains – Provides a barrier with beams of light from one source to a target so that if the sensing field is interrupted (broken) a machine will shut down or go into an alarm condition. These devices can be programmed to allow a “blanking effect” for areas in the beam that are deemed safe, versus other areas that require a halt. They are often used to eliminate the need for fencing/hard guarding in a work area that needs access on a regular basis. These can also be used with a corner mirror to provide a double area of protection, such as a 90 ° configuration.
3. Laser scanners — Provides a 180-degree wide path beam that scans a pre-programmed area to determine if an object has entered that space close enough to either (1) slow machine to a crawl or (2) stop the machine completely, depending on distances allowed for safety.
4. Safety Mats – Provides a pressure-sensitive, rubberized, safety mat that an operator will either (1) need to stand on to continue to use a machine or (2) step onto in order to halt a machine. Typically, choice 1 is used as it is a more fail-safe way of operating.
5. Safety Edges – Provides a pressure-sensitive area near the edge of a door or machine that can be used to shut down or reverse a device or whole machine when touched. A Bulletin 440F Safedge™ Safety Edge Profile is shown below. These are often used at the bottom edge of a door to assure nothing or no-one gets trapped under it as it is closing.
6. Safety chains/rope (Cable Pull) – Provides a means of E-stops via a rope or chain that, when pulled or stretched, will trigger a shutdown or halting of a machine’s action. This will need to be reset in order to reestablish action again.
7. Interlock Switches – Provides a physical interlocking of guard doors and equipment so that if the safety switch is interrupted, the machine or a function of operation will stop and require a reset to resume action. Some examples of these are guard locking, hinge, tongue interlock, limit switches, trapped key, or non-contact switches such as proximity switches.
8. Kick Plates – Provide a means, down near the floor, that an operator can touch with their foot to stop the action of a machine. Depending on how it is set up, this can halt a portion of the machine or halt the entire machine. Typically, a limit switch is used in conjunction with a metal plate that will swing up against the switch to activate it.
9. Hand Detection Sensors – Provides a means of making sure an operator is holding/pressing the safety sensor to continue operating the hazardous function of a machine. Often a two-hand control set of devices can be utilized to provide an extra safety measure, requiring both hands on the controls to start or continue a function.
a) Grip Enabling Switch (see below)
These grip Switches can be used as part of the conditions required to allow safe working inside a machine guard. They are lightweight and ergonomically designed for easy use. The standard model includes two independent, three-position, switches which are actuated by squeezing a trigger. Models are also available with an optional jog button or dual channel E-Stop button.
b) Reflective Safety Sensor — Provides a reflective hand detection at the opening of a hazardous machine access point to a work cell. (i.e. an SC300 safety sensor creates a detection plane in an opening of various shapes and sizes.)
1 10. Safety Relays — Safety relays monitor a safety system and either allow the machine to start, or execute commands to stop, the machine or control safety-related functions. From simple safety functions to fully integrated systems, several ranges of solutions are available.
11. Safety PLCs – A Safety Programmable Controller is a combination of at least 2 PLCs that provides redundancy and extra protection in case of failure. Many of these would integrate with Guard I/O modules
to expand the number of safety devices to be detected or controlled.
12. Audible/Visual Devices — Horns or lights or similar devices can provide warnings to operators.
— For more information on installing these and other automated safety devices contact Paul Myers at Segars Engineering