I applaud you for thinking about functional
safety! One thing I would add: part of your selection process should account for overtravel of the lift. When the
switch is activated it will take some amount of time for the lift to come to a complete stop. For example, if the
switch only provides an inch of travel before it's fully compressed and the lift stops in 3 inches, you can still shear toes or other soft, squishy bits. You'll need to figure out the time required to bring the lift (traveling at full speed with full load if going down and no load if going up) to a stop. This will then allow you to calculate the amount of distance stopping the lift will require. The
switch/sensing
edge/astragal will need this amount of overtravel. As part of out lift commissioning, we use a human analogue (a carrot) to test this. If the carrot doesn't break when striking the safe
edge at full speed, you should be good to go. Finally, we've had great success using the tapeswitch PRSU/4
relay for monitoring. It's the most affordable and reliable option we've found.
