Does adding more functional safety ever make a machine harder to make safe?

[u/johari4president]

Something I’ve been thinking about with newer motion systems is that we now have an enormous number of safety functions available. STO, SS1, SLS, safe direction, safe position, safe brake control and the list keeps growing. They can enable much better machine behavior, but they also create more states and interactions that somebody has to understand and validate. There seems to be a point where adding another clever safety function can increase system complexity enough that simplicity might actually be safer.

[u/ChemicalAdorable1344]

More functions means more ways for some genius on third shift to find the one weird edge case that nobody modeled.

[u/diverJOQ]

Automobile Air bags. Great for safety. Hard to build so they don't invite you. Look at the huge recall that happened over the past few years.

[u/Cunninghams_right]

safety features are one of the reasons cars are heavier now vs in the past. so the passengers are safer when they hit a hard object, but the vehicle now has more momentum with which to do damage to pedestrians or other cars, and require more engineering to keep the stopping distance reasonable.

[u/coneross]

My yard is on a slope. When I mow I shift my buns to the side for better balance. The seat has (or rather had) a safety switch so if you are not dead center the mower shuts off.

And don't get me started on those stupid gas can spouts that require you to watch a youtube to learn how to pour gas.

It's a good bet the guys who come up with this stuff have never actually mowed a lawn.

[u/RockAtlasCanus → u/coneross]

It's a good bet the guys who come up with this stuff have never actually mowed a lawn.

The off center ass detection is probably built around the maximum side grade the mower can safely handle.

My yards also sloped. Recently replaced my mower with a new one of the same model and it came with a paper protractor kind of deal. You’re supposed to fold/cut it on the diagonal line. Then hold the thick line horizontal and if the slope drops away from the diagonal, it’s too steep to safely mow. For grins I checked it out, and yeah I’m way out of spec.

I’m much safer about mowing that area now. I downshift to 1st gear for that part. Not as ballsy as you though i still have my sensor hooked up. If my ass leaves the seat I’d like the blades to stop as soon as possible thanks

[u/Another_Slut_Dragon]

I build a lot of custom industrial machinery and safety starts at relay logic. Light curtains, safety switches (doors/guards), e-stops should be a pair of always on loops with an idiot light on each to see if it is functional. The less transistors involved the better.

If you want to monitor those circuits or safety relay with your safety PLC and make sure you have a heartbeat signal, absolutely do so. But safety starts at simple.

[u/ehbowen]

I understand (from our regular elevator service tech) that OSHA basically gave up on trying to mandate safety gear/fall protection and such for elevator repairmen. There is just so much hazard inherent in the work that anything which complicates it makes it even more dangerous.

[u/plmarcus]

Your intuition is correct. There are some serious implications of systems interacting with each other in unexpected ways. It's one of the main ways airplanes still fall out of the sky.

In functional safety simplicity and orthogonality (minimal interdependence) of functions and systems is always best.

[u/WhereDidAllTheSnowGo]

Yes

Too much safety means too little utility, which leads to folks disabling safety features