ECN Forum Forums Safety Discussion and News Safety News and Product Recalls Escalator speeds up and injures several people.

http://sports.yahoo.com/mlb/news/ap/20020509/ap-baseballescalator.html

How did (does) this happen?

Any theories out there?

See Article 620, the subject of acceleration and speed is defined in 620.2, so I would suspect some sort of malfunction in the control system.

Let me rephrase that:

What kind of idiot would design a people mover that would go 3x faster than needed suddenly without warning in the first place?

I guess what I'm after is, did it suddenly go from say 120V to 277V (impossible, I know) and briefly speed up before burning the motor up, or is some controller inadvertantly design to allow just such an occurance...

I'm just having a hard time imagining a 60 Hz system suddenly becoming a 180Hz system, and on just one machine, I'm obviously missing something. Can motor windings fail in such a way to cause this type of symptom?

Am I being stupid? Am I the only one that sees the absurdity here?

I'll shut up now...

[This message has been edited by sparky66wv (edited 05-14-2002).]

I would guess that some sort of AC or DC Drive was feeding the motor. Maybe there is a current feedback signal that maintains steady speed while under varying loads. This control system may have been corrupted somehow.

Most likely an electronic servo drive system, and they either lost speed feedback or a shunt field on a DC drive. Either failure SHOULD have tripped a safety interlock on the drive system, rather than letting the motor speed "shoot for the moon".

Why they would have such a sophisticated drive system (with all the attendant problems) where a simple start/stop/reverse would seem enough is another question entirely....

OK, Wow I had no idea they were so complex...

I figured just a constant speed motor sized for maximum load...

Maybe I'm too simple minded...