Metal recycling crushers - speed monitoring

[Skogsgurra]

Never been close to one of these before. A guy phoned me and told me that the speed pick up didn't work.

It is none of my business. But he insisted that I am a specialist even if I tried to un-sell my expertise, without much success.

The motor is a fairly big one, he couldn't say but probably in the 500+ HP region. DOL and no speed control whatsoever. He didn't know why the speed pick up was needed. I told him that we are two that don't know then. At least. That didn't satisfy him.

My guess is that those crushers need to get up to speed (there is a fly-wheel) before you start to feed in the material to be crushed. If that is so, I guess that a simple proximity switch can be used and I am also thinking permanent magnet plus a robust reed switch with series resistor to reduce capacitive current at closure could work.

I don't have the time for this but everyone else seems to have shut off their phones (the holy 5-week holidays). Anyone out there with experience from this kind of machinery? Please.

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[itsmoked]

Not a lot of direct experience on that either but I would speculate that the in-feed may be speed controlled by the grind speed, meaning it could be more than a reed switch.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[OperaHouse]

It could be a crude form of torque measurement. If the motor slip reaches a certain percentage it shuts down.

 

[catserveng]

A company I worked for several years ago that helped build a number of diesel engine powered car shredder/crushers. The engines had a mechanical governor that was set with a hand throttle. As Keith speculated, the infeed feed control used the shredder speed to manage how fast it shoved the car into the shredder, if the shredder speed dropped, the infeed slowed down until the shredder speed came back up.

The builder of that system used two magnetic pickups, one on the supplemental flywheel driving the shredder, and one on the motor driving the gearbox for the infeed conveyor, both of those went to a small PLC in the shredder control box.

Is it possible this started life as an engine drive unit and was converted to an electric motor drive? I had heard this happened with a couple of units sent to the USA Southeast.

From what I remember the original machine design came from a company called TOR in partnership with the CAT dealer in Holland (Gveke).

Hope that helps.

 

[Skogsgurra]

That is probably how it works. I told them to follow the wires and tighten loose ones. They haven't come back. So problem seems to be solved. Not a very inspiring thing to work with and I don't know if I want to bring my car near a machine like that. A mistake could easily happen...

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[itsmoked]

Ah, but what a glorious mistake!

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Marke]

Hi Gunnar

I have also seen systems where they plug break the unit to bring it to a stop in a hurry. A rotation sensor / speed sensor is used to determine when the motor / load reaches close to zero speed.

best regards
Mark

Mark Empson
Advanced Motor Control Ltd