24v relay circuit - elp!

[wade88]

Im feeling like Whinnie-the-Pooh this morning "a bear of very little brain" so am I right in that the idea of this project is that:
Someone loads the auger with a known amount of mix, then the operator manually start the auger. The auger moves the mix up and into the ribbon mixer. The ribbon mixer has load cells on it and when they register the correct weight then the auger stops feeding the mix. (using a PLC signal). Is that how its meant to work?

That is most correct Spoon yes.

 

[Spoon]

I spent 25 Years in quarrying, mesh gaurds are no barrier to a plant opperator. One guys head was crushed by the bar he was poking through a mesh gaurd. It doesn't need to be a body part.

I don't know the circumstance but shouldn't the guy know better not to be pushing a bar through the mesh in the first place. People should use their common sense.

 

[Spoon]

That is most correct Spoon yes.

Doesnt the ribbon mixer have its own motor? How is that operated? I dont know a lot about augers but isnt it the case of, if you dump 200lb of mix in it will move 200lb of mix into the mixer? Why the load cells?

 

[wade88]

Doesnt the ribbon mixer have its own motor? How is that operated? I dont know a lot about augers but isnt it the case of, if you dump 200lb of mix in it will move 200lb of mix into the mixer? Why the load cells?

Really hitting that nail on the head today Spoony. Exactly my point all along. Load cells are not needed, if nothing else useful for digital read out to see what weight is in the mixer, but PLC involvement, is like using a robot to wipe your crack clean. Novel..... but you'll do a much better job on your own.

 

[Spoon]

Really hitting that nail on the head today Spoony.

Sometimes I astound myself. I can get things right...contrary to what my missus says..

 

[wade88]

It's a females prerogative to suggest we did things wrongly, we just did things a better way to how they first planned it.

 

[Knobhead]

I don't know the circumstance but shouldn't the guy know better not to be pushing a bar through the mesh in the first place. People should use their common sense.

After 40 years of doing plant control I’ve found something out. You can’t design out STUPID!
Another thing to bear in mind. The plant operator is far more ingenious than you ever thought you were.

 

[Knobhead]

BTW I have a dim view of plant opperators.

And people that think it's "just a simple job". They never think about things.

 

[wade88]

Can only take such precautions so far though. Do everything that is reasonably practical to defray the instance of danger to a person. If an operator wants to stick a bar through the mesh, then

a) he/she deserves the repercussions for being a total plank.
b) your right, you can't design against stupid, therefore everything else you have covered is fine, the stupid people will soon die out and Darwin will have his say
c) If immediate risk has been dealt with and the only way to cause serious harm is by an operator trying to hurt themselves, then.... there really is no other solution is there.

On this particular machine operation, the operator would have to reach into a hopper, first of all squeezing their hand through 1inch steel mesh, reach the depth of the hopper which is greater than average arms length, and then tickle the auger screw or wedge their hand in it. It would take a whole new breed of stupid, to do this.

 

[C&H]

i've met some rare quarry operators, one of them had a start button jammed in with bit a bit of wire last week. heard of another one who kept coming in bandages on his hand. he tried to stop the rocks spilling from the crusher, every time he tried to push one back in another landed on top of his hand lol

 

[wade88]

Such people don't deserve hands, they should be sent to Alaska to chew the bark off trees for a living.

 

[SheffSimon]

Can only take such precautions so far though. Do everything that is reasonably practical to defray the instance of danger to a person. If an operator wants to stick a bar through the mesh, then

a) he/she deserves the repercussions for being a total plank.
b) your right, you can't design against stupid, therefore everything else you have covered is fine, the stupid people will soon die out and Darwin will have his say
c) If immediate risk has been dealt with and the only way to cause serious harm is by an operator trying to hurt themselves, then.... there really is no other solution is there.

On this particular machine operation, the operator would have to reach into a hopper, first of all squeezing their hand through 1inch steel mesh, reach the depth of the hopper which is greater than average arms length, and then tickle the auger screw or wedge their hand in it. It would take a whole new breed of stupid, to do this.

So when somebody has been injured or killed and you or your employer is in court, are you going to produce a printout of this forum thread as evidence of your risk assessment etc etc etc???

Dont get caught up in some of the b******* being spouted on here. It might be a simple machine, it might not require a PLC, whatever. All of that is irrelevant. Either do the design correctly or dont do it at all. Just bear in mind that we are talking about peoples health and wellbeing, so take it seriously or let somebody else do it. Would you like to work on equipment that hasnt been designed correctly. Doubt it.

 

[plugsandsparks]

I guess once you have come across a few accidents, some nasty, some bizarre, you will take a different view. I am currently modifying some machines for two handed operation after nearly 20 odd years of being in service. Also be looking at light curtains to stop even remote possibility of a very small human getting into a machine. My view, FWIW, if its possible to get injured, design it out.
Operator intelligence etc is simply not relevant.
Also depending on your risk assessment you may want to look at what happenes under fault conditions of any part of the machine and control system.
Its a whole new world...... (well has been for a while lol )

 

[plugsandsparks]

After a really nasty accident, nothing to do with the operator do his job, i needed to sign off a reciprocating press. Operator very lucky to live
http://www.hse.gov.uk/pubns/indg375.pdf

Is a good read.......

 

[wade88]

So when somebody has been injured or killed and you or your employer is in court, are you going to produce a printout of this forum thread as evidence of your risk assessment etc etc etc???

Dont get caught up in some of the b******* being spouted on here. It might be a simple machine, it might not require a PLC, whatever. All of that is irrelevant. Either do the design correctly or dont do it at all. Just bear in mind that we are talking about peoples health and wellbeing, so take it seriously or let somebody else do it. Would you like to work on equipment that hasnt been designed correctly. Doubt it.

Ok Simon,

I officially invite you to the premises at which I work, with your note pad and high viz on to come and carry out another risk assessment against this machine and its operation. And you will come to resounding conclusion, that there is no more that can be done to it, short of putting it inside a vacuum and the operator stands 20ft back and throws the material at it... that can make it any safer.

The concern currently is not with the auger, it is simply an auger that material is fed into, like thousands currently used in manufacture around the world, the concern lies with the electrical integration into an existing system. This is being looked at tomorrow.

Before you spout off any concern for death and court cases, there is no more design that can be done on this auger. Man stands at the end of it, man applies sack of grain, man walks away in tact.

I am taking this all seriously, but seriously, we are not talking about the handling of uranium 235 here.