Unloading Silos

mapizarro · Apr 21, 2004

Hello everyone,

I need some help developing a program using AB RSlogix 500

The project is to unload material from 8 silos into 5 different hoppers. Each hopper have a low and high level sensor.

I know how to control the blowers, pipe diverters but I am not sure what is the best way to scan the low level hoppers and start the silo unload sequence.
Any help will be apreciated.

93lt1 · Apr 21, 2004

I am picturing an injection molding material loading system.

First I would come up with an ordered list of which hoppers are most important. If certain hoppers are more likely to empty faster, they need to have priority or at least an increased fill time.
I would probably also give priority to any hoppers with the low indicator on, and again in a prioritized manner if more than one. If all of the hoppers flow are somewhat balanced it will be easier to get the proper fill sequence and timing.

It really depends on how much the hoppers can hold, how much fill time per hopper is desired, and the rate of material flow into the hopper vs. the rate of material flow out of the hopper, to go into more detail.

As far as control of the 8 silos, it all depends on how you need it to work, empty one go to the next, try to keep all at the same level, etc.

I would definitely give operators the full manual ability to do a manual fill of any hopper from any silo.

As always, more info would be helpful.

mapizarro · Apr 21, 2004

At this time loading priority is not an issue. The output of the lines are low so the unload system will keep up serving one hopper at a time.

However I like your idea of having priority added to the code.
What is the tipical way use in plc programming to scan for hoppers?
The operator will select what lines are running(what hoppers are in use) using toggle switches.
How does a priority code look like?

93lt1 · Apr 21, 2004

mapizarro said:
How does a priority code look like?

Judging by this, I am guessing you are not very familiar with PLC programming??

by priority, I mean if 2 or more hoppers are calling for material at the same time, the one with greatest priority should get the fill first or longer.

So let me get this straight, You want to simply run a hopper from full till the empty sensor comes on, then fill it completely (till the full sensor comes on), and return the loading system into a "standby" mode waiting for any hopper (currently selected as "running" by the operator's toggle switches) to become low?

If this is the case it will be very simple. I was imagining a system where the loading system flow would be almost equally matched to the usage flow.

elevmike · Apr 21, 2004

a few months back testsubject and I helped a guy fill 5 hoppers from a silo using a blower, and 5 diverter valves. Only one diverter at a time could be opened since they were in series in a closed loop system. That required the hoppers to be filled in order of low level demand. this became a FIFO operation that required the order of demand to be placed in a memory stack, that would also compensate for the shutting down of any one or more hopper during the process. The diverter valves were equipped with open and closed limit switches, and were controlled by an air solinoid. The silo had a auger that fed the material into an air stream and if all the valves were closed, the material would be blown back into the top of the silo. The blower motor, and auger would shut down after a few minutes of no demand.

Does this sound familliar?

The program was written for an AD DL205. I think the CPU was a 250. If your working with an existing PLC than it wont be of much use. But if you havnet purchaced the plc this might be someting that you can use.

Let me know, MIKE

Eric Nelson · Apr 21, 2004

I don't think it hurts to give the LINK to that discussion in any case.

By the way, Mike, I just re-read that topic, and you and Bob never diclosed the 'final' solution (if there was one)...

beerchug

-Eric

Thomas Sullens · Apr 21, 2004

Hi mapizarro

The project is to unload material from 8 silos into 5 different hoppers. Each hopper have a low and high level sensor.

You didn`t say anything about the hardware, but be sure and add plenty of inputs. Make a program that will unload #8 silo to #5 hopper. You didn`t give much info so here`s a scenario. Say there`s an auger running over all 5 hoppers and over each hopper there is a gate in the bottom of the auger that when open will fill that hopper.
You push a button N.O.contact spring return that say`s 8 to 5 this brings on a relay that seals in.(internal relay) This relay look`s at limit in hopper 5 and say`s I`m not full so open the fill gate, the fill gate makes a sensor that says I`m open. So start the auger over the hoppers, the auger tells the plc I`m running so start the conveyor feeding me. This conveyor will tell what ever brings material out of #8 silo to come on. The hopper fills up to the Hi limit and stops everything in reverse order.Giving time to cleanout if necessary and everything should be interlocked so if something O.L.`s all behind it will stop. Hope this helps some. AB is a good choice. It takes alot of thinking and what ifs.
Have a nice day.
Tom

mapizarro · Apr 22, 2004

Silos are drained through the bottom using an airlock to feed resin
into a pressurized pipe.
Diverters direct the resin to the appropriate destination. Conveying
sequence begin when a low level sensor calls for material. Conveying
continues until the level sensor is actuated and stop the sequence.

This page is an excelente source of information. Thank you all for giving me ideas of how to solve the silos unload task.

elevmike · Apr 22, 2004

Eric,

If you read the last two or three posts on that thread youll see that we had to abandon the forum. We went to email faxes, and eventually phone calls. The guy sent me an email telling me that he just needed to make some minor changes but for the most part the program was working as intended. I ended up with a sizeable paper file on this complete with wiring diagrams he faxed to me, the programs, and layouts etc..

It appears that mapizarro is dealing with the same situation from a programming point of view. Too bad the final program isnt for an AB.

Mike

dandrade · Apr 23, 2004

mapizarro said:
Silos are drained through the bottom using an airlock to feed resin
into a pressurized pipe.
Diverters direct the resin to the appropriate destination. Conveying
sequence begin when a low level sensor calls for material. Conveying
continues until the level sensor is actuated and stop the sequence.

This page is an excelente source of information. Thank you all for giving me ideas of how to solve the silos unload task.

You do not import of add here, the screen of representation of the project.!?
It would be the return of gratitude.
-------portuguese---------
Você não importa de adicionar aqui, a tela de representação do projeto.!?
Seria o retorno de agradecimento.

Unloading Silos

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