Ladder Logic Question w/ Fermenter setup

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dhempy
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Ladder Logic Question w/ Fermenter setup

Post by dhempy »

I am wondering if it makes sense to move some control from process configuration over to Ladder Logic for my fermentation setup. The setup is a pair of jacketed conicals chilled by pumping glycol through converted window AC reservoir and using a couple of ball valves to control flow. The single state processes are fairly simple .. Chill Glycol, Ferment 1 and Ferment 2. Each controls the Pump and a valve (the glycol chill opens a recirc valve) and simply invoke a Hysteresis Coll setpoint for each of the outputs. This leads to changing 3 setpoints for the Glycol process (Pump, Valve, AC) and 2 each for ferment states (Pump/Valve). Does it make sense (or would it be preferred) to move the pump control over to ladder logic such that the pump runs whenever a valve is open? That would eliminate one setpoint for each process. With a little extra logic I could do the same for the glycol chill process and only set hysteresis control for the AC unit.

The reason this came up is that I've noticed that the BCS is short cycling my pump when it gets around set point temps for the fermenters turning it on for 1-2 seconds at a time. I will probably just add a delay state that will allow the temp to stabilize a bit once the setpoint exit condition is met and see if this solves the issue. This will add yet another place that requires a temp change based on the fermentation temp but that may be the cost of doing business.

Dan
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Re: Ladder Logic Question w/ Fermenter setup

Post by JonW »

Dan,

I thought we talked about this in our last chat on the fermenters? I do exactly what you're suggesting (as does Sam).
In the ladder logic below, whenever one of my 3 glycol valves open, it turns on the pump. Ferm 1 is Out1, Ferm2 is Out2 and bath recirc valve is Out9. Whenever one of those is open, it forces the pump on (Out10).

Additionally, if the chiller goes on (Out5), it forces the recirc valve to open (Out9).
Ferm_Ladder.PNG
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dhempy
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Re: Ladder Logic Question w/ Fermenter setup

Post by dhempy »

If we did I blocked it out because of "Ladder Logic" :o . Now that I've gotten a better handle on Ladder Logic implementation I'm more receptive :geek: .

That makes sense and is pretty much what I was thinking.

Another part of this sis because it seems like my Ferm 2 process leaves the valve open on occasion.

My Echo396 pump cycles sometimes too. Seems that it does this when it the setpoint has just been met. I put in a delay state and will see if that helps solve the issue. I'm searching for a new pump anyway as this one is leaking (I have it externally mounted) and I'd dissatisfied with the flow rate. Problem is I'll need to find a break in the fermentation schedule to rework that system.

Thanks for the response.
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