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Old June 16th, 2010, 09:18 PM   #1
24fretslater
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Lead/Lag/Standby SELECT from SCADA

Hello everyone.

I'd first like to say that I did in fact search the forums but I didn't find anything that really helped. I have somewhat of a unique situation here.

I'm working on an SBR and am programming a Disk Filter Feed Pump routine.

There are 3 pumps. Filter Feed Pump A, B, and C. I have programmed the Lead and Lag request conditions and now I must program a selectable (From RSVIEW32 SCADA)Lead/Lag/Standby routine.

I am somewhat of a novice at programming and could really use some help! Any reply would be greatly appreciated.

In the event of needing to service a pump, the client would like to be able to select one pump as standby and let the other two pumps operate on normal Lead/Lag sequence.

Kicker is they want to be able to select which pump is lead and which pump is lag as well! Also, the pumps are all on VFD's and if the lag pump is called on, they split the speed control.

I'm very frustrated and overwhelmed seeing as the boss returns tomorrow to see my work. After trying all day it seems I've become quite desperate. Does any one have any tips/templates that might help?

Thanks
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Old June 16th, 2010, 09:47 PM   #2
jrwb4gbm
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I know it is not SCADA but...
See the thread in this link, posts 39 and 61, might be some help:
http://www.plctalk.net/qanda/showthread.php?t=9499

Edit:

Last edited by jrwb4gbm; June 16th, 2010 at 10:10 PM. Reason: more info
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Old June 16th, 2010, 09:48 PM   #3
24fretslater
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There is one more thing. These pumps run all the time. The only thing that stops them is a Filter Feed Channel low level alarm.
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Old June 16th, 2010, 11:16 PM   #4
robo77
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post what you used for your lead/lag

try zipping your file and posting..it
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Old June 17th, 2010, 04:20 PM   #5
24fretslater
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Here's my first attempt. I think I'm probably way off.
Attached Files
File Type: zip Filter Feed Lead Lag Standby TEST.zip (33.5 KB, 72 views)
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Old June 18th, 2010, 07:09 AM   #6
Tom Jenkins
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We do this by having two sets of registers. One is designated as "current" lead/lag/standby and the other as "new". The operator enters his changes in the new fields, and the current fields are display only read from the PLC. We have an "execute" momentary push button on the HMI. When the operator is happy with his new entries he pushes it, and this sets a bit in the PLC. This bit moves the new lead/lag/standby values to the appropriate registers and initiates the stopping and starting of the appropriate equipment.
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Old June 18th, 2010, 10:19 PM   #7
Mike Lamond
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I don't have a triplex sequencer handy in A-B, but the attached file is a PDF printout of a quad that I programmed with just about every possible feature, as specified by the Owner's Engineer. It's not just belt-and-suspenders, but an elastic waistband too.
  1. Auto-1-2-3-4 lead pump selector switch on the control panel door.
  2. In 1,2,3 or 4, run the pumps in order with the selected pump as lead.
  3. In Auto, the operator can select Auto or Manual alternation through the HMI.
  4. In HMI-Auto, the pumps run in order with the lead pump advancing at a preset time of day.
  5. The pumps can alternate only if one pump is running;
  6. If the lead pump is not available (fault or switches not in auto), alternate to the next pump.
  7. If a lag pump is not availble, move the remaining pumps up as required.
  8. If a lag pump becomes available, do not restore it to the sequence until the corresponding lag stage is off.
  9. In HMI-Manual, the operator can set the pumps in any order. I used the New and Current registers as Tom described and validate the New values by checking their product (24) and sum (10). The HMI limits the input range.
I've gone as high as 4 of 5 with straight order sequencing and 4 of 6 with a requirement to balance the odd and even numbered pumps in operation. In that case, the isolation transformers on the pump VFDs were split between delta-delta and delta-wye in order to cancel some of the harmonic noise on the 480 volt service.
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File Type: pdf Quad_Pump_Rotation.pdf (172.1 KB, 239 views)
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