You are not registered yet. Please click here to register!


 
 
plc storereviewsdownloads
This board is for PLC Related Q&A ONLY. Please DON'T use it for advertising, etc.
 
Try our online PLC Simulator- FREE.  Click here now to try it.

New Here? Please read this important info!!!


Go Back   PLCS.net - Interactive Q & A > PLCS.net - Interactive Q & A > LIVE PLC Questions And Answers

Reply
 
Thread Tools Display Modes
Old May 24th, 2023, 07:49 PM   #1
829
Member
United States

829 is offline
 
Join Date: Aug 2022
Location: USA
Posts: 8
Triplex or Lead Lag Lag 2 rotation

Hello everyone. I am trying to figure out what the best way to control three pumps would be. I have searched the forums and cannot seem to find what I am looking for, so I will be as detailed as I can. The two attached files are pdf and the test "works", but does not increment, which I believe some math would take care of. However, I am looking for a simpler(sp?) and more streamlined way of do this.

Issue: Control 3 pumps in rotation.
Rotation: Lead, Lag, Lag2.

Control Tank calls for pumps, based on level setpoints. Lead is called, if unable maintain, lag is called, and if still dropping lag 2 is called.

Once level is met for the respective set point, the pumps turn off and rotate.

I am using 3 counters to keep track of the pumps rotation status.

My current crappy code is rotating mostly working like I want. I am forcing a position change if one of the pumps becomes unavailable. However, when the pump becomes available again, I am looking back at my original counter, which is not set to increment, so the pumps go back to their original position. I do not like this method at all and I am just not smart enough to figure it out. My preference is to have the pumps rotate normally, but if a pump is removed from service, the system will operate in a lead, lag operation, but when the 3rd pump comes back into service, it will hop back into rotation. Caveat, I need to always have them rotate in a lead, lag, lag 2(if available) sequence. For example, the operation would be L, Lg, Lg2, rotate after lead call drop, L2, L, Lg and so on. Lets say pump 1 is down down for maintenance, the L and Lg would rotate between 2 and 3, but when pump 1 came back online, it would find its place in the correct order. There are other things in the code, which may be left over from trying a bunch of different ways to achieve what I want.

Pump 1 rotation counter: C5:3, using the acc
Pump 2 rotation counter: C5:4, using the acc
Pump 3 rotation counter: C5:4, using the acc

I am moving the acc of each counter to N10:40, 41, and 42 respectively.


I hope the above word salad is somewhat coherent, if not, please let me know. If anyone has any examples of what I am trying to accomplish or can point me to a good resource for this, please let me know.

Thank you
Attached Files
File Type: pdf p_rotation logic 5-24-2023.pdf (194.1 KB, 12 views)
File Type: pdf PR_Test 5-24-2023.pdf (176.6 KB, 8 views)

Last edited by 829; May 24th, 2023 at 07:59 PM.
  Reply With Quote
Old May 24th, 2023, 09:46 PM   #2
829
Member
United States

829 is offline
 
Join Date: Aug 2022
Location: USA
Posts: 8
I forgot to mention that the PLC is a Micrologix 1400 and I am using RSLogix 500.
  Reply With Quote
Old May 25th, 2023, 12:04 AM   #3
ianingram
Lifetime Supporting Member
Australia

ianingram is offline
 
Join Date: Apr 2002
Location: Newcastle
Posts: 447
Hi,


I have done the same project as this, with a Micrologix - see the attachment.

I based the motor selection based upon calculating the motor with the least amount of runtime. The motor with the least amount of runtime then becomes the lead motor. If a motor is unavailable(say in alarm) then it cannot be the lead motor.

Have a look at the attachment and let us know what you think
Attached Files
File Type: zip MPH_VAC_.zip (127.7 KB, 6 views)
  Reply With Quote
Old May 25th, 2023, 02:52 AM   #4
cardosocea
Member
United Kingdom

cardosocea is offline
 
Join Date: Nov 2016
Location: Fields of corn
Posts: 2,451
Just a small reminder that things fail and if the pumps are exactly the same and have the same exact number of hours on them, they'll likely fail fairly close to one another.

It obviously depends on the duty, process, maintenance regime and so on, but it's worth bearing that in mind particularly if they're to be used in a safety layer of sorts.
  Reply With Quote
Old May 25th, 2023, 11:44 AM   #5
drbitboy
Lifetime Supporting Member
United States

drbitboy is offline
 
drbitboy's Avatar
 
Join Date: Dec 2019
Location: Rochester, NY
Posts: 6,706
Bookkeeping. I rotated the other way (L,Lg,Lg2 => Lg,Lg2,L).
Attached Files
File Type: pdf Lead_Lag_Lag2.pdf (352.8 KB, 16 views)
__________________
_
Brian T. Carcich
i) Take care of the bits, and the bytes will take care of themselves.
ii) There is no software problem that cannot be solved with another layer of indirection.
iii) Measurement is hard.
iv) I solemnly swear that I am up to no good
v) I probably have the highest ratio of forum posts to actual applications in the field (∞).
vi) Hakuna matata.
vii) Bookkeeping.
  Reply With Quote
Old May 26th, 2023, 08:44 PM   #6
829
Member
United States

829 is offline
 
Join Date: Aug 2022
Location: USA
Posts: 8
Thank you for the replies, I will be looking them over.
  Reply With Quote
Old May 26th, 2023, 10:11 PM   #7
g.mccormick
Lifetime Supporting Member
United States

g.mccormick is offline
 
Join Date: Jul 2012
Location: IN
Posts: 911
i will try to remember to pdf and upload some code that i have for doing this. mine in in studio 5000, however the basic idea is the same. i chose to alternate every sunday and i have built into the logic ramping of the the starting pump and stopping pump too. my process runs basically 24/7.

i will try to remember this this weekend
  Reply With Quote
Old May 27th, 2023, 07:25 PM   #8
829
Member
United States

829 is offline
 
Join Date: Aug 2022
Location: USA
Posts: 8
Quote:
Originally Posted by g.mccormick View Post
i will try to remember to pdf and upload some code that i have for doing this. mine in in studio 5000, however the basic idea is the same. i chose to alternate every sunday and i have built into the logic ramping of the the starting pump and stopping pump too. my process runs basically 24/7.

i will try to remember this this weekend
Thank you
  Reply With Quote
Old May 28th, 2023, 01:38 PM   #9
TheWaterboy
Lifetime Supporting Member + Moderator
United States

TheWaterboy is offline
 
TheWaterboy's Avatar
 
Join Date: May 2006
Location: State of Denial
Posts: 1,594
Rotate every Sunday.... I never even considered that option... What's the thinking there? Not that its wrong or anything, just wondering.

I have a unique twist in that many of my locations that have multiple duty pumps maintaining pressure and a single massive fire flow pump for .. well you can imagine.

So while I rotate through the others every call, I rotate that one at night (avoiding demand charges) once in every 50 cycles of the others just to keep it moving after finding that the bearing would be damaged from sitting too long. The floor vibrations would vibrate the balls into the races.

I wish they were on VFD's so I could just spin them slowly once in a while without spiking the system from the sudden pressure increase.
__________________
. . . Things are getting weird, and they're getting weird fast . . .
  Reply With Quote
Reply
Jump to Live PLC Question and Answer Forum


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Topics
Thread Thread Starter Forum Replies Last Post
Help with Lead Lag Standby? IlluminEyeTrickz LIVE PLC Questions And Answers 7 October 20th, 2022 11:34 AM
VFD lead lag water pumps cjjeeper LIVE PLC Questions And Answers 20 August 27th, 2019 07:26 PM
8 boiler lead lag system HELPPP plz !! HeroControlsInc LIVE PLC Questions And Answers 9 April 7th, 2016 12:34 PM
Star-Delta Starter SLaubach LIVE PLC Questions And Answers 58 December 5th, 2011 08:56 AM
FB80 Lead lag filter foreverandever LIVE PLC Questions And Answers 4 July 27th, 2011 01:02 AM


All times are GMT -4. The time now is 10:41 PM.


.