To control 6 pump sets in sequence. what can be ladder logic for it ?

[Anirban Hazra]

@Prashant

I personally think there should be a "Start" and "Stop" button in every system.But since you said you wanted a system where the pumps would run the sequence from the start on resumption of supply and stop on lack of supply here is how it's done by my logic of three timers. Just 3 rungs - not complicated at all.

Disclaimer: I strongly advocate against the use of any logic not having a "Start" and "Stop" such as the one below in a real system.This has been shown only to demonstrate how such a system can be programmed.

 

[hinddhindsa]

@Prashant

I personally think there should be a "Start" and "Stop" button in every system.But since you said you wanted a system where the pumps would run the sequence from the start on resumption of supply and stop on lack of supply here is how it's done by my logic of three timers. Just 3 rungs - not complicated at all.

Disclaimer: I strongly advocate against the use of any logic not having a "Start" and "Stop" such as the one below in a real system.This has been shown only to demonstrate how such a system can be programmed.

I need to choose a PLC which has PID functions,
AND i am looking to buy a DELTA plc.
which one will be best and
i need to tell you here that
if Water pressure is less than 4 bars, all 3 pumps should ON.
if water pressure is less than 5 bars , 2 pumps on.
if 5-6 bar , then only first pump should on.
if more than 6 bar, all pumps off.

so here we need to take input analog signal from field.

please friends write logic for it and help me .
thanks you very much

 

[Prashant1707]

@anirban

Your logic is perfectly fine for alternation of 3 pump sets. My idea behind using an acyclic pulse generator is to make a provision for allowing ample time for deceleration of the pump set after its supply is cutoff. with your 3 timer logic there will be an instant when 2 pump sets are rotating which may be a threat to the pipelines i.e. suppose as in your logic one pump set is rotating and the time is up second pump set will start running while the first set is still decelerating to stop. Think about it.

 

[Anirban Hazra]

@Prashant

As I have said earlier,the shown Logic is not for a real system.It was just to give you an idea of how it can be done using 3 timers.In a real system ofcourse every factor would be considered in the programming.

@Hindhindsa

i need to tell you here that
if Water pressure is less than 4 bars, all 3 pumps should ON.
if water pressure is less than 5 bars , 2 pumps on.
if 5-6 bar , then only first pump should on.
if more than 6 bar, all pumps off.

To do the above, just save the analog value from an appropriate pressure sensor to a register and use comparison instructions on it to turn on the appropriate number of pumps at the different pressure level.

 

[Lancie1]

First:

I need to control six pump sets.
Initially 2 pump sets will run, after two hours another two will run, and later the third pair.
5 bar pressure has to be maintained.
Can you please help me? How can I achieve this?

Second:

I need to tell you here that:
If Water pressure is less than 4 bars, all 3 pumps should go ON.
If water pressure is less than 5 bars, 2 pumps go on.
If 5-6 bar, then only first pump should go on.
If more than 6 bar, all pumps are off.

Hmmm...the specifications changed in the middle of the project, right when the programmers thought they were finished with the job! Does that remind you of what happens in the real world (instead of a student problem), or what?

 

[hinddhindsa]

yes that is true..
my boss did not explained me the things properly that what does he exactly want .
But Boss is Boss, and Boss is always Right

 

[Lancie1]

Your boss did mention the pressure, though you apparently assumed the 2 hour runs times were more important than maintaining a certain system pressure. I think that is due mostly to your experience level. As Chavak said back in Post #3:

Well, 5 bars of pressure is to be maintained, so the pressure switch is not a condition, it is a requirement. It means more pumps have to be added in, or taken away in case the pressure drops/increase.

This could be a training exercise to see how well you can write a program.

What model of Delta PLC are you using? Do you have the User Manual?

I would start my program by setting up some flag or status timers (to make sure that pressure is not fluctuating before switching pumps):

 

|    +--------------+                       RUN 3 PUMPS  |

|----|Pressure <= 4 |------------------------[Timer 3 ]--|

|    |Input         |                        [5 secs. ]  |

|    +--------------|                                    |

|                                                        |

|    +--------------+   +-------------+     RUN 2 PUMPS  |

|----|Pressure > 4  |---|Pressure <=5 |------[Timer 2 ]--|

|    |Input         |   |Input        |      [5 secs. ]  |

|    +--------------+   +-------------+                  |

|                                                        |

|    +--------------+   +-------------+     RUN 1 PUMP   |

|----|Pressure > 5  |---|Pressure <=6 |------[Timer 1 ]--|

|    |Input         |   |Input        |      [5 secs. ]  |

|    +--------------+   +-------------+                  |

 

[Lancie1]

I need to choose a PLC which has PID functions, AND I am looking to buy a DELTA plc. Which one will be best?

How many analog Inputs and Outputs do you need? How many digitial inputs? How many digital outputs? Do you need the PLC to communicate with an operator panel (HMI) or some other device? Do you need Ethernet communications capability? What voltage level do you need for your digital inputs, and for your ditital outputs? A dozen other questions need answering before you can pick the best PLC for the job. First make a list of all your Inputs and Outputs.

The Delta Electronics DVP-EX Series has 4 analog inputs, 2 analog outputs, and up to 238 digital I/O. See this link:
http://www.delta.com.tw/product/em/control/plc/control_plc_product.asp?pid=3&cid=1&itid=3

 

[hinddhindsa]

need a HMI also.

Dear Sir.
as i want to maintain 5 bar pressure and a sequence operation of pump sets.
i need a HMI also. Ethernet is not required.
So here i am thinking to order DVP-32ES 200R or DVP-30 EX200R.
which one will be most suitable, as DVP-30 EX200R is more suitable for temperature control but here in my project has to get analog input of pressure..

 

[Lancie1]

So here i am thinking to order DVP-32ES 200R or DVP-30 EX200R.

I do not think that either Delata PLC model has built-in analog pressure inputs, so you would have to buy at least one additional add-on module before you could use those models to read in an analog pressure value.

Also you have to decide whether you need a relay output version ("R" at the end of the model name). You would need PLC relay outputs if your Pump motor starters (contactors) have AC control coils. If they have 24 volt DC coils, then you can use the PLC Transistor ("T") Output type.

It appears that all of the Delta Electronics PLCs have 24 volt DC digital inputs only (no AC digital inputs). All of your control switches will need to operate at 24 Volts DC, if you use a Delta PLC.

Personally, I would not use a Delta PLC, simply because the user manuals are very poor (the English manuals). I could not find any information showing how to obtain analog input and analog output modules, or if there are Delta models that have built-in analog inputs and outputs, as there are in most other PLC brands.

 

[thucnd1410]

Hi every one. I also have a control situation. I want to control 3 pumps in succession for the waste water treatment tank. If the level is high(For ex.setting 80%) one of 3 pumps will run and the other standby. If the level is high high (For ex. setting 90%)one more pumps require to run. Pumps work in turn, in detail, If the level is high Pump1 run, Pump2 and Pump3 standby. The next time, if the level is high. Pump2 run, Pump1 and Pump3 standby. Continouly, Pump3 run, pump2 and pump1 standby. Using RSlogix5000

 

[Lancie1]

Thucnd,

The most commom method to alternate between two pumps is to use alternator logic. The RSLogix5000 software does not have a built-in alternator, but you can write logic do alternate two pumps. You would probably need two alternators to use 3 pumps. Search this site for "alternator" or "flip-flop".