runtime for pums , hints?

catalin78 · Oct 30, 2007

Hello ,

I have three small pumps on same pipe for wich is good to make runtime counters and auto switch to have similar running times for them , i use siemens step7 FBD and i am in ideea crisis , any hints are welcome

Thanks

milldrone · Oct 31, 2007

catalin78,

I'm going to make some presumtions here. And I can't help you at all on siemens.

As I read your post it looks like you want a pump alternating or lead lag system.

If I'm right then these threads may be of some interest.

http://www.plctalk.net/qanda/showthread.php?t=31492&highlight=alternation+pump

http://www.plctalk.net/qanda/showthread.php?t=22500&highlight=alternation+pump

http://www.plctalk.net/qanda/showthread.php?t=10099&highlight=alternation+pump

http://www.plctalk.net/qanda/showthread.php?t=26008&highlight=lead+lag+pump

Greg Dake · Oct 31, 2007

I don't get it

Why do you want your pumps to wear out at the same time? (being serious)...Every time I ask someone WHY they want to alternate or rotate lead pump, they fail to give me a good answer....other than "because".

Greg

SLC_Integrator · Oct 31, 2007

To my thinking it 'tests' the pumps on a regular basis to ensure they actually work.

Nothing worse than trusty ole pump #1 failing and pump #2, that hasnt run for years trying to start and failing miserably.
Then the process comes crshing down.
By testing if they work you can detect failures early and fix them before they 'fail on demand'.

catalin78 · Oct 31, 2007

Greg: It isn't useful or good in a conversation like this to answer my question with a question ( my opinion ) , this is my task to do : make runtimes for pumps almost the same .

Even so , it is not a problem because one pump follows the time of the other one so in don't think this will happen , even with equal times it is not a wriiten law that the pumps will fail at the same time , and i'm telling this from what i've seen in the field .
Same rule applies to compressors also and so on ...

So my query was in runtimes (software ) so we should keep it there.

Regards .

Greg Dake · Oct 31, 2007

I'm just trying to understand...

You may get more responses if the readers understand WHY you're doing what you're attempting. Your original post had very poor grammar and was unclear.

It is quite common to answer questions with another question to gain further understanding of the original question.

Didn't mean to offend,

Greg

Andybr · Nov 1, 2007

Greg is absolutely correct in raising his question. In maintenance management terms balncing run times in this type of application is almost always the wrong thing to do for precisely the reason that Greg states. Having said that SLC Integrators point is also valid so it is not unusual to provide exercise timers to allow each pump to run occasionally in order to verify that they are in working order and give the lubrication systems etc. a chance to work. A large part of the value of forums like this is to provide such "alternative thinking" which can be used or ignored as the poster wishes.

Andybr

catalin78 · Nov 1, 2007

Greg:

I like to have this kind of debates , but now it wasn't the time for me , as for my grammar i see from your question that you fully understood what i wanted to do .
This "runtime pump" is demanded from the main contractor of this project i'm in , i didn't have the time to ask why he wants it , but i will try see what is his reason for this feature .
However you should stop blaming my poor english and understading of my text , and it's good that you start a thread with your unanswered question

Of course i wasn't ofended and didn't try to offend nobody .

A good day to you all

Norml · Nov 1, 2007

Sometimes alternating pumps has nothing to do with even pump wear. Pumps are ofter alternated because of what they are pumping and the idea is to keep material settling, thickening and clogging pipes. Wastewater is a good example.

rsdoran · Nov 1, 2007

I disagree that from a maintenance standpoint it is the wrong thing to do, every pump has a MTBF and alternating them increases the time between possible failures. If you have a true preventive maintenance program then you have an idea when to service them to prevent downtime issues.

I have never been a proponent of running something until it fails then fix it.

mordred · Nov 1, 2007

we tried both schemes her and have found that running 1 pump then the other worked better when it came to being able to spot problems. Granted the more common excuse provided is to wear them out equally, which we know doesn't really work out. However you at least know they are both working we do the same for our duo rail and conveyer systems.

catalin78 · Nov 1, 2007

For this application there are 2 circuits with heating , (water at 60 degrees) so each circuit has two pumps .

Main contractor wants these pumps alternated so they have aprox. equal run time.

Andybr · Nov 1, 2007

I certainly did not suggest that pumps should be run until they fail. They should indeed be maintained regularly as part of a preventative or condition based maintenance system. This does not detract from the fact that balancing runtimes will leave all of the pumps due for maintenance at the same time rather than spreading the work. The other issue is that balancing runtimes will also result in the performance loss associated with wear affecting all of the pumps equally. By running one pump continuously until maintenance becomes due you should always be replacing a worn pump with one which will restore the system performance to "as new".
Andybr

catalin78 · Nov 1, 2007

I fully understand this point of view , i already put this in discution but ... let's say things in ROMANIA are not the same as it is normal to think or do

So again , i was thinking to use the hardware pulse provided by plc to improvise a counter for each pump , and i can specify when it is service time for each pump , still alternating them if that is the wish of main contractor .

Even alternating them there is enough time to service one pump when it is reached its time .

mordred · Nov 1, 2007

You could use the RTC clock to calculate the runtime on each then whichever value is the lesser, switch to the lower runtime pump. Or if they are too specific on accuracy then run one one day the other the next day with the off days excluded.

runtime for pums , hints?

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