CR4 - The Engineer's Place for News and Discussion ®


Previous in Forum: Coriolis Mass Flow Meter Selection   Next in Forum: Temperature Transmitter
Close
Close
Close
35 comments
Active Contributor

Join Date: Nov 2016
Posts: 15
Good Answers: 1

Product Water Flow

01/08/2017 12:51 AM

hi everybody

please share your views or suggestion regarding the problem below.

i am working in 15 MIGD RO plant.there are 6 RO units each having a capacity of 2.5 MIGD.we are facing a problem from last week that Product flow of RO plant per day is 14.1 MIGD and product water transfer flow from tank is 14.3 MIGD. i-e transfer flow from tank is more than product flow of RO plant.it means production is less but output is more.difference between production and transfer flow is 600 ton/day.

we are using electromag flow meter for flow measurement and as its sensor is fixed inbetween the main line.we need to stop the production to check the sensor.that is not affordable.

please share if some body faced this type of issue.is this flow meter problem or sensor error. or some other reason.

Register to Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Guru

Join Date: Apr 2011
Posts: 5892
Good Answers: 210
#1

Re: product water flow

01/08/2017 1:39 AM

What is the tank capacity? Have you checked the level?

If more is being removed from the tank than is being added, the level should be going down. If it is not going down, then the indication of what is being add or removed or both is not accurate.

__________________
Eternal vigilance is the price of knowledge. - George Santayana
Register to Reply
Active Contributor

Join Date: Nov 2016
Posts: 15
Good Answers: 1
#2
In reply to #1

Re: product water flow

01/08/2017 2:13 AM

tank level is maintained by closed loop control at 90 %. if production changes transfer pumps (vfd)will ramp up or down to maintain the level.

Register to Reply
Guru

Join Date: Apr 2011
Posts: 5892
Good Answers: 210
#3
In reply to #2

Re: product water flow

01/08/2017 2:18 AM

Have you verified tank level is being controlled acceptably?

__________________
Eternal vigilance is the price of knowledge. - George Santayana
Register to Reply
Active Contributor

Join Date: Nov 2016
Posts: 15
Good Answers: 1
#4
In reply to #3

Re: product water flow

01/08/2017 2:24 AM

i check the trend in dcs .level is maintained between 88-90 % all the time.

Register to Reply
Guru

Join Date: Apr 2011
Posts: 5892
Good Answers: 210
#5
In reply to #4

Re: product water flow

01/08/2017 3:34 AM

Have you personally checked the tank?

On second thought, if this is not a huge tank, there is no way it could be the cause of such a large discrepancy.

Looking back can you see when the divergence occurred if either the amount being taken out appears to deviate upward of typical, or the amount added appears to deviate downward of typical?

Are there other ways to get a measure of what should be flowing, like the feed input to RO minus the concentrate outflow?

__________________
Eternal vigilance is the price of knowledge. - George Santayana
Register to Reply Score 1 for Good Answer
Guru

Join Date: Apr 2010
Posts: 4959
Good Answers: 471
#11
In reply to #4

Re: product water flow

01/08/2017 6:34 PM

My calculations: 14.5/14.3 = 1.014. My guess is that the total of the inaccuracy of the two meters sums to 1.4 percent. (Both could be within 1 percent if they err in opposite directions.) Check with you manual to see what the stated accuracy is for the meters.

Here is another thought: How have you determined this discrepancy? If your control system turns on input and output pumps to control water level, this reading would fluctuate up and down. Are these instantaneous readings calibrated to MIG per day, or are they actual volume of water per day? If it's an average of instantaneous values, variations from the control system could give you an apparent error just by chance if there are not enough data points.

Register to Reply Score 1 for Good Answer
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain, and now disconnecting as Little England and Wales (not too sure about Wales bit, either). Kettle's on.
Posts: 25740
Good Answers: 677
#27
In reply to #4

Re: product water flow

01/10/2017 2:53 AM

Then the tank is too large. The only purpose of a tank is to allow the level to go up and down.

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
Guru

Join Date: Jun 2009
Location: South of Minot North Dakota
Posts: 7876
Good Answers: 729
#6

Re: product water flow

01/08/2017 6:23 AM

So you're running a 15 Million Imperial Gallon a Day reverse Osmosis plant and your financial management and system layout is so incredibly poor you can't shut down or isolate let alone do any on the go calibration checks and or adjustments to any key sensors in the system?

From what I understand RO treatment of bulk volumes of water costs about .5 - 1 cent per gallon and sells for at least double that so if you are doing ~ 15 million gallons a day that's a net financial profit value of ~ $150,000 - $300,000 dollars per day.

And a volume totalizing discrepancy between input and output flow seems like a bigger issue to be concerned with?

Register to Reply Score 1 for Good Answer
Active Contributor

Join Date: Nov 2016
Posts: 15
Good Answers: 1
#14
In reply to #6

Re: product water flow

01/09/2017 4:33 AM

tcmtech

hmmm. you should join finance & management.you are wasting time in instrumentaion

Register to Reply Score 1 for Off Topic
Guru

Join Date: Mar 2007
Location: at the beach in Florida
Posts: 17170
Good Answers: 976
#7

Re: product water flow

01/08/2017 11:03 AM
__________________
Life is like riding a bicycle. To keep your balance you must keep moving. A.E.
Register to Reply
Guru

Join Date: Oct 2008
Posts: 39041
Good Answers: 1533
#8

Re: product water flow

01/08/2017 12:19 PM

And how is the reject stream accounted for?

Register to Reply
Power-User

Join Date: Nov 2009
Posts: 274
Good Answers: 51
#9

Re: Product Water Flow

01/08/2017 4:50 PM

>we are facing a problem from last week that Product flow of RO plant per day is 14.1 MIGD and product water transfer flow from tank is 14.3 MIGD.

What were the product flow and transfer flow values a week prior to the 'problem'?

Register to Reply
2
Guru

Join Date: Apr 2011
Posts: 5892
Good Answers: 210
#10

Re: Product Water Flow

01/08/2017 5:44 PM

"...Product flow of RO plant per day is 14.1 MIGD and product water transfer flow from tank is 14.3 MIGD. i-e transfer flow from tank is more than product flow of RO plant.it means production is less but output is more.difference between production and transfer flow is 600 ton/day....."

.

The problem is even worse than you thought! 14.3 - 14.1 million gallons is 200,000 gallons. That should be close to 1,668,000 lbs, so 834 tons/day. But you only report missing 600tons/day!

Not only is your product missing, now even some of your missing product has gone missing!

__________________
Eternal vigilance is the price of knowledge. - George Santayana
Register to Reply Good Answer (Score 2)
2
Guru

Join Date: Oct 2008
Posts: 39041
Good Answers: 1533
#12

Re: Product Water Flow

01/08/2017 7:00 PM

If you really want to solve your problem (it is your problem isn't it?) at some point stopping the production to check the sensor will become affordable.

As tcmtech suggested, a lack of planning on your part does not indicate an emergency on our part.

A $40.00 dollar part is endangering a million dollar operation because nobody designed the system properly.

Register to Reply Good Answer (Score 2)
2
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain, and now disconnecting as Little England and Wales (not too sure about Wales bit, either). Kettle's on.
Posts: 25740
Good Answers: 677
#13

Re: Product Water Flow

01/09/2017 3:14 AM

<...electromag flow meter...> On RO permeate? Really?

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply Good Answer (Score 2)
Active Contributor

Join Date: Nov 2016
Posts: 15
Good Answers: 1
#15
In reply to #13

Re: Product Water Flow

01/09/2017 4:35 AM

yes.....

you need to know more about RO system

Register to Reply Score 1 for Off Topic
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain, and now disconnecting as Little England and Wales (not too sure about Wales bit, either). Kettle's on.
Posts: 25740
Good Answers: 677
#17
In reply to #15

Re: Product Water Flow

01/09/2017 5:03 AM

Please describe it, then, because it cannot be seen from here.

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
Active Contributor

Join Date: Nov 2016
Posts: 15
Good Answers: 1
#24
In reply to #17

Re: Product Water Flow

01/09/2017 10:53 PM

Elec conductivity of product water is more than 700 us/cm. according to farady's law of electromagnetic ,any conductor passing through magnetic field will generate emf.so that emf is proportional to flow of the conductive fluid. so we can use mag flow meter in RO system.

Register to Reply
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain, and now disconnecting as Little England and Wales (not too sure about Wales bit, either). Kettle's on.
Posts: 25740
Good Answers: 677
#26
In reply to #24

Re: Product Water Flow

01/10/2017 2:52 AM

<...700 us.cm...> That's new, and pertinent information to this thread. Mentioning pertinent information in the original posting does wonders to keeping threads on-topic.

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
2
Power-User

Join Date: Jul 2016
Posts: 253
Good Answers: 8
#19
In reply to #13

Re: Product Water Flow

01/09/2017 8:29 AM

With such a low signal from clean water, a small change in excitation, loose or corroded wire connections, or a coating on the electrodes could all contribute to less current from the mag meter, I'm surprised it worked at all...

Register to Reply Good Answer (Score 2)
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain, and now disconnecting as Little England and Wales (not too sure about Wales bit, either). Kettle's on.
Posts: 25740
Good Answers: 677
#21
In reply to #19

Re: Product Water Flow

01/09/2017 9:24 AM

Quite.

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
Guru

Join Date: Mar 2011
Location: Lubbock, Texas
Posts: 9118
Good Answers: 114
#33
In reply to #19

Re: Product Water Flow

01/10/2017 1:33 PM

What you said: " loose or corroded wire connections, or a coating on the electrodes could all contribute to less current from the mag meter, I'm surprised it worked at all..."

Appears to me that you were spot on with that answer without being presented critical information, way to go!

__________________
If it ain't broke, don't fix it. Just build a better one.
Register to Reply
Guru

Join Date: Mar 2011
Location: Lubbock, Texas
Posts: 9118
Good Answers: 114
#23
In reply to #13

Re: Product Water Flow

01/09/2017 11:58 AM

It is perfectly OK to use mag meter on RO permeate, provided there is sufficient TDS remaining (perhaps the source water is high brackish or seawater??).

One thing about mag meters, if you have the probe/meter located on a vertical run of pipe, there can be issues when the system is offline, that the meter will keep registering small amount of flow due to thermal currents, air bubbles, etc. in pipe.

It is preferred for absolutely the best results, to place mag meters on a horizontal run of pipe.

__________________
If it ain't broke, don't fix it. Just build a better one.
Register to Reply
Active Contributor

Join Date: Nov 2016
Posts: 15
Good Answers: 1
#16

Re: Product Water Flow

01/09/2017 4:41 AM

this is what instrumentation is. any thing can happened at any time. we need to resolve the problem and come with solution instead of poking and making fun.

Register to Reply
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain, and now disconnecting as Little England and Wales (not too sure about Wales bit, either). Kettle's on.
Posts: 25740
Good Answers: 677
#18
In reply to #16

Re: Product Water Flow

01/09/2017 5:04 AM

Please describe it, then, because it cannot be seen from here.

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
Guru

Join Date: Oct 2008
Posts: 39041
Good Answers: 1533
#20
In reply to #16

Re: Product Water Flow

01/09/2017 8:57 AM

Then CALL THE INSTRUMENT MAKER and get a field service tech out to the site!

You are taking the worst approach to solving your problem by hoping someone will guess what your problem is and tell you how to fix it for free.

Get a tech out there and be nicer to him than you are being to the forum!

Good luck getting help here with that attitude.!

Register to Reply
Guru

Join Date: Mar 2011
Location: Lubbock, Texas
Posts: 9118
Good Answers: 114
#22

Re: Product Water Flow

01/09/2017 11:52 AM

You overlooked to compensate for tank draw-down, quite possibly. Another thing, please consider most meters are probably going to only be accurate to +/-3%.

3% of 15 =0.45 which is larger than the difference of 14.3 and 14.1.

It is either nothing or everything. If it is everything, then it has to be one of those little miracles.

__________________
If it ain't broke, don't fix it. Just build a better one.
Register to Reply
2
Active Contributor

Join Date: Nov 2016
Posts: 15
Good Answers: 1
#25

Re: Product Water Flow

01/09/2017 11:03 PM

thanks everybody for your contribution.

As this is the product water, so it is treated chemically before sending to town water tank. we take out the sensor from the line and found the lime particles deposited on the electrodes as lime injecting point is near by this flow meter . clean the sensor ,dried and fixed back and problem is solved. also we change the lime injecting points .

Register to Reply Good Answer (Score 2)
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain, and now disconnecting as Little England and Wales (not too sure about Wales bit, either). Kettle's on.
Posts: 25740
Good Answers: 677
#28
In reply to #25

Re: Product Water Flow

01/10/2017 2:57 AM

Good. At least down-time has been found to enable basic maintenance and process improvement to take place.

Note that, on the basis of the information that the Original Poster has supplied to this point, no-one else in the forum was able to guess the cause of the problem apart from the Original Poster.

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
Guru

Join Date: Oct 2008
Posts: 39041
Good Answers: 1533
#29
In reply to #28

Re: Product Water Flow

01/10/2017 12:00 PM

I'd guess a contributing factor was the original, inadequate piping design. It was designed on the cheap, with no provision for PM.

Register to Reply
Guru

Join Date: Mar 2011
Location: Lubbock, Texas
Posts: 9118
Good Answers: 114
#32
In reply to #29

Re: Product Water Flow

01/10/2017 1:31 PM

If the system is designed to be up full time, it does make it hard to keep up with sensor maintenance schedules. However, there are things they could do to help themselves (like have a meter bypass loop so meter run can be isolated, probe cleaned, replaced, etc.).

__________________
If it ain't broke, don't fix it. Just build a better one.
Register to Reply
Guru

Join Date: Oct 2008
Posts: 39041
Good Answers: 1533
#34
In reply to #32

Re: Product Water Flow

01/10/2017 2:16 PM

Like this?#12

Register to Reply
Guru

Join Date: Mar 2011
Location: Lubbock, Texas
Posts: 9118
Good Answers: 114
#35
In reply to #34

Re: Product Water Flow

01/10/2017 3:20 PM

Yes, at least we can agree on that.

__________________
If it ain't broke, don't fix it. Just build a better one.
Register to Reply
Power-User

Join Date: Jul 2016
Posts: 253
Good Answers: 8
#30
In reply to #28

Re: Product Water Flow

01/10/2017 12:05 PM

Post 19, responding to yours...

Register to Reply
Guru

Join Date: Mar 2011
Location: Lubbock, Texas
Posts: 9118
Good Answers: 114
#31
In reply to #25

Re: Product Water Flow

01/10/2017 1:29 PM

Always good when OP solves their own problem.

You should do a complete statistical analysis of data to prevent fooling yourself, putting the sensors on a preventative maintenance schedule to ensure system metering accuracy.

__________________
If it ain't broke, don't fix it. Just build a better one.
Register to Reply
Register to Reply 35 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Copy to Clipboard

Users who posted comments:

Carl_E (1); James Stewart (6); lyn (5); PWSlack (7); Rixter (1); rwilliams (2); SolarEagle (1); tcmtech (1); truth is not a compromise (4); usmanjalil (7)

Previous in Forum: Coriolis Mass Flow Meter Selection   Next in Forum: Temperature Transmitter

Advertisement