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Participant

Join Date: Mar 2017
Posts: 2

03/15/2017 6:52 PM

Hi guys/gals

My name is Brent i am new to this site i am a qualified industrial electrician currently studying my second trade in instrument and measurement control im having some trouble with a question that i have come up against in some of my distance learning material and have come the net to find the answer but am unable to find what i need through google or my distance notes so i have come here to ask for some help. I have attached the question in what I am needing help with. Thanks in advance!!!

Pathfinder Tags: Ratio Mixing
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Guru

Join Date: Mar 2007
Location: at the beach in Florida
Posts: 19294
#1

03/15/2017 7:02 PM

First you put the measurements in similar terms.. liters per minute....

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Participant

Join Date: Mar 2017
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#2

03/15/2017 7:33 PM

yes I have got that far but as for an equation to calculate the ratio mix I cant find one

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Join Date: Mar 2007
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#3

03/15/2017 7:44 PM

So it's 480 to 20 or 24 to 1, and you need 40 to 1....

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Guru

Join Date: Sep 2006
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#4

03/15/2017 7:57 PM

All you do is multiply each term by the associated ratio (making sure they are in the same unit of measure).

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Join Date: Feb 2011
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#5

03/15/2017 9:39 PM

my best suggested ratio is 3 parts OJ: vodka

the fresher the OJ the better, I prefer pulp you may not

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Join Date: May 2009
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#6

03/15/2017 9:47 PM

If I could afford it, I would throw in half a part of Galliano.

Or for the Galliano, substitute a few drops each of vanilla and anise extract and a sprinkle of ground cloves.

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Guru

Join Date: Mar 2011
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#7

03/16/2017 10:22 AM

As Solar Eagle stated: reduce the variables to common units, either L/s or L/m.

Personally, you know that you need a maximum (apparently) of 8 L/s of A, and you know the flow of B is 1/40 of that, namely 8/40 = 0.20 L/s. To set the batch controller, have it derive the flow for B, based upon the observed flow for A.

0.20 L/s = 12.0 L/m (convert from seconds to the amount in 60 seconds).

Thus, the entire ratio factor is A*60/40 or 1.5 A (L/s) = B L/m

in other words, whatever the flow is on the A tube, the B tube reading is multiplied by 1.5 to get the proper dosing.

There is a \$200.00 surcharge for college student homework in here. Just kidding.

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#8

03/16/2017 7:22 PM

I get 40/24 = 1.66

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#10

03/17/2017 10:06 AM

How in the H E double sticks does 24 come into this between L/s and L/m?

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Guru

Join Date: May 2016
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#11

03/17/2017 11:05 AM

You know the answer is 42. You just need a plausible question.

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Join Date: Mar 2011
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#12

03/17/2017 11:10 AM

but I hate when that evil 42 keeps popping up!

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Guru

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#13

03/17/2017 3:26 PM

But it has the magic numbers: 2, 3 and 7, all magical and theologically rich prime numbers.

Guru

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#14

03/17/2017 3:48 PM

3? 42/2/3 = 7, etc.?

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#15

03/17/2017 3:57 PM

Yup, you obviously need to sign up for useful classes like Numerology 101 and Astrology 103.

Guru

Join Date: Dec 2010
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#9

03/17/2017 5:31 AM

Step 1 Multiply the full scale reading of sensor A by 60 to get the same units on both sensors 40x60=480

Step 2 Both at full scale the the sensors would deliver a ratio of 480:20

Step 3 Divide both sides by 12 so that sensor A has the 40 of the 40:1 desired ratio 480/12:20/12 = 40:20/12 or 40:5/3. at full scale reading

Step 4 Multiplying sensor B by it's inverse (3/5) gives you a value of 1 5/3x3/5 =1 3/5 is 60% or 0.6

By turning down the full scale reading on sensor B to 60% you get the correct ratio. So you set Sensor A to 100% and sensor B to 60% on the DCS controller

Guru

Join Date: Dec 2010
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#16

03/17/2017 7:41 PM

OK Brent, I have shown you how to get the answer, but if I was marking the question I would only award 4 marks. Now you tell me why I lost two marks for the correct working and the correct settings on the DCS.

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