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Two flow lines (pipes) meging into one

  1. Mar 14, 2017 #1
    I got two flow lines at 90 degree angle, Line A carrying acid and line B carrying water, each with 1 inch diameter, merging at point P. The third line C beginning at point P, also 1" diameter, should carry 90% water and 10% acid. I came up with option 1 but not sure how to achieve the same using the Option 2 or 3.

    Option (1) Using two flow meters and two valves. Install two manual valves, one on A line, and another on C line. Install two flow-meters such that each line has one flow-meter but at the upstream of these valves. Now fully open the valve on B line, check the flow-meter reading, and calculate 10% of this flow. Open the valve on A line slowly until the flow-meter reads 10%. (Of course I could do the same on B line).

    Option (2) Using two pressure gauges and two manual valves.
    Option (3) Using one pressure gauge and one flow meter with two manual valves.

    What's the most economic option considering the cost of a pressure gauge being $100 and flow meter being $2000, and the flow resistance being insignificant? Pls explain the procedure. Thanks.
    Last edited: Mar 14, 2017
  2. jcsd
  3. Mar 15, 2017 #2


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    How consistent is the supply pressure to each of the two supply flow lines?
  4. Mar 15, 2017 #3


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    Under option 1 opening valve A will likely affect the flow going through valve B.
  5. Mar 15, 2017 #4


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    Using two flow meters is the only way you can be assured of setting the correct mixture; but, even then unless you have very close control on the inlet pressures of both feed lines, and one valve on one line you will still be at risk of varying the mixture percentage if there is any change in the supply pressure of either line unless you have continuous flow rate monitoring and control.

    Trying to adjust your mixture using only valves without flow meters will not work because, apart of measuring the quality of the third line discharge while making the adjustments, you have no way of determining when you have attained the correct valve(s) position.

    On the other hand if you can be absolutely assured of continuous equal supply pressures on both lines then you have a fourth option of placing a flow orifice in the discharge of each line with the acid line orifice having flow rating 10% of that of the of the water line orifice.

    The ultimate factor in your selection of how you control your mixing is the quality requirements of your finished mixture. If a high quality product consistency is required then the only real solution to your problem is an automated chemical mixing valve.
  6. Mar 20, 2017 #5
    Of course. The forth option didn't cross my mind. I would now weigh my options between this and the original one. Thanks a lot.
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