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Thread: Help with KHD readings

  1. #1
    Join Date
    01.10.2020
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    34

    Default Help with KHD readings

    Hi all,
    I'm struggling to get the khd the read constantly or correctly

    I've measured and double checked the lengths I've calibrated the dosing heads with digital scales I've calibrated the probe at 25°
    All of the above seems fine and is correct I believe
    I don't have any air in any of the dosing lines the pH probe is new in August and I've even brought a cheap one from amazon just to check and they both seem fine
    I'm not sure what else to do
    Any help would be appreciated


    Screenshot_20211222-132006_GHL Connect.jpg

  2. #2
    Join Date
    27.05.2015
    Posts
    2,371

    Default

    What settings did you enter into the dosing pumps?
    Speed? Flow rate?

    What number did you enter into the KHD water sample volume?
    Are you in front of the device during a measurement? Do the pumps spin normally during each measurement?

    The KHD probe cannot be replaced with an ordinary pH probe, they are not the same.
    What fluids are you calibrating the probe with?
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  3. #3
    Join Date
    01.10.2020
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    34

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    Settings for dosing pumps are

    Pump1 water sample speed 3, 38ml/m
    Pump 2 reagent speed 0, 4.1ml/m
    Pump 3 waste speed 3, 34.2ml/m

    Sample line is 135.9cm, 11.9 for dosing head tube, 16 for connecting the doser to khd, and 108 for tube from sump to doser. No water filter is attached and the sample tube volume is 17ml

    I have sat in front and pumps all spin normally

    I am using the GHL probe just tried a different one to see if it'd make any difference.
    Am using GHL calibration fluids 4 and 7

  4. #4
    Join Date
    27.05.2015
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    2,371

    Default

    Those numbers look OK.

    Any reason why you are not using the water sample filter?
    Without a filter installed, one cannot rule out the possibility of sediment getting into the sample which is therefore skewing the end results.

    The widely fluctuating numbers is a general indicator of air bubbles or foreign matter getting caught in the water sample.
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  5. #5
    Join Date
    01.10.2020
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    The filters I have don't fit onto 4mm ID hose, they are GHL ones but can't get the line over the barb.

    Is there a way to clean out the measuring housing inside the KHD , the bit the pH probe sits in ?
    I've done flushes but maybe you know of a way of a more deep clean,
    You may also know how to fit the pre filters on 4mm hose

  6. #6
    Join Date
    27.05.2015
    Posts
    2,371

    Default

    Stock GHL tubing will fit over the GHL filter. It will fit very snug, but it will fit.
    Dipping the end of the tube in hot water will give it enough flex to connect the filter.

    You can press "Flush measurement cell" a few times to clean out the tubes and cell. Don't forget to vent the internal reagent tube before you run a new test after those flushes.
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  7. #7
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    01.10.2020
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    Default

    Should the filter be fitted to the line from the sump to the doser or fitted on the line from doser to khd?

  8. #8
    Join Date
    27.05.2015
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    As per the filter manual, from sump to doser.
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  9. #9
    Join Date
    01.10.2020
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    34

    Default

    OK I'll fit one now and flush the cell a few times

  10. #10
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    01.10.2020
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    34

    Default

    Im getting air bubbles from the filter into the khd line now

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