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Thread: Flow rate checking - duff meter ?

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    New Member ebon.hawk is an unknown quantity at this point ebon.hawk's Avatar
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    Flow rate checking - duff meter ?

    This might sound like a stupid question but here goes.....

    Just doing the flow rate checks on my Dolphin ( brought second hand, training done last month, and finally got a pass out from wife / work to go for a dive tomorrow )

    I was supplied with two flow meters with markings for 32/40% on one and 50/60% on the other.

    If I set up the valve to use the 32 or 40% jet and attach the flowmeter for 32/40, the floating ball seems to be read just over the mark for 32/40 - ok I think this is okay, its not sitting at the bottom or at the top of the meter.

    *but* if I set up the valve to use the 50 or 60% nozzle, and plug in the meter for 50/60% as soon as I open the valve the meter indicator ( little ball ) goes way high, almost coming out of the top of the meter, I've just checked on the 40% nozzle with the 50/60 meter and get the same results, 50/60 nozzles on the 32/40 meter and the reading is about half way up the meter, not pushing the ball out the top of the meter.

    I sort of get the feeling the 50/60 flow meter has gone faulty, does it sound like this to anyone ?

    Also just done the calculations for the fO2 in the loop and using the 40% jet with 47% mix is going to give me 34% with a metabolic rate of 2 in the sums, and 38% with 1.5, so I will run with the 40% nozzle for tomorrow.

    Regards
    Andy

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    Divemaster ken chung ar is on a distinguished road ken chung ar is on a distinguished road ken chung ar's Avatar
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    Re: Flow rate checking - duff meter ?

    Quote Originally Posted by ebon.hawk
    if I set up the valve to use the 50 or 60% nozzle, and plug in the meter for 50/60% as soon as I open the valve the meter indicator ( little ball ) goes way high, almost coming out of the top of the meter, I've just checked on the 40% nozzle with the 50/60 meter and get the same results, 50/60 nozzles on the 32/40 meter and the reading is about half way up the meter, not pushing the ball out the top of the meter.
    hi ebon.hawk,

    i also dive Dolphin and had the same kind of problems with flowmeters before.

    as you learned in class for Dolphin, the average flow rates for 32, 40, 50 and 60% orifices are 15.5, 10.4, 7.3 and 5.7 L/min, respectively. two standard flowmeters supplied by Draeger with Dolphin have marks corresponding to those flow rates.

    the problem you described shows two possibilities: either the flowmeter for 50/60% or the 50/60% orifices is malfunctioning. the possibility of simultaneous malfunctioning of two orifices, 50 and 60%, is probably small. accordingly, the 50/60% flowmeter is most likely to be blamed of.

    however, unless you check by an adequate flowmeter, you never know for sure. it is quite wise of you to avoid using 50 and 60% orifices till you get to know for sure that they are actually OK.

    because i had been annoyed by this kind of a problem several times, i now use the Draeger's 32/40% fllowmeter together with another one made by Dwyer Instruments. the model number is MMA-24, the range of which is between 2.5-25 L/min. MMA-24 can be used as a reference for ascertaining that the 32/40% flowmeter works right and also used for checking 50 and 60% orifices.

    good luck,

    ken chung ar

  3. #3
    New Member ebon.hawk is an unknown quantity at this point ebon.hawk's Avatar
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    Re: Flow rate checking - duff meter ?

    Hi Ken

    Been chatting to John Narked at 90 on this board and Yorkshire Divers, it might be that the service guy has turned up the IP too much and needs tweaking, noticed bubbles from the constant flow hose going into the Draeger first stage when I put the unit in the bath, you wouldn't believe the language from the wife when she saw what I was doing.

    I've made contact with an instructor down south from me who has offered for me to go to his house tonight and check the pressure.

    So should have an update tomorrow.

    Tempted to dump it in the north sea and break into my "return to the UK savings" and buy something else.

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