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Thema: Problems with pumps

  1. #11
    Registriert seit
    10.11.2012
    Ort
    Salamanca
    Beiträge
    40

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    Hi Vinny, there is something I don't quite understand. The pump producing the noise is the internal pump, the one mixing the sample water with the reagent in the internal cell. Can you modify the speed of this pump? If so, how do you do it?

  2. #12
    Registriert seit
    10.11.2012
    Ort
    Salamanca
    Beiträge
    40

    Standard

    Zitat Zitat von Shredded Beitrag anzeigen
    I was actually going to start my own thread but mine is so close to this I hope the OP does not mind me joining in. Please have this deleted if necessary. Here is mine, specifically...
    I have fought all the issues that everyone else has with my KHD, bad reagent, air in the tubing... my internal circulation motor went out and my unit was replaced. I am in the technology field and I get it. I have looked inside the unit, and I am very impressed for a piece of equipment designed for the aquarium. Still when my unit is running, it is wonderfully accurate and I do love it but it can be a little frustrating.
    Here was yesterdays events that led to this...
    My new unit (KHD) had been running for a couple weeks, dead on.
    Yesterday I saw a spike from 9 to 10.1 I watched it. Each run, it climbed a point or two higher. obviously had an issue. At lunch when i went home I checked with my Hannah. they normally match and now the KHD was high.
    I ran a manual KHD and watched. Head #3 failed. I pulled off the head cover (old style) and the internal guide in the cover was chipped. I blew out the head with canned air and the rest looked good. Vinny had sent me 4 new style covers, (post office destroyed 1) so I popped on a new one (my last one) and started to go thru and reset the KHD. I didn't take into consideration that they internal capsule had not fully been drained and when I went to flush the measurement cell, the cell overfilled draining into the vent tube. This in turn soaked and ruined the inline air filter. I removed, opened and inspected the unit. I let the unit incompletely drain. I removed the vent tubing, removed the air filter and reinstalled the vent tubing. I reassembled and reinstalled the unit.
    I ran another manual test. Head #1 failed. I thought this can't be, it's a new style head. Upon removing the head cover it was obvious what the issue was. The head cover was fine, no damage. The internal hose was very flat from running 6 times per day, every day plus all the running for calibrations and dialing in. Lots of black dust in the cover and on the rollers. I replaced all of the internals, new tubing, new rollers and new pizza roller guide. I again went thru setup. It took a couple of times to dial things in but I am now up and running again, dead on. Here are some of my observation and actually gets to my main question. Sorry this has been so wordy.
    1. From what I can tell, the heads on the pumps are different from the old style and even the European design. The heads rely on the tight tolerances of all components, tubing, pizza guide, rollers and head cover. There is no "gearing" or "direct drive" Any failure, even the eventual flattening of the tubing can cause a lack of fit and the the whole head to fails. Is this correct? If so, what would be the expected life of the internals? How often, running at 6 times per day, do I need to remove the cover and check for wear. I believe the screws for the caps are just going into plastic and that will probably wear. Maybe just the tubing replaced on a regular basis, failure or not?
    2. The new head covers are "Fast". They must be re-calibrated. One of my pumps is now actually 10 mls/min faster then it ever has been. All increased with the new covers. It is also visually obvious when running that they are smoother and faster.
    3. You just gotta remove that air filter.
    4. I need more parts! :-) Also, stock the screws. Tiny and difficult to handle. I keep a fish net with neodymium magnets in it to find and retrieve them when dropped.
    Jeff



    Comments or criticism?
    There is something somehow implicit in your observations and that is worrying me. If the speed of the dosing heads depends upon the type of head cover, that may mean that a worn out cover changes the speed of the dosing head. Then, you would have variable speeds depending on the degradation degree of the cover, which would modify the sample volume and the reagent volume resulting in differences in the measurements.

    I have observed that from time to time the KHD gives an alkalinity lecture quite different from the ones previously observed. Then, the following ones may be again in range.

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