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  • VBM Domobar brewing issue

    Hi guys, long time reader first time poster...

    I have VBM domobar which as been running like a dream since new. From new the brew pressure max's out at 12 bar.

    After reading some threads on this site about adjusting the OPV to reduce the brew pressure to 9 bar (10 bar on the gauge) I decided to give it a go and managed to do it with no real hassle. My coffee shots taste soo much better also!
    The only issue I have is I get this high pitched ringing noise from the water pump when I max out at 10 bar.
    I readjusted the OPV and realised the high pitched sound picks up when I set the OPV anywhere from 8 - 10 bar max. If it sits lower or higher on the gauge the sound goes away.

    I even tired replacing the water pump and OPV with no success...

    Will this affect the machine in the long run? If so, what could be the issue??

    Cheers in advance!!

  • #2
    This seems to be a fairly common phenomenon with vibe pump machines that have their brew pressure maxed out by an OPV. On my machine I have been able to at least reduce the squeak by unscrewing the internal part and soaking it in a descaling solution for half an hour or so. It may be that there is a tiny bit of scale deposit that somehow makes the OPV sensitive to this when you loosen the spring to reduce the pressure.

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    • #3
      Originally posted by degaulle View Post
      This seems to be a fairly common phenomenon with vibe pump machines that have their brew pressure maxed out by an OPV. On my machine I have been able to at least reduce the squeak by unscrewing the internal part and soaking it in a descaling solution for half an hour or so. It may be that there is a tiny bit of scale deposit that somehow makes the OPV sensitive to this when you loosen the spring to reduce the pressure.
      Thanks degaulle, I tried that with my old OPV with no success, and ended up purchasing a brand new OPV. The noise unfortunately is still there..

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      • #4
        I know this noise can be irritating. When I had my machine serviced, I asked the technician to adjust the OPV to 10 bar (where I had set it at previously after doing the descale). When I picked it up again, hè said hè could not get it to work below 11 bar, but I found the noise had returned nevertheless. After several months of use however the sound waned and I left it at that. Only recently I repeated the descale, provided a bit of thread sealant on the OPV outlet and readjusted it too 11 bar. Occasionally there is a bit of a squeak but it ceases If I run a few backflushes. Maybe the spring needs breaking-in. I have stopped worrying about it now, since unlike you I have not found a strong difference in taste between the stock setting of 12 bar and a lower setting.

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        • #5
          I have mine currently set to 11 bar and there isn't any noise.. I'd ideally like it at 10 bar and I'll happily put up with the noise if I know it won't lead to any issues.. based on your comments it appears that I should be fine so I appreciate your feedback! Would it be safe to assume VBM owners with rotary pumps dont have similar issues??

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          • #6
            At lower discharge pressures the pump is capable of greater flow - flow which needs to be diverted via the OPV. The whining noise may be a result of higher velocity flow through the OPV. I get it occasionally in my machine and that is what I have attributed it to.

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            • #7
              Originally posted by tampinator View Post
              I have mine currently set to 11 bar and there isn't any noise.. I'd ideally like it at 10 bar and I'll happily put up with the noise if I know it won't lead to any issues.. based on your comments it appears that I should be fine so I appreciate your feedback! Would it be safe to assume VBM owners with rotary pumps dont have similar issues??
              I think it is fair to assume they don't. On a rotary the pump has its own internal bypass that controls the pressure at the pump outlet, typically at 9 bar. The OPV is merely a safety device set considerably higher and shouldn't open during normal use unless the pump pressure controller fails.

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              • #8
                Originally posted by MrJack View Post
                At lower discharge pressures the pump is capable of greater flow - flow which needs to be diverted via the OPV. The whining noise may be a result of higher velocity flow through the OPV. I get it occasionally in my machine and that is what I have attributed it to.
                Thanks MrJack. Is your machine a VBM domobar and set to 10 bar??
                Reason I ask is because I'm trying to figure out if this noise is a VBM only issue or a HX machine with a vibe pump issue..

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                • #9
                  Nope I have a bezzera BZ99s.

                  Edit: It has a small fluid-o-tech OPV.
                  Last edited by MrJack; 9 May 2017, 11:15 AM.

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                  • #10
                    Originally posted by MrJack View Post
                    Edit: It has a small fluid-o-tech OPV.
                    I noticed on a certain coffee spare parts site (not sure of the forum rules regarding posting web addresses) I can purchase a fluid-o-tech OPV for VBM domobars... Do you think the change over could be of benefit?
                    I'm almost game to make the switch over if it'll make a difference and is possible... part costs $27.90 plus postage from NSW so it won't break the bank either..

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                    • #11
                      FWIW, I have a Domobar Jr set to 9 bar and it makes the same noise.

                      Regards,

                      Matt

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                      • #12
                        Originally posted by MattyRay View Post
                        FWIW, I have a Domobar Jr set to 9 bar and it makes the same noise.

                        Regards,

                        Matt
                        That's good to know thanks MattyRay. It appears that it's normal then, and I shouldnt stress too much over it..
                        Last edited by tampinator; 9 May 2017, 03:17 PM.

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