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Brass OPV Mod Questions

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  • Brass OPV Mod Questions

    Hi all,

    Going to upgrade my BES920 to a brass OPV and have a couple of questions:

    1. Must you get a pump with a brass neck or will a plastic one do the job? Reason I ask is I have a new unused pump with a plastic neck in my spares box.

    2. The 1/8" BSP to 4mm connector could in theory have 15 bar on it, so would this connector therefore need to be rated at 15 bar or more?

    Your thoughts would be appreciated.


  • #2
    It is advisable to get a brass necked pump but not required if you already have a plastic one. The big risk is cross-threading the plastic threads because the brass will go straight through them.

    It would only have what you set the OPV to, but yes if you open the OPV right up it could have the full pump pressure. I hadn't actually considered that and just bought them off ebay. I did mine at least 2 years ago and it has never showed signs of leaking. Make sure you use liquid thread tape and give it 48 hours to cure as the threads in the OPV are BSPP and the connectors tend to have BSPT which leaves a slight void.


    • #3
      level3ninja - Thanks for your comments.


      • #4
        Have just replaced my OPV with the Vibiemme OPV and found my shots needed to be dialled in again. Probably due to the pump not coming up to pressure as quickly. I gather this is normal?




        • #5
          Yes it's a bit of a different pressure curve. I found the same. Could also have been the pump and original OPV starting to die prior to the change so it wasn't a like-for-like comparison. Once you dial everything in again you'll find it just as consistent as before. The brass OPV does seem to have a little bit of a bedding in period but the difference is mainly in the sound with only a minor difference in pressure.


          • level3ninja
            level3ninja commented
            Editing a comment
            gregeeh might be worth checking for a leak. Doesn't sound far off though

          • gregeeh
            gregeeh commented
            Editing a comment
            Definitely no leaks.

            EDIT: Pre-Infusioin time is set to 7 secs and power 60%
            EDIT2: Just made a coffee and max pressure = 9 bar dropping to 8 bar when the extraction finished.
            Last edited by gregeeh; 3 weeks ago.

          • FNQ
            FNQ commented
            Editing a comment
            Hi gregeeh

            those preinfusion / pressure times specs sound about right. It is almost the default set up if my memory serves correct. Some beans/puck erode a bit more than that, but if you are happy with the pour results (taste results) then your new OPV is doing its job. well done

        • #6
          As it happens today I got around to opening my machine up again and adjusting the OPV down to 8.5 on the gauge when pulling a shot (so around 8bar at the puck). I also rotated the OPV so that the adjustment screw faces mostly to the back of the machine, and removed the small back top piece of the cover and drilled a hole in it where the OPV faces to enable adjustment without removal of the top cover.


          • #7
            hi level3ninja....... on the fly adjustments,... very cool old school car drum brake adjuster comes to mind
            gregeeh or anyone with knowledge..... are you setting your preinfusion in the software set up ( eg 55 % pump for 8 seconds ) or probably closer to 10 % if aiming for 1 bar.... and curiosity prevails 1 bar for how long? ( I am struggling to imagine 1 bar wetting the puck through..... Cheers Darryl