Announcement

Collapse
No announcement yet.

Portafilter pressure Gauge Shows Surprise Find

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • robusto
    replied
    Yes, EAdventurer, it is a rectangular manifold feeding water from the pump. I suspect you're right about it not being meant to be adjustable.

    Of course, being set at 15 bar doesn't necessarily mean I'm going to get 15 bar through the puck. I'm sure the puck will allow brew water through long before the overpressure valve needs to open.

    Leave a comment:


  • EspressoAdventurer
    replied
    The best 'assessment' I can make from your pic / post Robusta is that the expansion valve on the Mia is designed as non adjustable.
    Reference to it elsewhere that if its not at 'spec' then replacing the spring ( engineered spring rate) is the go to.

    Also looks like it is set in a 'Manifold' setup with inlet and brew group outlet...yes / no?

    Options might be to reset pressure by adding 'sealing washers' externally to relieve & reset pretension on the exp valve spring.
    Or a simpler barrel type flow thru adjustable OVP. Given that thread sizes can be married up etc.

    As PL says above the fun is in safely tinkering.
    Suggest take pics / notes for referencing as you go along.
    Keep us here posted pls.
    GL
    EA
    Edit: worth removing, dis-assy, soaking de-scaling, re-assy.

    Leave a comment:


  • PiccoloLatte
    replied
    Go for broke! It's fun to tinker. If you don't try it'll be forever there in your brain as a "what if I had just..."

    Leave a comment:


  • robusto
    replied
    After removing Mia's top, left and rear panels, and then another panel on which the water tank sits, I was able to see the Ulka pump and the tubes attached to it.

    I'm familiar with rotary pumps and how quick and easy it is to adjust their overpressure valve.

    But to be honest this vibe pump system had me perplexed. I didn't know where the opv was nor what it looked like. And it's fidly down there in Mia's basement.

    I was about to give up when I deducted the only place left where the valve could be was a 25mm hex brass fitting on which the silicone hose which returnes water to the tank is attached.

    Click image for larger version

Name:	20220615_183729.jpg
Views:	215
Size:	184.6 KB
ID:	916949


    I removed it, with a bit of force. Yep, inside was a strong spring and a seal.

    I gather that in its previous life it leaked, and someone screwed it down with force all the way to the housing, against a teflon washer. And possibly plumber's paste to boot.

    Obviously it had to be partly unscrewed to reduce brew pressure. But without seating against the washer, it leaks. Strange system.

    I didn't want to, but I put teflon tape on the threads. It's now working fine at 12 bar, 3 less than before. And no leaks after an afternoon and evening of tests.

    I'll fine tune tomorrow, try 10 bar. Or should I quit while I'm ahead?

    Leave a comment:


  • robusto
    started a topic Portafilter pressure Gauge Shows Surprise Find

    Portafilter pressure Gauge Shows Surprise Find

    Got my new portafilter pressure gauge from Jetblack today.

    Ordered it to check Grimac Mia's pressure. Click image for larger version

Name:	20220614_181047.jpg
Views:	284
Size:	152.6 KB
ID:	916865
    it's a cheap, small unit which screws onto the stub of the portafilter where the spout goes. Some teflon tape on the threads stopped the leaks under pressure.

    I was very surprised to learn Miss Mia has high pressure. Not 9, or 10 bar as expected of a vibe pump, but a whopping 15.

    Looks like another day on the spanners coming up (assuming it's adjustable. There's a return hose so it's promising)

    Big Grimac has an inbuilt gauge, and long ago I set the rotary pump overpressure at 9. The new gadget shows 8 bar, but I'll leave things be.
Working...
X