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viebemme pressure issues
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smasha
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Joined: 19 Feb 2012
Posts: 33
Location: Cambridge
Expertise: I love coffee

Posted Sun Nov 18, 2012, 11:38am
Subject: viebemme pressure issues
 

Hi

at work we have a viebemme HX machine with vibration pump.  often when pulling a shot the pressure gauge can read 5-7 bar other times it goes well over 12 bar and jumps up to 15 and back down to 12 bar.

I thought most HX machines are meant to pump at a constant 8-10 bar and grind and tamp effect flow time and the aim is for a 25 second flow for a double shot with 14 g or so of fresh ground coffee.

so I assume there is something wrong with this machine and that is probably the vibration pump or possibly the pressure gauge.  comments or suggestions of how to find the cause and plan for repair will be very useful!

thanks coffee geeks!
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frcn
Senior Member
frcn
Joined: 23 Dec 2001
Posts: 3,351
Location: Northern California
Expertise: Professional

Espresso: Vibiemme Domobar Double
Grinder: Mazzer Kony, Baratza...
Vac Pot: Hario, 2 Cory pots, 1 Cory...
Drip: Behmor Brazen, Bunn A10 mod...
Roaster: computer controlled Hottop,...
Posted Sun Nov 18, 2012, 12:34pm
Subject: Re: viebemme pressure issues
 

Likely there is nothing wrong with the pump if it can deliver 15 bar.
The problem is likely in the pressure relief valve. if it was working before properly and recently started doing this, it probably has the correct spring in it, so all that may be needed is to remove the adjustment screw, spring, and piston, clean as necessary, lube with DOW111 and reassemble and adjust.

 
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SStones
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SStones
Joined: 24 Nov 2012
Posts: 474
Location: Canada
Expertise: Professional

Espresso: Giga 5, ECM Giotto, Rocket...
Grinder: Anfim Milano-Best
Vac Pot: No  :(
Drip: Some $30 thing from Walmart
Roaster: I buy pre-roasted.
Posted Sun Nov 25, 2012, 7:21pm
Subject: Re: viebemme pressure issues
 

The pump can't control the pressure, it just creates flow.  If your grinds are loosely tamped or too coarse, the water will run through them easily and the brew pressure will be very low. Pressure rises due to your espresso grinds restricting the flow.
I would adjust the relief valve (OPV in these forums) to limit the maximum to about 10 bar for your pump's safety, and see if you get a steady 9 bar +20 second pull on a finely ground, evenly tamped double espresso.
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smasha
Senior Member


Joined: 19 Feb 2012
Posts: 33
Location: Cambridge
Expertise: I love coffee

Posted Wed Jan 16, 2013, 3:31am
Subject: Re: viebemme pressure issues
 

what I am confused about the issue on pressure is at home my rocket with a rotary pump produces a constant 9 bar of pressure.  If the grind is too fine and tamp too firm then the time taken is > 30 seconds for a double shot.  If the grind too coarse and tamp too light the time taken is < 15 seconds.  So to get a perfect brew I adjust grind and tamp top achieve a 25 second brew time.  In all situations the brew pressure is fixed at 9 bar.

the veibemme at work with a vibration pump varies the pressure dependent grind and tamp; sometimes the pressure is low at 6 bar, sometimes it is high at 14+ bar.

So is this difference that I have observed the difference between vibration and rotary pump?  or is something wrong with the veibemme vibration pump?
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DavecUK
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Joined: 21 Sep 2005
Posts: 1,392
Location: UK
Expertise: I love coffee

Posted Wed Jan 16, 2013, 12:45pm
Subject: Re: viebemme pressure issues
 

smasha Said:

what I am confused about the issue on pressure is at home my rocket with a rotary pump produces a constant 9 bar of pressure.  If the grind is too fine and tamp too firm then the time taken is > 30 seconds for a double shot.  If the grind too coarse and tamp too light the time taken is < 15 seconds.  So to get a perfect brew I adjust grind and tamp to achieve a 25 second brew time.  In all situations the brew pressure is fixed at 9 bar.

Posted January 16, 2013 link

This is because the pressure is taken from the pump head within the sealed brew circuit and the flow of the pump is so great that even with no portafilter in you will see a pressure of 9 bar. The size of the gicleur within the E61 group (0.6 mm possibly larger on your machine) is so small that a rotary pumps flow will always show at 9 bar (or whatever pressure you have set the pump to) because of the restriction.
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stefano65
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stefano65
Joined: 30 Oct 2004
Posts: 1,403
Location: Eugene OR
Expertise: Professional

Espresso: Vibiemme,Elektra,
Grinder: Vario,Macap,
Vac Pot: not
Drip: not
Roaster: not
Posted Wed Jan 16, 2013, 2:22pm
Subject: Re: viebemme pressure issues
 

insert the blind filter
activate the brewing
wait untill pressure build up
unscrew OPV valve until reads 9-10
release pressure
try couple of more times and see if the reading is constant

 
Stefano Cremonesi
info@espressocare.com
www.espressocare.com
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smasha
Senior Member


Joined: 19 Feb 2012
Posts: 33
Location: Cambridge
Expertise: I love coffee

Posted Thu Jan 17, 2013, 4:09am
Subject: Re: viebemme pressure issues
 

thanks for the replies and apologies for my poorly written post above .... did not proof read it :)
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