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Date: 17 Dec 2006 08:16:44
From: daveb
Subject: Results of pump pressure 'survey' on seven new Rancilio Silvias
Having seven new Silvias in here for customization, I thought it would
be useful to test the pump pressure and the OPV, settings as they come
from the factory. 7 units is not a large number but better than say,
one sample.

Method -- pressure gauge portafilter
NO heat connected
units at ambient temp. 66F
water at ambient temp. 66F
Line voltage 123 volts
All are the latest units -- "POD adaptable"
purged all air from system(s)

Results: ALL seven units = 10 bar +/- .25 bar.

Dave
www.hitechespresso.com
189





 
Date: 19 Dec 2006 13:23:30
From: gscace
Subject: Re: Results of pump pressure 'survey' on seven new Rancilio Silvias
I've measured this on a variety of machines. Some machines that bypass
a lot of water at the pump (rotary pump machines) are fairly
insensitive to pressure drop variations caused by inconsistency in
grind, dose and tamp, but lose pressure due to changes in direction
caused by bends in pipes, internal pathway through solenoid valves and
groups, and gicleurs. My Linea runs about 1 bar less pressure when
brewing coffee than it does when measuring with a blind filter basket /
pressure gauge deal like what Nuova Ricambi sells. Other machines can
have very large pressure variations depending on how much water is
flowing through the group. I recently tested a machine that used a
fluid-o-tech vibe pump with pressure relief valve set to 9 bars under
no flow conditions. As part of my normal testing procedure i like to
map out the pressure vs flow for the machine under test. At flowrates
corresponding to brewing a double shot, this machine only produced 4
bars of pressure, due to the design of the pressure relief valve and
due to the flow capacity of the pump. Tweaking the brew pressure up to
9 bars under brewing conditions substantially improved coffee taste.

Pressure measurement in espresso machines has been done pretty sloppily
in the past. I am currently fixing that particular sloppiness.

-Greg



jggall01 wrote:
> daveb wrote:
>
> > will - 1 bar to 9 bar make a difference?
> >
> > IMHO, not.
> >
>
> These are dead-head pressures being measured. I believe that friction
> losses would result in the puck seeing a lower pressure once there is
> flow. Anybody measured the magnitude of the drop?
>
> Jim



  
Date: 19 Dec 2006 15:35:20
From: Ken Fox
Subject: Re: Results of pump pressure 'survey' on seven new Rancilio Silvias
"gscace" <gregory.scace@nist.gov > wrote in message
news:1166563410.188744.287870@79g2000cws.googlegroups.com...
> >
> Pressure measurement in espresso machines has been done pretty sloppily
> in the past. I am currently fixing that particular sloppiness.
>
> -Greg
>
>
>

is a Scace Pressofilter in the works?

ken




 
Date: 18 Dec 2006 11:33:26
From: JoeIsuzu
Subject: Re: Results of pump pressure 'survey' on seven new Rancilio Silvias
> Right. As soon as you get some flow the pressure will drop a little. Dan

OPV = flow! Isn't that what happens when the boiler pressure exceeds
the pop-off pressure of the OPV? What you're really measuring is OPV
pop-off pressure (I think that's essentially what the OP said, although
the subject says "pump pressure"). Now, if you release the pressure
some other way (i.e. through a puck) before the OPV vents it, you're
not measuring pump pressure or even OPV pressure--you're measuring the
resistance of the puck only.

Jack



 
Date: 17 Dec 2006 10:27:39
From: jggall01
Subject: Re: Results of pump pressure 'survey' on seven new Rancilio Silvias

daveb wrote:

> will - 1 bar to 9 bar make a difference?
>
> IMHO, not.
>

These are dead-head pressures being measured. I believe that friction
losses would result in the puck seeing a lower pressure once there is
flow. Anybody measured the magnitude of the drop?

Jim



  
Date: 17 Dec 2006 13:57:51
From: Dan Bollinger
Subject: Re: Results of pump pressure 'survey' on seven new Rancilio Silvias
> These are dead-head pressures being measured. I believe that friction
> losses would result in the puck seeing a lower pressure once there is
> flow. Anybody measured the magnitude of the drop?

Right. As soon as you get some flow the pressure will drop a little. Dan


 
Date: 17 Dec 2006 10:18:33
From: jggall01
Subject: Re: Results of pump pressure 'survey' on seven new Rancilio Silvias

daveb wrote:

> Results: ALL seven units = 10 bar +/- .25 bar.
>

FWIW, I have seen similar results on a smaller sample size (5). I had
one that was just shy of 11. My measurements have all been taken with
the unit "at temperature" but I doubt this has much effect. Different
supplier, too.

Jim



 
Date: 17 Dec 2006 08:44:47
From: daveb
Subject: Re: Results of pump pressure 'survey' on seven new Rancilio Silvias
It would seem so. do you think 10 is a good number?

will - 1 bar to 9 bar make a difference?

IMHO, not.

dave

Dan Bollinger wrote:
> > Results: ALL seven units = 10 bar +/- .25 bar.
>
> Dave, I'm not surprised. They are getting those supplied from an OEM, and one of
> their services is presetting the valves to a specification. The mfgr. will have
> a precise, accurate, and repeatable test-bed for setting the valves before
> shipping. Dan



 
Date: 17 Dec 2006 11:35:38
From: Dan Bollinger
Subject: Re: Results of pump pressure 'survey' on seven new Rancilio Silvias
> Results: ALL seven units = 10 bar +/- .25 bar.

Dave, I'm not surprised. They are getting those supplied from an OEM, and one of
their services is presetting the valves to a specification. The mfgr. will have
a precise, accurate, and repeatable test-bed for setting the valves before
shipping. Dan