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Brew Pressure and Salvatore
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Discussions > Espresso > Machines > Brew Pressure...  
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HB
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Joined: 3 Apr 2003
Posts: 2,913
Location: Cary, NC
Posted Mon Jul 12, 2004, 9:50pm
Subject: Re: Brew Pressure and Salvatore
 

easyrotor Said:

Did you recognize the valve/solenoid in the first picture?

Posted July 12, 2004 link

Yes, it looks like the solenoid that controls the boiler refill and group.  If there is an expansion valve, it would be inline past that point between the pump and the grouphead.

Now it's time to decide what to do next... I have to do things like overstuffing the basket to get this to happen and the first shot is seldom as good as the ones that follow. This is, BTW, what the folks at Salvatore to do when I called. They said I should see the impression of the dispersion screen in the puck. This does not jive with what I read  elsewhere.

I agree with Rob, get da man on the phone.  It's plainly evident he knows how to put a machine together well and there must be "a failure to communicate."  I have heard of other plumb-in machine conversions removing the expansion valve and similar disappointing results.  If you hadn't already guessed, that's part of the reason I added a drain for Valentina -- as a direct plumb, it filled the driptrap more quickly and I really didn't like emptying it.

Keep in mind whatever the outcome, you're on the first steps of a journey.  Much of what you're reporting is perfectly normal when learning a new machine.  I consider myself lucky if I only burn through 1/2 pound before getting a decent shot from an unfamiliar machine.  ;-)

As for their comment about the puck impression -- I definitely agree.  Initially there is about 2mm of clearance but that's eliminated as the puck expands.  I often advise the "coin test" -- place a nickel on top of the puck, lock in and remove.  Did you see a very light impression?  Perfect.

-- Dan

PS: You shouldn't need a snubber for the dual gauge from EPNW since it should be liquid-filled (i.e., the needle of air-filled gauges will buzz when they're inline with a vibration pump; a snubber dampens this effect).

 
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easyrotor
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easyrotor
Joined: 23 Mar 2004
Posts: 63
Location: Brooklyn, NY
Expertise: I like coffee

Espresso: LaCimbali Junior
Grinder: Mazzer Mini
Posted Mon Jul 12, 2004, 9:59pm
Subject: Re: Brew Pressure and Salvatore
 

OK, I'll call again tomorrow. Thanks.
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MrHouse
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Location: Ohio
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Posted Tue Jul 13, 2004, 3:36pm
Subject: Re: Brew Pressure and Salvatore
 

Dan,

I'm really impressed with the way you jumped in and helped easyrotor try to solve his complicated espresso machine problem. You're awesome!

Mark
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easyrotor
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easyrotor
Joined: 23 Mar 2004
Posts: 63
Location: Brooklyn, NY
Expertise: I like coffee

Espresso: LaCimbali Junior
Grinder: Mazzer Mini
Posted Tue Jul 13, 2004, 4:15pm
Subject: Re: Brew Pressure and Salvatore
 

I just got off the phone with Salvatore and he spent quite a lot of time with me trying to figure out my problem. At first he insisted that the pressure readings I am getting are impossible but then he remembered that at some point they have switched from the 40watt vibe pump to a new 70 watt version.  I think he forgot about the bigger pump the last time we talked as he now acknowledged that I am seeing the high pressure readings.   The pump is a vibe pump made by Fluid Tech.  He felt that I could control the pressure by how I pack the coffee and I agree but I can't get the 25 second, 2 ounce pour and keep the pressure down below 16 bar. He suggested that I use a courser grind and pack harder.  He again said that I must pack the coffee so that it is above the line in the PF and that it must press against the dispersion screen BEFORE the pour. OK, I'll try that.  Actually, in order to get the desired pour, I have done that previously.  I find this makes a dryer puck after the pour. Lately I have been using more coffee and packing it below the line trying to leave a thin gap as suggested in other posts on the forum. If the gap is too big, the puck is wet after the pour. Harder to dump cleanly.    He is sending me some free LaVazza coffee and has asked me to report back how I do.  He really thinks it's the coffee I'm using that I'm using thats causing the bitterness.  As his experience is far more vast than mine, I will try it his way. It was really nice that he spent the time with me.  I' m glad you convinced me to call.

I have read enough about the high pressure issue to see that opinions are are all over the spectrum as to whether there is a difference or not. So who knows? I have begun to develop an opinion of my own. I think the high pressure is making the control of the pour more difficult (finicky). I plan to add regulation to the brew circuit and prove it.  Besides, I hate the idea that the idea that if I plug up the system the pump can fry. The taste issue is another story. I also know that the pressure in my machine is way higher than most people see in their systems. So perhaps we are getting to a problem that does compute. New size pump, new problem.

I work for a company that makes production intercom systems and every now and then the factory makes a "minor" change that makes my life as a application engineer a misery. It always take time and energy to sort these things out. The engineers always act the same way when you tell them about it: They say "Oh yeah, that." and then it evaporates from their consiousness as if it never happened.  Se La Ger.
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Rick
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Rick
Joined: 23 Dec 2001
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Espresso: Wega Mininova Inox Auto...
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Posted Tue Jul 13, 2004, 5:41pm
Subject: Re: Brew Pressure and Salvatore
 

easyrotor Said:

I just got off the phone with Salvatore. (snip).  He felt that I could control the pressure by how I pack the coffee and I agree but I can't get the 25 second, 2 ounce pour and keep the pressure down below 16 bar. He suggested that I use a courser grind and pack harder.  He again said that I must pack the coffee so that it is above the line in the PF and that it must press against the dispersion screen BEFORE the pour. OK, I'll try that.  Actually, in order to get the desired pour, I have done that previously.  I find this makes a dryer puck after the pour. Lately I have been using more coffee and packing it below the line trying to leave a thin gap as suggested in other posts on the forum. If the gap is too big, the puck is wet after the pour. Harder to dump cleanly.    He is sending me some free LaVazza coffee and has asked me to report back how I do.  He really thinks it's the coffee I'm using that I'm using thats causing the bitterness.  As his experience is far more vast than mine, I will try it his way.

Posted July 13, 2004 link

Wow, this doesn't sound right to me (he says, daring to contradict a guy who has been manufacturing espresso machines for decades!  Oh well, fools rush in!).  

Shot volume (and pressure) depends on grind, dose and tamp.  Grinding finer increases resistance (and pressure).  Tamping harder increases resistance (and pressure).  Filling more increases resistance (and pressure).  I can't see how his solution is going to help.

The right pressure for making espresso is ~ 9 bars.  A machine that pumps at 9 bars should read maybe 9.5 to 10 bars when pumping against a blind filter. As I understand your post, Salvatore finds it acceptable that his machine pumps at 16 bars into a blind filter?  Is that correct?

My experience is that with a pump generating 16 bars of pressure, no matter what you do you're going to get a sub-standard tasting brew and high susceptibility to channeling.  I think it will be impossible to dial in the right grind, dose and tamp. It is just too far outside the envelope.

The only way you can bring the pressure down to 9 bars by grind, fill and tamp is to increase the flow rate to a lot more than 2.5 oz in 30 seconds. Maybe 5 to 10 times as much.

I hope I'm wrong, but I don't think so.


Rick
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HB
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Joined: 3 Apr 2003
Posts: 2,913
Location: Cary, NC
Posted Tue Jul 13, 2004, 7:31pm
Subject: Re: Brew Pressure and Salvatore
 

Rick Said:

The only way you can bring the pressure down to 9 bars by grind, fill and tamp is to increase the flow rate to a lot more than 2.5 oz in 30 seconds. Maybe 5 to 10 times as much.

Posted July 13, 2004 link

That depends on the performance curve of that particular pump.  Jim posted awhile back a very good explanation that is worth repeating in its entirety:

jim_schulman Said:

Chris asked me to post a short explanation of what limiting a Vibe pump will and won't do for you.

The illustration is the "pump curve" (black graph) of most Ulka espresso pump models, showing the pressure (vertical axis) for a 25 second shot with the volume shown on the horizontal axis.

As you see can see, if you're pulling a ristretto or single on an unregulated Ulka, you're going to get a pretty awful shot, since it's pumping out at around 15 bar. If you're pulling a regular sized double of 50 to 60 cc, you'll be fine, getting 8 to 9 bar pressure.

If you put in a pressure limiting relief valve, you improve SHORT SHOTS ONLY.

Chris sets the Isomacs up at 10.5 to 11 bar, so all shots below about 50cc will be at that level. According to him, this is the industry standard setting for commercial vibe pumps. Reset it at 9 bar, and all shots below about 55cc will be at 9 bar.

If you insist on 80 - 90cc lungo shots, you'll be getting strong coffee brewed at 3 to 4 bar, not espresso. The pressure limiter won't help, the Ulka pump simply cannot maintain 9 bar pressure at that flow rate.

Hope this clears things up.

Posted September 11, 2003 link

That's Part A...

HB: ulka_pump_curve.jpg
(Click for larger image)

 
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HB
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Joined: 3 Apr 2003
Posts: 2,913
Location: Cary, NC
Posted Tue Jul 13, 2004, 7:44pm
Subject: Re: Brew Pressure and Salvatore
 

And now Part B.  I'm not certain which model of the Fluid-o-Tech Mono we're discussing.  I guessed at one of the pumps on their website rated at 70W.  Sooo-o, looking at the performance curve, this little wonder can put out 16 liters per hour (est.) at 10 bar (it's a continuous use commercial pump).  If I've done my math correctly, (16 liter / 1 hour) * (3600 seconds / 1 hour) * 25 seconds = 111ml per shot.  The puck absorbs about 35ml and for a double of 60ml, you're in the ballpark.  The problem arises, as Jim pointed out, when you want to pull a ristretto.

I see Salvatore's point and if you pull a true double in 25 seconds, it may just all work out perfectly.  Still, for the premium price of such a well crafted machine, I can't think of any practical reason to not have the ability to pull a shot at the pressure you want.  For example, you can't pull a Schomer-esque double at 8.2 bar.

-- Dan

HB: fluidotech-mono-perf-curve.jpg
(Click for larger image)

 
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easyrotor
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easyrotor
Joined: 23 Mar 2004
Posts: 63
Location: Brooklyn, NY
Expertise: I like coffee

Espresso: LaCimbali Junior
Grinder: Mazzer Mini
Posted Tue Jul 13, 2004, 7:48pm
Subject: Re: Brew Pressure and Salvatore
 

My earlier post neglected to mention another factor that Salvatore noted. My pressure gauge is never returning to zero. Salvatore thought it should until I told him my machine is plumbed in. It sits at city water pressure and even if it's off, there is a minimum of 40 pounds reading on the gauge. Maybe someone can tell me if this pressure gets added to what the pump can do. Depending on the answer, the 16+ bar pressure may finally be explained.
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HB
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Joined: 3 Apr 2003
Posts: 2,913
Location: Cary, NC
Posted Tue Jul 13, 2004, 7:56pm
Subject: Re: Brew Pressure and Salvatore
 

easyrotor Said:

Maybe someone can tell me if this pressure gets added to what the pump can do. Depending on the answer, the 16+ bar pressure may finally be explained.

Posted July 13, 2004 link

I can't say with certainty what the ratio is since all the machines I've used have an expansion valve.  Even so, the added line pressure does show up at the grouphead because the valve cannot vent all the pressure (pump + line pressure).  For example, Valentina on city line pressure of 60 PSI picks up almost 1/2 bar.  You can always measure yourself -- just drop the line into a water jug.

-- Dan

 
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Rick
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Rick
Joined: 23 Dec 2001
Posts: 773
Location: North Vancouver
Expertise: I love coffee

Espresso: Wega Mininova Inox Auto...
Grinder: Macap M4 stepped
Drip: Melitta #2 cone filter
Roaster: Stir-Crazy/Infinity Turbo...
Posted Tue Jul 13, 2004, 8:13pm
Subject: Re: Brew Pressure and Salvatore
 

Something still doesn't add up for me. A few posts back, easyrotor said:

" He felt that I could control the pressure by how I pack the coffee and I agree but I can't get the 25 second, 2 ounce pour and keep the pressure down below 16 bar."

That was a lot worse before easyrotor noted the 40 psi reading with the pump turned off, but it's still in excess of 13 bars for a 25 second, 2 oz. double.  At that pressure, it's still ~ 48% above the 9 bar "recommended" for espresso.  

I don't think that the measures suggested in Salvatore's advice:

"use a courser grind and pack harder the coffee  . . . is above the line in the PF and ... press against the dispersion screen BEFORE the pour"

should be necessary with a properly designed machine.  

Is it possible that Salvatore has started putting the more powerful pump in a machine that is still optimized for the old, less powerful one?  

Rick
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