I am trying to understand the brew pressure measurements I just made on my Salvatore machine. After reading several posts about adjusting vibe pumps on HX machines, it seemed like a good idea to find out what the pressure was on mine. I used a PF pressure gauge and got a bit of a shock when it read over 16 bar. The pump got quiet and I shut it down and the 3 way valve opened and the presure went away. Hmmm, sure seems like there is way more than the 8-12 bar I expected to see after reading the posts on the subject. Ok, time to call Salvatore, where a friendly voice (a friendly voice always answers the phone there) told me that it was quite normal to read that kind of pressure if the system is closed as it is with a PF gauge. He then followed up with a lecture on how the pressure is going to be dependent the many factors like coffee type , grind, tamping, my technique, etc.
My machine does not have a pressure gauge in the brew circuit so a dynamic reading was not possible... or was it. The 3/8 tube that goes to the top of the E61 group is fed off the top of the boiler from a Tee that had one side capped. I thought it might be a nice place to hook up my gauge and after a vist to Home Depot's depleted brass fitting selection, managed to do so. I did my normal setup and pulled a decent shot and watched the pressure as it went over 16 bar again. Can someone explain to me why my machine works the way it does?
Here is another question based on another_jims post and the picture associated with it.
My 3way valve is physically bolted to the bottom of the E61 group and not in front of the group as shown in the picture. I realize that internal group plumbing could place the valve ahead of the group as in the picture but is it really ahead of the group and for that matter is it really a three way valve? It does dump water in the waste tray after the shot is pulled. Thanks.
Posted Sat Jul 10, 2004, 5:43am Subject: Re: Brew Pressure and Salvatore
I respectfully disagree with the friendly voice at Salvatore. A static ("dead head") reading can be slightly higher than the pressure during a pull, maybe by as much as 0.5 bar (see related discussions in "Portafilter Pressure Gauge" and "Portafilter Pressure Gauge Question"). A reading of 16 bar is off-the-charts too high and indicates the expansion valve isn't venting at all. Just for kicks, I installed an external gauge much like you did. The reading from it and the portafilter pressure gauge are the same to the accuracy of the gauges.
As for Jim's diagram, I believe it is a profile shot; the exit he shows in his diagram is essentially the column that runs from the top of the group bolt to the solenoid at the bottom (i.e. it is not "ahead of" the group, it is part of the group). The Salvatore and my own Valentina probably have a very similar design, what I call a E60.5 (see the image below and "Re: Help with purchase:La Valentina or Wega Lyra or ECM Giotto Prem" if interested). It uses a solenoid and isn't a three-way valve as on an E61 lever operated machine, not that it necessarily matters.
easyrotor Senior Member Joined: 23 Mar 2004 Posts: 63 Location: Brooklyn, NY Expertise: I like coffee
Espresso: LaCimbali Junior Grinder: Mazzer Mini
Posted Sun Jul 11, 2004, 8:08pm Subject: Re: Brew Pressure and Salvatore
dan_kehn, thanks for your informative post, it was very helpful. I am convinced that the high pressure is responsible for some my issues with making cosistant shots. However as I finish reading Schomer's "Professional Techniques", it is also apparent that my technique is also an issue. It seems to me that fixing my technique is going to be easier than fixing the machine. I need to fix the high pressure problem but fear that the folks at Salvatore won't be much help given their responses so far. It would seem that they consider it a non-issue. I think that the machine was delievered with this problem as the first time I tried to backflush the system and left the pump run too long (10 seconds) , the system locked up tight as a drum. I could not even release the PF. Salavatore told me to let it cool down and then it would come apart. It did but does this seem correct?. They told me not to run the pump so long next time to avoid the same problem. Perhaps this a bad assumption on my part but it seems that they know that there is no hi pressure releif in the system.
I am at a loss to understand why they would deliberately set these machines up to work at such high pressure if in fact they are doing so. Is it dangerous? What will be the best approach to fixing the problem? As my system is plumbed in, is it possible to feed water back into the system to releave pressure or will it have to go into the waste tray? I'll post some pictures tomorrow of the inside components. I really can use some suggestions as my understanding of what really is happening is far from complete. Thanks.
Posted Sun Jul 11, 2004, 10:24pm Subject: Re: Brew Pressure and Salvatore
Technique is always important but getting your machine properly adjusted in the first step. My machine was delivered set at 12 bar; I found it "finicky" and the shots had a harsh edge. If your machine is indeed adjusted to 16 bar then there is little hope of pulling anything worthy of the Salvatore's premium price.
Let me ask a dumb question... your machine has a vibration pump, not a rotary pump, right? If it is a vibe pump model, then it must have an expansion valve (also called an over-pressure valve). I suppose in theory you could have an unregulated pump and adjust your tamp and grind such that it works out to your desired extraction pressure, but that's a challenge unworthy of your time. Since your machine is plumbed in, your expansion valve should vent water during a shot into the driptray.
Your other questions / comments... Running the pump for 10 seconds against a blind basket is no more harmful than pulling a ristretto. For that matter, you could have let it run for a full minute without the pump complaining -- not that I recommend it. I've never heard of a portafilter getting "stuck" in the grouphead. Keep in mind, however, that my machine is bolted to the countertop, so leverage is not an issue. :-o
I got the impression from other members that the folks at Salvatore are pretty sharp. If they understood that you measured 16 bar at the grouphead and didn't recognize it's a problem... well, that doesn't compute.
Actually my machine is pumping past 16 bar. It not really possible to tell what the actual pressure is as the gauge tops out at 16 bar and it goes past that. If there is a way that I can be mistaken about this, what is it? The machine has a vibe pump as far as I know and I will attach a picture of the only thing that could be a expansion valve. The valve shown below is fed from the pump at the bottom of the tee which also feeds the top of the boiler from the center of the tee. The top of the tee goes into the bottom of the brass block where the valve is mounted and the line from the top of the brass block goes to the bottom of the boiler. Is this the expansion valve? No visable adjustment and I would guess that it is a solenoid that is controlled by the main control module based on how it is wired.
OK, so here are the facts as I see them: There is high pressure is there, unless the gauge is broken. The 2 calls about the lock up and the high pressure to Salvatore have netted no response save to point to my technique. I definitely told them about the 16 bar+ measurement and was told that that would be normal in a closed system. Because my communication skills are not that great, I will try to call them again today and be as specific as I can.
I am simply too raw at this say that this is anyone's fault save my own. However "finicky" definitely describes this machine. I do not understand the circuit yet but if the valve is an expansion valve, how can it pass overpressure into to a plumbed in system? There is nothing dumping into the tray save the solenoid/3way valve bolted to the bottom of the group.
Some other useful(?) information: There is a Sirai widgit that is plumbed into the steam circuit with wiring back to the controller. With only a single tube feeding this, my guess is that it is a pressure sensor. The controller is a Giemme RL 1E/2C/F. There are no other visable valves save the hand controls for the hot water and steam. I'll do another post with a picture of the pump. Thanks for the help.
Hard to tell from the quality of the picture, but it sort of looks like a Fluid-o-Tech Mono (go to their website and click on "oscillating piston pumps" and then "Mono"; a good picture and specs are in the PDF). It definitely isn't a rotary pump (Procon for example). So we're back to the same question... the pump must vent some water when pulling a shot, otherwise it will ramp up to its max (or the puck resistance). Since it is direct plumb, the water must go into the driptray. If they didn't install an expansion valve and the pump can't be regulated, I'm baffled by their reasoning.
BTW, their "closed system" comment may assume that you'll get your tamp just perfect so the extraction rate and pressure is about 9 bar and two ounces in 25 seconds. Most rational home baristas would prefer to regulate the pump and thereby eliminate one variable. :-o
I'll post a couple pictures of expansion valves to clarify a bit more... here's one for an Isomac Amica.
And an expansion valve for La Valentina (image courtesy of Chris Beck). You can also see one in the instructions for Silvia Pressure Modification. Perhaps needless to say, good regulated pump pressure isn't a high-end feature nowadays.
I guess it is time to accept the facts although I feel a bit let down, the machine has no brew pressure regulation. I have just spent an hour reading about rotary pumps, pressure modifications and the effect of higher pressures brewing on alt.coffee. The 16 bar pressure readings I see do seem to be higher than most others mention.
dan_kehn, Good call on the pump, I think you are correct. I will confirm it the next time I dig into the machine. Did you recognize the valve/solenoid in the first picture?
Now it's time to decide what to do next. I ordered a dual gauge from EPNW and will replace the boiler pressure only gauge with it. I may need to devise a bit of damping for the gauge to prevent jitter. Of couse this does not fix the problem, just makes it easier to see. I could plumb in a pressure regulator/expansion valve and that seems the least expensive and simplest approach. Any thoughts on what might the best deivice to use? I do wonder what amount of water will be passed by the device and if that won't turn out to be a problem. I guess I could just use the machine as it has apparently been to designed to be used. I can get the 25 second 2 to 2.5 oz pours that are desirable but somestimes they seem a bit bitter to me. 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 think that this was my last call to them. Did I mention that they charged me $38 for two under cup gaskets?
I'm still puzzled at why a machine this expensive with so many high end parts has no brew pressure regulation. As mentioned previously, it does not compute.
Howard, I won't pretend to know even 1/10th as much as Dan when it comes to all the different parts of espresso machines. I use an Isomac Millenium at home matched up with a Mazzer grinder. This spring I was out in Seattle visiting my parents who I bought a Salvatore Semi auto, also matched up with a Mazzer. The Salvatore performed fantastic. Personally I liked it better than my Isomac. The quality of the construction appeared to surpass my Millenium and the espresso and steaming were great. My recommendation is to talk to Salvatore himself and see if you can clear up some of your concerns. The machine definately has a vibe pump. Also do yourself a favor and get the new tapered two hole tip. Rob
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