How can I adjust the brew pressure of a vibe pump espresso machine? - Page 2

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yapit

#11: Post by yapit »

Thank you for all the help so far and excuse me for disappearing for a while, as i wasn't where the machine is. I kept thinking a lot about it however....

Dan, seemingly you have identified the right spot for the OPV. I got a mail from someone pointing me to this website that talks about a pressure mod for the silvia. http://mysite.wanadoo-members.co.uk/m4t ... reMod.html. Apparently it doesn't seem to be as convenient as the Giotto by adjusting a screw but requires an additional copper gasket to be put into. That would probably mean that there is no fine adjustment possible if i understand that right. But i haven't gone further to take it apart yet. In fact, I have no idea where to get that copper gasket if it would be the way to do....

Instead i have been thinking about the post of erics and tried to time the flow from the OPV. Well.... I am still wondering if i understood that right so let me repeat it: does zero flow at the PF mean no flow from the PF as if you would put a backflush disc in or use a PF with a gauge that does not allow any flow? If yes, that is what i tried --- but i got the problem that i couldn't observe any flow at all from the OPV !!! In fact, i have never seen anything flowing from the tube connected to the OPV. The pressure gauge at the PF needs some time to get until up around 12.5 bar but then nothing happens and after some time if falls slightly. What do i do wrong here?

Of course, besides looking just at the numbers, the taste should rule. I never had the chance to have a good coffee before, that is a fresh roasted coffee. I had one now. A blend called Malabar Gold. While i can perceive the greatness of this blend that produces lots of crema, straight espresso gets rather sour in the cup. I have the idea that this might also be related to my pressure problem, especially as a friend praises this roast as his favorite -- but i just cannot produce a balanced shot from it.


I like to add a general question about rotary pump vs. vibration pump. The former are of course rather expensive. Are they also easier to adjust in terms of brew pressure? Would that be one more reason to get a machine with a rotary pump?

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HB
Admin

#12: Post by HB »

yapit wrote:does zero flow at the PF mean no flow from the PF as if you would put a backflush disc in or use a PF with a gauge that does not allow any flow? If yes, that is what i tried --- but i got the problem that i couldn't observe any flow at all from the OPV !!!
It could be set higher than the pump's maximum pressure. Or what we think is an OPV is actually a fixed-pressure safety release valve. I've seen those on rotary machines; they allow water to escape from the closed system during warm-up (and hence why OPVs are also called "expansion valves").
I have the idea that this might also be related to my pressure problem, especially as a friend praises this roast as his favorite -- but i just cannot produce a balanced shot from it.
Maybe you should try Malabar Gold prepared by your friend? In my opinion, it's one of those "love it or hate it" blends.
I like to add a general question about rotary pump vs. vibration pump. The former are of course rather expensive. Are they also easier to adjust in terms of brew pressure? Would that be one more reason to get a machine with a rotary pump?
Yes, rotaries are much easier to adjust, but that wouldn't justify their cost. Their undisputed advantage is their quietness. Some feel they produce a superior shot, but that's hotly debated. In your case I would recommend deciding if there is indeed a problem.

Remember that for a true double, all this OPV stuff is irrelevant because the flow rate of the pump is such that the pressure is 9 bar at that volume. Only for ristrettos will you see any difference. Or to put it another way, if you pull true doubles, the OPV isn't supposed to open. For that matter, some very good machines (e.g., the Salvatore) don't have an OPV at all because they assume any serious barista would only pull doubles.
Dan Kehn

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erics
Supporter ◈

#13: Post by erics »

yapit wrote:Thank you for all the help so far and excuse me for disappearing for a while, as i wasn't where the machine is. I kept thinking a lot about it however....

Dan, seemingly you have identified the right spot for the OPV. I got a mail from someone pointing me to this website that talks about a pressure mod for the silvia. http://mysite.wanadoo-members.co.uk/m4t ... reMod.html. Apparently it doesn't seem to be as convenient as the Giotto by adjusting a screw but requires an additional copper gasket to be put into. That would probably mean that there is no fine adjustment possible if i understand that right. But i haven't gone further to take it apart yet. In fact, I have no idea where to get that copper gasket if it would be the way to do....

Instead i have been thinking about the post of erics and tried to time the flow from the OPV. Well.... I am still wondering if i understood that right so let me repeat it: does zero flow at the PF mean no flow from the PF as if you would put a backflush disc in or use a PF with a gauge that does not allow any flow? If yes, that is what i tried --- but i got the problem that i couldn't observe any flow at all from the OPV !!! In fact, i have never seen anything flowing from the tube connected to the OPV. The pressure gauge at the PF needs some time to get until up around 12.5 bar but then nothing happens and after some time if falls slightly. What do i do wrong here?

Of course, besides looking just at the numbers, the taste should rule.

I never had the chance to have a good coffee before, that is a fresh roasted coffee. I had one now. A blend called Malabar Gold. While i can perceive the greatness of this blend that produces lots of crema, straight espresso gets rather sour in the cup. I have the idea that this might also be related to my pressure problem, especially as a friend praises this roast as his favorite -- but i just cannot produce a balanced shot from it.


I like to add a general question about rotary pump vs. vibration pump. The former are of course rather expensive. Are they also easier to adjust in terms of brew pressure? Would that be one more reason to get a machine with a rotary pump?
That's good that you haven't taken it apart because, in fact, you may not need to. The copper gasket for your particular machine should be available from a variety of espresso machine dealers and you could always start with whomever you originally bought the machine from. Should you eventually take your OPV apart, it would be nice to have a spare gasket on hand. While copper gaskets can be reused, it is good practice to replace.

I BELIEVE your OPV is adjustable as per Dan's previous instructions but the only way to know for sure would be to disassemble it. But I wouldn't disassemble it before I knew what the true brew pressure is and had a spare gasket on hand.

If you try to measure brew pressure simply with a gage attached to the PF and normal basket in place, you should get some leakage between the basket and the PF body. The amount of this leakage will depend upon the "seal" between these two parts. In this case, your flow is the leakage plus whatever is flowing in the OPV line.

Under normal espresso brewing conditions, you don't need a "perfect" seal between these two parts because there is essentially zero pressure on the joint - the espresso is flowing from the PF spout(s).

When you use a blind basket, you are NOT subjecting the seal I speak of to any pressure but are depending on the seal between the rolled ridge at the top of the basket and the grouphead gasket to prevent any leakage. When the blind basket is in place and pump running, you should have no leakage at the grouphead, but you SHOULD have flow in the OPV line back to the tank. That flow SHOULD be ABOUT 110 cc/min at 12.5 Bar pressure. If such is NOT the case, then something else is amiss and we will need to "talk" further.

When you use any basket other than a blind basket, attach the pressure gage, and run the pump, you should get some leakage between the basket and PF body. Depending upon a couple of factors, this leakage may very well be close to "normal" espresso flow rates - you can choose your own numbers here but 2.0 oz in 25 seconds is certainly not unreasonable. If this is the case with YOUR machine, then your true brew pressure is 12.5 Bar as you measured.

BTW, I would disconnect and put a small piece of electrical tape on the heating element wires while doing all of this experimentation to simply avoid getting splashed with hot brew water.

You said "Of course, besides looking just at the numbers, the taste should rule."

Absolutely, positively, let there be no doubt that this is CORRECT.

That, by itself, should not be on a "list of reasons" to get a machine with a rotary pump. Espresso machines which have rotary pumps are high-end prosumer/commercial machines which are a cut above what you have and many cuts above what I have. But, as I said before, it appears you have quite a gem and I'm pretty happy with what's on my countertop although I do have this strange Brewtus itch that comes and goes.

Eric S.

glenn.magill

#14: Post by glenn.magill »

Hi,
First of all, I'm impressed with the amount of knowledge demonstrated on this site. You guys seem to be in the upper
echelons of the espresso machine tuning business.

Sadly i'm kind of at the other end of the scale :oops: . I've recently upgraded from my rancilio silvia to a rancilio Epoca.

The Epoca is a great machine, however I am a little disappointed in the amount of steam it can create and am wanting
to increase the steam output... can this be done without affecting the quality of shots I can create?

I've had a look over all the camera shots above of my machine, but wouldn't know which screw/valve to adjust to increase
the steam....

Can anyone point me in the right direction?

regards
Glenn

User avatar
HB
Admin

#15: Post by HB »

I've not opened an Epoca myself, but the black plastic box in the upper left corner looks like a pressurestat to me. If so, there will be a wide-slotted screw underneath the cover that presses against a spring plate. It is marked with ± arrows. If it is a Sirai, the adjustment is fairly small, around 1-1/2 turns for a 0.1 bar increase. You will have to adjust the flush amount to compensate for the hotter boiler.

Another option instead of raising the boiler pressure is changing the steam tip. The specs say it has a 1600W heating element and a 3.9L boiler. That's should give you some serious steaming power anywhere at 0.9 bar or higher. Maybe it is the smaller water surface, but I've noticed vertical boiler machines will have more "oomph" at the same boiler pressure compared to the same sized horizontal boiler.

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Dan Kehn

glenn.magill

#16: Post by glenn.magill »

Hi Dan,
you were 'right on the money' the black box is the pressure control. Have fitted a commercial steam tip and also turned up the pressure on that black box and it steams milk like a commercial machine.... I mean my cats run for cover when I turn on the steam wand!!! Can froth half a litre of milk at a time no problem and very fine froth too. The pressure does drop off consistently while steam wand is on full power, but it takes a couple of minutes to run out of oomph, and recovery time is very good... perhaps 1 min to return to normal.

Just wanted to say thanks very much for your advice! :D

DaveC

#17: Post by DaveC »

HB wrote:Another option instead of raising the boiler pressure is changing the steam tip. The specs say it has a 1600W heating element and a 3.9L boiler. That's should give you some serious steaming power anywhere at 0.9 bar or higher. Maybe it is the smaller water surface, but I've noticed vertical boiler machines will have more "oomph" at the same boiler pressure compared to the same sized horizontal boiler.
I found this on many of the machines I reviewed. My personal belief as to the reason for the increased steaming power size for size is: The vertical boilers of the machines are filled with a greater % of water than a Horizontal boiler machine. The larger mass of water acts as a bigger steam "battery" and can create more steam for longer.

I don't think this is due to any planning by the manufacturers to achieve this result, but an issue of practicality to ensure the element is fully covered.

P.S. This also accounts for some of the longer recovery times of the HX units in these type of machines (as they are often sized the same as for HX units in a horizontal boiler), because more of the HX is submerged. This because of the rule when adjusting the water level in a HX machines (Horizontal and to a much lesser extent Vertical) boiler:

Increase boiler water level = better steaming, longer HX recovery/cooler brew temps

Decrease boiler water level = weaker steaming, quicker HX recovery/Hotter brew temps

I have many times come across people who have lowered boiler water level in the mistaken belief they will get better steaming (rationale is a larger area of steam) and actually got the opposite effect.