Valentina brew pressure adjustment

[James]

Today I got a pressure gauge to measure my brew pressure on my La Valentina, and I concluded that my pressure was to high (12 bar) and I would like to reduce the pressure to approx. 9 bar. The problem is i can't figure out how to lower the pressure, I have open the Valentina but I don't think it is so simple to figure out. I have taken a couple of photos and thought that some of might where able to describe it for me, the pictures are on my website:

http://www.james.dk/side1.jpg
http://www.james.dk/side2.jpg

Hope someone can help me )

Brgds
James

[malachi]

From Dan's excellent "Buyer's Guide to the La Valentina"...

"The expansion valve, which determines the maximum brew pressure, was initially set at 12 bar (this valve is also called an over-pressure valve or "OPV"). If the pump is unregulated, it can produce an overextracted, bitter shot. Adjusting it down to nine bar helped the consistency of my shots immensely, especially when pulling ristrettos. You'll need a portafilter pressure gauge to adjust it because there is no brew pressure gauge. I recommend asking 1st-line to do the adjustment before shipping.

Valentina's expansion valve is an industrial-grade fluid control valve, rated for two years of continuous use. That translates into forever in a home environment. The expansion valve allows for very fine adjustments. The one-bar adjustment of some non-commercial expansion valves corresponds to a slight turn of a small screw; Valentina's is finely adjustable and is done simply by turning the end of expansion valve itself. This means that you have a lot of control without fear of overshooting the desired maximum pressure by a slip of the pliers."

[HB]

The Andreja Premium has the same expansion valve as Valentina. FAQ #13 at http://www.chriscoffee.com/faq has a good picture of it:



(image courtesy of Chris' Coffee Service)

[shadowfax]

Dan, I brought mine down a bunch the other day. I have it flushing out 2 oz of fluid in 37 seconds (incl. the "preinfusion" ramp up...). That is, it's flushing out 2 oz in 30 seconds after the pump bogs from being at full pressure. Is that the right measurement as Jim describes to get the 8.5-9.5 bars, or should I be getting 2-2.5 oz within 30 seconds of the beastie turning on?

By the way, the pump on Levetta is the EX5, the same as the one Jim refers to from the Isomacs and others... I understand yours is the EP5, with a plastic barrel thingy? but they are otherwise the same pump, I assume?

I am too cheap to buy a special PF for this, and I don't feel like tinkering to the point of installing my own brew pressure gauge just yet. I like the pressure runoff measurement idea for getting in the ballpark, though.

[HB]

Jim's "runoff method" assumes the system is fully pressurized, so you'll need to wait until the expansion valve (OPV) overflow tube is running steadily. Then you can indirectly calculate the effective brew pressure:


(image courtesy of Ulka S.p.A.)

So 100cc / 30 seconds ~ 10 bar, 150cc / 30 seconds ~ 8 bar. According to the Ulka website, the EX5 pump is one minute on / one minute rest. Keep that in mind when testing the brew pressure.

Your Levetta has the EX5? Mine has the EP5, which like you said means the barrel is plastic. Oh well, must have been out of stock the week I ordered.

[shadowfax]

yeah, has the pretty brass thingy. It is $100 more than the one you have, so maybe that's one place they spruced it up, other than the full E61 group.

I'll shoot for 125 cc in 30, I guess. I understand that having the OPV set right at 9 bar makes your shots tend to brew a little bit lower (like 1/2 bar less), though, so I don't want to shoot any lower.

[shadowfax]

just in case the original poster is interested, here's a shot of where it is on my valentina... Just beside the Gicar flowmeter thingy.



Thanks, Dan. I've got it all up and running at about 2.2 oz/30 seconds. I think that should put my shots around the high 8/low 9 bars for brewing. Maybe someday I'll check for real.

and just for kicks:



as Chris would say, she's getting all bauhaus on me!

[James]

Thank you for the reply, I have now managed to reduced the brew-pressure, although it seems the European model is a bit different from the US-models.

James

[shadowfax]

Well, I would guess. I think they can put much higher-wattage toys in European espresso machines because you guys have 220 V connectors. What's different about yours?

[James]

The things I have noticed so far is that my boiler is copper or something that looks like copper, and my "Gicar flowmeter" and my OPV is not on the same side of the boiler.

James

[shadowfax]

Well, there are bound to be some layout differences. Mine is not even the same model as yours... it's the Levetta version, AKA BFC Junior Plus. I went back and looked at your pictures, heh. those things are ridiculously big!

Anyway, I think your boiler is brass. Copper would just turn green in a hurry. I have a brass boiler too, it's just nickel plated, which is exciting to me, because it really helps resist scaling. Looks like you have the Ulka EX5 pump, though. I think Dan has the same version as you, only his pump is the EP5, which is the same but with a plastic barrel rather than the brass one.

you should plumb her in and get a rotary vane pump

[HB]

Anyway, I think your boiler is brass. Copper would just turn green in a hurry. I have a brass boiler too, it's just nickel plated, which is exciting to me, because it really helps resist scaling.

Minor correction. Both are copper, and newer models are nickel plated (link).

[James]

you should plumb her in and get a rotary vane pump

What advantages is there in a rotary vane pump? instead of the one I have?

James

[shadowfax]

smooth pressure delivery. vibratory pumps deliver pulsing pressure, which is one reason unbuffered manometers tend to jump around when monitoring brew pressure.

You can actually see the vibrations in the brewing if you have a naked portafilter, sometimes. It's sort of a sinusoidal contour along the cone flow of the espresso extraction. Sometimes I can even see it in my shot pictures... I don't really know what taste advantages this has, other than what Chris Tacy and some others say; I have never used a machine with a vane pump.

[HB]

I'll be lazy and excerpt some of my observations from The Buyer's Guide to the La Spaziale S1:

Some espresso aficionados claim to taste a difference at various pressures. If you are inclined to tweak the pressure to discover for yourself, it is easy to do so with a rotary pump since it has a built-in bypass valve that allows you to set the pressure directly. That is, unlike vibration pumps, which put out their maximum pressure for a given resistance and rely on an expansion valve for pressure regulation, a rotary pump puts out the same pressure independent of the flow rate. In a commercial environment, one rotary pump may service several groups, plus it doesn't require the pauses that a vibration pump must have (about one minute maximum before resting for one minute).
...

One other advantage of rotary pumps is they are quieter than vibration pumps, especially when the pump is external to the machine under cabinet as is often the case in commercial setups.

The last point is the big selling point -- rotary pumps are much, much quieter than vibration pumps.

[another_jim]

That is, unlike vibration pumps, which put out their maximum pressure for a given resistance and rely on an expansion valve for pressure regulation, a rotary pump puts out the same pressure independent of the flow rate.

Andy pointed out this was technically wrong; although you'd need to get 5 groups and the boiler refill going before you'd notice.

If the long rumored vibe-sized rotary makes its debut in the LM, and then becomes available for other single groupers; it'll probably show flow to volume limits similar to vibes.

[Bradley Allen]

just in case the original poster is interested, here's a shot of where it is on my valentina... Just beside the Gicar flowmeter thingy.

Hey there mister shadowfax. It is time. Enough is enough. Operating the La Valentina Levetta way over 9 BAR (as shipped) is just killin' me. Argh! I'd love to understand why someone would sell them that way by default. But I digress.

So I have the back off and can now see inside. I feel so nerdy!... but I'm not sure how I would reach that 12mm adjustment nut which is trying to hide behind the Gicar water refill circuit.

Did you remove anything else in your photo before adjusting? Or did you use a special, magical wrench? The depth of field in your photo makes it seem right next to the Gicar, where from my vantage point at home it appears beside... yet just a little bit below it - and nearly out of reach.

[shadowfax]

If you loosen the mounts (I think with an allen wrench) of the Gicar flowmeter, you can push it out a little bit to make the OPV more accessible. other than that, you do have to do wrist acrobatics to get your 12 mm wrench around that thing. just keep working at it. good luck!

[Bradley Allen]

If you loosen the mounts (I think with an allen wrench) of the Gicar flowmeter, you can push it out a little bit to make the OPV more acessible. other than that, you do have to do wrist acrobatics to get youer 12 mm wrench around that thing. just keep working at it. good luck!

Thanks! I took another look at it and yeah, I'll just take the Allen wrench to the Gicar... it should be easy then.

[Bradley Allen]

Okay. Here I am at the threshold. I've got a few questions/observations...

First, I want to double confirm that the OPV valve is 'lefty loosey, righty tighty' (left lowers the pressure, right increases the pressure). I've cranked to the left and to the right, and either way this is what happens:

The needle on the manometer rises to 1.2, then it slowly falls to just under 1.0, then the green light switches on, then the needle rises to 1.2, and then it slowly falls again. Rinse, repeat.

This is with the machine on "at rest" (not lifting the levetta to pull a shot or operating the steam wand, etc.) ... it just does this over and over. Flow and ebb. I was hoping that the machine would just hang out at .9 with some sense of stability without the green light having to kick in every few seconds. Maybe this is a separate issue altogether but I'm still curious what's going on here.

Maybe I'm not turning the valve enough? Maybe I'm turning it in the wrong direction? Maybe I'm turning the wrong thing? Either way, I'm feeling pretty clue-less right now.