Lelit Bianca Needle Valve; Does It Control Flow or Pressure?

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mr2andy

#1: Post by mr2andy » Apr 21, 2019, 2:21 pm

Hey all,
I have a question in regards of the lelit Bianca.
The paddle on Bianca is controlling the needle valve which then controlling the flow or the pressure at the group?

If the pump is maintaining say 10 bar and but restricting the water at the needle bar, shouldn't the group head still be seeing 10bar but the flow can be restricted? But instead, the pressure as the paddle moving left.

Moderator Note: This discussion was split off from Lelit Bianca User Experience

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Jake_G
Team HB

#2: Post by Jake_G » Apr 21, 2019, 5:15 pm

mr2andy wrote:Hey all,
I have a question in regards of the lelit Bianca.
The paddle on Bianca is controlling the needle valve which then controlling the flow or the pressure at the group?

If the pump is maintaining say 10 bar and but restricting the water at the needle bar, shouldn't the group head still be seeing 10bar but the flow can be restricted? But instead, the pressure as the paddle moving left.
You may want to check out my reply here to a similar question.

Cheers!

- Jake

JayBeck

#3: Post by JayBeck » Apr 21, 2019, 9:19 pm

mr2andy wrote:Hey all,
I have a question in regards of the lelit Bianca.
The paddle on Bianca is controlling the needle valve which then controlling the flow or the pressure at the group?

If the pump is maintaining say 10 bar and but restricting the water at the needle bar, shouldn't the group head still be seeing 10bar but the flow can be restricted? But instead, the pressure as the paddle moving left.
The paddle controls flow. Flow ultimately impacts pressure. Pump pressure is only the maximum the pump will push water at once it meets the resistance of the puck. So once you have built pressure via the resistance of the coffee puck, then the needle will adjust flow which will in turn adjust pressure.

mr2andy

#4: Post by mr2andy » Apr 30, 2019, 10:22 am

Jake_G wrote:You may want to check out my reply here to a similar question.

Cheers!

- Jake
Jake,
Thanks for sharing the information. It took me a while to read through and digest your post. Can I conclude that pressure profiling and flow profiling are basically the same thing because controlling one control the other?

Lately, j have heart ppl start referring the la marzocco gs3 mp as a flow profiling machine instead of pressure profiling but it was referred to as a pressure profiling machine when it was first introduced.

Cheers

pcrussell50

#5: Post by pcrussell50 » replying to mr2andy » Apr 30, 2019, 10:42 am

You have a BDB. Were you aware that it is capable of full blown flow profiling, with a simple, reversible, nearly cost-free re route of a couple of stock lines? All you do is cap one line, and pull one end of two others and swap them and voila. Plug and play profiler with full capability.

Quick summary:
1) Bianca, and the BDB with a simple mod (by that I mean you don't add any parts, you just cap a line, and switch places with two others, for beginning to end, on-the-fly flow profiling. You can adjust your flow, to anything you want, as the shot progresses. Think continuously variable transmission, or a newfangled automatic with eight speeds so you never feel like you are "stepping"

2) Slayer: has two "speeds" (flow rates), low and high. Accomplishes more or less what the above machines do, but only two speeds, not continuously variable. It's kind of the "grand daddy" of the flow profiling movement. With only two speeds, not as "flexible" as being able to set your flow to anything in between as you go.

3) DE machines. Possibly the most capable of all, but so far, you pre program it and let it run. If you don't like what you get, you re program it. Repeat until you have it how you like it. Later this year, an update is expected where you can adjust flow on the fly.

4) GS/3 MP can kinda sorta do what the machines in (1) can do, but not through a needle valve. The pump runs at full power. At low flow, it merely dumps all that excess water into the drip tray. If you do a lot a profiling, you will fill your drip tray very rapidly. I have heard that it does not have the sensitivity and control that the machines in (1) do. In the message traffic, it does not seem to be a big player in the profiling space.

5) GS/3 AV Has no inherent profiling capability. BUT Jake has one, and a lot of know-how and fabbing skill, and he is going to make his into an on-the-fly, needle valve profiler. Others here at HB have radically modified their AV's in other ways to make them fully competent profilers.

HTH

-Peter
LMWDP #553
★ Helpful

mr2andy

#6: Post by mr2andy » Apr 30, 2019, 9:02 pm

Peter,
Sent you a PM asking about the flow profile mod for BDB.

In regards to gs3 MP, the new mp post 2016 do have a conical valve which is very sensitive when adjusting the brew pressure on the fly.

They do sell a kit for those who has the gs3 mp pre 2016 to upgrade to the new conical valve.

On my BDB, I have been doing pressure profiling by turning the hot water dispensing knob. I'm not aware of the mod you mentioned.

pcrussell50

#7: Post by pcrussell50 » replying to mr2andy » Apr 30, 2019, 9:17 pm

PM forthcoming, Andy.

Yes, the GS/3 conical valve, all it does is divert unwanted pump flow to the drip tray. If you are doing light roasts with say, a 30s pre infusion like you can do with the Bianca (and the needle valved BDB), and you are doing it on the GS/3 MP, you will be filling your drip tray at a prodigious rate because the pump only runs at full power and you will only be using a trickle of water to the puck during long low pre infusion. The rest will be gushing into the drip tray. In the case of the Bianca (or the modded BDB), when you dial down the paddle to low flow, the trickle you want gets through the valve and the rest remains in the lines before the valve. Ironically, the profiling you have been doing with your BDB is like the GS/3 MP in that the water you're not using ends up in the drip tray, too. But now with Bianca (and BDB, there is a better way). As for the sensitivity or lack thereof of the conical valve, I have no personal experience, other than what I've read here, where the big dogs of GS/3 profiling are heavily modified AV's. I don't read often of seriously long profiling with the conical valve MP. What I have read about it suggests what I call "light duty" profiling.

In keeping with the spirit of this thread, you should read the first page of Jim's bench review of the Bianca. It's only one page, but it's the best description I can think of as to what heavy profiling is all about: Lelit Bianca Review
This ^^^ should be bookmark number one in your browser if you are interested in the cutting edge of extraction.

-Peter
LMWDP #553

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Jake_G
Team HB

#8: Post by Jake_G » May 02, 2019, 3:09 pm

mr2andy wrote:Can I conclude that pressure profiling and flow profiling are basically the same thing because controlling one control the other?
They are different, but intimately tied to one another. The difference is primarily in the control scheme.

The other primary dividing line is whether the control is open loop or closed loop. Open loop systems have no feedback, so when you make a change, the change is fixed and the system adjusts to that fixed change (I'll explain a bit more a little later). In an open loop system, you set a relationship between pressure and flow and the two still interact dynamically based on the rest of the system. Closed loop systems have feedback, so if you set a flow rate in a closed loop system, the pressure actively adjusts to attempt to hit the flow target. Likewise, if you set a pressure target, the flow actively adjusts to try to hit the pressure target.

Closed loop comes in a few flavors:
  • •Variable bypass - mechanical/passive control
    •Variable displacement - electrical/active control
Active control comes down to flow meter or flow modeling for flow control and pressure transmitter for pressure control.

The adjustable OPV is a closed loop manual pressure control device using a variable bypass. If one were to dynamically adjust the OPV while pulling a shot, they would be fundamentally profiling the pressure. This is because the OPV diverts flow from the group to ensure the pressure never exceeds its setpoint. The spring inside of the OPV forms the feedback loop. So, to control pressure, the OPV modulates the flow. If you want zero pressure using an OPV, you divert all the flow from the group to someplace else where it can't make espresso.

Then you've got the closed loop automatic pressure control systems. These generally use a variable displacement (gear) pump and a pressure transmitter in the brew path. The pump speed (flow) is modulated to hit a pressure target. Choked shots require less flow and lower speed to hit a pressure target than a gusher would. Zero pressure would mean near zero flow leaving the pump.

Next you have a closed loop flow control scheme. There are pressure compensated flow control valves out there, but by and large, most flow profiling setups use a specialized pump (or a carefully pulsed vibe pump (or two) in the case of Decent Espresso), a flow meter and a controller to achieve control over the flow rate. Truth be told, the DE1 series of machines may well be the only true closed-loop profiling machines on the market right now. Duvall is the other one that is making inroads in this space.


Next you have the open loop methods, which can be grouped largely into 3 categories:
  • •Variable displacement (gear) pump
    •Variable bypass
    •Variable restriction
The first is the same as the gear pumps above, but the control system doesn't actively manage the pump speed. You command a speed and the pump runs at that speed. An open loop paddle-controlled machine let's you sweep the pump speed from off (no pressure or flow) to some max speed (max flow and thus max pressure). This system is a "profiling" machine for sure, but its controlling the flow. The puck controls how much pressure that flow generates. A gusher will generate less back pressure than a puck that chokes the machine... the fancy thing about a gear pump is that you can set it to a very low flow rate and have a slow ramp up to a very high pressure.


Next you have the GS/3 MP and stock BDB with the water switch mod. This is similar in approach to using the OPV, but there is no spring in the valves used, and there is no feedback loop. When you open the valve a little bit, some pressure is generated and that pressure results in some amount of water leaving the system. In the case of the GS/3, the waste water goes to the drain box. With the BDB, it goes out the hot water spout, where it can be collected or allowed to drain into the drain box. Back to the whole "open loop" thing. The amount of water that leaves the spout is variable on these machines because the pressure at the puck changes during the shot and the pressure directly controls how much water is allowed to escape. What you control is how much water can escape at a given pressure, and this, in turn, determines how much pressure reaches the puck. It's the same function as the OPV, but your eyes and hand replace the spring and diaphragm. It works ok, but its imprecise and a bit wasteful. In general, high bypass is the similar to a gear pump running slow, except that the bypass controlled machine will not ramp up to a higher pressure without manual intervention. High bypass equals low pressure, pretty much always.


Finally, you get to the variable restriction machines like Bianca and the modified BDB, or the Dalla Corte Mina. These machines are extremely versatile. They work in concert with an OPV to give you a veriable relationship between flow and pressure. You run a constant inlet pressure to the valve, and depending on the flow through the valve and the valve opening, you get a variable pressure at the outlet. The valve really is controlling the pressure drop across it and nothing else, but when you change the pressure at the puck, the flow through the puck changes, so it changes both pressure and flow in a way that none of these other methods can.


I use my needle valve to control the flow out of the puck into my cup. I ignore the pressure at the puck because I find that it is immaterial compared to the flow rate through the puck as long as I know I have sufficient pressure available on the inlet of the needle valve.


Sorry for yet another verbose response. But saying they are the same is not quite right. Likewise, saying the needle valve controls flow and pressure follows isn't quite right either. It's a complex and "organic" relationship between the two, and that's a factor of the physics behind making espresso. Each of the schemes listed above have their unique pros and cons. Frankly, I think that the active closed loop restriction is the end-all be-all for the future of espresso aside from what Decent has done, which is every bit as capable and more energy efficient but basically requires vibe pumps to pull it off.

Ok, I'm done rambling for now.

Cheers!

- Jake

Nunas
Supporter ♡

#9: Post by Nunas » May 02, 2019, 7:21 pm

Jake,
Swell tutorial! I'm sure everything the OP wanted to know and so much more.
I use my needle valve to control the flow out of the puck into my cup.
Do I understand correctly that whereas the Bianca has the needle valve high in the group, you have yours on the bottom of the portafilter? If so, did you perhaps document this mod somewhere? Edit...oh ...and you use this to make coffee, not just for testing. Thanks.

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Jake_G
Team HB

#10: Post by Jake_G » May 02, 2019, 7:48 pm

Maurice,

My valve is in a similar location to the Bianca valve, it's just that I have a commercial Rancilio group instead of an E61. What I mean by the statement is that I monitor the flow into the cup and regulate the valve in the group to control what I'm seeing. The results are pretty much instantaneous.

I've document most of the mod in My short and concise build to preinfusion/pressure profiling.

Cheers!

- Jake