How to decrease the flow rate

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9coffee

Postby 9coffee » Jun 13, 2018, 10:56 am

I'd like to decrease the flow rate for extraction of my espresso machine.
I use Marzocco FB80 EE for 2group.
I installed a 0.6mm gigleur and a rotary pump(150L/1h).
The flow rate is as follows now.

265g per 30seconds at 9bar

Are there any customizes to decrease the flow rate?
How about replace the current motor to the small motor?

Nunas

Postby Nunas » Jun 13, 2018, 11:56 am

The flow rate is not a function of the pressure, providing the machine is set up to provide the nominal 9 barr. The brew pressure is a function of what's going on in the portafilter. With a super fine grind and the machine choked you should see about 9 bar. During brewing it will vary. More (& fresh) coffee, finer grind is the answer. Smaller motor will not do it, as the working pressure is not controlled by the motor; you just risk burning out the motor as it would labor. The jet (I don't know why English markets persist in calling it a gicleur, as that is simply the French word for jet) is there to slow the rate at the onset, providing for a gentle preinfusion. Once the preinfusion chamber is full and flowing it has little effect on the brew flow rate. A smaller jet gives a longer preinfusion. I can't comment on the proper size for your machine...simply don't know, but 0.8 mm is a common size.

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another_jim
Team HB

Postby another_jim » Jun 13, 2018, 12:12 pm

You can decrease the flow rate by installing an adjustable needle valve at the head of the pump. Closing down the valve will slow the flow when there is no puck present, and during the preinfusion/dwell phase, in essence giving you a customizable gicleur (sure it's a jet, but in espresso machines, it's always called a gicleur). Once the static pressure of the water rises as the puck resists flow, the valve will play little part.

In some profiling machines, there is a needle valve with an automatic actuator; so it can be operated during the shot. By reducing the outlet very far down, the flow can be controlled. IIRC, the Hydra uses this system.

How easy, or even doable, any of this is on your machine, I don't know.
Jim Schulman
★ Helpful

9coffee

Postby 9coffee » replying to another_jim » Jun 14, 2018, 8:12 am

Thank you Jim, your advice is very helpful.
I ordered an adjustable needle valve immediately.
However I worried about damages for a rotary pump and a mortar.
Is it no problem?
I'm looking forward to trying it!

9coffee

Postby 9coffee » Jun 14, 2018, 8:30 am

Nunas wrote:The flow rate is not a function of the pressure, providing the machine is set up to provide the nominal 9 barr. The brew pressure is a function of what's going on in the portafilter. With a super fine grind and the machine choked you should see about 9 bar. During brewing it will vary. More (& fresh) coffee, finer grind is the answer. Smaller motor will not do it, as the working pressure is not controlled by the motor; you just risk burning out the motor as it would labor. The jet (I don't know why English markets persist in calling it a gicleur, as that is simply the French word for jet) is there to slow the rate at the onset, providing for a gentle preinfusion. Once the preinfusion chamber is full and flowing it has little effect on the brew flow rate. A smaller jet gives a longer preinfusion. I can't comment on the proper size for your machine...simply don't know, but 0.8 mm is a common size.


Thank you Nunas, your opinion would be helpful.
I understood you opion, but I always use full city roast coffee beans for espresso. I don't wanna grind coffee beans finer to not extract bitterness. That's why I'm looking for other ways. I ofter see that some barista extracts espresso on lower flow rate at 9bar.

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Jake_G

Postby Jake_G » Jun 14, 2018, 9:02 am

9coffee wrote:I'd like to decrease the flow rate for extraction of my espresso machine.
I use Marzocco FB80 EE for 2group.
I installed a 0.6mm gigleur and a rotary pump(150L/1h).
The flow rate is as follows now.

265g per 30seconds at 9bar

Are there any customizes to decrease the flow rate?
How about replace the current motor to the small motor?

Hello again!

You can easily cut your water debit (flow rate measured with no portafilter) in half by installing a pump kill switch between your machine and your pump. You need a pressure regulator to ensure that your line pressure is sufficiently lower than your pump pressure (the Linea MP I use on occasion has 8 bar mains pressure :shock: ), but 3 bar or so will readily drop your water debit down to the 125g per 30S range.

My work flow on my Rancilio S20 is that my pump is disabled normally so that boiler fill, flushing and preinfusion all take place at line pressure. Only when I am ready to extract at full pressure do I enable the pump with a switch located next to my group on the machine. It is easy and just works. The needle valve will work too, but brew pressure will taper off as the shot progresses if you choke the flow beyond the natural flow rate of the puck (if the tail end of your shot would be 2.5g per second at 9 bar but you only supply 2g per second, you wont have 9 bar...). Also, I can't remember if the FB80 uses an HX in the steam boiler to preheat the brew boiler water, but if it does using a needle valve at the pump discharge can yield unpredictable flow due to flash boiling in the HX if you choke the flow too much.

Cheers!

- Jake

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another_jim
Team HB

Postby another_jim » Jun 14, 2018, 12:49 pm

9coffee wrote:Thank you Jim, your advice is very helpful.
I ordered an adjustable needle valve immediately.
However I worried about damages for a rotary pump and a mortar.
Is it no problem?
I'm looking forward to trying it!


I have no personal experience. However, Andy Schechter pioneered the use of needle valves to regulate flow about 15 years ago; and I've heard no adverse reports since then. Also, as far as the pump is concerned, the valve is just a resistance to flow, same as the puck, or at its most extreme, a blind filter. So there is no rational basis to expect it is bad for the pump either.
Jim Schulman

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homeburrero
Team HB

Postby homeburrero » Jun 14, 2018, 2:08 pm

In case it's not clear, the flow rate measured with no portafilter in the group (often referred to as 'water debit') is affected by the gicleur (jet) size in this machine. I think it's a 0.6mm ruby by default, although you can get larger ones (0.7mm and 0,8mm). That jet helps to moderate the pressure ramp up of the initial flow at the puck, not really the flow during the brew, exactly as Jim said earlier.

If you are for some reason trying to get a slower brew without tightening the grind, you may want to experiment with dialing down the pressure on your rotary pump. Easy to do, but in my opinion it would be best to first leave it at the conventional 9 bar and experiment with different baskets and different coffee doses to get the taste you're after.

If you want to change the pressure profile so as to get a longer/slower pre-infusion, I think you can do some of that by programming the pre-infusion times on the FB80. ( I may be wrong about that - am just going by what I read online, for example: La Marzocco FB/80 preinfusion? ) *

For real on-the-fly pressure profile control you could resort to the suggested hack of adding an adjustable needle valve after the pump. It wouldn't harm the pump, but I suspect it might be difficult to shoehorn into a machine like this. It may be easier to trade in the FB80 for a machine that is designed to do pressure profiling.

P.S.
You can find data on La Marzocco flow restrictors (gicleurs) and unrestricted (no portafilter) flow rates in this tech bulletin: http://www.lamarzoccousa.com/wp-content ... Guide.docx

* edit addition - Looking closer, I see that the OP has an EE model, which apparently doesn't have the programmable preinfusion feature.
Pat
nínádiishʼnahgo gohwééh náshdlį́į́h

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AssafL

Postby AssafL » Jun 14, 2018, 2:22 pm

another_jim wrote:I have no personal experience. However, Andy Schechter pioneered the use of needle valves to regulate flow about 15 years ago; and I've heard no adverse reports since then. Also, as far as the pump is concerned, the valve is just a resistance to flow, same as the puck, or at its most extreme, a blind filter. So there is no rational basis to expect it is bad for the pump either.


The standard rotary vane pumps used in espresso machines have a recirculating valve. If the pressure exceeds the set pressure, the valve opens and water swirls from the outlet back to the inlet. So a needle valve will have no affect.

But, if you use a vibrating pump or a gear pump - those rarely have recirculating valves so one has to be careful not to choke them. If the LM is stock - then there should be no problem expected.
Caution! Water, heat, pressure and electricity don't mix! I want an espresso.

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AssafL

Postby AssafL » Jun 14, 2018, 2:25 pm

9coffee wrote:Thank you Jim, your advice is very helpful.
I ordered an adjustable needle valve immediately.
However I worried about damages for a rotary pump and a mortar.
Is it no problem?
I'm looking forward to trying it!


If you want to achieve good resolution of the needle valve (metering valve) you'll want to pick a medium Cv valve. That is that the orifice is of a certain size that at low pressures can give you ample resolution around the 60ml/min target flow rate.
Caution! Water, heat, pressure and electricity don't mix! I want an espresso.