Commercial Espresso Machine - Average Steam Pressure - Page 2

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HB
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#11: Post by HB »

Simon345 wrote:I expect that if I use the same steam tip as a Linea Mini with the same 1.2 Bar (or whatever) that the Linea mini steam boiler is set to on an alternative prosumer machine (Profitec, ECM, Rocket etc..), that I would steam the same pitcher of milk in the same amount of time?
No, because the steam pressure would fall rapidly for the prosumer espresso machines because they have a smaller steam boiler. For example, the Profitec Pro 700, which is no slouch, has a 2.0 liter steam boiler and 1400W. The La Marzocco Linea Mini has a 3.5 liter steam boiler and 1600W. Steam speed is about the volume of steam leaving the boiler over time; the steam tips are tuned to the capacity of their associated boilers.

On a related note, I've noticed that La Marzocco espresso machines typically have higher steam pressure as delivered from the factory, around 1.6 bar. An urban legend says that Starbucks went with La Marzocco because they demonstrated the Linea steaming flat out with no drop in steam pressure. Indeed, I have a two group Strada, and even with both wands wide open, the drop in steam pressure is negligible. For what it's worth, I have it set to 1.2 bar and two difference steam tips. The one is stock ("fast") and the other is the Espresso Parts Sproline Vortex. I use the latter for volumes of 6 ounces or less.
Dan Kehn

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Simon345 (original poster)

#12: Post by Simon345 (original poster) »

Is anyone aware of a model that would predict the drop of steam pressure in a steam boiler after a given amount of time:

1. For a steam boiler size of x
2. Steam boiler pressure of y
3. Total hole size (and shape?) on the steam wand nozzle of z

Something like this would really help people to think through upgrades to their espresso machine steam systems, just not sure how to work it out?

For example, in the previous example of my last post. Clearly something like a Pro700 would run out of steam before a Linea Mini when using the exact same steam tip over a considerable performance test, but when simply steaming just enough milk for 1 cafe latte would they not be very similar in performance if you had the linea mini tip on the pro700 and had it set to the same boiler pressure?

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Compass Coffee
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#13: Post by Compass Coffee » replying to Simon345 »

No, but in addition would need to also know both the wattage of the steam boiler element and whether or not it would able to be on full time during steaming while pulling a shot etc....
Mike McGinness, Head Bean (Owner/Roast Master)
http://www.CompassCoffeeRoasting.com

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another_jim
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#14: Post by another_jim »

Simon345 wrote:Is anyone aware of a model that would predict the drop of steam pressure in a steam boiler after a given amount of time:
Seriously? I'm a sociologist and even I know this is elementary physics.
  • the equilibrium pressure doesn't require knowing the volume of the boiler, but it does require knowing the steam tip size and heater wattage. The boiler pressure will drop to whatever level can be replaced by the wattage of the heater, given the heat outflow of steam at that pressure/temperature through the tip.
  • The time it takes to reach the equilibrium pressure is exponential curve of the loss of the energy stored in the water weight of the boiler at its excess pressure above the equilibrium pressure computed above. You'll need to know the weight of water in the boiler (not just its volume) to work this out
The key information is the water weight in the boiler, the heater wattage, and the "steam tip curve," i.e. the rate of steam it emits at different steam pressures (I have no idea how well the approximation using the hole number and size, assuming an ideal nozzle, will work -- I'm guessing you will have to approximate it by measuring the actual nozzle's equilibrium pressure in some espresso machine of known wattage)
Jim Schulman

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#15: Post by Compass Coffee »

another_jim wrote:Seriously? I'm a sociologist and even I know this is elementary physics.
Now Jim how curmudgeonly sounding, I'm so proud! :lol:
Mike McGinness, Head Bean (Owner/Roast Master)
http://www.CompassCoffeeRoasting.com