vacuum breaker on your steam wand valve?

la marzocco, synesso, simonelli, cimbali etc

vacuum breaker on your steam wand valve?

Postby scottlucey on Thu Nov 09, 2006 12:59 pm

alright, i want to see how common this fix is.

i was hangin with friends from intelly this last weekend, shootin the shit with a couple of their techs, beers, whatnot... and i was discussing how difficult it is to explain to my own tech guys here in milw. the type of imperfections i get with my milk.
using a linea, all systems checking out; water level, steam pressure, clean wand tip seemingly normal to the non.obsessive.barista's eye, but a nit-picky barista may say, "WTF?! my milk sucks, it separates quickly and has visible bubbles rise to the surface." violent steaming and imperfect milk.
i've noticed the fix to this is replacing the steam wand valve, but i think its odd that the same problem can emerge again in a matter of 2-3 or 4 weeks.

i was enlightened when mr.jim karr asked if we had vacuum breakers on our valves.
no, we do not, please tell me more. i say.
mr. karr was kind enough to show me how they tap into their steam wand valves and add in a vacuum breaker (similar to the one on the steam tank itself, but different, smaller) right onto the steam wand valve.
he mentioned that with this tweek the need to replace valves is much much less.

interesting, very interesting, and i thank the intelly dudes for sharing with me this.

now i wonder, is this tweek something alot of people are doing, or are you just replacing wand valves when milk textures wane in quality... and if you don't have problems with perfect milk texture and dont need to replace your valves often, is there something i'm missing with this?
even when taking cleaning seriously, steam wand valve life span seems to be somewhat short for something as serious as la marzocco steam wands. yes/no?
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Postby xristrettox on Thu Nov 09, 2006 6:19 pm

you too!!!

thanks for the idea! this has been buggin the shit out of me for, like, 5 years!
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Postby Matthew Kolehmainen on Thu Nov 09, 2006 7:58 pm

sounds interesting. thanks for sharing this.
can you post some picture?
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Postby nick on Thu Nov 09, 2006 8:13 pm

Sloosey:
What do you mean "replace the steam wand valve?" Are you talking about taking the steam valve apart and removing the crud buildup? I hope you guys aren't just buying a whole new valve assembly!

That said, I don't understand what you guys are talking about.

In my experience, the milk texturing on our Lineas gets worse when there's crud buildup in the steam valve assembly. The lower effective steam power, because of the restriction in the valve (by the crud), means bad texture to the milk. The steam has to move the milk with enough power to keep things smooth (with a well-trained barista, of course).

I don't understand this breaker thing. Despite what everyone says, I don't believe that milk ever gets up into the valve body. Sure, you can get buildup at the tip, clogging holes, etc., but I've never experienced crud buildup inside the wand shaft itself. Granted, our staff is fairly well-trained about such things... but there are always those new baristas.

What we DO get is crud buildup in the valve body.

In my estimation, it's related directly to water quality, not milk-sucking.

How would milk get all the way up into the valve body? Let's try and imagine how we'd attempt to do that on purpose:
- heat up the steam wand by letting it run
- turn it off and stick it into a pitcher of cold milk
- let it cool down

This would suck up milk into the wand. But how much? What % would the air/steam inside the want contract? In order for milk to make it up into the steam valve boy, the air would have to contract 100% of its volume, which is physically impossible. Of course, assuming that the entire length of the steam wand was full of pure steam (gasous H2O), the cooling could theoretically result in a ton of milk going up into the wand, but that's hard to do. Have you ever seen two ounces of milk come out of the wand during a purge? Well that's about how much volume is in a Linea wand (I'll measure tomorrow to be more certain). And that would have to happen more than once for that much crud to end up in the steam valve.

In my view, it's water quality. Impurities build up over time. That said, how a "vacuum breaker" plays into that, I have no idea.
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Postby scottlucey on Thu Nov 09, 2006 11:39 pm

yes. that sucker gets replaced.

you would think that if there is gunk collecting in the valve body, it would slow the steaming process down, but in my experience loss of pressure doesnt really happen. oddly enough, pressure seems to "get out of hand" and i must note that this is different than just having too much pressure. i could try and explain that more if you'd like, but its long-winded... blasting versus texturizing to keep it simple.

-- when our techs listen to us describe the problem as blasting and sending the milk out of hand, they instinctively turn down the pressure... and with these adjustments, we would be steaming with the steam gauge reading well below 1. well then yes, the pressure slows down, but steaming doesnt return to texturizing with the quality desired. not a fix, and i can't believe we've tolerated it as long as we have.

i'm not sure how dirty the body actually is, i'd have to ask for the autopsy from our tech man... for now the only fix has been to replace the valve. mr. karr from intelly mentioned that before this tweek, his team was replacing valves once every 3 or so weeks. sounds about the same amount of time perfection wanes.

otherwise...
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Postby scottlucey on Fri Nov 10, 2006 1:18 pm

for the Linea, the best fitting v.breaker is made by Caramali, which can be ordered from Nuova Ricambi USA, pt#618968. the breaker needs a fitting which can be gotten from McMaster-Carr; pt#9171K231. this fitting doesnt fit as is, its orig. 1/8" dia needs to be tapped to 1/4" to fit into the breaker.

thank you j.
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Postby nick on Fri Nov 10, 2006 2:07 pm

scottlucey wrote:you would think that if there is gunk collecting in the valve body, it would slow the steaming process down, but in my experience loss of pressure doesnt really happen. oddly enough, pressure seems to "get out of hand" and i must note that this is different than just having too much pressure. i could try and explain that more if you'd like, but its long-winded... blasting versus texturizing to keep it simple.

Drop the pressure down on the steam boiler (to like 0.5 bar) and see what that's like with a new "valve." I'll reckon about the same as a gunked-up valve.

It's the same reason that a small home machine is better off with a one-hole tip. In my estimation, the steam pressure does three things: heats the milk, it is the vehicle for the air-steam mix that creates bubbles, and it moves the milk around. #1 and #2 can be accomplished with any old steam boiler, with a smaller or low-pressure one merely taking longer. But will you get the same foam-quality, just in a longer amount of time? No. You'll get that weird "it makes bubbles and I can't get perfect microfoam no matter what I do" phenomenon. That's cuz the milk needs to move, and it isn't being moved enough.

Next time you get the gunked-up feeling, do the toothpick-trick: jam the tip of a tooth pick and break it off, plugging the hole. Do it to two, opposite holes, and steam the milk. My hypothesis is that you'll be able to now foam nicely, but it'll take a bit longer than normal.
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Postby Robert Goble on Fri Nov 10, 2006 4:09 pm

nick wrote:In my estimation, it's related directly to water quality, not milk-sucking.

This was my thought too on reading this thread. Any way we can test this out or get some specific expertise to comment on this?
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Postby Mike Gregory on Sat Nov 11, 2006 11:13 am

Robert Goble wrote:
nick wrote:In my estimation, it's related directly to water quality, not milk-sucking.

This was my thought too on reading this thread. Any way we can test this out or get some specific expertise to comment on this?


No idea, but I would first check the boiler sight glass and see if there's any sediment in there (carbon from filters, etc).
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Postby nick on Wed Nov 15, 2006 5:31 am

I love the cross-posting that happens out there on the interweb.

Unless there's some eerie "milk-vapor" type phenomenon that I didn't know about, it's NOT MILK!

In thinking about it more, could it be the food-grade lubricant that some of us use on the O-rings? Someone also mentioned it on a.c (link above). What does all those high temps and steam do to that grease?

It's not milk...
It could be water quality...
It could be the grease...
It could be Satan.
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Postby Lennoncs on Sun Nov 19, 2006 3:04 pm

High temps, moisture and agitation tend to make food grade grease turn into a rather disgusting cottage cheese texture.

washdown robots used in the food industry have all three present and are a real maintenance nightmare, especially the pneumatic valve systems that use foodgrade lubes.

It would not suprise me if the gunk that is clogging up the steam wands is essentially the same type of stuff.

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Postby Andy Schecter on Sun Nov 19, 2006 4:27 pm

Lennoncs wrote:High temps, moisture and agitation tend to make food grade grease turn into a rather disgusting cottage cheese texture.


Yes, but how does it taste? Might be pretty good with pineapple.
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Postby Lennoncs on Mon Nov 20, 2006 3:27 am

AndyS wrote:Yes, but how does it taste? Might be pretty good with pineapple.


A wonderful mild, nutty flavor as I recall from my last grease change.


Sean

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Postby jmc on Tue Nov 28, 2006 6:22 am

I will talk w/Jim and get some more details and pics for y'all....I think we got this idea from Vince and the fine folks at Artigiano.
nick wrote:I don't understand this breaker thing. Despite what everyone says, I don't believe that milk ever gets up into the valve body. Sure, you can get buildup at the tip, clogging holes, etc., but I've never experienced crud buildup inside the wand shaft itself....

Maybe you're not making enough drinks at Murky Nick. :twisted: When you purge and milk shoots out, where do you think that milk went? I have a customer who despite our best efforts is (likely) not purging before and after steaming and we've had to work on her steam valves repeatedly - you can see crusty, burnt milk build up and around the valve body. Since we've put on a mod valve (And berated her again for not purging.) we have not been back. It isn't as extreme on our machines....Maybe water plays a role in it too (Or milk?), but we've fixed a major recurring problem.
Last edited by jmc on Tue Nov 28, 2006 11:59 am, edited 1 time in total.
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Postby Robert Goble on Tue Nov 28, 2006 11:58 am

I would love to see some pictures of these valves.
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Postby barrett on Sat Dec 02, 2006 2:55 pm

I'll see what I can dig up for photos.

At the top of the steam wand, underneath the flat cover (it covers the back of the switches and gauges) there is a pressure release valve on all artigiano machines. The first one ever was on my machine in Park Royal, and after a couple of months of testing, and ensuring that it did not hamper performance, and was indeed cutting down on the number of steam wand replacements needed, they were installed on all of our machines - including the second half of the machine in PR. We've been using them for almost 2 years now. Biggest advantage is that we go through a lot less steam wands than we used to. We used to go through a lot of them - either training, the volume of milk going through each of them, combined with the high pressure, makes it easy to plug them up.

What they are:
A simple valve, installed on the top of the steam wand, where the joint is between the wand and the supply line from the boiler. When the steam valve is opened, the pressure pushes the valve closed, when it's turned off, it breaks the vacuum. In addition, there is a little bit of water that will accumulate on the valve, whenever the wand has had a rest. We put a little piece of rubber hose/pipe stuff on there, and it evaporates, rather than dripping hot water on your hand.

They are, as the kids say today, "the cat's meow."
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Postby jmc on Fri Dec 08, 2006 12:02 pm

Had lunch w/Jim Karr today and we chatted for a bit about this. (mmmmm, tacos arabes.)
The problem is particularly heightened by busy, latte art shops because of the practice of steaming small amounts often. What happens is the superheated gas (steam) left over in the wand is "shocked" when it is plunged into a cool pitcher, this rapid cooling causes a momentary vacuum. Steam is expanded water, when it contracts from contact w/cold milk there is extra space in the arm, something has to fill that space - all of this happens to occur submerged in milk so you end up w/milk pulled up in your arm. When you're steaming pitcher after pitcher like this, it can become a big problem. I would imagine that the cooler your pitcher and milk (We used to keep a fridge full of pitchers w/milk in them ready to go.), the more dramatic the problem could become.
Synesso's have insulated steam wands and avoid the problem altogether.
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Postby jmc on Fri Dec 08, 2006 12:57 pm

Image
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Postby barrett on Fri Dec 08, 2006 2:43 pm

wicked picture.

that's the problem vince was looking to solve. with a second or two between milks, that wand never gets a chance to cool down. thanks for the photo - I don't have anything near that detailed.
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Postby scottlucey on Sat Dec 09, 2006 1:10 pm

that was just beautiful. i hope you like it nicky!
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Postby Mike Gregory on Mon Dec 11, 2006 8:29 pm

JMC wrote:I would imagine that the cooler your pitcher and milk (We used to keep a fridge full of pitchers w/milk in them ready to go.)


Why did you stop, Jay? Obviously not because of the milk vacuum...
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Postby terry on Wed Dec 13, 2006 11:02 am

Milk Scale is a problem on most machines including Marzocco. The Following picture is a valve from a machine I was working yesterday. Classic example.
Last edited by terry on Wed Dec 13, 2006 11:07 am, edited 1 time in total.
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Postby terry on Wed Dec 13, 2006 11:05 am

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Postby jmc on Tue Jan 02, 2007 1:03 pm

trabant wrote:
JMC wrote:I would imagine that the cooler your pitcher and milk (We used to keep a fridge full of pitchers w/milk in them ready to go.)


Why did you stop, Jay? Obviously not because of the milk vacuum...

Apologies for the delay. We stopped because we felt it was an unnecessary shortcut; the way we build drinks leaves us enough time (At least right now...) to pour the milk as the orders come in.
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Postby Phil Robertson on Thu Jan 04, 2007 2:31 pm

The alt.coffee thread that Nick referenced above eludes to a different steaming assembly on the FB-80.

Do you guys know if this issue is addressed on the FB-80?
Last edited by Phil Robertson on Mon Jan 08, 2007 1:05 pm, edited 1 time in total.

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