La Marzocco Linea Mini Flow Control Mod - Page 7

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#61: Post by cf »

Peppersass wrote:Are the quick-connects leaking from the hose side or the BSPP side?

If it's the hose side, are you using a tubing cutter? I've found that to be essential when cutting tubing for John Guest fittings. It's not a good idea to eyeball the cut with a razor or Exacto knife.

If the BSPP side, maybe adding a thin coat of lube to the O-ring would help.

I don't see temperature or pressure specs for the quick-connects from I've had my concerns about high pressure with quick-connect fittings, which is why I went with the Aventics units Jake recommended for the GS/3 project, which are rated up to 16 BAR and 150C. As I said above, they're only available in lots of 25, and I may have some available when I finish my project (probably in a week or two.) That said, I haven't actually installed the mod, so I can't swear to a leak-free experience (and I'll be using four extra quick-connects to add a solenoid bypass valve to the needle valve mod.)
The leak is on the hose side, coming out of the black insert and the hose itself. I am using a speciality PTFE tube cutter that is making straight cuts from what I can see. I've replaced the black inserts. On one of the two quick connect fittings that solved my issue, on the other it did not. I notice that the quick connect has tiny 'teeth' for lack fo a better term that seem to clamp on the hose, I'm assuming they are fragile and maybe we were to aggressive with ensuring a tight fit? I may try it a few more times if I have time to see if I can get it leak free but otherwise I will replace it.


#62: Post by cf »

Brief update on my progress.

As Peppersass suspected, I think the tolerances on the quick connects from hoseandfittings are not within spec for the Mini. I don't see the specs directly listed on the site, but similar looking quick connects I've found from other sites claim a 140 degree F temp and 150 PSI (around 10 bar). Mini believe surpasses both of those, so Aventics or other high quality quick connects would probably work better.

I've gone the route of buying flexible copper tubing and compression fittings as recommended by Jake as well, should get here late this week/early next. I bought some higher quality (though not as good as Aventics) quick connects just as a backup.

Due to the leaks from the quick connects, I've put back the LM cross temporarily until I have the new parts in house. Not the best endorsement, but I'm not giving up because of a few minor leaks :wink: Before that I did make a short video explaining the setup and provided a picture I hope helps.

Picture showing the cross setup with quick connects. Note this is just an illustration, I think these actual connections would be too big to fit into the Mini comfortably, but I wanted to show the connections. The photo uses 1/4 BSPP Tee, I ended up using a 1/8 BSPP Tee which is a bit smaller.

Video describing the setup, I couldn't edit out my feet!
I will try and use the copper tubing and compression fittings next and upload some photos/videos if and when I get that working.



#63: Post by khaledsha »

That's a very cool and smart solution. I have a question...
If you close the value to tight, that no water goes in the group head, where will the pressure goes behind the value ( boiler?!!)
And if you lit the machine on in the way for a long time, is it a problem or it's safe??!

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#64: Post by Peppersass »

khaledsha wrote:If you close the value to tight, that no water goes in the group head, where will the pressure goes behind the value ( boiler?!!)
Not a problem. Pressure in excess of the pump setting (nominally 9 BAR) will be dissipated by the bypass valve, which circulates excess water from the pump output back to the pump input.

I'm not familiar with the internal architecture of the LMLM, so I don't know if it uses an expansion valve like my LM GS/3 AV. If it does, and the expansion valve is between the pump and the "Jake Valve", the boiler pressure will be capped at the expansion valve setting (12 BAR on my LM GS/3 AV.)

[Unfortunately, the gear pump I replaced my GS/3 rotary pump with doesn't have a bypass valve, and my Jake valve is between the pump and the expansion valve. So the answer for me is "Never close the Jake Valve all the way." Not a problem for me because I don't do dynamic flow control with the Jake Valve. Instead, I simulate Slayer shots by switching in the Jake Valve with a bypass solenoid for preinfusion, then out at max pressure, then ramp pressure down during the back end of the shot by reducing the gear pump speed. In other words, I set the Jake Valve to the desired pre-infusion rate and leave it there.]
khaledsha wrote:And if you lit the machine on in the way for a long time, is it a problem or it's safe??!
Don't know what you're asking here. Are you asking if its safe for the Jake Valve to be closed down for a long period of time? If so, the answer is yes.

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#65: Post by Peppersass »

cf wrote: I've gone the route of buying flexible copper tubing and compression fittings as recommended by Jake as well, should get here late this week/early next. I bought some higher quality (though not as good as Aventics) quick connects just as a backup.
FWIW, I've been using seven Aventics quick-connects in my GS/3 for about six weeks and have had no leaks.

That said, I had to be careful to cut the tubing ends square with the tool I use for John Guest plastic tubing, and make sure the tube is fully inserted into the quick-connect. Sometimes it's hard to get a good grip on the tube, especially in tight quarters inside the machine, so sometimes the tube only goes partway into the quick-connect.

If the tubing is removed and then reinstalled, the end where the quick-connect grabbed the tubing must be cut off. I've found small shards of plastic inside the quick-connect after removing the tubing. If these aren't removed the quick-connect may not seal. It's likely that the shards come from not fully depressing the release when removing the tube, which isn't easy to do. So far, the best way I've found is to use the flat side of a small box wrench to depress the release. It's also possible that the quick-connect metal "grabbers" get compromised when the release isn't fully depressed. So it's best not to remove the tubing, and if you do try to depress the release as fully as possible, inspect the quick-connect for debris and/or damage and cut the previously-inserted end off the tubing.


#66: Post by cf » replying to Peppersass »

Thanks for the reply, and good information regarding the quick connect fittings and how to properly depress them while checking for bits of tubing left behind. I recall I did check my quick connects after I de-installed them and didn't find anything to my naked eye.

It's been a while since I posted an update, so here it goes. The mod is still a work in progress as I'm waiting on new parts, so it's not currently in my machine anymore. I had purchased some better spec'd quick connects from Parker Legris (at least better than the ones from hoseandfittings) and used those with a combination of both PTFE and copper tubing over a period of a few days. The PTFE tubes eventually bursted on me twice, this time from two different sets of tubing from different vendors on Amazon. Alternatively, I purchased 4mm OD flexible copper tubing as recommended per Jake but ran into issues with leaks from my quick connects yet again.

Fed up with the leaky quick connects and the bursting tubes, I decided to give it one more go with higher quality components of each I could find. So I bit the bullet and ordered Aventics quick connects which I'm presently waiting to arrive (3+ weeks now), along with Parker PTFE tubing that I hope is of higher spec. Aventics quick connects are the only ones I've found that meet both the temperature and pressure requirements I think would be needed in an espresso machine of which I think the others we've mentioned in this thread so far would lack. The Parker PTFE tubing doesn't specify the working pressure at high temps, but at 23 degrees C its 20bar. I have my doubts it will hold up in the high temperature and high pressure of the espresso machine and it's position close to the boilers. I'm leaning towards starting off with PTFE tubing due to the ease of install, and if that should fail I would go back to the copper tubing which should not bust.

In the end, if for some reason I can't get this to work problem free anymore, I've been enjoying the Mini with the.6mm gicluer which has helped to tame channeling. To me, this is the biggest benefit of the flow profiling that I miss the most. WIth the .8mm gicleur I had channeling pretty regularly, with the .6mm its become less common. But with the mod and the long and slow pre-infusions that went away almost entirely. I should say, I have a newer Mini with the adjustable pre-infusion and have been using that setting (without this mod) with 2s on and 5s off.


#67: Post by pcrussell50 »

joey22 wrote:Interesting that seems odd to me, I would have expected the reading on the brew gage with the needle valve wide open would be essentially unchanged from the pre-mod reading with maybe a minor drop in pressure to account for losses through the needle valve assembly. Unless you had previously changed your pump pressure on the back of the machine I'd have to assume it was set at 9 bar from the factory.

PS are those the LM walnut paddle and knobs? they look sharp on the white Mini!
Sorry to be jumping in after not having read this whole thread yet...

"Needle valve wide open" is a term that needs attention. I have the same needle on my machine. Now, first I have to say that my machine (which is the same type Carlos used to have), has an actual group pressure gauge.

So this needle (I named it the "Jake valve" a couple of years ago when I got it):
1) It rarely (if ever) takes more than one full turn open to get 9 bar during an extraction
2) at one full turn open my (rotary) pump delivers about 8ml/s, at two 12ml/s, at three turns open it delivers about 18ml/s and I haven't even bothered to see what it does at actual FULL open

So with this valve, one needs to consider whether by "full open" you mean "as far as you need to open it to get the flow you want", or actually physically FULL open

Yes, it helps to have a group pressure gauge. But I don't think one is entirely flying blind just by watching the flow, and using the wheel to make the flow what want it to look like.

LMWDP #553