Vibe pump question (related to low-flow at brew-group)

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RAS

#1: Post by RAS »

OK, so my Pasquini Livietta restoration is going full-tilt right now. The frame and case are back from getting powder-coated, and they look great (pictures coming upon completion of reassembly).

When I first got the machine, the Fluid-o-Tech pump didn't work. I figure some scale jammed it up. I took it apart, did a visual inspection (nothing obvious), then reassembled it. It did have some scale build-up, but more on that later... After reassembling, it worked!

Next, after cleaning everything on the machine and replacing gaskets, I reassembled and tested it. Again, the pump didn't work :( . A quick loosening of the four bolts holding it together, then reassembly did the trick. Next up, descaling.

Did a good descaling of the boiler and HX (man these Olympia-made machines are a dream to descale); after dumping the water from the boiler, I was shocked at all the crap that came out. :shock:
Now is when I began to do some functionality tests, and that's when I noticed the pump output at the brew-group seemed lacking. I suspected scale lodged somewhere in the "food-chain". Took everything apart from the pump to the HX - all the way to the shower-screen. No obvious blockage. All back together, and the flow was still low (about an ounce of water from the group in about 20-30 seconds)

Out of curiosity, I tried to back-flush the group, and I could barely get the pump to choke... even after running for about 30 seconds.

Next, I disconnected the feed hose from the 3-way solenoid, and checked the output there. Still lower than I'd expect it to be. Moving closer to the pump, I disconnected a coupled-adapter that contains a check-valve, and still too low. Next up was another adapter, this one including what I'd call either a flow-restrictor, or pressure-regulator, and tested the output again. Bingo. Good flow, and when I tried to back-flush, the pump strained after just a few seconds. That sounds more like what I'd think it should be. Question is, do I need the insert that I removed? My guess is that it was there for a reason. I know the question will be if the espresso is any good, but I'd still like to get input from the espresso-brains here on HB. I don't have a means for testing the pressure at the group, but a test shot I pulled with a known grinder setting and my normal tamp pressure resulted in normal espresso output and decent crema.

Here's a picture of the insert I removed, and an indication of where I removed it from (shown by ballpoint pen head).




And on the subject of the pump, if I need to replace it for some reason, I've found a source for Fluid-o-Tech 1106 pump... but I've got to specify either NPT or gas fittings. My guess would be they're gas because there's no Teflon tape on any threads... any ideas?

Thanks for all your input on this. This machine restoration has been a great education... and I'm eager to get it back together and make some coffee.
Bob

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HB
Admin

#2: Post by HB »

RAS wrote:...do I need the insert that I removed? My guess is that it was there for a reason.
As you suspected, that's a flow restrictor. Its purpose is to slow the pressure build up as a form of preinfusion. Without it, the machine will be more fussy about imperfections in your barista technique
Dan Kehn

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RAS (original poster)

#3: Post by RAS (original poster) »

Dan, so you confirm my concern - thanks for the reply. Hmm, looks like a new pump may be the right solution. As I mentioned, I'm a long way away from 9-bars at the brew-group if the restrictor is in place. And for a new pump, I'll just have to figure out the thread-type (NPT or gas).
Bob

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HB
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#4: Post by HB »

Something isn't making sense here. The restrictor will affect the flow rate to the grouphead, but once the brew pathway is completely pressurized, the puck should provide far more backpressure than the restrictor. That said, there's no great harm in removing the restrictor; plenty of cafes in Italy have none at all simply because they're a maintenance headache due to scale buildup.
Dan Kehn

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erics
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#5: Post by erics »

If you need to replace the F-O-T pump, opt for the one with 1/8" gas threads (1/8"-28 BSPP). The FOT pump has near ideal flow rates at brew pressure and that restrictor (can you measure the hole size?) makes it even more ideal.



Measure the flow into a pyrex cup with nothing in the portafilter and report back :)
Skål,

Eric S.
http://users.rcn.com/erics/
E-mail: erics at rcn dot com

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RAS (original poster)

#6: Post by RAS (original poster) »

Dan & Eric,

Thanks for your expertise on this. Dan, I've been experimenting a bit, and my guess is that the 25-year old pump is weak; I think the added resistance of the restrictor is too much. I will do some more experimentation with the restrictor removed and shots. The one time I tried this, flow from the puck seemed acceptable, though slightly choppy (less than ideal description, but the flow was less smooth, or continuous as I used to have with my Andreja).

Eric, thanks for the pump thread details - my guess was they're gas threads, but it helps hearing it from the pros. Now to find a pump...
Bob

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erics
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#7: Post by erics »

The pump is here: http://espressocare.com/Qstore/Qstore.c ... -tech+Pump . Maybe Stefano has the parts to convert this to one w/o the bypass attached, identical to your installation. If not, the pump, in your configuration, is available from F-O-T:

161 Atwater St
Plantsville, CT 06479
Phone 860-276-9270
Fax 860-620-0193

Shawn Thompson
Pump Analysis and Sales
shawn@fluid-o-tech.com
Skål,

Eric S.
http://users.rcn.com/erics/
E-mail: erics at rcn dot com

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RAS (original poster)

#8: Post by RAS (original poster) »

Thanks Eric. I've already been in contact with Shawn. Very helpful guy, and unfortunately, they only stock the pumps with NPT threads - he can get gas, but it would take a month or so. I'll call Stefano and see if I can get one without the OPV adapter.

Another thought I had was to get an higher-pressure ULKA and use an OPV. Others have commented that this does improve what an Olympia machine can do, providing more constant pressure at the puck. Question there would be if I'd feed the OPV return back into the reservoir, or back into the pump inlet - as I've seen others to. Any thoughts there?

In the meantime, I think I'll use the machine without the flow-restrictor.
Bob

streezz

#9: Post by streezz »

Dear Eric

I've an old Maximatic from 1979.

Approx. 4 weeks ago I've replaced the pump with a new fluid-o-tech one w/o bypass.

I've reinserted the injection nozzle (single hole disc) as well.

With empty portafilter (two outlets) I get approx. 460g/min.

edit: remeasured today 3 times, I got approx. 540 g/min

Unfortunately I've not measured the hole diameter, but I estimate it was a dia of about 1 to 1.5mm.

Best regards
streezz :mrgreen:

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erics
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#10: Post by erics »

With empty portafilter (two outlets) I get approx. 460g/min.
Much thanks for posting that info - its helpful for anyone reading this thread. That amount APPEARS to be very universal in the home machine areana - i.e. 450 to 500 ml/minute flow through an empty PF is the norm.
Skål,

Eric S.
http://users.rcn.com/erics/
E-mail: erics at rcn dot com