Testing Brew Pressure - Page 3

Need help with equipment usage or want to share your latest discovery?
handysteel

#21: Post by handysteel »

Hi All,
Does any one know how to check and set the over pressure valve on a gaggia classic without using a manometer?

Have read that it is normally set to high from the factory and can effect the the quality and amount of crema in the shot.

User avatar
Compass Coffee
Sponsor

#22: Post by Compass Coffee »

I've read some ways to sort of guesstimate adjust OPV based on volumes. But seems to me setting shot pressure without a gauge is kind of like adjusting a car's engine timing without a timing light if even that accurate.
Mike McGinness, Head Bean (Owner/Roast Master)
http://www.CompassCoffeeRoasting.com

User avatar
Ozark_61

#23: Post by Ozark_61 »

I've been bugging Dan offline about installing a brew pressure gauge, and thought I better just do it here so others can be awed at the man's cornucopia of information.. I would like to install a dual gauge on my giotto (standard). Does anyone know if there is a dual gauge that would fit on the round port that is just a single boiler pressure on my machine? Also, off the top of your heads, do you know if the od is 3/8 or 1/4?

Cheers
Geoff
HB wrote:shadowfax is correct, it's easy to add a brew pressure gauge to an espresso machine. I've done it for several machines without problem. Here's the installation for the Giotto Premium by adding a tee:

<image>

The tube leading from the pump to the expansion valve conveniently has the same diameter as required for standard John Guest fittings. One snip and two pushes are all it takes. The same trick worked on the Cimbali Junior with a different set of fittings:

<image>

Both were temporary modifications for evaluation machines, but I'm confident it will hold up if you use the properly rated fittings and tubing. I used 230 PSI / 70F commercially rated; be aware that Home Depot stocks 120 PSI / 70F tubing made by Watts, which will burst if used in this application.

Ideally you should get a liquid-filled gauge:

<image>
(Courtesy of the GaugeStore.com)

They cost more but hold steadier. Otherwise you can use a dry gauge and a snubber. They aren't 100% effective at eliminating needle flutter, but prevent most of it.

Building your own pressure gauge portafilter is a straightforward matter of plumbing. Some people get fancy and add a bleed valve to simulate pulling a shot (Andy Schecter, Bob Roseman). I believe the portafilter threading is 3/8" BSPP (when in doubt, see the fittingsAndAdapters thread identification charts).

User avatar
erics
Supporter ◈

#24: Post by erics »

The only machine that I am aware of that has a dual gauge (two separate movements in one case) is the Vetrano. I would be VERY surprised if the connections for this gage are anything but 1/8"-28 BSPP threads as that appears to be a fairly standard size for gages on espresso machines.

The actual cutout for the gage in the stainless is PROBABLY 50 mm vice the 40 mm cutout you PROBABLY currently have. I do know a coffee shop in Albany that could give you the size (and the price):

http://www.chriscoffee.com/
Skål,

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

User avatar
cannonfodder
Team HB

#25: Post by cannonfodder »

erics wrote:The only machine that I am aware of that has a dual gauge (two separate movements in one case) is the Vetrano. /
Elektra 60 series (T1, A3) LaMarzocco, La Spaziale Vivaldi II, Quickmill Vetrano, Isomac Mondiale, Pasquini Livia 90 (I think), Nuova Simonelli Appia Single group, a couple of Faema's, just to name a few.
Dave Stephens

User avatar
Ozark_61

#26: Post by Ozark_61 »

Dave - now there's a guy who knows his machines! Thanks for the suggestion- I'll shoot Chris' an e-mail.

Geoff

User avatar
cannonfodder
Team HB

#27: Post by cannonfodder »

I added a brew pressure gauge to my Isomac along with a HX preheat loop and insulation a couple of years ago. Worked quite well and still going strong.

Or you could just build a pressure portafilter, about $15 in parts.
Image
Dave Stephens