Fitting a pressure gauge to Rancilio Silvia

by **paperpig** on Wed Feb 11, 2009 9:48 am

I'm wanting to fit a pressure gauge to my Silvia. I have a suitable gauge with a 1/8" BSPT fitting.
I'm planning on fitting a T-piece just after the pump and piping this to the pressure gauge. My question is, does anyone know what the fitting size is just after the pump? (Circled on the photo.)

Thanks!

by HB on Wed Feb 11, 2009 10:16 am

I believe your question is answered in Pressure gauge on Rancilio Silvia:

erics wrote:It is difficult because of the close quarters you are working in and the various fittings can become a nightmare. See here and look at the pictures in the folder "silvia undressed":

http://users.rcn.com/erics/

The easiest place to temporarily read the brew pressure (while brewing) is where the steam line attaches to the boiler. The fitting on the boiler is 1/4-19 BSPP and a normal US pipe thread fitting is 1/4-18. With a little teflon tape on the boiler's threads and the use of brass fittings, it will seal.

If you wanted to do something more permanent, Chris Coffee sells a pressure gage cap tube setup:

http://www.chriscoffee.com/produc...arts/capillarytube

I believe these have 1/8-28 BSPP threads vice the US standard of 1/8-27 and you would need to tee into the steam line and adapt from there. Going between the boiler and OPV, you are faced with the prospect of undoing those fittings where the teflon line connects and reassembly can be iffy depending on machine age and other factors. In addition, there is not enough play in the teflon line to do what you want.

The most non-intrusive & easy solution is the PF gage and, if you build one, use a liquid filled gage.

Eric S.

http://users.rcn.com/erics/ · by **erics** on Wed Feb 11, 2009 11:21 am

Dan is correct and sharp in his reference link. The 90 ell connected to the pump outlet does indeed have 1/8-28 BSPP threading. Make sure the gage you plan on using is "oil filled" - typically with glycerin. Lots of standard UK gages have their male connector stub fitted with a small removable orifice BUT this does little to dampen the pressure "vibrations" from that pump.

The easiest way to measure Silvia's brew pressure (other than a PF gage) is to temporarily adapt to the steam line connection at the boiler whose fittings have 1/4-19 BSPP threading. Measure the pressure during YOUR NORMAL SHOT, adjust the OPV as necessary and reconnect the steam line.

by **paperpig** on Thu Feb 12, 2009 5:54 am

Thanks for the info guys. I'd already seen those articles you pointed out to me, but I can't see anywhere that they talk about the thread on the pump output on Silvia. Where the 1/8-28 BSPP thread is mentioned in erics' thread "Pressure gauge on Rancilio Silvia" it's actually referring to Chris Coffee's pressure gage cap tupe setup. But no matter, erics has confirmed in his response that the "90 ell" has 1/8" BSPP thread so if I'm going to tee off there I know what I need. Has anyone got any experience of whether the reading I get teeing off that point would be different from the reading I'd get if I teed off the steam outlet on the boiler as erics article suggests. It seems to me that teeing off down near the pump has advantages of ease of access - it's not cramped in that area - and possibly cooler water at that point. The gauge I have is glycerine filled and good for >100 deg C so I should be fine in either location.

by **gbovino** on Thu Feb 12, 2009 3:06 pm

I added a pressure gauge to my Silvia.... and added a M-M-F (1/8 BSP) tee right before the OPV.

Here's a write up of the procedure on CG, using the gauge from Chris Coffee: http://coffeegeek.com/forums/espr...mods/356656#356656

Here's a pic showing where I added the tee.

Cheers!
Gabe

by **paperpig** on Thu Feb 12, 2009 5:00 pm

Hi Gabe, Thanks for that, it was very helpful. The flickr set was great!
I have few pics of adding an auber PID to my Silvia here http://flickr.com/photos/robives/sets/72157612560672607/.
I'm currently trying to find a UK source all the parts to add a pressure gauge. Out of interest, what do you use to cut the holes in the chassis?
Thanks
Rob

by **gbovino** on Thu Feb 12, 2009 6:01 pm

I used a knockout punch kit... which set me back a cool $16 USD. There's a link in my previous post regarding where I bought it. You should be able to find something similar in the UK. My biggest problem with the entire project was sourcing the BSPP (British Standard) fitting. You should have no issue with that since you are on the other side of the pond.

Great job with the PID!

http://users.rcn.com/erics/ · by **erics** on Thu Feb 12, 2009 7:15 pm

The only item to be a little cautious about re Gabe's fine work is this:

The connection between his pump and OPV is/was M6x4 teflon tubing which is easily trimmed with a tubing cutter or carefully with a razor blade. Your connection is SS braided tubing at a fixed length so you really need to put a tee at the pump to keep the length the same or make some other modifications depending on tee placement. The glycerin filled gage you have does not require any small, coiled tubing as a "normal" pressure gage would.

by **gbovino** on Fri Feb 13, 2009 1:18 am

Good catch Eric. I didn't even realize the SS braided tubing in the picture.

by **thefly** on Mon Jun 08, 2009 12:22 am

erics wrote:The only item to be a little cautious about re Gabe's fine work is this:

The connection between his pump and OPV is/was M6x4 teflon tubing which is easily trimmed with a tubing cutter or carefully with a razor blade. Your connection is SS braided tubing at a fixed length so you really need to put a tee at the pump to keep the length the same or make some other modifications depending on tee placement. The glycerin filled gage you have does not require any small, coiled tubing as a "normal" pressure gage would.

Eric, any issues with tieing in as done in this link - same area as OP was suggesting.
http://www.home-barista.com/espresso-ma ... ml#p115858

http://users.rcn.com/erics/ · by **erics** on Mon Jun 08, 2009 7:55 am

No issues there as long as you have the SS braid connecting line. I would have put the gage in the front panel but that's an individual issue.

Keep in mind also that doing something like this has questionable impact on Silvia's resale value. Knowing what I know now, I would just set Silvia's OPV at 9.0 bar with a blind filter and keep it there.

by **thefly** on Mon Jun 08, 2009 11:22 am

Thanks.

I wouldn't do it for resale value, but more as something to do I guess, although cutting through the face doesn't sound like a great job.

by **thefly** on Thu Jun 11, 2009 1:15 pm

erics wrote:Knowing what I know now, I would just set Silvia's OPV at 9.0 bar with a blind filter and keep it there.

What is it that you know now that has changed what you did in terms of installing a gauge? Just that it isn't necessary?

http://users.rcn.com/erics/ · by **erics** on Thu Jun 11, 2009 1:49 pm

That's correct - in my opinion, it is not necessary. There's probably about a dozen or so other issues that will improve shot production with continuous monitoring of brew pressure being way down on the list. "Way down" that is, once it is set to a value that the end user desires via a good gage connected to a blind filter.

A Rancilio Silvia can be as simple or as complex as one wants to make it and surely there are examples of that on the forums. I'm a big fan of modifications (hopefully improvements) that can be done to machines which improve their ability to produce more consistent espresso but that are also easily reversible.

I believe that if Silvia's OPV is set such that blind filter pressure is 9.0 bar, the resultant pressure during a typical shot will be "just right" - i.e. in the region of 8.5-8.6 bar.

by **paperpig** on Thu Jun 11, 2009 5:28 pm

although cutting through the face doesn't sound like a great job.

I fitted mine round the side at the back of my Silvia. It is easy enough to access and use on a day to day basis without cluttering up the front of the machine. It also makes fitting easier.
I used a gauge with a max. pressure of 300psi - approx double the expected range. This was at the recommendation of the gauge supplier.
Photos showing the process of fitting the pressure gauge including a full list of parts and suppliers are here
http://www.flickr.com/photos/robives/sets/72157612560672607/

by **trzynkaa** on Sun Jun 14, 2009 9:22 pm

I helped my friend fit a gauge to his Silvia last summer (2008).
In this case we used a 1 1/2" diameter, silicone filled, 11bar/160psi, stainless gauge purchased from McMaster-Carr (catalog number 9780T21).
Link to McMaster-Carr: http://www.mcmaster.com/#9780t21/=2big51
We used 1/4" diameter plastic tubing and 1/4" brass compression fittings to connect the gauge into the high pressure output line from the pump. Cutting the hole in the face plate was accomplished by removing the faceplate and clamping it to a drill press table and then use a metal-cutting hole saw.

The silicone fluid damps the pump vibration effectively and overall it works very nicely.

by **dizzillusionist** on Tue Oct 13, 2009 11:05 pm

Thanks, paperpig. I more or less modified my Silvia for a pressure gauge like you did. I did find a source of supplies that made things both easier, and less expensive:http://shop.hoseandfittings.com/catalog/Fitting/Brass/Push_to_Connect.html I elected to use their push to connect and so far am using the Nylon pressure pipe, since none of this is in the hot zone. Item 50210 for example allow you to cut about 2 cm of the teflon pipe (mine does not have the metal jacket) and simply slides in, and gave me 1/4" NPT for an output. Then there are pushconnects so that a connector can be screwed onto the gauge and you then simply slide the hose in.

SO-here's my problem that needs a troubleshoot. I did this because my PID'd silvia has been making me unhappy. I find that when I turn on the hot water, the pressure climbs up to 10 bar. But if I fire up the coffee valve, the same gauge shows no pressure. The pump is running either way. I certainly get water under pressure out of the group head. This can't be the OPV, and the pump is running. WHAT don't I understand?

by **dizzillusionist** on Tue Oct 13, 2009 11:19 pm

Erics' idea of a temporary mans of reading the brew pressure--what would it take to scerw a pressure gauge fitting into the pipe in place of the steam nozzle? With the needle valve open, I wonder how much pressure drop there is.

http://users.rcn.com/erics/ · by **erics** on Tue Oct 13, 2009 11:53 pm

Silvia's steam wand has M5 x 0.80 female threading - keep in mind this is a 10 yr old Silvia and things MAY have changed. It can be done but would be relatively expensive because of the adaptor to go from the M5 threading to a pressure gage. A good PF pressure gage is perfectly adequate and, in addition, is always transferable to other machines.

http://users.rcn.com/erics/ · by **erics** on Wed Oct 14, 2009 12:02 am

If you simply activate the hot water switch, the group solenoid valve remains closed and you are simply reading the same pressure you would read when using a blind filter. Adjust your 10 down to 9 and you may be happier.

When you simply pump flushing water through the group, there is pressure at the pump discharge but it is essentially zilch - maybe 0.1 bar or less.


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