I have a v2 Silvia (adjustable OPV, professional PF) which I picked up new 3 weeks ago.

As there was a lot of posts on Silvia's being set to incorrect pressure I decided make a pressure gauge to test it. I decided to make my gauge with an ability to allow water flow so as to not incorrectly measure a blind filter pressure which I understand could be quite a bit higher.

Below is what I put together using a liquid filled gauge (thanks to the previous work of bobroseman) see link: Help with La Cimbali Jr.







I allowed for water flow of 60ml in 25sec. This gave a pressure reading of 9.8 bar. I subsequently reduced this to 9.0 bar. I don't know if there was any recognizable difference but the first 2 shots I puled looked good and no channeling or squirting using my naked PF (I had some previously).

What may be of interest to some is that when I closed the valve to stop all water flow I did not measure any increase in pressure - that is once the system was closed (like a blind filter) the gauge did not record any increase in pressure over the pressure recorded for water flow of 60ml in 25sec. When the value was opened to allow for increased water flow the pressure did decrease.

I tested this further by taking about my setup and installing only a 90 degree angle off the PF directly to the gauge. This read the same pressure as when recording with the valve setup (open for 60ml in 25sec).

Has anyone else tried this? I know there are several people who were recording their pressure with a blind filter and then wondering whether this was accurate - if my machine is anything to go by it would seem that there is no difference.

Damon: Very nice look overall of your machine. I like how the PID kinda blends in with the overall look.

Mark

Thanks Mark, wish I could take credit for the PID, but can't. It is an Auber PID and they designed it to fit in with the style of the Silvia. I agree it seems the work well.

thefly wrote:I allowed for water flow of 60ml in 25sec

Nice set up, I have made a similar arrangement witn a gauge and needle valve sadly my gauge is not damped so I have to contend with the flutter, anyway I thought 30 mil in 25 seconds was the flow rate to aim for, I would like to know which is correct.

thefly wrote:I have a v2 Silvia (adjustable OPV, professional PF) which I picked up new 3 weeks ago.

As there was a lot of posts on Silvia's being set to incorrect pressure I decided make a pressure gauge to test it. I decided to make my gauge with an ability to allow water flow so as to not incorrectly measure a blind filter pressure which I understand could be quite a bit higher.

Below is what I put together using a liquid filled gauge (thanks to the previous work of bobroseman) see link: Help with La Cimbali Jr.
I tested this further by taking about my setup and installing only a 90 degree angle off the PF directly to the gauge. This read the same pressure as when recording with the valve setup (open for 60ml in 25sec).

I was thinking about doing the same, being unsatisfied with the adjustment I have made to my Silvia using only the OPV overflow measurement. Can you confirm what pressure gauge you have used and if any, your recommendations on choosing/buying one for a vibe pump? I guess I'm looking for something that is both cheap, exact and readable... (if this is possible!)

I guess my issue is more with the inherent variation between different Ulka pumps... that would explain why my adjustment seems to have brought the pressure too low even if the overflow measurement is very precise.

Also, thanks for your confirmation that pressure doesn't change while further reducing the flow.

vicroamer wrote:Nice set up, I have made a similar arrangement with a gauge and needle valve sadly my gauge is not damped so I have to contend with the flutter, anyway I thought 30 mil in 25 seconds was the flow rate to aim for, I would like to know which is correct.

The aim is for a 60ml double shot in 25 sec. See quote from erics and link:

erics wrote: A very acceptable standard rate is 3 ml/sec which equates to putting 60 ml in the cup and leaving 15 in the puck in 25 seconds - and then you can play from there.

Building a Portafilter Pressure Gauge

Louis wrote:I was thinking about doing the same, being unsatisfied with the adjustment I have made to my Silvia using only the OPV overflow measurement. Can you confirm what pressure gauge you have used and if any, your recommendations on choosing/buying one for a vibe pump? I guess I'm looking for something that is both cheap, exact and readable... (if this is possible!)

I guess my issue is more with the inherent variation between different Ulka pumps... that would explain why my adjustment seems to have brought the pressure too low even if the overflow measurement is very precise.

Also, thanks for your confirmation that pressure doesn't change while further reducing the flow.

I bought it locally - it is listed on my receipt as:

Part No. 72141-200 ENFM 1.5" 200 PSI/BAR, 1.8" CBM LF Pressure Gauge. Price was $25.48 CAD.

What I asked for was simply a liquid filled pressure gauge that displayed BAR. The place I went to had several - I chose this one because it was small (about the size of the steam knob) and went to 15BAR. They had a 300 PSI (21BAR) gauge, same size, but I thought it would be harder to read and the additional 6 BAR wouldn't be needed. Once my warranty expires I may install it permanently, since I have the gauge and it seems like a fun thing to do.

I don't think you need to worry about brands etc - just get one that is 200 to 300 PSI, displays BAR and is liquid filled (they are a few $ more).

I ended setting it to ~ 8.6 BAR and I have noticed a more even flow from my naked PF. Needed to dial back my grind slightly as a result.

If you read Greg Scace's post in this thread, Why difference in pressure between blind filter and brewing?, you may have a better understanding of WHY there must be a difference in pressure gage reading during blind filter trials and representative flow trials. I cannot offer any explanation of why there was no visible difference in Damon's runs.

The flowrate I gave, 3 ml/sec (60 in the cup, 15 in the puck) is meant to be an average flowrate over a 25 second period and, of course, is meant to be a good STARTING point from which you can play. The origin of that flowrate is here: WBC Procedure for Measurement of Brewing Water Temperature - see section 4.3 . To keep this flow, you would need to be flowing 75 ml in 25 seconds past the ball valve - not a trivial adjustment to make. One item that can substantially influence Silvia's pressure reading is the cycling of the heating element and you would need to make the choice as to whether you want the heater on or off during these trials.

A good source of gages is these guys: http://www.gaugestore.com/ and the particular gage I would recommend is this one: http://www.gaugestore.com/prodinfo.asp?number=38141 . It is 0-300 psi but has +/- 1% accuracy in the 100-200 psi range. Naturally, there are lots of good gage manufacturers out there.

erics,

I am unsure why my gauge recorded no difference between the no flow and your recommended flow. I confirmed this through various trials at various pressure settings. I am hoping someone else can confirm with their setup for the Silvia. Greg Scace did note that it would vary from type of machines from no difference to substantial (can't recall if it was in the quoted post or somewhere else).

For my test I did set it so that the boiler was off - I will re-run the test again with the boiler on at full temp and see if it makes any change in what I set it at with the boiler off.

EDIT:

Ok, so I had adjusted the OPV so that I was reading 8.6 BAR with the boiler off (both with flow and without). I just re-did the test now at full temperature (102.5 C using Auber PID).

With no flow (ball joint closed) it read 8.6 BAR. When I opened the joint to produce the flow of 75ml (recorded in 29 sec) the pressure dropped to 8.2 BAR. I will let the machine cool and see what happens with the boiler off again to see if I somehow received incorrect results initially.

EDIT EDIT:

Ok, so I re-tested now with the boiler off (was still reading ~40 C). This time I was able to see the 0.4 BAR difference between the valve being open and closed. The only thing I can think of was during my first tests the other day there was some minor leaking around the grouphead. Today I was able to lock in the PF a little tighter and there were no leaks. I am not sure if this could be the reason.

I performed the tests several times at difference OPV settings and each time saw a 0.4 BAR difference.

As a result I increased the pressure from 8.2 (which I incorrectly measured at 8.6) to 8.6.

I tried this today with some parts from the local hardware. I was surprised to find water squirting out around the top of the basket rather than sealing up.

This does not happen with the same handle when I use the blind filter. With the backflush (blind) basket inserted, it locks up tight when the pump is turned on, as I would expect.

Any idea why a standard basket would gush around the seal gasket in this particular application?

Also no leakage issues when brewing. If I choke the machine, it locks up tight - I never get any weird spillage like this.

I realize that the obvious answer is a hardened group gasket that could be replaced, but there are no similar issues when brewing or backflushing.

This is on an older Silvia.

ap