Rancilio Silvia v1 - Pressure drop problem

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Schroinx

#1: Post by Schroinx »

I have had pressure problems and have taken the OPV valve apart for cleaning and inspection. Is there any guide for how to set the pressure when I reassemble it, or will it do with setting it approximately the same distance as before?

Kind regards, Troels

EDIT: See my first post below.

JRising

#2: Post by JRising »

You could set it to where it was before and if too much water flows over the OPV, tighten it more. If it stalls the pump, let it off a little.
Or you could buy a gauge for it.

Schroinx

#3: Post by Schroinx »

My problem originated as a pressure drop problem, where the pump would start and then only a few drops of espresso would come out. As it has been some time since it has been descaled, I did that and have cleaned the machine, back flushed it, and I changed the gasket for the portafilter and the main screen. It did not solve the problem, so I have now taken the OPV valve apart and cleansed it put it back in and installed a new pump. I'm still having the same issue with the pressure drop.
I did quite a bit of descaling, but the water comming out was still bluish, possibly indicating that there is more calcium deposits inside.

I have to say that I am pretty much at a loss of what it can be.

RogerP
Supporter ♡

#4: Post by RogerP » replying to Schroinx »

I recently had to check (and adjust) the pressure on my old Silvia. I don't have a pressure gauge set up to work with my portafilter adapter, so I used the method to measure the flow rate of water from the OPV valve - and converted it to pressure using a chart. I ordered some 17mm x 21mm washers in thicknesses of 1mm and 1.5mm so I can check and adjust it later. The stock washer is 1mm. With these two sizes I can change the pressure by adjusting in increments of 0.5mm washer thickness.

This post references a website for a flow/pressure chart:
https://www.schneordesign.com/diy/diy-c ... ure-gauge/

The goal is usually 9 bars. Using this method I got 190cc in one minute before I added the washer, which is around 12.5 bars. The stock washer is 1mm thick. I added a washer to reduce the pressure (see photo). The washer is 17mm ID and the thickness is 1.7mm. That was thicker than I wanted but it was all I had laying around, so I thought I would install it and check the flow. The OPV hose flow (with blind basket) changed from 190cc/min to 350cc/min. That indicates the pressure is around 8.2. I plan to check and adjust the pressure to 9 bars after I receive the new washers. By that time I hope to have a working portafilter pressure gauge.
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John_Doe

#5: Post by John_Doe »

Another thing to keep in mind is that the 3-way solenoid can clog and cause a loss of pressure during extraction, diverting the excess flow to the drip tray instead of properly sealing. Usually a good backflush will help fix this, but have you noticed any excess flow?

Schroinx

#6: Post by Schroinx »

Sorry for being a bit late with replies.
JRising wrote:You could set it to where it was before and if too much water flows over the OPV, tighten it more. If it stalls the pump, let it off a little.
Or you could buy a gauge for it.
I have set it to where it was before.

Schroinx

#7: Post by Schroinx »

RogerP wrote:I recently had to ...
So the way to check the flow by this method is to use the blindfilter and then measure how much water is coming through the return/overpressure tube?

Schroinx

#8: Post by Schroinx »

John_Doe wrote:Another thing to keep in mind is that the 3-way solenoid can clog and cause a loss of pressure during extraction, diverting the excess flow to the drip tray instead of properly sealing. Usually a good backflush will help fix this, but have you noticed any excess flow?
Thanks. It all comes through the return/overflow tube and none in the drip tray.

Schroinx

#9: Post by Schroinx »

I have adjusted the pressure as indicated. It has not solved the low pressure problem when brewing. Any ideas are welcome.

RogerP
Supporter ♡

#10: Post by RogerP »

Schroinx wrote:So the way to check the flow by this method is to use the blindfilter and then measure how much water is coming through the return/overpressure tube?
This method is to test the approximate pump pressure by measuring the flow. But in my case I had too much pressure. I got 190cc in one minute (12.5 bars). I added a washer to reduce the pressure. Then I got 350cc in one minute (8.2 bars). But I don't know what version Silvia you have. Later versions don't require washers for adjustment.

If you are confident that your pressure is around 9 bars then it would seem that the grind is too fine.