Adjusting Rancilio Silvia brew pressure (OPV) - Page 2

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SigCool

#11: Post by SigCool »

Why a glycerin filled gauge?

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erics
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#12: Post by erics »

To dampen the gage needle fluctuations and allow you to obtain a reasonable reading.

Coiled 1/8" tubing works also but then you are into finding adaptors for the location I suggested.

Eric S.

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SigCool

#13: Post by SigCool »

I can not find an adapter to go from the small steam tube to a large 1/4 NPT.

I originally got a 1/4 bspp to 1/4 NPT fitting but that's Way too big. I'm not sure what the 1/4 stands for because the I.D. is 3/8".

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erics
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#14: Post by erics »

The male stub on Silvia's boiler has 1/4-19 BSPP threads. These are parallel (straight) pipe threads and their "sizing" is, IIRC, more tuned in to the NOMINAL ID of the pipe to which they are sized.

A 1/4-18 NPT (US tapered pipe thread) brass fitting will screw onto Silvia's fitting and, with about two wraps of Teflon tape, will seal. Its not right but it works. Using a brass fitting will minimize the chances of screwing up the threads on Silvia's boiler. The "correct" way to do it is with the adaptor as you described.

FYI, here is a hydraulic diagram and some nominal flows for Silvia. This shows the old style OPV but the only change is that you can adjust the amount of spring compression internal to the OPV with the newer style.



Skol,

Eric S.

SigCool

#15: Post by SigCool »

I was first thinking of connecting it to the steam wand, which is M5 or 10-32...But I just instead hooked it to the steam output of the boiler.

With the OPV mod of adding one washer I was reading only 105 psi (7.2 bar). Taking it off and back to original setup it was 150 psi (10.3 bar). I'm going to just stay with the original setup, 10 bar should be OK, and I prefer the shots I am getting with it.

By the way, the glycerin filled gauge worked great and it was very steady.

doug_m
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#16: Post by doug_m »

I purchased a Silvia and Macap M4 in September. I am using Kid O's 6 days old, 15 gram measured doses, reverse surfing starting temp at 200F going to 198F at the end of 25 secs. I am getting 2 ozs finally.
Before I adjusted the OPV I was reading 145 psi 10 bar and now it is at 127 psi 8.75 bar.
Before the adjustment every shot I tasted was harsh and bitter. I do not know if it was from being too hot or the beans being too old or dosing too much - I was dosing 17-18grams. I reduced my dose based on Ken Fox's thread on reducing dose. Shots taste less bitter and are not harsh.
Because I'm just starting I'm sure my technique is lacking and caused my shots to be bad initially - I think I might be getting a bit better on dosing, distribution and tamp. The pressure adjustment did seem to contribute to an improvement in taste.

I adjusted the OPV by loosening the jam nut CCW which is 20mm like Jeff said. I have a 20 mm combination wrench but it was not thin enough - it was turning the jam nut and adjustment nut at the same time so I used a slip joint pliers. The jaws are much thinner. It was very easy to loosen. I used the 20 mm wrench to turn the adjustment nut 1/2 turn CCW. The instructions in the Silvia manual are clear. For my machine it produced a drop of 18 psi or 1.24 bar. All the pressure measurements were taken with a Scace 2 thermofilter device.
I will continue to test the pressure occasionally to see when the spring in the OPV begins to wear and affect the pressure setting like erics mentioned.

This my first post - thanks to all for great, sometimes overwhelming info. This is great fun.

doug

EspressoObsessed

#17: Post by EspressoObsessed »

With the newer Silvia OPV, you will not need to loosen the jam nut to lower the pressure (loosening the pressure nut will bring the jam nut down with it). You will need to tighten the jam nut after loosening the pressure nut.

If you need to raise the pressure, loosen the jam nut first. Check to see if you need to tighten it after the pressure adjustment.

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doug_m
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#18: Post by doug_m »

Thanks EspressoObsessed.

I will try your method the next time I adjust the pressure. Makes sense since both nuts have to go in the same direction for reducing pressure.
From the illustrations in the manual it looked like I had to loosen the jam first before turning the pressure adjustment nut and I didn't want to chance damaging the machine since I was adjusting the OPV for the first time.

doug