How do I check brew pressure without a gauge?

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jfb_1973

#1: Post by jfb_1973 »

I just ordered a new gasket to modify the brew pressure on my silvia. I currently only have a naked pf, so I'd need to buy a pressure gauge and new portafilter if I wanted to precisely set the pressure. Can I do it without a pressure gauge?

If so, is there a way to tell that you're close to the 9 bar range?

Thanks

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HB
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#2: Post by HB »

Re: Silvia Pressure Modification

Yes. I modified three of them. The adjustment is very small and twitchy; I would have had little hope of any accuracy without a pressure portafilter. Borrow one or rig up a temporary brew gauge by tee'ing one in (see Testing Brew Pressure for more). In theory you could use Jim's runoff method, but if you're going through the trouble of taking the machine apart, may as well go the extra mile.
Dan Kehn

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erics
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#3: Post by erics »

Yes, you can do it without a pressure gauge but it would be nicer to actually measure the before and after both on the machine and with your taste buds.

Image

Method 1 - Insert a blind basket in Silvia, start the pump, and measure the flow in the OPV line going back to the tank. This is the line without the bevel cut on the end. Measure the amount of time it takes a Pyrex cup to go from, say, the 4 ounce mark to the 8 ounce mark and convert this to ml per minute. Use the attached image and draw a vertical line upwards from your measured flow to the solid line in the drawing. This drawing was taken from the Ulka website and while there is no "official" explanation for the dashed lines above and below the solid one, I assume it to indicate production tolerance. The Ulka pump in Silvia is rated for a duty cycle of 1 minute on/1 minute off. Going from the 4 ounce mark to the 8 ounce mark should take a little over one minute and while I would foresee no problem in doing this, you may want to cut the measuring delta down to stay within their published duty cycle. The pressure you arrive at via this method is approximately 1.0 bar greater than actual brew pressure (when pulling a 2 ounce shot in 25 seconds). Total cost - zero.

Method 2 - With the power off and cord unplugged, remove and tape over one of the connections to the heating element. Detach the steam line from the boiler and clamp a suitable flex hose and hardware store pressure gauge (0-200 psig) with 1/4" male NPT threads to the 1/4" male BSPP threads on Silvia's boiler. Insert your blind basket, fire up the pump and read the gage. About 12" of 1/2" ID hose from an industrial hose supplier with two hose clamps should work nicely. Make sure the hose is rated for the pressures you will see. Total cost - $15

Pull a cold shot (2 ounces in 25 seconds) and read the pressure gage. Notice the difference in pressure? There are numerous variations on the above - Do a search on this site for Bob Roseman's setup. Fill out your profile and let people know where you're located. :D You might have a portafilter pressure gage right in your neighborhood and not know it. :D

Eric S.

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another_jim
Team HB

#4: Post by another_jim »

As you see from the curve, the runoff method is plus/minus 2 bar, **even** if you can set the OPV to a precise runoff volume. I published this technique, along with stuff like the $10 TC, since I firmly believe that one shouldn't need to pay a kings ransom to tune a machine. However, buying good instruments will improve accuracy and allow the data to be reviewed by others.

As to shot taste, my advice is to use whatever instruments you have to 1) get in the ballpark, 2) understand how your machine responds to adjustments; then do the fine adjusting using your tastebuds and your understanding of the machine.
Jim Schulman

jfb_1973

#5: Post by jfb_1973 »

Thank you all for your help. I think I'll see if I can find an austinite with a gauge, or try measuring the volume flowing from the opv.

BuzzedLightyear

#6: Post by BuzzedLightyear »

I have a naked portafilter for my silvia and cannot use a portafilter gauge to check my pressure. Is there another way to check my pressure

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HB
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#7: Post by HB »

Buzz, I merged your question with a similar topic.

Bottom line: You can guesstimate with the runoff technique or build your own portafilter gauge. BTW, if you want to learn more about over-pressure valves (OPV or sometimes called expansion valves), see DaveC's I am going to muck with my OPV valve.
Dan Kehn

BuzzedLightyear

#8: Post by BuzzedLightyear »

is there a way to make a gauge for my steam wand to measure pressure, I do not want to buy another portafilter if I do not have too.

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HB
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#9: Post by HB »

I suppose you could adapt the steam wand exit to a gauge, but you can use your existing portafilter and parts from your local hardware store as shown below. The only hard part is getting the portafilter spout off; it does come off with difficulty.

Image

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 like Bob get fancy and add a bleed valve to simulate pulling a shot. I believe the portafilter threading is 3/8" BSPP (when in doubt, see the fittingsAndAdapters thread identification charts).
Dan Kehn

BuzzedLightyear

#10: Post by BuzzedLightyear »

Thanks Dan for the info

However I no longer have a standard portafilter, I have converted mine to a naked pf. Hence the reason for my post.

Since measuring water debit does not seem to be accurate, would a gauge on my steam wand be as accurate as a portafilter gauge?