Testing Brew Pressure

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framey

#1: Post by framey »

Whilst I'm trying to take a more holistic approach to my coffee making, I still feel the need to test certain parameters. With that in mind I want to hear about my options for building or buying a PF pressure gauge. Any comments or experience, positive or otherwise with these two?
pressure gauge kit
whole unit
Advice on how to construct a gauge I can attach to my existing PF would be much appreciated. The type and size of the parts needed would also be handy.

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shadowfax

#2: Post by shadowfax »

If you can unscrew your spout, then all you have to do is take off the spout and attach the pressure gauge instead. I don't know if you need teflon or something to make it seal, never done it. Make sure you can get that spout off before you go order one, though. I never could get the spout on my Rancilio portafilter off. go figure. Maybe it had thread glue on it.

I would say, though, go for the full unit from Chris as long as you're getting one. It's only $15 more, but it has free shipping. EPNW's shipping charges will bring it a lot closer to that, and you don't get the portafilter.

framey

#3: Post by framey »

Now that you mention it, I haven't been able to unscrew the spouts on my PFs either. I thought is was just me.
I'm hoping to hear from first hand experience whether the screw on gauges are accurate.
shadowfax wrote:I would say, though, go for the full unit from Chris as long as you're getting one. It's only $15 more, but it has free shipping.
Last time I asked, Chris' Coffee wouldn't ship to Australia. That is another reason the do it yourself version appeals to me.

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shadowfax

#4: Post by shadowfax »

The portafilter brew pressure gauges we are talking about have limited usefulness. If you want to set your overpressure valve (OPV) they are perfect. You hook it up to your machine, turn on the pump, and the pressure will rise to the max pressure, at which point the OPV will kick in and hold it at the max pressure. Then you can adjust your OPV and retest till you have it where you want it.

The accuracy of an OPV should be limited, though, by whether it has a leak, I guess. I would think you would hear that, of course.

The problem with these types of gauges, though, is that you can't use them while brewing as you can with a gauge that it mounted between the brewhead and the pump. Such a gauge ("brew pressure gauges" common on nicer HX and dual boiler machines) will tell you what your espresso is brewing at, and you can also pop a blind filter into your normal PF and check the OPV with this type of gauge.

You might be able to get a more standard manometer from somewhere locally that would hookup via copper tubing to the boiler, perhaps requiring you to connect a T somewhere in the line (say, right as the brew path exits the boiler, or at the head of where the pump line enters the boiler).... Maybe Dan or someone else could offer more help, as I must admit I have no experience with this; I seem to recall reading about Dan making his own brew pressure gauge for (I think) his Valentina.

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HB
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#5: Post by HB »

shadowfax is correct, it's easy to add a brew pressure gauge to an espresso machine. I've done it for several machines without problem. Here's the installation for the Giotto Premium by adding a tee:

Image

The tube leading from the pump to the expansion valve conveniently has the same diameter as required for standard John Guest fittings. One snip and two pushes are all it takes. The same trick worked on the Cimbali Junior with a different set of fittings:

Image

Both were temporary modifications for evaluation machines, but I'm confident it will hold up if you use the properly rated fittings and tubing. I used 230 PSI / 70F commercially rated; be aware that Home Depot stocks 120 PSI / 70F tubing made by Watts, which will burst if used in this application.

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

framey

#6: Post by framey »

Thank you Obi Dan Kehnobi :D

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luca
Team HB

#7: Post by luca »

Have you emailed Pedro at http://www.coffeeparts.com? They're based in Sydney and I seem to remember that they had the whole assembly on offer.

That said, it would be cooler to go Dan's route and chop a hole in the machine for a gauge, if it fits!

Cheers,

Luca
LMWDP #034 | 2011: Q Grader Exam, Brewer's Cup #3, Australian Cup Tasting #1

framey

#8: Post by framey »

Yeah Luca I've spoken to Pedro a couple of times lately. I'm going to go silly when I get to the warehouse.

After shadowfax mentioned:
The problem with these types of gauges, though, is that you can't use them while brewing as you can with a gauge that it mounted between the brewhead and the pump. Such a gauge ("brew pressure gauges" common on nicer HX and dual boiler machines) will tell you what your espresso is brewing at, and you can also pop a blind filter into your normal PF and check the OPV with this type of gauge.
I'd be keen to have the gauge incorporated into the brewing line.

Can you replace the existing boiler pressure gauge with a dual gauge that gives you both boiler and brew pressure?

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HB
Admin

#9: Post by HB »

If a dual gauge fits in the allotted space and you're willing to spend the extra money, go for it. In that case, it will definitely be a dry gauge, so you'll want some sort of dampening agent. A generous looping of 1/8" OD copper tubing keeps most of the heat away from the gauge and dissipates the vibe pump's pulsing for a steady reading. I'm sure the good people at http://www.coffeeparts.com will be able to advise you well.
Dan Kehn

russell

#10: Post by russell »

To the question as to whether a PF gauge measures the same as a built-in gauge: on my Eliane the answer is yes, within 1/2 bar. That's comparing the Espresso Parts NW PF gauge reading with the Eliane's built-in gauge measuring the pressure with a blind filter.

I wanted to check the pressure on the Solis SL-90 also, but the PF is different. Rather than drilling and tapping the PF, I suppose the suggestion for teeing off inside for test purposes might be a lot easier. Thanks for the suggestion and pictures.

Russell