Testing Brew Pressure

[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.

[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]

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.

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.

[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.

[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:



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:



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:


(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).

[framey]

Thank you Obi Dan Kehnobi

[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

[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?

[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.

[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

[cannonfodder]

So if I am reading HB's posting correctly, all I need to add a permanent brew pressure gauge to my millennium is a couple of fittings and this gauge from the gaugestore.com? The spec on that gauge is for a max of 140f, wouldn't it get dosed with the same 203f water that hits my E61?

If I decide to do this I will post some photos. The hardest part looks to be putting the hole in the face of the machine. I would take it to my local fabricator and have them laser cut the hole so it is exact. I also thought about insulating the boiler.

This one also includes the snubber to reduce the pulse.

[HB]

I tee'd the tubing coming from the pump, so the water isn't heated at that point. The drawback of this placement is that the gauge is subjected to more intense pulsing, so needle flutter is more likely. Manufacturers install it further downstream and use a coil of thin copper tubing to avoid flutter even with a dry gauge. The thin tubing also dissipates heat which would otherwise be transmitted to the gauge. See the tee below from the Andreja Premium:



If you're considering a permanently mounted gauge and it will be close to the boiler, all copper tubing similar to this would be best. The splicing of the pump outlet tubing works well for an externally mounted gauge or a temporary setup.

[cannonfodder]

I see now, I thought you were putting the splice between the HX and the brew group. I have to give it some thought but I may give it a go. After all, it is just plumbing, it's not rocket science. They wife may have my head, the new Mazzer was a surprise to her. I just ran new water line and installed a filter in line just for the machine my float valve from Chris arrives Friday to complete the process.

This is starting to turn into one of those consuming passions. I have to ask myself 'will this make any difference in my quality'. Then I think, who cares, it looks cool.

[shadowfax]

This is starting to turn into one of those consuming passions. I have to ask myself 'will this make any difference in my quality'. Then I think, who cares, it looks cool.

Oh, buddy, don't I know all about that! I spent an extra $250 on La Valentina Levetta over, say, an Andreja Pro... I tell myself it's for the great components, and that's probably true, but in the end, there's definitely a "who cares, it looks cool" to it. I could probably get just about the same from either machine, and reliability is still an odds game either way...

[russell]

Dan remarked that some people have added bleed valves to the PF gauge setups to simulate the pressure while coffee is being brewed. But ideally, it doesn't matter, does it, whether some pressure is released through the PF during brewing and some through the OPV or whether all is released through the OPV (as with a blind filter). I found a difference between max pressure during brewing and with a blind filter, presumably due to non-linear spring action in the OPV, but it wasn't more than half a bar. So I don't see the value of a bleed valve.

Is there a difference of opinion about the 1 second pressure bounce during brewing with a PID working? Dan says he turned his Amica PID off during brewing but others say it doesn't matter. I would think the pressure oscillation dwarfs any difference between a rotary and vibration pump. If it doesn't make a difference, then how could the slightly smoother action of a rotary pump make a difference? I'm just looking for informed opinions here.

Russell

[badbean]

for those that want to tune their OPV using parts commonly found at most hardware or tool stores for around $20: buy a small p.s.i. gauge, 3/8 male pipe thread, and the scale must be capable of at least reading 130 psi which is equivalent to 9 bar. Preferably 130 should be the middle range of the scale as that is where gauges have the best calibration. Buy 3/8 female to 3/8 female pipe connector either barrel, 45 or 90 degree(brass) and teflon tape. Remove the spout from your portafilter. Screw on the barrel connector using tape. Connect gauge to barrel connector using tape as well. Install portafilter minus basket to machine and hit brew button. Check for leaks, tighten if necessary and read gauge. The needle will bounce but you are shooting for reading of the middle range. Discussed here as well.

[pinpoint]

do anyone know if there's an how-to on how to add a pressure gauge to Rancilio Silvia? Would really like to know the pressure of the shots I'm pulling... and, is there a way to add the ability to adjust the pressure on the Silvia?

[HB]

CG and alt.coffee have a huge Rancilio Silvia fan base. Sometimes searching them isn't easy without a very good idea of what you're looking for. I found some nice matches with the rather obscure keywords "+Silvia +SwageLok". HB's own Resources page links to related topics, notably the famous Silvia Pressure Modification.

[pinpoint]

But the problem is what parts do I need to get this done? (and links to where I could get them)
Does the pressure gauge come with a hose which I just have to connect to a T-fitting between the brewer and the boiler? And where do I find the parts needed for the pressure control (like the one from the post "pressure gauge on miss silvia?"

[HB]

But the problem is what parts do I need to get this done?

It's difficult to give precise weblinks beyond what I've already noted earlier in this thread since you're in Sweden and few online vendors based in the US will ship overseas. I advise you to follow the previous discussions, which include specific parts from places like www.gaugestore.com:

Silvia's Pressure Regulator?
Expobar with Gauge
How to adjust the brew pressure of a Giotto Premium?

It shouldn't be difficult to source them locally. Our neighborhood hardware store has the gauges, but I had to order the snubber online. BTW, don't be put off by the titles, these threads do address your question if you're willing to read past the extraneous information.

PS: I see that you cross-posted your question on CoffeeGeek (link) with pretty much the same responses. In general, I discourage cross-posting across sites since there is some overlap in membership; if you must, please consider including a pointer back to your other posts to avoid redundant responses.