Pressure Testing with portafilter mounted gauge

[Grant]

I have some concerns about my machine which I will add to this thread later, but I wanted to test a couple things first.

Because I have no machine brew manometer, I built one by screwing a liquid filled pressure gauge onto the spout of a PF, but I have noticed water leakage from the water sneaking under the basket and over the rim of the PF as there is no seal. What is the best way to stop this....or, is the amount that sneaks out in some way almost emulating flow (so if the volume was lucky enough to be correct), would this actually make the reading more accurate?

Grant

[jesawdy]

Why is there no seal? You need to have a PF basket installed if you do not already.

Nevermind, I see now that you say the basket is there and it is sneaking under. I have seen some home jobs that allow for some water to pass through a separate valve... let me dig up that thread.

EDIT - Dan beat me to it!

[HB]

Bob shows a nice DIY portafilter pressure gauge (linked from the Resources page).

[DaveC]

Because I have no machine brew manometer, I built one by screwing a liquid filled pressure gauge onto the spout of a PF, but I have noticed water leakage from the water sneaking under the basket and over the rim of the PF as there is no seal. What is the best way to stop this....or, is the amount that sneaks out in some way almost emulating flow (so if the volume was lucky enough to be correct), would this actually make the reading more accurate?
Grant

Grant, if you remove the basket, then it should solve your problem. I don't know if your machine is an E61 bottom or not, but usually the PF will lock on tight enough without the basket. Don't do it too tight, because the rim is thin and you don't want to deform your group gasket. With a basket in the portafilter, it is actually not possible to get a seal, and water passing through the basket, will always push back under the rim (it's only steel on steel).

[Grant]

Grant, if you remove the basket, then it should solve your problem. I don't know if your machine is an E61 bottom or not, but usually the PF will lock on tight enough without the basket. Don't do it too tight, because the rim is thin and you don't want to deform your group gasket. With a basket in the portafilter, it is actually not possible to get a seal, and water passing through the basket, will always push back under the rim (it's only steel on steel).

Wow....that was simple. And works great...not a single drop leaks out now. And that leads in perfectly to my problem....or at least to a question.

My Bricoletta has a rotary pump, and also on OPV. I have adjusted the adjustment screw on the pump, but what I have noticed now is that the pressure ramps up to the 9 bar I want (which I hope should be around 8.5ish actual brew pressure), but then it slowly continues to rise to almost 12 bar over the course of the next 7-8 seconds. From what I have read about rotaries, this should not happen, no?

Does this perhaps indicate the bypass in the pump is not working as it should?

Grant

[DaveC]

Wow....that was simple. And works great...not a single drop leaks out now. And that leads in perfectly to my problem....or at least to a question.

My Bricoletta has a rotary pump, and also on OPV. I have adjusted the adjustment screw on the pump, but what I have noticed now is that the pressure ramps up to the 9 bar I want (which I hope should be around 8.5ish actual brew pressure), but then it slowly continues to rise to almost 12 bar over the course of the next 7-8 seconds. From what I have read about rotaries, this should not happen, no?

Does this perhaps indicate the bypass in the pump is not working as it should?

Grant

It might be, but I doubt it.... If the balanced bypass was fault, I wouldn't expect the pressure to keep ramping up (possibly the opposite). Logically when your machine hits 9 bar and holds for a few seconds....then pressure goes up. If the bypass was at fault...how on earth would the thing be closing again to get more pressure. It doesn't actually make sense mechanically. When thse pumps fail, you tend to get a constant flicking of the gauge from 3 bar to 12 bar

Whats probably happening is you pull the shot, theres some steam etc.., pressure up to 9 bar, then the steam condenses and the group keeps filling finally ending up at 12 bar. I think there is almost certainly nothing wrong with your pump, just adjust the maximum pressure down to 9 bar. The OPV is just a secondary safety device of course and will probably be set to vent around 14 bar (don't touch the OPV).

My rotary pump sometimes can take a while to build the pressure. Try an experiment: fill the PF with cold water, then lock it in the group and measure the pressure......you'll see a big difference in the way it builds.

Presumably your machine/pump is not very old or had a hard life?

[HB]

I have adjusted the adjustment screw on the pump, but what I have noticed now is that the pressure ramps up to the 9 bar I want (which I hope should be around 8.5ish actual brew pressure), but then it slowly continues to rise to almost 12 bar over the course of the next 7-8 seconds.

I saw the exact same thing when our house's pressure regulator seals were failing. Disconnect your Bricoletta and try putting the inlet into a jug of water. If that's what's happening the pump pressure will not change because the inlet pressure is no longer changing.

[Grant]

I never thought of it being line pressure as I have a regulator on the inlet set to 40PSI, but I will give it a try out of curiosity.

Grant

p.s. thanks for fixin up the google video above Dan....the .ca vs. .com thing never dawned on me...

[miKe mcKoffee]

My Bricoletta has a rotary pump, and also on OPV. I have adjusted the adjustment screw on the pump, but what I have noticed now is that the pressure ramps up to the 9 bar I want (which I hope should be around 8.5ish actual brew pressure), but then it slowly continues to rise to almost 12 bar over the course of the next 7-8 seconds. From what I have read about rotaries, this should not happen, no?

Does this perhaps indicate the bypass in the pump is not working as it should?

Grant

Your query got me curious so I tested my Bric. (using PF mounted gauge from EPNW) Initially ~9 bar then it crept up to ~12 bar! Tried starting with empty and filled PF same results. Next tried line pressure only (lever half way up.) Initially ~4.25 bar as I expected then crept up to ~12 bar now too!. Ok, figured it's gotta be boiler pressure related some how so dumped the boiler pressure via hot water wand forcing a couple boiler fills and immediately tried again before valve even pressure seated. Now PF test pressure stayed put, line pressure or pump.

[jesawdy]

Your query got me curious so I tested my Bric. (using PF mounted gauge from EPNW) Initially ~9 bar then it crept up to ~12 bar! Tried starting with empty and filled PF same results. Next tried line pressure only (lever half way up.) Initially ~4.25 bar as I expected then crept up to ~12 bar now too!. Ok, figured it's gotta be boiler pressure related some how so dumped the boiler pressure via hot water wand forcing a couple boiler fills and immediately tried again before valve even pressure seated. Now PF test pressure stayed put, line pressure or pump.

So you think it is pressure created by water flash-boiling in the heatexchanger tube? I'm not sure I follow.

[miKe mcKoffee]

So you think it is pressure created by water flash-boiling in the heatexchanger tube? I'm not sure I follow.

I have no idea for sure but sounds possible, simply reporting what I observed! Could have to do with thermalsyphon heat or something else unbeknownst to me. I really don't know the root cause.

[Grant]

I have no idea for sure but sounds possible, simply reporting what I observed! Could have to do with thermalsyphon heat or something else unbeknownst to me. I really don't know the root cause.

Interesting test....I ran a couple tests after flushing the boiler, and after hitting 9bar on the meter, it still began to creep up - but much more slowly.

I let the Bric cool off for an hour, and from cold, the pump pins the meter at 9bar and just sits there until the boiler element kicks in....then, even when still quite cool, it starts to creep up as the element kicks in.

Grant

[HB]

Try letting even a few drops per second escape from the grouphead. That should be enough to compensate for thermal expansion.

[Grant]

Well it took some doing, but a note/suggestion from Jim at 1st-Line got me testing a few things and it seems to be solved. He thought from the sounds of it I should check the OPV operation...sounded flakey to him.

So, removing the OPV, taking it apart (is there a special tool for that!?!?!) , descaling it (there was a tiny bit of scale in there..but not much), and working the spring etc., and then putting it all back together seems to have fixed the problem. Seems that at times the OPV would work, and at other times is wouldn't.

Very strange, but seems fixed now...with a static gauge on the PF, the pressure ramps to 9.2 bar or so, and pins there without moving, hot or cold.

"Thanks Jim!"

Grant

[Kristi]

Yeah, that was my thought as I read this thread - stuck OPV. Glad you got it!

[HB]

Very strange, but seems fixed now...with a static gauge on the PF, the pressure ramps to 9.2 bar or so, and pins there without moving, hot or cold.

Very strange indeed. The "OPV" on a rotary pump espresso machine doesn't regulate pressure like it does for a vibe pump, it acts as a safety (it's called an expansion valve when it serves this role). I suppose you could regulate it low enough so it cracks open during an extraction, but that's really the job of the pump's bypass valve. Eric explains further in Rotary pump conversion - balanced bypass or standard bypass model?

The "relief" valve on the pumps typically used in the beverage industry (that's us) is of the by-pass type in that a certain amount of flow (certainly enough for pre-infusion) is allowed to pass from the inlet side of the pump to the discharge side of the pump when the pump is NOT OPERATING.

The "relief" valve can be a "balanced" type such that it will regulate to a certain (factory set/user adjustable) pressure regardless of what the inlet pressure is (flushing toilets, taking showers, etc., etc.).

The "relief" valve can be a "standard" type such that it will regulate to a certain (factory set/user adjustable) differential pressure between inlet and outlet. If one were to set the relief valve to 150 psi with 50 psi inlet pressure, it would rise to 175 psi with 75 psi inlet pressure. This would likely not be the case with a "quality" pressure regulating valve installed in the supply line to the pump because then the inlet pressure would be reasonably constant regardless of events (flushing toilets, taking showers, etc., etc.).

But the best of all possible worlds, especially at no $ differential, as Coffee_Monkey pointed out, is to spec a pump out with a balanced bypass relief valve.