How is this possible? Pressure portafilter leaks?!?

[Worldman]

My Expobar has NO instrumentation, i.e. gauges, etc.


OK, no problem...I made the simple $10 steam pressure gauge which mounts to the steam wand for checking/setting the boiler via pressurestat adjustment. I also just today received the Pump Pressure Check Kit from 1st-Line: http://1st-line.com/parts/other/V512_pump_pressure_check_kit.htm


Simple, right? Just remove the PF spout and affix the Pump Pressure Check Kit. OK, the "kit" part seems t be the inclusion of a nylon ring which fits inside the female threads and an O-ring which fits in the middle of that. No problem...

Well, tonight (minutes ago) I removed the Expobar's PF spout and affixed the Pump Pressure Check Kit. Using the double basket which I mostly use the PF was inserted into the GH as usual and the pump was switched on and WATER flowed out of the GH/PF interface!!! The Expobar's PF is usually used at zero degree position, i.e. sticking straight out the center of the machine. I tightened the PF beyond zero degrees to a couple of degrees to the right (more tight) and water still poured out of the GH. I further tightened the PF into the GH and water still leaked. #&$@! <----- cartoon swearing!!!

This led me to think that the GH gasket might be bad and to confirm that it wasn't this, I used the rubber blank insert which I use for back-flushing into the double basket and the PF was put back into the GH (still with the pressure gauge attached) and again turned the pump ON. This time (with the PF at its normal zero position) the pump built pressure and then the water was shunted to the drip tray via the OPV.

So, do any of you have any idea why my machine might leak with the gauge in use - but won't leak with the same gauge still in the "circuit" but when the blank insert is in use? Please help!!!!

Len

[mogogear]

So to completely bail on your "possessed" machine, but avoid the problem you so clearly explained , or at least I hope to dodge it and recommend you hook up said "devil gauge" to the steam wand and see what your pump pressure is , before it wants a human sacrifice!!

[miKe mcKoffee]

So, do any of you have any idea why my machine might leak with the gauge in use - but won't leak with the same gauge still in the "circuit" but when the blank insert is in use? Please help!!!!

Len

IIRC you need to use it without a basket sealing to the GH gasket with the PF rim itself. The basket does not make a seal on the PF rim so when the water hits the resistance of the gauge it finds it's way out there. I can't verify my memory 'cuz mines been on a round robin loan tour for a couple months and not back home yet but I'm fairly sure...

[framey]

miKe picked it in one.

The water is coming back around the outside of the basket in between the PF wall and the basket.

Dump the basket and all should be well.

[Worldman]

Um...dah...Of course, it was leaking between the PF & basket...but, heck, I couldn't figure it out.

Thanks guys for the advice! She is working just fine and reading ~10.5 bar. BTW, at what pressure do you guys (or yunz guys, as some in Pittsburgh say) set your OPV to dump. IIRC, some use exactly 10.5 bar while others use less.

Len

[cannonfodder]

Morning Len.

I run my vibe pump Isomac at 9.5 bar deadhead pressure (blank basket max pressure) which gives me around 9 with coffee in a real basket. On my rotary Faema, 9 bar deadhead, 8.5-8.75 with coffee.

Keep in mind that you will drop a few .x bar between a blank, or pressure gauge adapted portafilter verses a real basket with coffee so you need to set you OPV just a bit higher than your target pressure.

If you use the same blend all the time, check with the roaster and see what they recommend for pressure. It does make a big difference.

[jesawdy]

Worldman-

I have used the same pressure gauge kit from 1st-line with my Silvia. Out of curiosity, how well were you able read the pressure? On my machine, the needle bounces a good bit, and about all I can measure is an average of the bouncing. I am not sure if this is a function of the pump, OPV function, gauge or all three.

-Jeff

[jason_casale]

I bought a e61 manometer gauge put together complete with the portafilter from a known vendor we all know to get an idea what the pressure was from the group head compared the manometer gauge for pressure from the linea. It was about 1 bar difference between the 2 still helpful information and those portafilter manometers are like gold everyone should have one and most machine techs you will find do own them. Between that and my scace and fluke meter I am set. Good investment on your part if your machine does not have a pump pressure gauge.

[Worldman]

Morning Len.

I run my vibe pump Isomac at 9.5 bar deadhead pressure (blank basket max pressure) which gives me around 9 with coffee in a real basket. On my rotary Faema, 9 bar deadhead, 8.5-8.75 with coffee.

Keep in mind that you will drop a few .x bar between a blank, or pressure gauge adapted portafilter verses a real basket with coffee so you need to set you OPV just a bit higher than your target pressure.

Dave,

OK...it makes sense that the reading would be higher with a blocked PF vs. one with coffee grounds therein...though, in another sense I would think the readings should be the same since it is the pressure at which the OPV shunts the pressure side of the pump to wherever it goes. Pressure is what it is <---man, that IS an obvious statement. Still, there is a side of me that says that the pressure value would shift based on whether the resistance was a hard resistance (blocked PF) vs. a soft resistance (grounds in a basket).

In any event, I accept what you say as true. Should I then set my P-stat to allow ~9.5 bar on the PF gage?

Len

[Worldman]

Worldman-

I have used the same pressure gauge kit from 1st-line with my Silvia. Out of curiosity, how well were you able read the pressure? On my machine, the needle bounces a good bit, and about all I can measure is an average of the bouncing. I am not sure if this is a function of the pump, OPV function, gauge or all three.

-Jeff

Jeff,

Hello! On my Expobar, the reading is quite stable...after the initial hooplah. When I switch on the pump, there is a split second where the gage reads ZERO, then another split second where the water is being shunted to the drip tray and the gage reads ~9 bar. This is all followed by the gage coming up to and holding at its max. pressure reading. It is pretty smooth and other than the 2 jumps mentioned, all is stable.

I can't think of why yours would be erratic EXCEPT that when you buy a pressure gage to install in your machine, for example, they always come with a coil of tubing whose purpose is to smooth the reading. Hum, come to think of it, my reading should be erratic, as well.

Len

[Worldman]

I bought a e61 manometer gauge put together complete with the portafilter from a known vendor we all know to get an idea what the pressure was from the group head compared the manometer gauge for pressure from the linea. It was about 1 bar difference between the 2 still helpful information and those portafilter manometers are like gold everyone should have one and most machine techs you will find do own them. Between that and my scace and fluke meter I am set. Good investment on your part if your machine does not have a pump pressure gauge.

Jason,

You say the 2 gages weere off by ~1 bar. Was the PF gage the higher? Does "pressure from the linea" mean pressure from the line, i.e. the line from the pump as displayed by the machine mounted gage?

Len

[HB]

...I would think the readings should be the same since it is the pressure at which the OPV shunts the pressure side of the pump to wherever it goes.

The mechanical engineers can give you a more technical explanation; my understanding is that the OPV spring's resistance is not directly proportional to the applied pressure. Thus the more the flow, the more it's compressed, the more it resists. That's why you see a slight increase in the gauge reading when the OPV is bypassing the pump's full output against a blind basket instead of a fraction of it during a real extraction.

You can also build a "bleed valve" like Bob's to simulate the extraction flow:


(Click image for more details)

I can't think of why yours would be erratic EXCEPT that when you buy a pressure gage to install in your machine, for example, they always come with a coil of tubing whose purpose is to smooth the reading. Hum, come to think of it, my reading should be erratic, as well.

The E61 has a gicleur (small holed-jet) that calms down the gauge reading. Silvia doesn't have one, so you see the full effect of the vibratory pump. A snubber on the portafilter pressure gauge will smooth out the reading.

[cannonfodder]

Dave,

OK...it makes sense that the reading would be higher with a blocked PF vs. one with coffee grounds therein...though, in another sense I would think the readings should be the same since it is the pressure at which the OPV shunts the pressure side of the pump to wherever it goes. Pressure is what it is <---man, that IS an obvious statement. Still, there is a side of me that says that the pressure value would shift based on whether the resistance was a hard resistance (blocked PF) vs. a soft resistance (grounds in a basket).

In any event, I accept what you say as true. Should I then set my P-stat to allow ~9.5 bar on the PF gage?

Len

That is what works best for me, your mileage may vary. Different machines behave a little different, but I believe this is a relatively standard observation. I run my two machines at two different pressures. My Isomac works better with a little higher pressure while my Faema works best just a little lower. Vibe pump vs rotary, preinfustion vs no preinfusion etc.

In the end, your taste buds are all that matter. The over pressure valve is easy to adjust so you can make a change, pull a few shots (and taste them), make another change pull a few more shots, until you are happy with the results. You may want to call your local roaster and ask them what they have their machine set at and what their dose is. Use that as a starting point and play with the settings until you are happy with the cup. Keep in mind that as you change the pressure, you will need to change your grind so you can burn through some beans getting it set.

[VS_DoubleShot]

Len,

How did you make your steam wand boiler pressure gauge contraption?

Care to share?

[Worldman]

VS,

Hello! The "wand mounted" pressure gauge is pretty simple and an idea I got on-line. It is an inexpensive tire pressure gauge + a 8" long piece of (IIRC) 1/8" rubber tubing + 2 hose clamps...all bought from a local NAPA auto parts store.

The whole cost me ~$10.

You simply open the steam valve and read the pressure with an HX machine. With a single boiler machine (such as Silvia) you will need to assure that the machine is up to steam pressure by switching the high temp element on and waiting as long as you would to start steaming.

Len

[VS_DoubleShot]

Thanks a lot, Len. I really appreciate it.

-Vince