Pump is acting weird - how to test for steady pressure?

by **LeoZ** on Tue Mar 13, 2007 12:00 pm

im in need of testing my machine out.

my pump has been acting weird lately, getting too quiet during backflushes and midway through pulls, and i cant tell if the pump is supplying steady pressure during these times. anyone want to rent me a scace thermofilter?

i have a multimeter and im pretty sure it does pressure readings (a fluke 187), so that may not be necessary..

i can paypal you a rental fee, and ill only need it a few days! any help is appreciated.

by **erics** on Tue Mar 13, 2007 4:37 pm

Leo -

It would help quite a bit if you filled in your profile as regards location (Anytown, Anystate) and make/model of machine. The make and model of the machine is sorta important because the difference between blind basket pressure readings and actual puck pressure on a typical E61 is about 0.2 to 0.3 bar whereas on a Silvia, it is more like 0.75 to 1.0 Bar dependning on where the OPV is set in the first place.

Secondly, it appears from your post that what you are wanting to rent is a portafilter with attached pressure gage. There are a couple of threads here about constructing your own PF gage setup but you will be miles ahead with a liquid filled gage to dampen the pressure pulses.

You can also put the blind basket in and watch for steady flow (or unsteady as the case may be) in the return hose from the OPV to the tank.

Skol,

Eric S.

by **cannonfodder** on Tue Mar 13, 2007 9:31 pm

I believe the Thermofilter uses a type 'N' thermocouple. The fluke 187 (I have a 189 which is a 187 with data logging) uses a type K. They are incompatible. Most people use a Fluke 54II or 53II thermometer.

As Eric posted, it sounds like you are looking for a pressure gauge, not a temperature gauge. Take your portafilter, grab hold of the spouts and twist for all your worth. Those spouts will unscrew. Take the de-spouted portafilter to the local hardware store and get yourself a 1/8 NPT threaded pressure gauge, a female/female reducing coupler, I think ½ NPT to the 1/8 NPT gauge. Give the gauge a wrap or two of Teflon tape, give the portafilter a heavy wrap of Teflon tape and screw it all together. The portafilter threads will be BSP (metric) but the NPT to BSP thread difference is very small. A heavy wrap of Teflon tape is needed but you will get a high pressure seal.

by **jesawdy** on Tue Mar 13, 2007 10:06 pm

The Thermofilter uses a type T thermocouple, and no, no pressure measurement YET...

Apparently Greg has some pressure measurement with the thermofilter in the works as alluded to here... no details yet whether it is an integral gauge or what yet, buts seems it will measure during flow conditions:

gscace wrote:Rotary pump machines with little flow restriction may see little pressure drop. Small diameter gicleurs, long flow paths, small passageways, and proximity and configuration of group solenoids all affect pressure drop under flow conditions. Sweeping the difference under the rug is a very bad idea, because it can vary widely and complicate machine setup needlessly. I propose that folks measure under flowing conditions. It will become much easier to do so in the very near future.

Also, TerryZ of EPNW has discussed a thermofilter kit of sorts in the past.

by **LeoZ** on Tue Mar 13, 2007 10:13 pm

erics wrote:Leo -

It would help quite a bit if you filled in your profile as regards location (Anytown, Anystate) and make/model of machine. The make and model of the machine is sorta important because the difference between blind basket pressure readings and actual puck pressure on a typical E61 is about 0.2 to 0.3 bar whereas on a Silvia, it is more like 0.75 to 1.0 Bar dependning on where the OPV is set in the first place.

Secondly, it appears from your post that what you are wanting to rent is a portafilter with attached pressure gage. There are a couple of threads here about constructing your own PF gage setup but you will be miles ahead with a liquid filled gage to dampen the pressure pulses.

You can also put the blind basket in and watch for steady flow (or unsteady as the case may be) in the return hose from the OPV to the tank.

Skol,

Eric S.

profile updated. i thought it always was. sorry about that!

by **LeoZ** on Tue Mar 13, 2007 10:22 pm

cannonfodder wrote:I believe the Thermofilter uses a type 'N' thermocouple. The fluke 187 (I have a 189 which is a 187 with data logging) uses a type K. They are incompatible. Most people use a Fluke 54II or 53II thermometer.

As Eric posted, it sounds like you are looking for a pressure gauge, not a temperature gauge. Take your portafilter, grab hold of the spouts and twist for all your worth. Those spouts will unscrew. Take the de-spouted portafilter to the local hardware store and get yourself a 1/8 NPT threaded pressure gauge, a female/female reducing coupler, I think ½ NPT to the 1/8 NPT gauge. Give the gauge a wrap or two of Teflon tape, give the portafilter a heavy wrap of Teflon tape and screw it all together. The portafilter threads will be BSP (metric) but the NPT to BSP thread difference is very small. A heavy wrap of Teflon tape is needed but you will get a high pressure seal.

my mistake. i thought the scace was a pressure gauge. maybe im thinking of what he was planning on making?

anyway, it sounds like you are talking about making this.

my concern is that i dont know how accurate it is. ill have to try to get a crappy phone vid of it ramping up and the sound going quiet.

i have a vid here of a backflush. its low volume, but, youll see, big change in sound. :/

by **cannonfodder** on Wed Mar 14, 2007 9:03 am

Yup, that is the little monster. You can get uber precise certified gauges but they are very expensive and just not necessary for your application. I have made a couple of these as well as installing an on-board pressure gauge. While there is a slight discrepancy between gauges they are always within .1 bar of each other. That should be more than sufficient to tell you if your pump is going wacky. If you 8-9 bar you are ok, if it goes from 0 to 8 to 6 to 9.... Then you know you have a problem.

On a side note, if you are concerned about the pump suddenly going out, just purchase a spare. Vibe pumps are not very expensive and easy to replace, two wires, two hoses and you are finished.

by **TomP10** on Wed Mar 14, 2007 9:26 am

Read this thread on coffeegeek --- tells you exactly what to do!

http://www.coffeegeek.com/forums/...so/machines/194464

- Tom

http://users.rcn.com/erics/ · by **erics** on Wed Mar 14, 2007 9:58 am

Leo -

The gage you are holding in your hand looks like an automotive compression tester gage - perhaps it has seen a few bumps in its life

Here's a freebie you can do:

Measure the flowrate in the OPV line going back to the tank with a blind filter in place. Measure the amount of time it takes for, say, 4 ounces to flow into a Pyrex measuring cup and convert this to cc/minute. The best way to do this is to fill the cup with a couple of ounces to begin with and then simply measure the time it takes to go from the 4 ounce mark to the 8 ounce mark. Certainly a Pyrex cup is not "lab accuracy" but the delta may not be too far off the mark.

Use this formula to determine pressure in bars:

P = (-.02333)(cc/min) + 15

This is just a simple equation derived from this:

This should very closely approximate what a gage would read with zero flow from the PF. True brew pressure is about 0.2 to 0.3 bar less than what is calculated or measured with a typical E-61 group. Obviously, the better method would be to use an accurate, liquid-filled gage and a needle valve arrangement to measure the pressure at YOUR chosen flowrate as discussed in this HB resource topic:

http://www.home-barista.com/forum...-machine-t420.html

by **LeoZ** on Fri Mar 16, 2007 9:18 am

TomP10 wrote:Read this thread on coffeegeek --- tells you exactly what to do!

http://www.coffeegeek.com/forums/...so/machines/194464

- Tom

isnt this what i did, pic above?


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