Noisy/faulty OPV and use of OPV in general - Page 2

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
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erics
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#11: Post by erics »

cafeIKE wrote:An OPV should not squeal.
For sure, you are correct. Unfortunately, the OPV on the QM machines is a little different than others. All (well, at least within the past couple of years) QM machines equipped with vibe pumps have their OPV on the outlet side of the hx. When the flow of hot water goes past the OPV in just the "right" amount at just the "right" opening of the OPV the combination of the valve, the spring, the pump flow characteristics, and the mfg tolerances on the assy, together with any scale present inside exacerbate any vibration present and hence the squeal.

I can easily duplicate the effect on my laundry room faucets by reducing the flow to a small stream. Perhaps the quality of the faucet enters into the equation.

How to fix:

As dsc has done, soak the OPV valve internals in lemon juice, citric acid, vinegar, etc. It might not be a bad idea to remove the housing and soak it also but be advised that the straight threads at the OPV inlet need some form of sealant (loctite, teflon tape, copper washer, etc.).

Chris Coffee sells new inserts for the valve and anyone with a QM machine should add these to the "to buy" list along with an o-ring for the adjusting nut and food grade lubricant for same.

Reinstall the OPV and attach hardware store tubing to the OPV outlet. Plug the existing machine's OPV tubing line with a golf tee. This makes OPV adjust easy as you are not kinking and untwisting the PITA original short hose.

Run the pump with a blind filter in place and adjust the OPV with the heating element disabled. What pressure do I adjust to? Everybody has their favorite but I would suggest 9.0 bar. IIRC, this should give about 8.5 bar at the puck and a little less when the element kicks in during normal ops. If it squeals, make it 9.1 or 8.9 bar.

Reattach all original hoses, undo the disabling of the heating element and pull some real shots with the covers off. Readjust as necessary - hopefully NOT.
Skål,

Eric S.
http://users.rcn.com/erics/
E-mail: erics at rcn dot com

Beezer

#12: Post by Beezer »

Thanks for the tip Ian. I may have to order some of the Lubrifilm. That squeal is really annoying.
Lock and load!

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cafeIKE

#13: Post by cafeIKE »

erics wrote:QM machines equipped with vibe pumps have their OPV on the outlet side of the hx.
Coolish fresh water is not going to scale the OPV or wash out the lube.
Why feed hot water back into the tank. Enhanced operation in Siberia?
Any 'sensible' idea why they do this?

Seems like the perfect opportunity for another brilliant Eric Svendson kit. 8)

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erics
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#14: Post by erics »

cafeIKE wrote:Seems like the perfect opportunity for another brilliant Eric Svendson kit.
Like this?

Skål,

Eric S.
http://users.rcn.com/erics/
E-mail: erics at rcn dot com

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mhoy

#15: Post by mhoy »

Eric: Please say that's a quiet rotary pump that will drop into my Anita....

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erics
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#16: Post by erics »

Fortunately, no.

It is, purportedly, a very quiet and high quality vibe pump - the FOT 1106 - see above performance curves. It will be the subject of a separate post in a month or so.
Skål,

Eric S.
http://users.rcn.com/erics/
E-mail: erics at rcn dot com

JimG

#17: Post by JimG »

erics wrote:It is, purportedly, a very quiet and high quality vibe pump - the FOT 1106 - see above performance curves. It will be the subject of a separate post in a month or so.
The cost to revise all of the "15 bar pump" marketing materials will doom it to failure. 8)

Jim

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erics
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#18: Post by erics »

DSC -

I watched your video and noticed that your Andreja is an older model (?). Perhaps your hydraulic system is a little different than the current version, e.g. do you have the little bleed valve installed onto the snout of the Ulka pump and where does your brew pressure gage pick up its measurement? Is your machine even equipped with an Ulka pump?
Skål,

Eric S.
http://users.rcn.com/erics/
E-mail: erics at rcn dot com

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dsc (original poster)

#19: Post by dsc (original poster) »

Hi everyone,

When it comes to the way how an OPV works I understand it this way:

- coffee in the basket acts as resistance, sort of like a small hole that restricts the flow

- the pump it self, based on its characteristics, gives a certain flow rate at different pressures, for example 240ml/min at 9bars

- if the OPV is set to 9bars the pressure in the installation won't go above that value, well because simply the valve will open at pressures > 9 bars

- so basically 9 bars is the max we can get in the installation, meaning that with the OPV opening the flow rate will be what the characteristic shows = 240ml/min, which is 4ml/s

- with 4ml/s and nothing in the path of the water we would get 100ml in 25s

- well we all know that we get values even lower than 60ml in 25s (ristrettos for example), so I'm guess that coffee acts as resistance, lowering the flow, absorbing some of the water, etc.

Hope this makes sense:)

I turned the OPV down to 9bars again and it's still silent, so I guess that disassembly helped. I am however still having pulsating flows:|

Oh and as for the voltage of the pump I doubt it would change anything, as the vibe speed is dependant on the frequency (vibrating with 50Hz). It might be however possible to lower the flow rate by installing a flow restrictor, or making the existing one a bit smaller (sticking a small wire in the whole).

Eric -

you mean the video with the additional pressure gauge that shows how the OPV opens after a flush (the one I placed in this topic)? if that's the one you are talking about I have to clarify that it's not my machine and not my video:) That's not even an Andreja:) As for my machine I believe it's the newer model, it has got a CEME pump which is very loud and blue. I tried disassembling it once but there seems to be a metal clump around the pump's case which makes it impossible to remove. I will try to upload some picture of the inside so you can see how it's connected.

Cheers,
dsc.

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erics
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#20: Post by erics »

dsc wrote:Hope this makes sense:)
Reread Jim Gallt's explanation to you of how the OPV functions in an espresso machine. It is correct and to the point. You could also do an HB search on "OPV" and while this would return many threads, the appropriate ones are easy to pick out. All of the manufacturers that produce pumps for our espresso machines provide pump performance curves that depict how an average production pump will perform with NO regulating/relief/bypass valve in the system. All other factors being reasonably equal, you can change the grind and/or dose all you want and that will NOT change the flow from the pump but will, of course, change the flow through the coffee puck.

Changing the voltage applied to the pump will alter the flow - look what happens to the pressure when the heater element kicks in and voltage available to the pump drops down about 5 volts. You may not experience that because you're operating at ~230V and your wiring is sized for 120V. Do an HB search on "Variac" and you'll find some posts by Jim Schulman wherein he described the application of a Variac to control the Ulka pump.

The flow characteristics of the CEME pump may be quite different than that of the Ulka - hence A need for the OPV to compensate for different pumps. Look at the rather dramatic difference between the Ulka and the FOT 1106. The OPV in a machine that has the FOT could easily "take a nap" and probably remain closed its entire life. :lol: And now that I see where CEME has purchased Ulka - http://www.cemeeng.com/index_en.htm , espresso machine pumps might have further developments. :D

Your pulsating flow MIGHT be as a result of a faulty "bleed valve" (if so equipped) on your pump/machine.
Skål,

Eric S.
http://users.rcn.com/erics/
E-mail: erics at rcn dot com