Unreliable Ulka pumps - Page 3

Need help with equipment usage or want to share your latest discovery?
Nate42 (original poster)
Posts: 1211
Joined: 11 years ago

#21: Post by Nate42 (original poster) »

If your pump is setup like mine, it has a thermal fuse positioned in a slot on top of the pump that is designed to trip if the pump itself overheats. This has nothing to do with your heating element. Using cool water helps but the pump coil generates its own heat and it will overheat if operated continuously.

Doesn't really matter what is shutting it down though, I see this as a sign from the coffee machine gods that you shouldn't be running it so long. When I'm refilling my boiler I shut the whole machine off after 30ish seconds, and give it at least that much time again before turning it back on.

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civ
Posts: 1148
Joined: 17 years ago

#22: Post by civ »

Hello Eric:
erics wrote: Here is an updated drawing of the Ulka pump.
Thanks a lot for this and the very sound explanation of how it works.
Much obliged. =-)
erics wrote: ... BELIEVE that the cause of the problem is a less than robust suction check valve (shown in red).
Makes sense to me.
erics wrote: This is a spherical plastic ball (the exact plastic is unknown) that has a nominal diameter of around 0.156".
I wonder what it could be replaced with?

Cheers,

CIV

mteahan
Posts: 141
Joined: 19 years ago

#23: Post by mteahan »

Miscellaneous notes, not meant to be advice or recommendation.

The water in the tank gets hot from sitting, that increases the feed temperature to the pump.

The High Limit can be bypassed without much trouble.

Plumbed in machines are a problem because the pump delivers 14 bar of force internally and when plumbed with line pressure, they can blow themselves apart at 19 bar. The piston hits the seat with too much force.

Cimbali uses these pumps (low voltage works better) with an pressure regulator built into the machine.

The factory is highly automated, I doubt that Ceme dismantled the tooling when the bought and moved the plant, though they may have made material changes.

Fluid-o-techs have higher watt ratings but require external diodes, you have to wire them in to make them work.

The output check valve sticks when the machine rests for too long, easy to unseat without taking it apart.

The little ball sticks less frequently, but is damaged by excessive pump pressure (not output pressure, input).

Decalcifier can cause problems, which is why you have to use a product designed for espresso machines.

Air bleeder valves can be a problem, they don't always vent like they should.

Expansion valves should not be used as pressure regulators. Vibe pumps rarely exceed 9 bar in the group when the coffee is setup properly.

Pumps vary widely in lifespan, but I think its environmental rather than a production issue. Hate to say this, but if you are eating a pump a year, its probably not the pump.

Don't be afraid to use a 41 watt instead of a 52 and vice versa. Both develop the right pressure, the lighter extends the pre-infusion duration--just a little.

If the whole machine goes down, it isn't the pump, the high limit only affects the pump.

Angelo had a pump that cycled on and off during the shot for months before he gave up and replaced it. Removed the bleed valve and the pressure regulator and hasn't had an issue since.

I know it can be frustrating, but vibe pumps have historically been pretty reliable, as much so as rotary, and their low volume is well suited to home espresso machines. The low pressure build ramp evens makes some coffees perform better.
Michael Teahan
analogue | coffee

Nate42 (original poster)
Posts: 1211
Joined: 11 years ago

#24: Post by Nate42 (original poster) »

Thanks for all that information Michael. A few questions:

What is the "high limit" you are referring to?

What and where is the air bleeder valve?

When you say the expansion valve shouldn't be used to regulate pressure, are you saying I should turn UP the pressure seen with a blank, so that the valve doesn't open during a normal shot? Right now regulating the pressure down to 8 bars is the only thing helping my injured pump limp along, but once I get a new pump in I can always change my strategy.

I've already ordered another 52 watt pump to replace this one, but I just might try the 41 watt next time around.

I have a hard time believing that I am the problem. I only pull a few shots per day and I try to treat the pump with respect. I have a hard time believing the average consumer is more careful than I am. I AM using the expansion valve to regulate pressure, which you say I shouldn't do. Although I know many HBers do the same I'm willing to try anything at this point.

Thanks again for all the insight.

mteahan
Posts: 141
Joined: 19 years ago

#25: Post by mteahan »

I am back to my old espresso machine at home for a while, a simple as dirt machine with a PID controller. The Ulka Pump has no regulator, no bypass and no bleeder valve. When the machine gets to full pressure or when I backflush, the pump gets so quiet it seems to be off. As soon as the pressure drops it comes right back on.

When the piston can no longer move water, it stops and the electricity is dissipated as heat. If you pump cannot move water above 8 bar, the coil is either weak or something is inhibiting the movement of the shuttle.

The 41 watt pumps do not create as much heat when at full pressure. They still deliver just fine, though.

Heat is pretty much the only thing that will weaken a coil.

I am not saying you are doing anything, just that there is something about the environment of your machine that is affecting pump life.

Expansion valves are supposed to protect the heat exchanger from expansion, usually set to around 11 bar. The pump itself, especially a 41 watt pump, likely need no regulation at all.

The coffee in the portafilter, by virtue of the allowable flow rate, is the only pressure regulator you need.
Michael Teahan
analogue | coffee

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erics
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#26: Post by erics »

The coffee in the portafilter, by virtue of the allowable flow rate, is the only pressure regulator you need.
That's false thinking for the typical Ulka EX5 pump but close for the Fluid-O-Tech 1106.



The typical amount of water that flows in an E-61 machine AVERAGES 3.0 ml/sec as per section 4.3 of this:
http://www.worldbaristachampionship.com ... chines.pdf

The excess water being pumped needs to go somewhere and that is the function of the OPV in a vibration pump machine.
Skål,

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

mteahan
Posts: 141
Joined: 19 years ago

#27: Post by mteahan »

The high limit refers to the temperature protection attached to the side of the pump.

Those familiar with my position on espresso machine design theory will understand that analysis that attempts to reverse engineer Italian design are, to me, not very compelling.

80ml at 25 seconds for an E61 lever group approaches the 200ml flow rate and with the 1mm orifice most common in home machines, the actual flow rate is greater. It is also not linear. The actual delivered pressure to the coffee is close to 10, but the coffee filter bed is more fluid than that.

Even at 10 bar, no regulation is required. The OPV valve was NEVER designed to be a pressure regulator for a vibe pump except for the higher output Fluid-o-tech.

Pretty sure false thinking was never on my resume.
Michael Teahan
analogue | coffee

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