Cafelat Robot Piston Seal Life - Page 6

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#51: Post by Nate42 »

Just recently pulled my first shots after having been gone all weekend. I'd say the water went about half way up the part of the tube that is visible from the front. That or a little further is what has always been typical for me, although I don't normally pay a lot of attention. I don't have a good explanation for why the discoloration goes all the way up to the gauge. My son does use it sometimes, maybe he applied some super human strength and squeezed it all the way up there a few time? If there is any leaking happening I don't hear it. The front face on my gauge is cracked, has been for a while. I assumed that was superficial but maybe it's an air leakage path? Again though, it seems to me to be performing the way it always has.


#52: Post by jpender »

My pressure tube was covered with the metal sleeve so I never actually saw whether there was water or not. I was just going by the fact that when I took it apart the hose was clean. Maybe that's more a reflection on the cleanliness of the water above the screen rather than how far up the tube it went.

Now I'm motivated to reinstall my pressure gauge, without the sleeve.


#53: Post by Jonk »

The plastic covering my gauge is also cracked and has been for a long time. Not sure when the crack first appeared, but it's growing. I have on occasion pushed the Robot up to about 12 bars, though rarely above 10.


#54: Post by jpender »

I took a look at my original pressure tube and, even though I removed it in April 2020, there are faint, clear droplets of liquid extending about halfway up the tube.

You'd think water would have evaporated even from that skinny tube in two and half years. I used a needle to extract one of the largest droplets near the end. It beaded up into a little ball on the needle and felt oily in between my fingers.


#55: Post by Nate42 »

Finally got around to replacing my 2nd seal, so 2nd seal lasted me a year and some change. It never did full on fail, but I told myself the next time it came off I would just replace it rather than put it back. Taking portafilter on and off is definitely less of a pain with the brand new seal in place, but there is no significant difference in performance otherwise. Including how far the liquid goes up the pressure 000000000tube.


#56: Post by jpender »

I reinstalled my pressure gauge, tube, fittings. After 2 1/2 years without it my Robot is Barista model again. I did not reinstall the metal sheath, however. And, what do you know, with the first test shot the water rose halfway up the now visible transparent tube.

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#57: Post by Ken5 »

Must be a reason that Paul uses a screen up by the gauge. Always assumed it was to keep the grounds out of the gauge if the water ever made it up that high. Luckily I have never seen any water, or condensation, in the gauge.

I have read a couple of times that one puts boiling water inside the piston to preheat it. State that they just turn the whole robot over to dump it. Wonder if they have the barista model, and if so if any water gets up in the gauge.

So much for an air space between the piston and the screen, must be touching for water to get halfway up the tube.


#58: Post by Miltonedgebert »

I'm not the one that originally mentioned filling the piston to preheat, but I've tried it and have the barista model. I don't see any way the water in the piston would get into the gauge. I only use this pre heat method and I'm almost convinced that it's intended because it works so well.

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#59: Post by Ken5 »

Definitely not from inside the piston, I was thinking more from the water that might be left in the tube after the shot, though just thinking about it most of it probably gets pushed out when the gauge pressure is released. Jpender did mention though that his tube, that was off his robot for a while, had some form of liquid in the tube.


#60: Post by jpender »

I don't think turning the Robot upside down will encourage water to flow to the gauge. There may be some droplets in the tube after you release the pressure but they adhere to the walls of the tube and aren't greatly affected by gravity. For that matter when the arms are down the tube itself is "upside down" leading into the gauge.

In any case water vapor will surely make it into the gauge and there will likely be some condensation. Does it matter? Who says the gauge will be harmed by water? Coffee sediment is a different issue. Despite being careful not to lose the little screen I nonetheless can't find mine. Fortunately the water is very clean so I'm not worried. But apparently that isn't true for everyone.