Espresso Machine Pumps: Vibration vs. Rotary - Page 2

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#11: Post by okmed »

Here is a copy of the pump plumbing for Strega model "Top" which allows plumbing in direct or tank operation. Obviously tank operation will not allow preinfusion but I have mine plumbed in direct with a pressure regulator set at 2.5 bar.

The outlet of the vibe pump goes directly to the cross tee fitting via item 29 and water travels through the tee and item labeled "TAV.3" ( which may be what Jim referred to as a bypass valve, not sure) that I call the relief valve ( it relieves pressure above 11 bar to the drain pan when pulling a shot using the vibe pump). Item 17 connects directly to the heat exchanger in the boiler and then flow goes directly to the group (lever). When I pull the lever down and the piston goes past the opening in the cylinder I get immediate flow. As you can see the flow must pass through the vibe pump for this to happen and yes the switch I installed cuts the power to the pump.

The 2.5 bar pressure in my case must be enough to lift the inlet ball and spring as well as the outlet check and spring because I assure you flow and preinfusion are occurring. No offense has been taken on my part and I'm not trying to be difficult but just wanted to point out that flow can occur through a vibe pump without it running. Different groups with different gicleur sizes and piping arrangements with different solenoid arrangements will definitely have an effect.


#12: Post by Flitzgordon »

TAV 3 is the OPV.

it's interesting to know that you can bypass by just disconnecting the cables and allow water pressure to push through.

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#13: Post by okmed replying to Flitzgordon »

And Bezzera refers to it as a "suppression valve". Confusing I know.

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#14: Post by kolu »

I have successfully plumbed in standard tank Strega by connecting the water line to the Ulka input, no bypass, no TOP model. Few bricks to counterbalance, line pressure around 3-4 bar, completely disconnected pump, no problem...


#15: Post by robertD »

Perhaps apropos of nothing, but the missing consideration for me is that the motor connected to a rotary pump can become the weakest link. With my La Spaziale, I didn't realize until after the motor seized that a small leak in the seal between the motor and pump created scale and rust. Certainly not an area I thought needed descaling! Perhaps this is not a problem with other manufacturers. Nevertheless I went with a new vibe machine this time around.

goalerjones (original poster)

#16: Post by goalerjones (original poster) replying to robertD »

My (will be here Friday) Vetrano 2B EVO has the pump cage mounted underneath the motor. The EVO PDF I read from the BellaBarista site said this was the best way to mount them.

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#17: Post by radudanutco »

okmed wrote:...water travels through the tee and item labeled "TAV.3" ( which may be what Jim referred to as a bypass valve, not sure) that I call the relief valve
in fact, there are both of them...
that relief valve pictured in detail in TAV.3, which is named suppression valve,
or OPV - over pressure valve, we all know about, associated with any vibration pump to limit its pressure during extraction in a pump machine, or, in this case, to limit its pressure at the end of the pressure ramp, to a value which equals the initial one of the springs;
but actually it contains in its assembly at the output end towards the HX hose, pos. 1-4, another valve, a check valve!