Can E61 flow control damage the pump?

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Ursego

#1: Post by Ursego »



From FB.

What do you say?

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Ursego (original poster)

#2: Post by Ursego (original poster) »

The RELATED TOPICS section suggested this: Flow Control vs the Pump. There is no long discussion there, but the question could be serious.

Giampiero

#3: Post by Giampiero »

A rotary pump has a bypass valve that limit the max pressure, a vibratory pump has often an OPV valve that limit the max brewing pressure.
In all situations both types pump will reach a max pressure value, so it's a normal condition.
I can't imagine why the use of a flow valve could harm the pump at the point to suggest to avoid the use of a flow valve.
Maybe the fb user is worry about that a long preinfusion at low flow rate could "stress" the pumps due to the high pressure value is reached faster?
I personally never heard about such problem, as well i can't imagine the real problem, but i'm only speaking about home use machine, as well i never heard about any commercial machine with a manual operative flow valve, (apart LM gs3 with paddle group head maybe) but i could be wrong.

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Jake_G
Team HB

#4: Post by Jake_G »

An authorized factory service technician advices against aftermarket modifications?

Shocking!

I suppose they also advise against backflushing the group with blond baskets, and pulling ristretto shots, as well? Pardon the sarcasm, but this is utter hogwash. Vibe pumps work by pulling a spring back with electricity and then letting the spring push water through a check valve. Aside from a few very fancy implementations (DE1, and "dimmer mod" style machines, including the adjustable preinfusion on Breville machines) the electrical current in the coil always pulls the spring all the way back. Additionally, in machines equipped with an OPV, the spring always pushes the piston somewhere between all the way and the point where the spring reaches the OPV pressure, so there is no difference to the pump running with a flow control device or without aside from the potential for longer shots. This is different for machines without an OPV, but those machines are just as likely to have a dual wall basket, which also limits the flow of the pump and would arguably be just as stressful to the pump, which is to say "not at all".

Now, the caveat would be really long shots where the pump itself overheats from exceeding its duty cycle. Cheaper pumps have more plastic bits in them and are rated for 50% duty cycle. Run for 30s, rest for 30s. This is to give the parts time to cool down between use. Even so, if you did a really long shot and ran the pump for 60 or 90s, resting it for 60 or 90s before pulling another shot would be well within the recommended 50% duty cycle.

Don't believe everything you read.

Or do. But be prepared to become very confused, because there are a whole lot of conflicting opinions out there.

As for flow control on commercial machines, Slayer patented it with their low-flow "Pre Brew" setting that routes the pump through a needle valve in the brew path prior to ramping up to full flow. I designed and installed flow control on my LM GS/3 that has been implemented by several other users without issue.

Cheers!

- Jake
LMWDP #704

JRising
Team HB

#5: Post by JRising »

I think "Tony" isn't using the machine correctly, and the un-named "Faema Technician" didn't care to teach him how to use the machine.

Obviously, if your machine is stalling the pump at less than relief pressure, then it is very easy to burn out the pump quickly.
Because he said "Burnt out the pump" rather than "the pump motor" we should assume it's something with a vibe pump. There really isn't much info in the bit copy/pasted. With no flow, the vibe pump will heat up and destroy itself. If it's an SBDU that isn't controlling its boiler level, and you choose to let the water out that can't be replaced because you've already burnt your pump out, you can burn out the element as well.
It's a good thing these forums exist so that we can learn the most basic things about our type of machine and not destroy them.

Using the handbrake to stop a car causes no more wear than using the hydraulic brakes, the handbrake just wears only the rears, rather than all four. You can not create nor eliminate energy. Think about what the person is saying when you decide whether or not it has any value.

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HB
Admin

#6: Post by HB »

Jake_G wrote:Now, the caveat would be really long shots where the pump itself overheats from exceeding its duty cycle. Cheaper pumps have more plastic bits in them and are rated for 50% duty cycle. Run for 30s, rest for 30s. This is to give the parts time to cool down between use. Even so, if you did a really long shot and ran the pump for 60 or 90s, resting it for 60 or 90s before pulling another shot would be well within the recommended 50% duty cycle.
Agreed! People often forget about duty cycles and do things like run their home grinder for 30 minutes straight grinding pound after pound of coffee to "season the burrs". :shock: Friction = heat = potential problem. The Ulka website has duty cycle tables somewhere, but my simple rule of thumb for both grinders and vibratory pumps is ~30 seconds on, 1 minute off, just as you recommended. Newer espresso machines with vibratory pumps usually have a heat-sensitive switch to cut power if the pump is too hot.

As for a flow control device, it may cause the pump to heat up slightly faster since the water flow itself helps cool the pump. But I would have no concerns about running it for 45-60 seconds, though again, I would opt for a longer rest time in that case, say 2-3 minutes.
Dan Kehn

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bringyoutomyhell

#7: Post by bringyoutomyhell »

If you don't extend the zero flow for more than a few minutes (like a mega extended bloom phase) it shouldn't be a problem. For sure it stresses the pump a little more, and possibly it could break faster, but definitely not after a year.

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Jeff
Team HB

#8: Post by Jeff »

Especially if your pump doesn't have a "Klixon" thermal protector, it is possible to overheat it if running too long. Doing so may permanently damage the coil, to the point of portions of it melting. Depending on the specific model, it may be rated for 1 or 2 minutes on time. That is with 20°C water flow and 25°C, which typically isn't the case in a home espresso machine. Though not stated, that is probably with moderate flow, which probably helps cool the coil. I'd be on the cautious side of things, keeping things below a minute on. A less-cautious approach would be to stay within the on-time rating of the pump in your machine.

I don't know what caused this failure in another user's machine, but you can see what too much heat can do to an Ulka or similar (this one from a machine without a Klixon over-temperature switch installed).


DaveC

#9: Post by DaveC »

E61 flow control fully closed, won't damage a well set up vibe pump, as it will be pumping water, just out of the expansion valve. So even a 1 min shot at home wouldn't be a problem, as it won't get hotter any faster than normal.

A rotary pump will whizz the all water around the bypass (if the FC valve is fully closed) this agitation in the bypass loop does cause the water to heat up and it will eventually cavitate. However producing a long shot or backflushing with a blind filter for 30 sec is well within the pumps capabilities.

There should be no concerns over using a flow control.