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AndyJH

Sage DB dropping pressure during extraction

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My Sage DB has started to drop pressure whilst extracting and I can’t figure out why. Pressure of tamp hasn’t changed and I’m generally using the same beans so variables haven’t altered. Start of extraction the machine sits around 8 bar but during the extraction it will gradually drop to around 5 bar.

 

Any ideas on what could cause this?

 

 

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Is it doing the same with a blind basket in?


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Is it doing the same with a blind basket in?


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Sorry, being stupid here what do you mean by a blind basket?


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32 minutes ago, AndyJH said:

 


Sorry, being stupid here emoji51.png what do you mean by a blind basket?


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With Sage DB it the little rubber insert that you use to either backflush the machine every now and again. Most likely it is just the way the water is passing through the puck, I wonder if it's always done it to an extent but you've started to notice or for some reason you're getting a lot of channeling or similar. I have a fairly significant drop in pressure when using an EK43 and Sage DB almost every time, with other grinders less so but it always changes at least a bit. 

Also you say it's the same beans does that mean same batch or same type and roaster? As they might vary anyway either due to ageing or roasting etc. 

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With Sage DB it the little rubber insert that you use to either backflush the machine every now and again. Most likely it is just the way the water is passing through the puck, I wonder if it's always done it to an extent but you've started to notice or for some reason you're getting a lot of channeling or similar. I have a fairly significant drop in pressure when using an EK43 and Sage DB almost every time, with other grinders less so but it always changes at least a bit. 
Also you say it's the same beans does that mean same batch or same type and roaster? As they might vary anyway either due to ageing or roasting etc. 


Ok thanks. I’ll give it a try with the rubber insert to see the pressure.

It’s always been fairly consistent in its pressure tbh, normally around the 8 bar point, previous owner had reduced the pressure slightly.

Same roaster, I’m on a subscription so beans are nearly always only a few weeks old. Appreciate there will be some variation but the drop to 5 bar is slightly concerning.


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Flow almost always increases during an extraction meaning the back-pressure on the pump (the gauge reading) will reduce as the flow increases.

A vibration pump such as that installed on the DB is capable of ~14 to 15bar max with zero flow (dead-headed)

If the OPV has been set to 8 bar then it will open during the initial part of extraction to bleed away excess pressure back to the tank (or pump suction depending on design), thus maintaining 8 bar back-pressure. As the flow continues to increase through the puck the back-pressure drops and the valve will gradually close and divert more water to the group. If it gets to the point where the OPV is fully closed the pressure will start to drop on the gauge.

So it could be a perfectly normal part of the machine operation, especially if you have coarse ground beans, or stale beans, channelling etc.. Or the OPV could be sticking or the pump performance could be reduced. But probably it'll be the grind or the beans, or channeling.

 


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Flow almost always increases during an extraction meaning the back-pressure on the pump (the gauge reading) will reduce as the flow increases.
A vibration pump such as that installed on the DB is capable of ~14 to 15bar max with zero flow (dead-headed)
If the OPV has been set to 8 bar then it will open during the initial part of extraction to bleed away excess pressure back to the tank (or pump suction depending on design), thus maintaining 8 bar back-pressure. As the flow continues to increase through the puck the back-pressure drops and the valve will gradually close and divert more water to the group. If it gets to the point where the OPV is fully closed the pressure will start to drop on the gauge.
So it could be a perfectly normal part of the machine operation, especially if you have coarse ground beans, or stale beans, channelling etc.. Or the OPV could be sticking or the pump performance could be reduced. But probably it'll be the grind or the beans, or channeling.
 


Thanks for this, very interesting

I don’t believe it’s the beans or channelling, beans are always within 4 weeks of roasting date and I use a naked portafilter and rarely see evidence of channelling. No process hasn’t changed and I use a sprung tamp to ensure consistency to a degree.

The machine is fairly old, guessing about 5 years and has had a few issues in the past 18 months, repairs being carried out by Coffee Classics. So I am think pump and or OPV could be the issue


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Needs a bit more info really. You could take out any problems with puck by fitting the rubber disk in the single ideally even the pressurised one.

Assuming that you still have 6sec of pre infusion the pressure should swing up smoothly but more rapidly than with a puck and stay there intill the end of the cycle.

Best get this out of the way 1st. If not sure what to do  and haven't got the manual download it from sage and look at cleaning cycle.

John

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Needs a bit more info really. You could take out any problems with puck by fitting the rubber disk in the single ideally even the pressurised one.
Assuming that you still have 6sec of pre infusion the pressure should swing up smoothly but more rapidly than with a puck and stay there intill the end of the cycle.
Best get this out of the way 1st. If not sure what to do  and haven't got the manual download it from sage and look at cleaning cycle.
John
-


Apart from the OPV being wound down slightly by previous owner, the rest of the machine settings are default, so pre infusion is still 6 sec. yes it does swing up smoothly to approx 8 bar after pi but then steadily drops down to around 5 bar. It’s been doing this for the last month or so, I just haven’t had the time to look into it. This has been with a number of bags of coffee through it so assuming not a bean issue, more machine.

Suggesting to use cleaning disc and run a normal shot cycle to see if pressure remains constant? If so I can give this a try tomorrow when back home again.


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36 minutes ago, AndyJH said:

 


Apart from the OPV being wound down slightly by previous owner, the rest of the machine settings are default, so pre infusion is still 6 sec. yes it does swing up smoothly to approx 8 bar after pi but then steadily drops down to around 5 bar. It’s been doing this for the last month or so, I just haven’t had the time to look into it. This has been with a number of bags of coffee through it so assuming not a bean issue, more machine.

Suggesting to use cleaning disc and run a normal shot cycle to see if pressure remains constant? If so I can give this a try tomorrow when back home again.


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Yes . Using the cleaning cycle with the rubber disk checks the basic operation of the machine. I'd expect the pressure to go a touch higher than it does in normal used due to increased flow through the OPV.

On the other hand running say a 30sec or more shot with the cleaning disk in would show that the machine can hold pressure throughout a shot so is a better option as it doesn't hold full pressure for long during a cleaning cycle. ;) Silly me for not suggesting that initially.

To be honest if you have been using the machine for some time without problems I doubt if it relates to the puck itself. Channelling for instance is obvious and can be clearly seen on the top of a used puck. It leaves a hole often with a degree of funnel at the top. Low fills, too low a tamping pressure can cause all sorts but neither are the sort of thing some one is likely to suddenly start doing.

What I expect to see in relationship to the puck is pressure going up to circa  3 or 4 bar during infusion and may hang their briefly then ramping up to what ever the opv is set to and remaining there until the shot ends. I usually find myself using ratios of around 2.5 to 3.5 depending on the bean. Also due to a tamper not actually tamping the grinds but hitting the basket instead I did have a channel a couple of days ago and even that didn't result in any pressure drop.

John

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Ok, thanks for the response. I’ll give the cleaning disc a try when I get home tomorrow and see if the machine can hold pressure. If it can then it must be something I’m doing but I can’t really think what as I’ve been doing the same process for ages. I generally measure out 18g beans and grind though my Niche, check that I get the same out. Manual shot aiming for about 35g to stop the shot at and checking this is normally around 30-35 seconds to achieve.

I have noticed that since the pressure drop I’ve also lost the crema on top of the shot and the taste is not as good. Comparing to my girlfriends Sage Bambino machine which produces a lovely crema, appreciate that’s not the important element


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Right, finally got home and tried with the cleaning disc in place, it holds pressure! So, seems like the machine is ok and something is wrong with my process

Not sure what as I’ve been doing the same for a while but think I will reset the machine to ensure everything is default, although I can’t remember how to do that right now!

Also opens up the old question of do I have enough ground coffee in the portafilter? I use the standard basket and dose 18g, I’ve always thought the standard Sage baskets are designed for 20-22g so perhaps there is too large a gap for the water?


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When you see the pressure dropping do you also notice an increase in flow? Has the time to reach target yield dropped?


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When you see the pressure dropping do you also notice an increase in flow? Has the time to reach target yield dropped?


I don’t believe so. I normally aim for stopping at 35g to give a final yield of 40g with an input of 18g, this normally takes around 35s inc pre infusion. Having said that I normally use the manual button but tonight I used the double dose button as that was set for 34s just to see and it yielded almost 50g, so in this yes! Need to tests tomorrow…


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37 minutes ago, AndyJH said:

Right, finally got home and tried with the cleaning disc in place, it holds pressure! So, seems like the machine is ok and something is wrong with my process emoji849.pngemoji51.png

Not sure what as I’ve been doing the same for a while but think I will reset the machine to ensure everything is default, although I can’t remember how to do that right now!

Also opens up the old question of do I have enough ground coffee in the portafilter? I use the standard basket and dose 18g, I’ve always thought the standard Sage baskets are designed for 20-22g so perhaps there is too large a gap for the water?


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Brew by hitting a ratio.  Not time

Suspect you may need to grind finer.   

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Yeah it’s sounding more and more like staling beans - it happens. As Mrboots said, go finer.

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Glad it's not the machine.  If O rings I would have thought that you would notice water dripping out but if it was the 3 way acting up it would go to the drip tray.

I often find 17g is about right for the double but beans can alter that upwards. Then I try and find a weight that never sticks to the shower screen. The IMS shower screen I use drops the dose a touch but not by much.

Niche can produce very fluffy grinds with a fair amount of air in them. A change to how you load the filter basket can need a change to the grinder setting. it depends on how they are loaded and I'm still playing around with that.

John

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What grinder are you using with the Sage DB?

You could do a video of your shot and shot prep.


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Will be going finer tomorrow, day at home so lots of coffee :)

Using a Niche grinder. Will try and do a vid tomorrow.

Odd on the coffee but I do get where you are coming from based on my description. I buy in 250g packs and they are usually never more then a month after roast date by the time I use them. I keep them in a cupboard so not in direct light. Once opened they are in a Airscape canister so air is evacuated each time, does take me a week normally to use a bag so they are going stale at this point I guess.

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If you’re still getting the issue post up a video of the shot prep and shot


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11 hours ago, AndyJH said:

Odd on the coffee but I do get where you are coming from based on my description. I buy in 250g packs and they are usually never more then a month after roast date by the time I use them. I keep them in a cupboard so not in direct light. Once opened they are in a Airscape canister so air is evacuated each time, does take me a week normally to use a bag so they are going stale at this point I guess.

Coffee will vary depending on all sorts of things. It could be the green beans, or it could be the temperature / humidity in your house that affects how fine you need to grind. It's never going to be a static thing. 

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Opened a fresh packet of coffee today and tightened the grinder up a little. Pressure only dropping about 1 bar during extraction which I think is normal. With the tighter grind and fresh beans the extraction of 18g to 40g took about 45 seconds and the output was very nice 😃

Thanks for all the help, this was entirely down to me then. Need to keep an eye on the beans and how long they have been opened for and watch for the shots changing as the beans go off....

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