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Thread: Inexpensive home made portafilter pressure gauge

  1. #1
    Member SamR's Avatar
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    Inexpensive home made portafilter pressure gauge

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    Recently changed the OPV valve on my V2 Silvia. Seemed to operating at a higher than normal pressure and given the propensity for the Silvia's to be wound up a bit high out of the box I rigged up an inexpensive portafilter pressure gauge and made the appropriate OPV adjustment. It's now bang on 9 Bar (900 ATM) and pulling much better shots.

    For those interested, it's a liquid filled Holman pressure gauge from Bunnings for $15.90 and a brass reducer from 'Total Eden' for $6.00.




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    There is now a guy out of Spain I think on ebay, who sells one for about $35, which I decided was worth while vs making my own, only catch for me was it was not till I was trying it out today, I realized Lelit grind out two slots in the group, making my purchase now somewhat useless.

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    Nice job Sam.

    Two questions for you:

    - is there a hole to allow flow anywhere? (If not, your flowing group pressure may not be what you think it is)
    - What is the pressure rating of your brass fitting?

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    Good headup Sam

    BTW do you recall the thread sizes on the reducer?

    Quote Originally Posted by MrJack View Post
    Nice job Sam.

    Two questions for you:

    - is there a hole to allow flow anywhere? (If not, your flowing group pressure may not be what you think it is)
    the flowing group pressure is going to be a reducing pressure through the system from the set value of the OPV to atmosphere at the exit of the Group head regardless.
    By gagging the group head you will see pretty close to the OPVs adjusted value as the pressure would rise throughout the system to very close to the static pressure of the OPV (unless there is a leak somewhere).

  5. #5
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    Nice cheap gauge for sure but for this purpose the guage really needs to go up to ~16bar. 10bar may have been ok in this case because the machine was already set to roughly 10bar but many will be running much higher pressure (up to aprrox 17bar) and will destroy the gauge pretty quickly. Sorry to put a damper on things.

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    Quote Originally Posted by koshari View Post
    Good headup Sam

    BTW do you recall the thread sizes on the reducer?



    the flowing group pressure is going to be a reducing pressure through the system from the set value of the OPV to atmosphere at the exit of the Group head regardless.
    By gagging the group head you will see pretty close to the OPVs adjusted value as the pressure would rise throughout the system to very close to the static pressure of the OPV (unless there is a leak somewhere).
    A few thing to consider:
    A) you're not interested in the OPV setpoint, you're interested in the group head pressure
    B) When flowing, there is pressure drop between the OPV and the group, so the group pressure will be slightly lower than the OPV setpoint.
    C) Dead heading the group means that all the flow is directed to the OPV - this may increase the pressure at the OPV.


    The effect is small, but real.
    Last edited by MrJack; 8th December 2014 at 08:40 PM.

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    Sam - do you recall the thread sizes on the reducer?



    the flowing group pressure is going to be a reducing pressure through the system from the set value of the OPV to atmosphere at the exit of the Group head regardless.
    By gagging the group head you will see pretty close to the OPVs adjusted value as the pressure would rise throughout the system to very close to the static pressure of the OPV (unless there is a leak somewhere).[/QUOTE]

    So given that Sam progresses to STAGE 2 group pressure gauge - IF he adds a 'T' piece thread adapter ( in place of the female / male thread adapter there now) - with an adjustable tap to allow adjustable flow up to 30ml in say 30sec
    The question is would this more closely replicate group head pressure as measured as per a normal shot situation?

    PS anyone care to comment who has seen / used Greg Pullmans 'gauge on the road' and how itis setup?

  8. #8
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    Greg's gauge is pretty much set up as you've described, with what appears to be a bespoke needle valve downstream of the pressure gauge connection.

  9. #9
    Senior Member LeroyC's Avatar
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    I was of the understanding that the no flow or 'static' pressure should be 10bar as this generally indicates a dynamic (with flow) pressure of 9bar. Also the problem with a standard gauge from Bunnings is that it's temperature range probably only goes as high as 50-60degC. So when you are testing water that is obviously hotter than this you can't guarantee an accurate reading. These are all the reasons that stopped me doing the same thing and had me searching the net for a suitable gauge. I actually found one on the bay, purpose built for the task, sold by Edesia Espresso in the UK. I've tested it once and it seems to work well.

    ImageUploadedByTapatalk1431207481.561100.jpg

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    Quote Originally Posted by LeroyC View Post
    I was of the understanding that the no flow or 'static' pressure should be 10bar as this generally indicates a dynamic (with flow) pressure of 9bar. Also the problem with a standard gauge from Bunnings is that it's temperature range probably only goes as high as 50-60degC. So when you are testing water that is obviously hotter than this you can't guarantee an accurate reading. These are all the reasons that stopped me doing the same thing and had me searching the net for a suitable gauge. I actually found one on the bay, purpose built for the task, sold by Edesia Espresso in the UK. I've tested it once and it seems to work well.

    ImageUploadedByTapatalk1431207481.561100.jpg
    Leroy. All guages are calibrated at 20 degrees c.

    Cant see it being a problem at 100 degree c. At work we put pressuse gusges on piping with much greater temperature. Besides with a small length of pipe/hose the there is little chance the actual guage will even get warm.
    Last edited by koshari; 10th May 2015 at 07:07 AM. Reason: Additional
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  11. #11
    Senior Member LeroyC's Avatar
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    Quote Originally Posted by koshari View Post
    Leroy. All guages are calibrated at 20 degrees c.

    Cant see it being a problem at 100 degree c. At work we put pressuse gusges on piping with much greater temperature. Besides with a small length of pipe/hose the there is little chance the actual guage will even get warm.
    Interesting. I looked at getting a gauge from Horshams as we can get them through work and they're a high quality gauge. But they said the operating temp range only went up to 60degC. They said it would probably work fine well above that, but they couldn't guarantee its accuracy. I guess they just have to say that for a bit of risk aversion.

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    You aren't going to pull shots through it nor leave it connected to the machine for long periods so it's not going to reach brew temp.

  13. #13
    Senior Member LeroyC's Avatar
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    Yeah I realise that, I don't think they're worried about the gauge getting hot. I think it's pretty standard for industrial instruments to have an operating range and for these gauges that are calibrated at 20degC their operating range doesn't extend beyond 50 or 60deg. I guess as the density of the product that's being tested changes this could affect the reading given by the gauge. It's probably minimal, but I wouldn't know. Maybe there's an engineer here that can explain it better.

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    Quote Originally Posted by LeroyC View Post
    I was of the understanding that the no flow or 'static' pressure should be 10bar as this generally indicates a dynamic (with flow) pressure of 9bar.
    Maybe, maybe not. This will depend on the OPV and the piping between the pump and the group. It's possible that machine designers typically aim for a pressure drop of 1 bar at normal flowing conditions, but if you're going to the effort of building a measurement assembly, why rely on such an assumption?

    I did test this with Greg's gauge, but I forget what the difference was on my machine.


    With respect to temperature, I suspect that the 60C limit has more to do with the gauge itself (and any fluid within) than the fluid being measured.

    There could be other reasons for such limits (although most a likely to be more relevant in industry than at home), such as material issues with soft components or corrosion.

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    Similar to MrJack, it does make a bit of a difference but I can't recall the amount. It wasn't enormous, I think it might have been a bar or maybe a bit less, not a lot but it's there which is why I put the bleed mechanism into mine. I always think being able to check the pressure at the group is the most important factor, my Giotto has a boiler and pump pressure gauge but invariably the pump pressure gauge doesn't correlate exactly with what's at the group.

    I've got one of those Holman gauges at home for checking mains pressure but they do only go up to 10 bar. I bought my gauge several years ago now but made sure I got one which went up to 16 bar (heck if it's pushing out more than that you shouldn't be drinking it! ). IIRC the whole assembly cost around $100 (the gauge itself was about $60 but it was a fairly good quality one), and the fittings, bleed mechanism etc added the rest. It's just about to come back to me for a check-up but last time I got it back it was still running fine.
    Last edited by gregpullman; 22nd May 2015 at 10:25 AM.

  16. #16
    Senior Member noidle22's Avatar
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    This is one I built today. I required it to test the group pressure on a Boema being boosted by a Flojet that is pulsing rather than being continuously running during a shot.
    As a result, the inlet water pressure pulses (as seen on the machine's water pressure gauge) but whether the rotary pump takes care of the pulses and outputs steady pressure to the group I'm not sure. The rotary pump doesn't sound like it is pulsing and the shots coming out of the machine are steady and taste good so it should be ok but I wanted to be sure.

    Total cost of this was around $75 from Masters. If I went to Bunnings and got the gauge there I could probably have saved around $20 or so.

    Standard fitting sizes for most portafilters as far as I can tell is 3/8" BSP. The gauges and needle valve weren't available in 3/8" so I used reducers to get 1/4".

    boema pressure gauge.JPG
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  17. #17
    Senior Member LeroyC's Avatar
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    Quote Originally Posted by noidle22 View Post
    This is one I built today. I required it to test the group pressure on a Boema being boosted by a Flojet that is pulsing rather than being continuously running during a shot.
    As a result, the inlet water pressure pulses (as seen on the machine's water pressure gauge) but whether the rotary pump takes care of the pulses and outputs steady pressure to the group I'm not sure. The rotary pump doesn't sound like it is pulsing and the shots coming out of the machine are steady and taste good so it should be ok but I wanted to be sure.

    Total cost of this was around $75 from Masters. If I went to Bunnings and got the gauge there I could probably have saved around $20 or so.

    Standard fitting sizes for most portafilters as far as I can tell is 3/8" BSP. The gauges and needle valve weren't available in 3/8" so I used reducers to get 1/4".

    boema pressure gauge.JPG
    With the gauge being off to the side is there not an opportunity for the flow to bypass it and give an inaccurate dynamic reading?

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    Nice! That's basically how I set mine up. Though at $75 you have to consider whether it's worth the effort when 1) a purpose-built gauge from coffeeparts etc is around the same price, and 2) you only need to use it once! Still it's a useful DIY project you can take some pride in! I originally had a tap like that at the bottom of mine but found it didn't give fine enough adjustment of the flow rate so went to the needle valve instead. Leroy, so long as the flow is minimal this wouldn't be an issue, and once the flow rate is set the pressures would equalise.

  19. #19
    Senior Member noidle22's Avatar
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    That is a needle valve at the base, just looks like a tap. I did consider the price of the coffeeparts one as I was purchasing the parts yesterday haha. I can remove this and fit it onto another pf which is the benefit.

    I have the E61 gauge from coffeeparts at work which I use but this one will end up being used many times on many machines.

    LeroyC, once the fittings have filled up with water, the pressure will stabilise and be effective on both the tap and gauge. If there a problem I'll fiddle with positioning and see if it changes.

  20. #20
    Senior Member LeroyC's Avatar
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    Quote Originally Posted by noidle22 View Post
    That is a needle valve at the base, just looks like a tap. I did consider the price of the coffeeparts one as I was purchasing the parts yesterday haha. I can remove this and fit it onto another pf which is the benefit.

    I have the E61 gauge from coffeeparts at work which I use but this one will end up being used many times on many machines.

    LeroyC, once the fittings have filled up with water, the pressure will stabilise and be effective on both the tap and gauge. If there a problem I'll fiddle with positioning and see if it changes.
    Cool, good to know. I did think that was a tap rather than a needle valve. Nice work.

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    Quote Originally Posted by noidle22 View Post
    This is one I built today. I required it to test the group pressure on a Boema being boosted by a Flojet that is pulsing rather than being continuously running during a shot.
    As a result, the inlet water pressure pulses (as seen on the machine's water pressure gauge) but whether the rotary pump takes care of the pulses and outputs steady pressure to the group I'm not sure. The rotary pump doesn't sound like it is pulsing and the shots coming out of the machine are steady and taste good so it should be ok but I wanted to be sure.
    I would suspect that the pump is single speed, so would expect increasing the suction pressure will likely result in a corresponding increase in discharge pressure. Since the pump itself isn't changing speed you might not hear any "pulsing".

    Quote Originally Posted by LeroyC View Post
    With the gauge being off to the side is there not an opportunity for the flow to bypass it and give an inaccurate dynamic reading?
    Not necessarily. That's how industrial pressure sensor/gauges are typically connected.

    Bernoulli's equation is a reasonable model of laminar flow (based on an energy balance). According to this equation, the difference between pressure at static conditions and under flowing conditions is primarily the impact of frictional losses and velocity head: Frictional losses are pressure energy which is lost as heat due to friction (both within the fluid and with the pipe wall) - there are no frictional losses between the tee and the gauge, as the fluid there is essentially static.

    Velocity head is the pressure energy which is 'lost' accelerating the fluid through an area of reduced cross section (like in a venturi). Some of this is "recovered" as the cross section increases again (and thus the pressure increases). If your gauge was connected to a tee which had a reduced cross section, then you might get a less representative measurement. It would still be an accurate measure of the pressure in the tee; but the pressure in the tee would be different to that downstream.

    Clear as mud?

  22. #22
    Senior Member noidle22's Avatar
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    Well I tried the gauge and I've done something differently from everyone else somehow.
    When the connections fill with water and pressure starts to build, instead of the needle valve acting as a small pressure relief, the water is pushed back up the fittings and squirts out between the filter basket and portafilter rim.

    Even with the needle valve fully open the same thing happens, the water squirts back out of the top. The gauge doesn't read at all.

    I will have to fiddle with the positioning of the gauge components I think, not sure why this is happening. I tried it on a few different machines and it happens on them all so it's not the Boema that's the problem.

    You seem particularly knowledgeable about these things MrJack, do you know why this might be happening?

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    Are you testing this with or without your filter baskets?

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    Sorry, i just re-read your post. Seems you are testing it with the filter basket. You shouldn't be doing this with your filter basket.

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    I have a vague recollection of Gregs instructions including a cardboard gasket between basket and portafilter?

    Otherwise jjjones could be on the money; the portafilter is not designed to seal against the filter, the filter is designed to seal against the group head.

  26. #26
    Senior Member noidle22's Avatar
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    Yes these suggestions make sense. The proper ones from coffeeparts don't use baskets either.
    I should have remembered that.

    Thanks for pointing out the obvious things that I miss sometimes haha. I'll give it a go and see what happens.

  27. #27
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    Nice thread - FWIW there's several others on other coffee forums and a common suggestion in lieu of a needle valve or similar (to provide a very minor release/flow point of ~1ml/sec) it's suggested that by screwing it to the PF with NO teflon tape - and leaving a very slightly leaky joint the same result could be accomplished.

    Now obviously yo'd have to adjust to get right (as those with needle valves etc have to) but is a simple solution that should in theory give the same result. :-)

    Also with the Edesia Espress gauges I was JUST ABOUT to buy one and then noticed that it wasn't liquid filled. Now I know that given it'll prolly only be used a handful of times this isn't an issue but it strikes me as a very cheap gauge (you can buy suitable Chinese ones for as little as $AUD3 posted) dolled up as something a tad special.

    I'm thinking I'll get the Holman one from Bunnings....BUT as it only goes to 10 bar I'll dial my Silvia down IN ADVANCE - and then just wind it back on up until I get it to the desired setting, presumably 9bar.

    Sounds logical and then I can use the superior quality gauge, thats available todayand not worry about if my machine is at 10+ bar damaging it. Win-win.
    Last edited by nikko.the.scorpio; 15th July 2015 at 09:29 AM.

  28. #28
    Senior Member nikko.the.scorpio's Avatar
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    FWIW got the spout off the Silvia V3 PF (drilled two holes in a piece of scrap wood and twisted).

    All the different pipe/connector etc sizes have confused me a tad......the Silvia's male PF spout thread is ~15mm in diameter, which concurs with it being 3/8"BSP. However nearly all the pressure gauges I can find on Ebay (local Bunnings didn't have the Holman and said they wouldn't be getting it back!) are ~10mm connectors, which is 1/8"BSP.

    Essentially getting a 3/8"BSP male to connect with a 1/8"BSP male is a bit tricky (especvially when generally the gauges have the connectr on their rear, so needing an elbow joint tossed in)! Any ideas welcomed .

    PS. NVM, ended up finding a 3/8"BSP (0.55"NPT) gauge which will fit into a 3/8" BSP elbow - no reducers etc needed - total cost ~$AUD8 delivered. ;-)
    Last edited by nikko.the.scorpio; 15th July 2015 at 02:52 PM.

  29. #29
    Mal Dimal's Avatar
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    G'day Nikko...

    Just as an aside...
    When you get around to the stage where you are using your new pressure gauge setup, ensure that your machine is up to operating temperature before adjusting your OPV. A Cold setup result can vary quite a bit from a Hot result, I've measured up to as much as 1.0Bar difference, so it is important that if you're going to go to all this trouble, that you take into account all influencing factors...

    All the best,
    Mal.
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  30. #30
    Senior Member nikko.the.scorpio's Avatar
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    Quote Originally Posted by Dimal View Post
    G'day Nikko...

    Just as an aside...
    When you get around to the stage where you are using your new pressure gauge setup, ensure that your machine is up to operating temperature before adjusting your OPV. A Cold setup result can vary quite a bit from a Hot result, I've measured up to as much as 1.0Bar difference, so it is important that if you're going to go to all this trouble, that you take into account all influencing factors...

    All the best,
    Mal.
    Thank you Mal, I'll be sure to ensure I follow your advice - thank you for taking the time to share it. Cheers and thanks, Nick
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    I tried to do a pressure test on a Carimali Beta E2 and with the basket it does not work. Without the basket it does not seal even with a new seal. The portafilter has 3 lugs and a stop. Meaning you can not turn it past a certain point in order to get the portafilter to seal.
    Do you have any suggestions?

  32. #32
    Mal Dimal's Avatar
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    G'day Marc...

    Do you have any photos of your PF Gauge?

    Mal.

  33. #33
    Senior Member artman's Avatar
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    Get an old basket and hack a hole in the bottom. Unless the holes are very small and the flow significant (which both shouldnt be) the basket should not effect the reading greatly.

    Cheers
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  34. #34
    Mal Dimal's Avatar
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    Behmor Brazen - $249 - Free Freight
    Snap...

    What I was going to suggest after seeing what is currently being used...

    Mal.



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