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Does flow rate matter when testing pressure on Silvia?

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  • jazzleg
    replied
    Originally posted by MattAttack View Post
    Hi snobs,

    In the quest to improve the espresso coming from my Silvia, I want to test the pressure and adjust the over pressure valve if necessary. There are some commercial portafilter-fitted pressure gauges that are not too expensive, but I have a question about their function.

    The commercial gauges don't appear to allow any water to flow through. An alternative would be to assemble a T-piece coming off the pf, with a drain valve on one side and a gauge on the other. One could then adjust the drain valve to allow about 1-1.5ml/s of water out (roughly a good espresso flow rate), and check the pressure at that flow rate.

    My question is, does the function of the opv make the flow on the pressure test unnecessary? Will the machine max out at whatever pressure the opv allows, regardless of the flow rate (or lack thereof)?
    OPV defines the maximum pressure. Therefore, simulating water outflow from the portafilter is irrelevant for this purpose (i.e. to adjust the OPV pressure). Without any OPV, the pump has the power to generate much higher pressure (up to 20 bar if I remember correctly). The pump constantly runs at 100% power (let's assume it's 20 bar), but the OPV will release the extra pressure so that the pressure that hits the group head will always max out at the OPV pressure limit.

    However, it is a different situation if you want to use the pressure gauge to measure custom pressure profiling (e.g. modulating the pump power to ramp up / down the pressure), which will need some resistance to simulate a coffee puck (hence, some limited water outflow might be relevant).

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  • Jackster
    replied
    The testers generally leak a bit, so that is some flow..

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  • MattAttack
    replied
    Originally posted by barlo View Post
    I don't know how much your planned design might cost but have you looked at Greg's loaner? https://coffeesnobs.com.au/forum/equ...ge-on-the-road
    His design does a damn fine job.
    Thanks barlo, I wasn't aware of that so I might send Greg an email

    Leave a comment:


  • level3ninja
    replied
    No for pressure you don't need flow, as you say it just goes out the OPV. With temperature the flow matters, but pressure not so much.

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  • barlo
    replied
    I don't know how much your planned design might cost but have you looked at Greg's loaner? https://coffeesnobs.com.au/forum/equ...ge-on-the-road
    His design does a damn fine job.

    Leave a comment:


  • Does flow rate matter when testing pressure on Silvia?

    Hi snobs,

    In the quest to improve the espresso coming from my Silvia, I want to test the pressure and adjust the over pressure valve if necessary. There are some commercial portafilter-fitted pressure gauges that are not too expensive, but I have a question about their function.

    The commercial gauges don't appear to allow any water to flow through. An alternative would be to assemble a T-piece coming off the pf, with a drain valve on one side and a gauge on the other. One could then adjust the drain valve to allow about 1-1.5ml/s of water out (roughly a good espresso flow rate), and check the pressure at that flow rate.

    My question is, does the function of the opv make the flow on the pressure test unnecessary? Will the machine max out at whatever pressure the opv allows, regardless of the flow rate (or lack thereof)?
    Last edited by MattAttack; 2 August 2020, 09:04 PM.
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