PSV Cannot Supply Pressure and Caused ill-conditioning

I have a model setup that has a PRV and PSV in series. The PRV opens only if the pressure on side A of the system drops below 40 psi, otherwise it is closed. The model ran fine with the PRV. I then added a PSV to control the pressure on side B of the system. If the pressure dropped below 100 psi then the valve is to close. When I go to Analysis-> validate, no problems are found. However, when I run the model I get warnings saying PSV cannot supply pressure and PSV caused ill-conditioning. I am using this run to see how much fireflows will be increased on side A of the system, however, due to these warnings all fireflows are calculated at zero. Do you have any advice on how to troubleshoot this?

Thank you!

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  • Hello Scott and Jesse.

    I wanted to write this comment 3 years ago, but forgot, and now while working on one model, searched again and found this post

    As a addition to your suggested process, I noticed that biggest problems is when PSV is controlling downstream demand nodes. To avoid that, while simulating big consumers for which I need to reduce flow due to pressure drops, most beneficiary method was to introduce a water tank, empty one, and add demand to that water tank. Tank needs to be dimensioned so that available flow is not filling it, rather used only for satisfying added demand. In this way, PSV works great with no ill-conditioning.

    Hope you can try this method and add it to Wiki as an option.

    TANK (base elevation as node elevation, maximum little bit higher and initial level is 0) --> add demand with demand curve to that water tank, the same one that was on demand node --> set PSV as you want 

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  • Hello Scott and Jesse.

    I wanted to write this comment 3 years ago, but forgot, and now while working on one model, searched again and found this post

    As a addition to your suggested process, I noticed that biggest problems is when PSV is controlling downstream demand nodes. To avoid that, while simulating big consumers for which I need to reduce flow due to pressure drops, most beneficiary method was to introduce a water tank, empty one, and add demand to that water tank. Tank needs to be dimensioned so that available flow is not filling it, rather used only for satisfying added demand. In this way, PSV works great with no ill-conditioning.

    Hope you can try this method and add it to Wiki as an option.

    TANK (base elevation as node elevation, maximum little bit higher and initial level is 0) --> add demand with demand curve to that water tank, the same one that was on demand node --> set PSV as you want 

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