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How can I adjust the pressure on the system?

Hello everyone,

I´m using Hammer Bentley v8i and I can´t  get the discharge pressure on the system, I´m trying to simulate a positive displacement pump, and I should have a discharge pressure of 1100 psi and the program estimated  869 psi, instead. What kind of variable can I modify to adjust the discharge pressure according to the required value?  

Best Regards,

Parents
  • Hello,

    Similarly to this case, I want to simulate a positive displacement pump and I added a "Periodic Head-Flow" but on my network I have two check valves and when I run the system gets the error "Node is not connected to, or is isolated from, a boundary (reservoir or tank)" And I don't understand what happen because the direction of check valves is correct.

    For the other hand, I want to know how consider the viscosity changes for a heavy crude along the network.

    Thanks

    Regards
  • Lyanne,

    In addition to Mark's response, I will add that all modeling elements need to be hydraulically connected to a boundary condition; a reservoir or tank. The periodic head/flow element with a flow pattern injecting a specific flow rate into the system does not count as a boundary. In order to calculate the hydraulic grade, it needs to be connected to a tank or reservoir.

    If you still need help, you can provide a copy of your model. There are two options for sharing your model files on Communities. If you would like the files to be visible to other members, compress the files into a zip file and upload them as an attachment using the ‘Advanced Reply editor’ before posting. If your data is confidential, you can follow the instructions in the link below to send it to us via Bentley Sharefile. Files uploaded to Sharefile can only be viewed by Bentley.

    communities.bentley.com/.../7079.be-communities-secure-file-upload


    Regards,

    Jesse Dringoli
    Technical Support Manager, OpenFlows
    Bentley Communities Site Administrator
    Bentley Systems, Inc.

  • Thanks MPachlhofer and Jesse for your answers,

     Jesse I’m sending my model, I’ll explain you the main data:

    • The fluid is Crude 16°API
    • The total flow is 8750 gpm
    • The viscosity changes along the network as I show on the graphic:

     

     

    I used other simulator (Pipephase) to evaluate the data provided from final user where I considered the viscosity between 3494 @122°F and 791.9 @100°F, and I got the pressure on the network approximately (The initial and final pressure is 1538 psig and 18 psig respectly). I assumed average viscosity (1482.8 cS), this was used in Hammer but I'm not sure if this is correct. The operation temperature is 100 °F.

     First the fluid starts it's route through a screw pump (I want to simulate through “Periodic Head-Flow”) to a storage tank, also on the network I have two check valves in pipes P-127 and P-224 as you can see on the model. When I run the system it gets the error, and I remove the check valves and the system runs correctly. I have tried with Check Valve tool and the result is the same.

    Original TPC(1)-2.wtg_1_1.zip

    Thanks

    Regards

Reply
  • Thanks MPachlhofer and Jesse for your answers,

     Jesse I’m sending my model, I’ll explain you the main data:

    • The fluid is Crude 16°API
    • The total flow is 8750 gpm
    • The viscosity changes along the network as I show on the graphic:

     

     

    I used other simulator (Pipephase) to evaluate the data provided from final user where I considered the viscosity between 3494 @122°F and 791.9 @100°F, and I got the pressure on the network approximately (The initial and final pressure is 1538 psig and 18 psig respectly). I assumed average viscosity (1482.8 cS), this was used in Hammer but I'm not sure if this is correct. The operation temperature is 100 °F.

     First the fluid starts it's route through a screw pump (I want to simulate through “Periodic Head-Flow”) to a storage tank, also on the network I have two check valves in pipes P-127 and P-224 as you can see on the model. When I run the system it gets the error, and I remove the check valves and the system runs correctly. I have tried with Check Valve tool and the result is the same.

    Original TPC(1)-2.wtg_1_1.zip

    Thanks

    Regards

Children
  • Hello Lyanne,

    I'm not able to reproduce the "Node is not connected to..." issue. When I compute initial conditions in your model, it calculates correctly. There is a downstream boundary (the tank) and the check valves seem to be oriented correctly. I tested this both in your version (08.11.05.61) and in the latest version (08.11.06.58).

    Can you confirm that you've attached the correct model and the exact message you're currently encountering?

    There are some other problems that prevent the transient solver from calculating, but they are due to large negative pressure on the upstream side of your pump (at periodic head-flow "PER-6"). Do you need to include that in the model? If I remove the upstream side elements, the transient calculation completes without error, though there is very little happening during the transient simulation, since you have a reduction in inflow occurring over a 10,000 second period (and the simulation is only 300 seconds long)


    Regards,

    Jesse Dringoli
    Technical Support Manager, OpenFlows
    Bentley Communities Site Administrator
    Bentley Systems, Inc.

  • Hello Jesse,

    Yes, this is the model, I reproduce the error when I valid the network with the “Validate” tool, however when I use the "Compute initial conditions" and "Compute" tools, it doesn’t reproduce the error, now I don’t know if I should pay attention to the “validate” tool or not.

    Thanks for your attention.
  • Lyanne,

    Thanks for pointing that out. I do see the "node is not connected to..." notifications when using Validation. It appears that this occurs in a specific condition when you have a check valve between an inflow (negative demand or negative flow on a periodic head-flow element) an its downstream boundary condition (the tank).

    The validate procedure is likely thinking that the nodes in the model are downstream of the tank (normally the case if you have demands instead of an inflow) so when it reaches the check valve, it thinks the elements beyond are disconnected. I've reported this to our developers so they can clear up this confusion for a future release by amending the Validate tool to realize that the hydraulic connectivity check needs to be aware of the presence of inflows. (I see some challenges with this though, for example if demands on the nodes that exceed the periodic flow rate, then some might indeed be downstream of the tank)

    For now, yes, I would ignore those particular messages in the Validate tool, since the initial conditions calculation is successful.


    Regards,

    Jesse Dringoli
    Technical Support Manager, OpenFlows
    Bentley Communities Site Administrator
    Bentley Systems, Inc.

    Answer Verified By: Sushma Choure 

  • Thanks Jesse for your help,

    I appreciate your time and answers, they were very helpful. I hope we can keep communicating if I another problem continues presenting itself
  • Happy to help. If you have any questions in the future that you cannot find an answer to in our Support Solution (wiki) section, feel free to start a new thread on the forum.


    Regards,

    Jesse Dringoli
    Technical Support Manager, OpenFlows
    Bentley Communities Site Administrator
    Bentley Systems, Inc.