This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Design a new piping layout for piped water supply

The modeling is done as per following philosophy;

The pump is delivering 200 cu.m/h water in two Overhead tanks (Top Filled). The pump is having a head of 35 m of H2O. But, I am surprised to see that the pipe towards tank 2 is not being able to carry any flow in this system. Please suggest the mistake that may be detected in this model.

One more thing I want to draw your attention that, while estimating the pump head by replacing the pump by two nodes (One with positive demand & other with the negative demand of same magnitude), the head comes out to be 35 m of H2O which is quite high as compared to as calculated by means of the Hazen William formula. Please throw some light on the design basis of pump head estimation by the above referred method (As Calculated by Water Gems) .

Also, we have tried to use Darwin designer in this connection. But, improvement of flow condition could not be achieved. The feasibility check unfortunately failed. While designing we generally provide some terminal head of 5 m at the tank inlet to nullify any unforeseen losses of head, how these terminal head can be implemented in this model. Please provide some guideline to design a new piping layout for piped water supply terminating with multiple no.s top filled over head storage tank while limiting the flow velocity in the range of 0.6 to 2.5 m/s.

The model is attached as zip file.

Regards,

Sujoy De

Bentley Mail 04-08-2016.rar

Bentley Mail 04-08-2016.rar

Parents
  • Hello Sujoy,

    Regarding the flow into the tanks, the reason there is no flow to tank T-2 is that the setting for the invert level for the inlet pipe is incorrect. The inlet pipe invert is a "level", not an "elevation". This means that the inlet pipe invert level is a value relative to the base elevation of the tank. You entered a value of 20.5 meters. However, for T-2, the invert level should be 5.5 meters. You will also want to chance the invert level for the inlet pipe for T-1, as this was not entered correctly either. For more information on modeling top file tanks, see the following link: communities.bentley.com/.../16833.modeling-top-fill-tanks-and-throttling-inlet-valves.

    Regarding the system head curves that Dr. Walski mentioned, the following link has some additional information on system head curves and how they work in WaterGEMS and WaterCAD: communities.bentley.com/.../24627.system-head-curves-in-watergems-and-watercad.

    Lastly, for the Darwin Designer question, Darwin Designer does perform an initial feasibility check where it uses the largest pipe sizes and checks minimum pressures. In your case, even with the pipes at the maximum diameter, there are nodes with a pressure less than the minimum pressure. That means the feasibility test has failed. The area with the low pressure is on the suction side of the pump. Low pressures on the suction side of a pump is not unusually, since the pump and reservoir may be at the same or similar elevations. However, this is making it difficult for your design study to work. I would removing J-9 from the Pressure Constraints tab in your design study. Designer will run past the feasibility test after that. You can find more information on Darwin Designer in the Help documenation and this link: communities.bentley.com/.../using-darwin-designer

    Regards,
    Scott

    Answer Verified By: Sushma Choure 

Reply
  • Hello Sujoy,

    Regarding the flow into the tanks, the reason there is no flow to tank T-2 is that the setting for the invert level for the inlet pipe is incorrect. The inlet pipe invert is a "level", not an "elevation". This means that the inlet pipe invert level is a value relative to the base elevation of the tank. You entered a value of 20.5 meters. However, for T-2, the invert level should be 5.5 meters. You will also want to chance the invert level for the inlet pipe for T-1, as this was not entered correctly either. For more information on modeling top file tanks, see the following link: communities.bentley.com/.../16833.modeling-top-fill-tanks-and-throttling-inlet-valves.

    Regarding the system head curves that Dr. Walski mentioned, the following link has some additional information on system head curves and how they work in WaterGEMS and WaterCAD: communities.bentley.com/.../24627.system-head-curves-in-watergems-and-watercad.

    Lastly, for the Darwin Designer question, Darwin Designer does perform an initial feasibility check where it uses the largest pipe sizes and checks minimum pressures. In your case, even with the pipes at the maximum diameter, there are nodes with a pressure less than the minimum pressure. That means the feasibility test has failed. The area with the low pressure is on the suction side of the pump. Low pressures on the suction side of a pump is not unusually, since the pump and reservoir may be at the same or similar elevations. However, this is making it difficult for your design study to work. I would removing J-9 from the Pressure Constraints tab in your design study. Designer will run past the feasibility test after that. You can find more information on Darwin Designer in the Help documenation and this link: communities.bentley.com/.../using-darwin-designer

    Regards,
    Scott

    Answer Verified By: Sushma Choure 

Children
No Data