Negative pressure can be due to several reasons, please see this support solution. It doesn't say that pump can’t deliver the flow or head.
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Forum Post: RE: Pump Selecting
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Wiki Page: What is the meaning of the message "The difference between calculated peak flow and interpolated peak flow is greater than x%"?
Applies To Product(s): Bentley PondPack Version(s): 10.00.XX.XX Environment: N/A Area: Calculations Subarea: Original Author: Terry Foster, Bentley Technical Support Group Error or Warning Message The difference between calculated peak flow and interpolated peak flow 21.5% is greater than 1.5%. Computed peak flow=3.09 ft^3/s Interp. peak flow= 2.43 ft^3/s. Output increment for this catchment may be too large. Explanation This warning is related to the SCS Unit Hydrograph Calculation. By default, the program computes an internal calculation time step based on .133TC for each subarea (each subarea has it's own unique time step for runoff). This procedure typically results in runoff time steps that differ from the overvall network time step specified on the GO dialog. Once the subarea runoff hydrograph is computed using this internal time step, the GO dialog time step is used to interpolate and create flow ordinates using the standard network time step so that all routing and hydrograph addition will be using the same time base. The default threshold for printing this error is when the interpolated peak differs by 1.5% (or greater) compared to the internal peak. This default threshold can be adjusted in version 7.5 via the Options / Global Settings menu item. For example, if you feel the 1.5% is too strict you can set PondPack to trigger the warning if there is 2.5%. How to Avoid This error message can usually be avoided by narrowing the timestep on the GO dialog in order to include an ordinant closer to the internally computed time peak. For an illustration, see the graph below. As you can see from the picture, using a timestep of 1 hour would have taken readings at the two places marked. The peak outflow occurs between those two places, and therefore there is not an interpolated peak at the true calculated peak.
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Forum Post: RE: Pump Selecting
Sushma Is inserting a useless reservoir to remove the Error Message (as I did above) correct or a better option can be suggested? Sim
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Forum Post: Help With setting up a VSP or VFD with 4 pumps.
Hi, Working with SewerGEMs, GVF-Convex solver. I need your assistance in setting up a VSP or VFD with the below on and off (elevations) controls. I want to use the fixed head VSP type and use my control node as the Wetwell. probably with a target HGL at midway of the lead pump. I have read around quite a bit about the VSP battery and does not seem to get me to where I need to be. Can the experts help me on this?? All my pump curves for the 4 pumps are set up already. Anybody?? LEAD LAG 1 LAG 2 LAG 3 OFF -8.35 -8.35 -6.85 -6.85 ON -6.35 -4.35 -2.35 -0.35
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Forum Post: RE: Help With setting up a VSP or VFD with 4 pumps.
The concept of a fixed head is fundamentally inconsistent with the idea of pumps coming on at different levels. Either you have a fixed head or you have pumps that come on at different heads. For this complicated of a case, you could either set a level that you will maintain and use the VSPB or you could set up individual pumps each with several control statements along the lines of IF(Level x and Level y) THEN Pump setting = 0.z
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Forum Post: RE: Help With setting up a VSP or VFD with 4 pumps.
Good. So, if I decide to use option one which is the using the VSPB, what will be the optimum control level I need to use to accomodate all 4 pump settings? As you can see 4 pumps OFF and ON settings spanning from -8.35 and -0.35. It appears I would not be able to associate additional levels with the VSPB. Correct??
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Forum Post: RE: Help With setting up a VSP or VFD with 4 pumps.
VSPB attempts to maintain a constant wet well level and will automatically turn pumps on and off to do so. It turns on an additional pump as soon as the current pumps can no longer keep up with inflow.
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Forum Post: RE: Help With setting up a VSP or VFD with 4 pumps.
Ok. I am trying to set up the VSPB. What is the difference between Battery Pump Definition and a Constant Speed pump definition??
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Forum Post: RE: Help With setting up a VSP or VFD with 4 pumps.
No difference, except that the one you select for the VSPB represents the pump definition of all the pumps in the battery whereas the one selected in the regular pump node represents that single pump. However, VSPBs and regular VSPs in parallel assume the pump definitions are the same, so you'd need to use the same pump definition anyways if you had multiple regular pump nodes in parallel, set as VSPs. The pump curve should represent full speed. The program automatically adjusts the speed (and scales the pump curve) during the simulation to maintain a fixed level in the wetwell (match the inflow) when the wetwell is selected as the target node.
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Wiki Page: How do I input the elevations for an irregular weir cross section in composite outlet structures?
Applies To Product(s): Bentley SewerGEMS, Bentley CivilStorm, Bentley PondPack Version(s): 08.11.04.54 Environment: N\A Area: Modeling Subarea: N\A Original Author: Mark Pachlhofer, Bentley Technical Support Group Problem Description How do I input the elevations for an irregular weir in composite outlet structures? Steps to Resolve The inputs for the elevations of an irregular weir cross section are based upon the invert elevation which is assigned to the weir located here: Any value you put in the cross section table is added to the invert elevation that you define. Therefore, if you just wanted to enter the physical elevation of the weir in the cross section table you'd enter the invert elevation as 0.
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Forum Post: Negative Demand
Hello Is HGL of a Junction that has a negative Demand equal to HGL of lowest Tank or Reservoir of the network? Sim
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Forum Post: Darwin Scheduler
Hello 1- In ‘Pumps to Optimize’ Tabs (In ‘Darwin Scheduler’), we can specify Pumps as ‘VSP’ or not (Decision Type column), in spite of specifying it before in property grid of those Pumps. Why we do it here again? Maybe we have specified a Pump in property grid as what is unlike in ‘Decision Type’. What will happen? Which Type is considered by software? Please explain a little more about. 2- Another question is that when we define ‘Pump Stations to Optimize’ Tab, it means that we have defined PUMPS of Pump Stations. Why do we have to define Pumps of Pump Station one by one again in ‘Pumps to Optimize’ Tabs. It seems repetitive and defining ‘Pumps to Optimize’ Tabs is not necessary. Sim
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Forum Post: RE: Negative Demand
Can you attach the model that you used to test this? Regards, Mal
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Forum Post: RE: Darwin Scheduler
The 'Decision Type' in Darwin Scheduler is independent of the setting in the main application. If you pick a pump for use in Scheduler you can specify whether you want it to act as a fixed speed pump (on/off) or as a variable speed pump (one which can have relative speeds 1.0). This allows you to determine whether there is any benefit, for example, to changing an existing fixed speed pump to a variable speed pump. You are right, it's not necessary to redefine pumps that are in a pump station under the pumps to optimize tab. Actually it's not able to be done since if you do it, Scheduler will generate a validation error, so I guess you didn't try this? Maybe if you could provide the context of your queries we would be able to assist better.
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Forum Post: RE: Negative Demand
Dear Mal Actually this question is sequel of the topic which you can read it and see the model here: communities.bentley.com/.../300764.aspx Have a look at model please. Mark suggested an idea to design and define Pump for network. For a closed System, I inserted a useless Reservoir (which has no flow) to remove Error message (Node is not connected to a boundary). After running the model, it shows that all Junctions have negative pressure which is related to low HGL of Reservoir, I think. This is all I have problem with it. Please help me finding out it. Sim
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Forum Post: RE: Negative Demand
Mal Have a look at this adapted model, run it and see what happens: R-3 has the lowest HGL between Reservoirs (ignore R-1) which is 10 m. Just J-3 and J-5 have HGL more that 10 m and these two Junctions will have negative pressure after running and another junctions which have HGL less that 10 m have positive pressures. Now compare the HGL of J-10 with HGL of Reservoirs. It means that "HGL of a Junction that has a negative Demand is equal to HGL of lowest Tank or Reservoir of the network". Sim
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Forum Post: RE: Reading Transient Results Viewer From WO.NET
Hi Jesse, I just uploaded the file following the instructions of the link you sent to me yesterday. I uploaded two files: a .zip file with my source code (called "ProgramaTesis_V01 - Bentley") and a ReadMe file explaining a little bit what I'm facing. Let now If you receive the file and If there is anything else I can do. Thanks in advance. Jessica B.
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Forum Post: RE: Reading Transient Results Viewer From WO.NET
Thanks for sending the files. We received them and will take a look shortly.
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Forum Post: RE: Help With setting up a VSP or VFD with 4 pumps.
Jesse and Tom - I went with Tom's recommendation (option 2) which is setting up individual pumps each with several control statements along the lines of IF(Level x and Level y) THEN Pump setting = 0.z as he shared above. I am analyzing a lift staion power failure and so I added an IF (Time from start is X) turn pump A off but my model is not responding to the pump off control at that time. I can see pumps turning on after that time. Am I missing something?? Please help..
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Forum Post: RE: Reading Transient Results Viewer From WO.NET
Jessica, Here are some recommendations based on a review of the source code: 1. Consider simplifying the approach. Don’t try to create an application (i.e. custom ApplicationModel, ParentFormModel, ParentForm, etc. classes) 2. Create a utility class that creates the instances of the Toronto classes (i.e. TorontoApplicationModel and TorontoParentFormModel should be sufficient). 3. Using the utility class you can open up the .WTG file. 4. With the TorontoParentFormModel instance you can cast the CurrentProject to TorontoProject in order to setup the classes needed to get to the transient results (summarized in another email). 5. There is a compute method on the TorontoParentFormModel that takes a scenario ID (or not). If no id is provided it assumes the active scenario should be computed. 6. Using the Compute method in the TorontoParentFormModel will configure the licensing automatically. If there is a license available then the computation should work. There would be a user notification if there is no license available.
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