Applies To Product(s): Bentley SewerGEMS, Bentley CivilStorm, Bentley StormCAD, Bentley SewerCAD Version(s): 08.11.XX.XX Environment: N/A Area: Original Author: Mark Pachlhofer, Bentley Technical Support Group Problem What does the "Conduit discharge is above design discharge" user notification mean? What is the difference between the Capacity(Design) and Capacity(Full Flow) results fields? Solution This user notification means that the flow through the conduit is greater than the theoretical (Mannings equation based) capacity that you are designing for, which is given in the Capacity(Design) field. If this is a problem then you'd resolve it by making your conduit diameter larger. The automated design feature can also be used to size the pipes so this does happen (increase the pipe diameter until the flow is less than the design capacity). If you are already doing automated design and are seeing this notification, there are a few possible causes: There are no larger sized pipes in the conduit catalog with the same shape and material, with the check box set to be available for design The conduit type is set to user defined. Automated design will only work when set to a catalog conduit You have a design constraint set to limit the section size. See Section Size tab of the Default Design Constraints dialog. You may also notice that the same value is shown in both the "Capacity (Design)" and "Capacity (Full Flow)" fields. The difference between the two fields is that the Capacity (Design) can be a fraction of the Capacity (Full Flow) if the user has elected to do a "part full design". The default design options are set to design the pipe based on it being 100% full. This means selecting a pipe size at which the flow through the pipe is less than the Mannings-based flow through the pipe when the depth is equal to the rise (in other words the conduit is 100% full). In some cases, though you may want to design a conduit to a partially full value like 75% of the Capacity (Full Flow) of the conduit. This is done in the default design constraints manager, which can be accessed by going to Components > Default Design Constraints and clicking the check box for "Is Part Full Design?". See Also What is the difference between Capacity (Full Flow), Capacity (Design), Capacity (Excess), Capacity(Excess Full Flow)?

Hi Mark, I copied the file that you told me into the output folder, but the error is still appearing. Don't I need to make a reference? or am I missing another DLL file? Juan Sebastian.

Applies To Product(s): Bentley StormCAD, Bentley SewerGEMS, Bentley SewerCAD, Bentley CivilStorm Version(s): 08.11.xx.xx Environment: N/A Area: Calculations Subarea: Original Author: Scott Kampa, Bentley Technical Support Group Problem Description Why does the profile for the system appear to be at odds with the results for the capacity? For example, the profile does not show a conduit as being full, but the capacity results indicate that it is. For example, "Capacity (Full Flow)" = 50 ft^3/s and flow through a pipe is 60 ft^3/s, but the hydraulic grade is below the top of the pipe in profile view. The opposite symptom can also occur, where the profile shows the conduit as being full/surcharged yet the flow through it is less than the reported Full Flow Capacity. Steps to Resolve In short, it may be that the water in the pipe has not had a chance to reach a normal depth condition yet, in which case the result you see in the profile view should be considered, rather than the capacity result. The full capacity is the flow through the pipe if normal depth were equal to the top of the pipe. Using Manning's equation as shown below, the program calculates the "Capacity (Full Flow)" results of a pipe. The "Capacity (Full Full)" results are based on assumption that the flow through the pipe is absolutely at normal flow condition and the normal depth equals the rise of the pipe (for circular pipe the rise = diameter). Q = k/n*A*R^(2/3)*S^0.5 [Manning's Equation] At normal flow: • The water depth, flow area, flow, and velocity distribution at all cross-section and throughout the entire length of pipe remains constant. • The Energy Grade Line (EGL), Hydraulic Grade Line (HGL) and the Channel Slope are parallel. • The velocity/depth ratio is constant. • There is no acceleration or deceleration of the moving mass. You can verify this by using a simple Manning's equation normal depth calculator, such as Bentley Flowmaster. However, in SewerGEMS, CivilStorm, StormCAD, and SewerCAD, water does not always flow at normal flow; it computes a varied flow profile . As a result, the HGL slope can change over the length of the pipe. Because of this, the actual depth in the conduit can be different than normal depth and the "full flow capacity" results may not be a good comparison, especially with short pipes that may have otherwise achieved a normal depth condition if extended further. In the case of a pipe that does not appear full in profile, but has a flow that is greater than the capacity, then the gradually varying flow results that the model computes are telling you that the pipe is not flowing full, but the normal-depth based capacity results indicate that the pipe is full. The gradually varying flow results as seen in the profile should be considered in this case since they are a more true representation of what would happen in the real system, rather than the capacity result, which makes the assumption of normal depth. In this example case, to help visualize this in the actual model, try increasing the length of the pipe in question by 10 times the original length and then look at the profile of that pipe. You will notice that the upstream end of the pipe will extend above the top of the pipe as it tries to find a normal depth condition. If not, increase the length of pipe again. What this means is the initial pipe length is not long enough for the water surface to settle on the surcharge condition even though the flow exceeds the maximum capacity and therefore the HGL in the profile is not above the pipe crest elevation. If you see a discrepancy between the profile and the capacity results, that likely means that the profiles are likely not flowing at normal depth. In such a case, you may want to look at the " Depth (Average End)/Rise " result field instead. This is the middle depth of the pipe divided by the conduit diameter or rise, which gives you an idea of how full the pipe is at the midpoint when normal depth conditions are not met. In other words, it shows the actual calculated depth in the pipe in the gradually varying flow condition - the true result that the model predicts and should be considered over the capacity result. Example #1 - Flowing above full capacity yet not surcharged in profile Observe the following example pipe, whose "Capacity (Full Flow)" is 50 ft^3/s. This means that if normal depth were equal to the top of this pipe, the flow through it would be 50 ft^3/s. In this case, the flow through the pipe is 60 ft^3/s, yet the pipe is not surcharged. Now, observe what happens if we extend this pipe upstream. Notice that the hydraulic grade eventually reaches the top of the pipe, indicating the surcharge condition. This surcharging is not seen over the entire length of the pipe because there is a transition to a steeper downstream pipe. Example #2 - Flowing below full capacity yet surcharged in profile In this example we have a pipe with capacity of 29 CFS and a calculated flow through the pipe of 21 CFS, however, the profile shows that pipe is surcharged. The reason is because there is a tailwater / backwater effect from other flow entering downstream and causing a backup. Since the network is solved as a whole and the downstream HGL is essentially communicated upstream during the backwater analysis (SewerCAD and StormCAD solvers) or dynamic wave calculations (SewerGEMS and CivilStorm Implicit or Explicit solvers), the pipe in question becomes surcharged. The full capacity figure of 29 CFS is based on a normal depth assumption, but a normal depth condition is not experienced in this case, so the capacity figure is at odds with the profile/HGL.

Applies To Product(s): Bentley HAMMER Version(s): 08.11.xx.xx Environment: N\A Area: Modeling Subarea: N\A Original Author: Nancy Mahmoud, Bentley Technical Support Group Problem How to resolve the following user notification: "Initial pressure less than vapor pressure. At the pipe end(s), the elevation(s) or head(s) are incorrect". Solution Because of HAMMER's assumption of pressurized pipes, the occurrence of sub-vapor pressure in the initial conditions means that you would actually have a vapor pocket at that location, before the transient event even starts. Basically it means the model is not in a true steady state and the model needs to be fixed so that the pressures are correct. The solution to this is different for every model, as there are a number of factors that effect the pressure at a node. Trace the HGL from that node to the upstream boundary condition to get a better idea of why the pressure is that low. In one possible resolution, make sure that the pressures in your system in the initial conditions are above the vapor pressure. Review the pipe connections, and make sure the the elevation and head values correct. For instance, you should review the elevation data at junctions, pump, and reservoirs/tanks. For the reservoir, make sure that the value for "Elevation (Inlet/Outlet Invert)" is set correctly and makes sense in relation to the "Elevation". In some cases, these negative pressures could occur at a high point where an air valve would actually exist. In such a case, you can place an air valve at the high points to help with this issue. More information on this can be found in the Modeling air valves at high points TechNote. You would need to set the air valve property "Treat as junction?" to False and the program will know to have the upstream pump add enough head to overcome the high point. You may still end up with negative pressure downstream of the high point though, which means that the pipe will not be flowing full past the local high point at that flow rate. (It may flow full at other flow rates.) If the pipe is flowing partially full, then you may need to reevaluate your downstream boundary condition. The equations in HAMMER are based on full pipes. Once you get to partly full pipes, you need to change the approach. The downstream end of the HAMMER model should be the last pipe that is flowing full (crest of the last high point). You could end the system at a reservoir, demand or discharge to atmosphere element. Pump startup If you are simulating a pump startup event and you have high points that would normally experience part-full flow when the pumps are off, you could encounter this situation. The problem in this case is that the initial conditions solver is only aware of the downstream boundary condition - the reservoir elevation. So, if you look at a profile of the system, you will see a flat HGL. In the real system, assuming there is a check valve at the pump, water will probably remain in the pipes even after the pump turns off (with some air), and the weight of the water would result in an initial pressure above vapor pressure, but this is a challenging condition to simulate in a hydraulic model (initial conditions). The program is built upon the assumption that pipes are flowing full and energy is balanced based on boundary conditions. Even by placing the air valves on the main line and setting "treat as junction?" to "false", it can be difficult for the model to solve the "correct" initial conditions with zero flow. Here are three possible approaches to consider: 1) Set the transient calculation option "specify initial conditions?" to "true", then manually enter what you believe to be the correct initial HGL at each pipe. This will force the initial conditions for your pump startup run. You may need to specify an initial air volume at the air valve locations where part-full flow is expected. Related article: Purpose of the specify initial conditions calculation option 2) Start the initial conditions with the pumps on, use the "variable speed/torque" transient pump type with a pattern that gradually turns the pumps off (ramps down to zero RPM), waits for a while, then performs the desired start up. Basically allow enough time for any transient effects of the pumps turning off to settle down and establish a more accurate initial conditions, then have the pump start up. With this approach, you may find that air pockets continue to increase in size as long as the pump is off. This is due to limitations of air volume tracking, whereby (by default), the transient solver does not know the extent along the pipeline that the air pocket would travel and instead assumes that they are concentrated at the air valve location. You can consider using the Extended CAV transient calculation option to help with this, but it can only track the air/liquid interface to the extend of the adjacent pipe(s). Related article: Assumptions and limitations of tracking air or vapor pockets in HAMMER 3) End the system at the first high point that experiences part-full flow when the pump is off. You could use a discharge to atmosphere element to represent the opening at the top that essentially discharges to the part-full downstream pipe. This may be an acceptable approach if you only expect severe transients to occur in the segment of pipe between the pump and the the high point, since transient waves won't propagate across an air gap. However, you may want to assess possible transient effects of the release of air from the other air valves after the pumps start back up. See Also Modeling a case where an empty pipe is filling using Bentley HAMMER

Applies To Product(s): Bentley HAMMER Version(s): 08.11.xx.xx Environment: N\A Area: Modeling Subarea: N\A Original Author: Scott Kampa, Bentley Technical Support Group Problem Description How can I model a case where an empty pipe is filling using Bentley HAMMER? Steps to Resolve There are cases where a user may want to model an inrush event, or a case where an empty pipe is filling. Transient events can occur when the air in the empty pipe is expelled. It is possible to model such a case using the Discharge to Atmosphere element, but the user must be aware of some limitations with regard to the tracking of air pockets in HAMMER. When a pump turns back on in a water system or a sewer force main system, it may expel some air from the downstream end. The headloss through the discharge opening causes a resistance that can result in a severe upsurge once the water column reaches the opening. For example, if there is a small orifice at the end of the empty pipe, an upsurge can occur when the flow reaches it since the water cannot exit the pipe fast enough. If you need to analyze the transient effects of the air being expelled, this can be done by using the Discharge to Atmosphere element, operating as an orifice. The initial conditions must describe the low head condition (zero pressure at the discharge to atmosphere element) and you must enter a volume of air in the "Gas Volume (Initial)" field. You would then have the head increase during the transient simulation ( pump turning on or periodic head element on the upstream side with head value increasing, for example.) The "Flow (Typical)" and "Pressure Drop (Typical)" of the discharge to atmosphere would be estimated using the orifice equation. Basically the higher the "Pressure Drop (typical)", the smaller the orifice size, and the more resistance to flow, resulting in a higher upsurge after the air pocket is expelled. It is important to note that the larger the air volume you introduce into a HAMMER model, the less accurate the results may be, since you are deviating further from normal transient theory. Information on the assumptions made in HAMMER related to air and/or vapor in a transient simulation can be found in the theory section of the Help documentation. Also, the value entered for "Gas Volume (Initial)" will impact the timing of the release of the air. The value you enter will be up to your engineering judgment, but a good starting point may be the volume of the "empty" pipe. A larger volume of air for the same size orifice will take longer to be expelled from the D2A. This, in turn, will impact the head increase at the source. The most important impact on the system will occur with the air is fully expelled, which is when the transient would occur. So while a large air volume will take longer to expel, the setup and size of the D2A may prove to the be most important part of the transient event. Note also that if you're interested in simulating the time it takes for an empty pipe to fill, the timing of that will be influenced by the assumption that the air pocket is located at a discrete point (the D2A / high point). Using the D2A approach with the initial air volume set equal to the empty pipeline volume, the upstream pump would not "see" the correct head. Meaning, when it starts up, it will be pushing against an HGL equal to the high point, whereas in the real system, it will be pushing against a very lower head (since the pipe is drained) which will gradually increase as the rising pipe fills with water. This effects the flow rate from the pump operating point and therefore the time taken to fill the pipe. An alternative to consider would be to use the Implicit solver in SewerGEMS. See Also Modeling Reference - Discharge to Atmosphere "Initial pressure less than vapor pressure. At the pipe end(s), the elevation(s) or head(s) are incorrect"

Applies To Product(s): Bentley HAMMER V8i Version(s): 08.11.xx.xx Environment: N/A Area: Modeling Subarea: N/A Original Author: Jesse Dringoli, Bentley Technical Support Group Overview This technote describes the process by which a user can model a pump startup transient event in HAMMER V8i. It also provides an example model file for demonstration. Background In the previous version of HAMMER, V8 XM, a lengthy procedure was required to model a pump startup. (See [[Modeling a Pump start-up transient event in Bentley HAMMER|Modeling a Pump start-up transient event in Bentley HAMMER V8 XM]]) The user needed to first obtain the rated operating point of the pump by turning it on, then turn the pump off, copy the initial conditions to the user defined fields and enter the rated head/flow, along with valve initial status. This can be cumbersome in some situations. For this reason, HAMMER V8i introduced a new transient pump type called "Pump Start - variable speed/torque". This allows the user to specify the rated head and flow of the pump without having to specify initial conditions. This can greatly simplify the steps need to model a pump startup event. Setting up the Model for a Pump Start-up Before performing these steps, ensure that the demands, physical properties and other settings in the model describe the condition that you would like to represent. Meaning, if you would like to see the transient effects of the pump turning on during high demands and low tank level, ensure that the demands and tank level are adjusted as such. Ensure that the efficiency and transient rotational speed in your pump definition represent the "nominal" conditions. Meaning, the speed should be the speed at which the pump produces the flow/head seen when the pump in question is on (usually full speed), and the efficiency should be the efficiency at that nominal flow/head. This walkthrough also assumes a steady-state analysis for the initial conditions and that you have storage downstream of the pump in question, or other pumps, either of which could supply the demands you have entered when the pump in question is off. 1. First, turn the pump on by selecting "On" as the "Status (Initial)" under the Initial settings section of its properties. 2. Go to Analysis > Compute Initial conditions. This invokes the pressure engine to allow us to see the point where it would operate on its characteristic curve, when it turns on. 3. Double click the pump in question to view the properties. Under the "Results" section, you will see the pump operating point. Write down the values seen for "Flow (Total)" and "Pump Head". We will use these later on. If you have any active valves in the model (TCV, GPV, PRV, PSV, FCV, PBV), in places where the flow is zero or near zero in the initial conditions, you will need to find the correct discharge coefficient during this step. To do so, either check for the computed discharge coefficient in the results section of the properties, or temporarily select "true" for "specify initial conditions?" in the transient calculation options, click the valve, then go to Tools > Copy Initial Conditions, choose "selection", then OK - you will now see the discharge coefficient in the "transient (initial)" section of the properties. Record this value and set the "specify initial conditions?" calculation option back to "false". For any valves that you need to do this, morph them into a TCV, choosing "discharge coefficient" as the type, "Active" as the initial status, then enter the discharge coefficient that you recorded. If you do not do this, then HAMMER may use a discharge coefficient that will be inaccurate for higher flow rates once the pump turns back on. (since it will be based on zero or near-zero flow). 4. Under the "Transient (Operational)" section of the pump properties, select "Pump start - variable speed/torque" as the "Pump type (transient)" and enter the appropriate diameter. If the pump has a built-in check valve, enter "0" for the "Time (for valve to operate)", else enter the time that it takes for the built in valve to open (5 sec, 10 sec, 30 sec, etc...). To simulate a pump with no check valve enter a very small number like 0.1 seconds, so the valve is open immediately. Most likely you will enter zero for this. This is an important consideration - please read this article for more. 5. Enter the pump flow and pump head found in step 3, in the "Flow (nominal)" and "Head (nominal)" fields. 6. Change the pump's Status (Initial) under the initial settings to "off" and re-compute initial conditions. 7. Now we must define when and how fast the pump starts up. Go to Components > Patterns to open the Pattern manager. Right click on "Operational (Transient, pump)" select "new" and enter a name. On the right side of this window, enter zero for the starting multiplier, since the starting speed multiplier should be zero (meaning the pump is off.) In the bottom-right table, define the pattern of time versus speed multiplier. IMPORTANT NOTE : the multipliers you enter here multiply against either the speed or the electrical torque, depending on the selection you make for the pump's "Control Variable". If you choose Speed (the default), the multipliers multiply against the full speed entered in the pump definition, so 1.0 means full speed. This means that you cannot simply "flip the switch" in the pattern and have it go instantly from zero to 1.0 (or within a very small time frame) as it would normally take some time for the pump to "ramp up" to full speed. In the example below, the speed jumps from zero to 1.00 (full speed) between 6 and 7 seconds, and then stays on for the duration of the simulation. If the pump takes longer to "ramp up", then the pattern needs to be adjusted. 8. Close the pattern manager and select the pattern that you just created, from the "Operating Rule" dropdown in the pump properties. At this point, the pump properties should look similar to this: 9. The model is now correctly set up and you can compute the transient simulation. Go to Analysis > Compute. Note: If your pump is a variable speed pump ("Is variable speed pump?" = "True"), then you may encounter a notification stating that the rotational speed must be greater than zero. If you encounter this problem, you will need to re-run the initial conditions with the VSP turned on, note the computed relative speed factor, enter it as the "relative speed factor (initial)", set the initial status back to "off", set "Is variable speed pump?" to "false", re-compute initial conditions, then compute the transient simulation. Viewing the Results The results of this model can be viewed just like any other transient simulation. Go to Analysis > Transient Results Viewer. To view a graph of head and flow for the pump, you may want to select a time history for the pipe end adjacent to the pump: As you can see, when the pump starts up, a transient occurs. After about 40 seconds, the head/flow stabilize to the nominal conditions. Note that in many cases, you may not see flow start to occur through the pump until the speed has increased enough so that the downstream head can be overcome. You can also select a transient profile and click the "animation" button: As you can see, there are some problems with vapor pockets forming upstream of the pump when it starts up. A surge tank may be required in this case. Note that you can also view extended data specific to the pump, by entering a number for the "report period" attribute of its properties. For example, "10" would mean that extended data will be reported every 10 timesteps. You can view this report by going to Report > Transient Analysis Reports > Transient Analysis detailed report. At the very bottom of this text report, you will see the table of flow, speed, upstream and downstream head: Why is the Transient Simulation not Settling Exactly on the Nominal Head/Flow I entered? In some cases, once the pumps turn on in the transient simulation, they may not settle exactly on the nominal head/flow that you saw when you ran a steady state with the pumps on. This can be due to many reasons: If you're not ramping the pumps up to full speed but instead a relative speed factor other than 1.00, make sure the initial relative speed you entered is correct. The nominal head/flow are the pump head/flow corresponding to the relative speed value you put for "relative speed (initial)", even if the initial status if off. Their values should be equal to the values seen if that pump were to be turned on (at the same initial relative speed factor). For example, say you want a pump to start in the off position, then ramp up to 50% of full speed. First, set the initial relative speed factor to 0.5, initial status to off and transient pump type to pump startup. The nominal head/flow are set to the values seen in a steady state run at 0.5 relative speed. The transient pump pattern then goes from 0.0 to 1.0 multiplier. With that configuration, HAMMER understands that the nominal head/flow values correspond to a relative speed of 0.5. From the transient pump type, it knows that the pump will be initially off (zero flow/head) and that multipliers in the pattern multiply against the initial relative speed factor. This way, 0.0 represents the pump still being off and 1.0 represents the pump being at the initial relative speed factor, which corresponds to the nominal head/flow values. If you have any valves (GPV, TCV, PBV, FCV, PRV, PSV) that are active in the initial conditions, but in a location where there is zero flow due to the pumps being off, the calculated discharge coefficient (which the transient calculation engine uses) may not be an accurate reflection of that valve, when higher flow occurs. As seen earlier in this technote, you may need to compensate for any occurrences of this by finding the discharge coefficient in a steady state run with the pump(s) on, then replacing the valve with a TCV using that same discharge coefficient. Otherwise, the headloss across the valve in the transient simulation when the pump turns on will likely not match the steady state run that you based the nominal head/flow on. The biggest cause of this difference is with HAMMER's handling of friction coefficients. The transient calculation engine needs to use Darcy Weisbach friction factors (f), so a conversion is sometimes done. So, differences can occur if you use another method such as Hazen-Williams. This conversion is always done, even if you're using the Darcy-Weisbach method for the initial conditions, since the coefficient you enter for each pipe is the roughness height (e), not the friction factor (f). In pipes with non-zero initial flow, the Darcy Weisbach coefficient is calculated based on the headloss across the pipe. In pipes that have zero flow in the initial conditions (which may be the case for many of them, since the pump is off), the Darcy Weisbach coefficient will be computed based on the entered Hazen-Williams or Darcy-Weisbach coefficient. However, calculation 'noise' can sometimes occur in the initial conditions, causing the flow in a pipe to be near-zero instead of exactly zero. In your transient calculation options, you will see the tolerance that HAMMER uses to determine pipes that have zero flow, to account for this situation. In some cases, you may need to either make the "accuracy" value smaller in your steady state calculation options, or increase the flow tolerance value in the transient calculation options. Similar to the valve discharge coefficient item, if the flows are near zero but above the flow tolerance, the coefficient that HAMMER computes to use for that pipe may be unreasonable (since it's based on a tiny headloss), especially when higher flows occur when the pumps are on. This situation can happen even if your pipe has a 'real', non-zero flow that is relatively small. To check HAMMER's computed friction coefficients, open the "Output log" under Report > Transient Analysis Reports, and scroll down to the section titled "Pipe Information". Note that even if the zero flow pipes are correctly identified, the Darcy Weisbach friction factor that is computed based on the user entered friction coefficient may still differ from that of the ones based off a positive flow pipe's start and stop head. To check for this difference, run the transient simulation with the pump on and check the aforementioned Output log. If they differ by a lot, you may consider the "Unsteady - Vitkovsky" Transient friction method in the transient calculation options. Another approach to handle this would be to run the initial conditions with the pump on, record the friction factors from the output log, set the "specify initial conditions?" calculation option to "true", run the initial conditions with the pump off, use the "copy initial conditions" tool from the tools menu, then modify the transient initial flows so they are zero (when they should be) and initial friction factor (f) to the values seen in the output log with the pump on. This will force the pipes to use the correct friction factors. Note that version 08.11.01.32 and below of HAMMER have a known issue with the way that the friction factors are computed for zero flow pipes. A patch set is available for this version, which will be incorporated into future versions. Similar to the last item, if you have significant minor loss coefficients on pipes that have zero flow in the initial conditions, you may need to account for them with a different method. The reason is because those pipes will have their friction factor computed based on the entered friction factor only and will not account for the minor loss coefficient. Headloss across the pipe during the transient simulation will be based on the friction factor only. So, the pump may operate at a higher flow and lower head than you would expect, since it doesn't have as much losses to overcome once the pump is on. In this case, you may need to insert a TCV node and enter the headloss coefficient or insert an Orifice Between Pipes element and enter the flow and headloss seen during the initial conditions when the pump was on. If you have any tanks in your model, make sure their hydraulic grade is correct in the steady state run that you retrieved the pump nominal head/flow from. For example, you may want to choose "true" for "treat as junction" for a hydropneumatic tank, so the HGL at that tank in your pump=on steady state will be the value that it would settle on. Then, in the pump=off steady state run that your transient simulation starts with, either keep the tank treated as a junction, with the correct initial gas volume entered, or choose not to treat it as a junction, but enter the hydraulic grade that it would settle on when the pump is off. It is important to understand that HAMMER uses a special four-quadrant pump characteristic curve during the transient simulation, not the pump definition you entered for the initial conditions. These four-quadrant curves are based on your specific speed selection in the transient tab of the your pump definition and allow a pump to operate in all four quadrants (which can sometimes happen in a transient). The values from these curves are relative to your nominal head/flow, so for relative speed factors other than the one used for your nominal head/flow, it can result in slight differences. Since a pump startup case will be settling on the nominal head/flow, this should not make for a significant difference. However, a small difference could occur if the nominal operating point doesn't fall exactly on the four quadrant curve. In the pump properties, check the value for "Time (for valve to operate)". For pumps with zero initial flow, this represents the time to OPEN the valve. So, either enter a small number or enter zero, to represent a check valve. If you accidentally entered a large number here, the pump won't operate at the expected point since it will be working against a closed or partially closed valve. If all else fails, you could consider starting your transient simulation with the pumps on, then use the variable speed transient pump type to have them turn off then turn back on again. You can use the "Report history after" transient calculation option to have the transient reports begin after the pumps have settled in their off position. My pump operating rule is not be followed as expected See below article - this may be due to the "Time (for valve to operate)" Operating Rule not being followed after computing pump shutdown or start up Flow from pump is delayed after pump startup See below article - it typically takes some time for the pump to overcome the discharge hydraulic grade before is can pass flow. Flow from pump is delayed after pump startup Startup appears to occur too quickly / Initial surge too high If the pump appears to start up too quickly and the initial positive pressure spike appears to be higher than expected, it could be related to the Control Variable and the Operating Rule. See below article. Pump Startup occurs too quickly / initial upsurge too severe Error about pressure less than vapor pressure at high points If there are high points in the system, the initial conditions may not reflect the true system conditions with the pump off. See below article: "Initial pressure less than vapor pressure. At the pipe end(s), the elevation(s) or head(s) are incorrect" Example Model Click to Download Note: the above model is for example purposes only. It can be opened in version 08.11.00.30 and above and you can find additional information under File > Project Properties. See Also Modeling a pump shut down event in Bentley HAMMER Operating Rule not being followed after computing pump shutdown or start up Product TechNotes and FAQs Haestad Methods Product Tech Notes And FAQs External Links Hydraulics and Hydrology Forum Bentley SELECTservices Bentley LEARN Server Comments or Corrections? Bentley's Technical Support Group requests that you please confine any comments you have on this Wiki entry to this "Comments or Corrections?" section. THANK YOU!

Product(s): Bentley SewerCAD, Bentley SewerGEMS Version(s): 08.11.XX.XX Environment: N\A Area: Modeling Subarea: N\A Original Author: Scott Kampa Problem What is the difference between capacity (full flow), capacity (design), capacity (excess full flow), and capacity (excess design)? Problem ID#: 47015 Solution Capacity (Full Flow) is the capacity when the slope of the HGL (or friction slope) is equal to the pipe slope. Capacity (Design) can be less than the full capacity if the user specifies design based on some percentage of full pipe diameter ("rise" in a non-circular pipe). However, if you have your part full design under Components > Default Design Constraints set to 100%, this will be the same as the value for Capacity (Full Flow). Capacity (Excess Full Flow) is the difference flow of the calculated and the Capacity (Full Flow). Likewise, Capacity (Excess Design) is the difference of the flow calculated and the Capacity (Design). See Also The profile is at odds with the capacity (Full Flow) for a conduit

Jesse, Thank you so much for explaining the problem. I really appreciate your time in answering this question for me.

Applies To Product(s): Bentley WaterGEMS Version(s): N\A Environment: N\A Area: Layout and Data Input Subarea: N\A Original Author: KATHY WIGGINS, Bentley Technical Support Group Problem User gets error message 'There are no results available for the given input parameters. Please verify your data and try again.' when trying to import files into LoadBuilder. Solution This error message is generated when the units format of the file being imported and the WaterGEMS model do not match. The user needs to change the units format of one of the files so that the format of both files match.

I want a help. what about pressure benifits in Darwin designer? what about the equation ?

Hello Colleagues, I have a model set up in WaterGEMS and elevation extracted for each node using Trex.I need now to assign my demands to my nodes.My demands are per each sub-zone in an Excel spreadsheet I was able to draw thiessen polygons around my nodes but i am interested to know how i can now assign my demands to the respective nodes for the area served by each node. Any help will be appreciated. Kind regards, Simon

Hello Issam, Here is the information about pressure benefits in Darwin Designer.

If you had the demand data in the form of shapefiles for the zones, then you could use the tool called Loadbuilder. See the below information on that. With the demands in the excel sheet, you should have demands distributed to all the nodes. And then import them using Modelbilder.

Applies To Product(s): Bentley WaterGEMS, Bentley WaterCAD Version(s): 08.11.XX.XX Environment: N/A Area: Modeling Subarea: Original Author: Jesse Dringoli, Bentley Technical Support Group Problem What is the difference between Dimensionless and Unitized in the Benefit Type dropdown in the Design Type tab of a Darwin Designer Study? What is the purpose of the Pressure Benefit Coefficient and Exponent? Solution The “Benefit Type” allows you to choose how Designer considers pressure “benefit” (increase in pressure above the desired minimum) as it goes through trials of finding an optimal design and also the format of how it displays the overall benefit in the summary of a particular Solution. This applies to the “Maximize Benefit” and “Multi-Objective Trade-off” Objective types, where the “consider pressure benefit?” option is used in design events. After calculating a manual or optimized design and clicking the "Solutions" folder, you will see a "Total Benefit" column. This will show as either an overall percent increase (dimensionless) or overall average pressure increase (unitized). With the Benefit Type set to Dimensionless, Designer will consider the pressure benefit of a particular node based on a percent increase (unitless) of pressure above the desired minimum and will also display the overall benefit as an overall percent increase. On the other hand, with the Benefit Type set to Unitized, Designer will consider the pressure benefit of a particular node based on the actual increase in pressure above the desired minimum using actual pressure units (such as psi or Kpa). The overall benefit will be displayed as the overall average pressure increase for the saved solution.

I am a new user and i am trying to built simple network but i don't know where to put tanks. I also don't know about full purpose of tank and criteria about tank.

I am from Nepal and i want to buy book ( Advanced Water Distribution Modeling and Management) but here is not any distributor. So i think to buy from UK through my relatives so what should be the procedure to buy through my Student Account. And What is the difference between book for Users, Educators and Students other than price.

Can you buy it using the following link? https://store.bentley.com/en/products/9781934493014--Advanced-Water-Distribution-Modeling-and-Management Price is the only difference that I'm aware of.

Hello Dilip, The location of tanks in a water distribution network depends on the site and how you want to design it. The book Advanced Water Distribution Modeling and Management contains information on tanks that I recommend reading. I see from your other post that you are already interested in purchasing the book. The WaterGEMS help article "Tanks" and "Tank Attributes" contains information on how tanks function in the product. I recommend reading through those references, then post any remaining questions you have in detail.

Product(s): Bentley WaterGEMS, Bentley SewerGEMS, Bentley CivilStorm, Bentley StormCAD, Bentley PondPack, Bentley SewerCAD, Bentley HAMMER, Bentley WaterCAD Version(s): 08.11.XX.XX Environment: N\A Area: Modeling Subarea: N\A Problem Elements deleted from the model still appear in the flextable or in the drawing pane. Is there a way to fix this? Problem ID#: 71490 Solution This is a rare occurrence and is usually an indication that there is some sort of corruption in a file. Option 1 - Compact the database Run the compact database tool found by going to Tools > Database Utilities > Compact Database Option 2 - Delete the backup and report files Or isolate the model files Delete all the backup (.BAK) and report files (.OUT, .RPC, .ALM, etc...) or move them to a different folder location. When you have only the .wtg and .wtg.mdb (.wtg.sqlite) (or .stsw and .stsw.sqlite for the storm and sewer products) files in a folder open the model file and trying to deleting the errant element(s) or run the compact database again. Option 3 - Import the database Import the database file by going to File > Import > database and choose the database file.

Thank you for reply sir. I already gone through article Tank and Tank attribute but i don't know theory behind it where to locate and criteria behind it.