A Basic InfoSewer Wet Well, Pump and Force Main System

Note:  A Basic InfoSewer Wet Well,  Pump and  Force Main System

Pump / Force Main System in InfoSWMM and SWMM 5 - with Emojis

Subject: 🚀 Pump / Force Main System in InfoSWMM and SWMM 5

Introduction: 💡 The Pump/Force Main system in InfoSWMM and SWMM 5 is a critical component for effective wastewater management. It ensures that wastewater flows smoothly from its source to the desired destination. Let's explore its components and the steps to set it up!

📌 The Basic System:

• Wet Well with its parameters 🕳️
• Pump Type 🔄
• Defined Pump Curve 📈
• Downstream Pressure Node 📍
• Downstream Force Main 🛤️

Figure 1:  The Basic System

Step 1: Wet Well Data 📋

• Input the invert elevation and maximum depth of the Wet Well.
• Define the shape, considering evaporation or infiltration factors.

Step 2: Define the Pump Type 🔄

• The pump's operation is guided by its Pump Curve and the set On and Off elevations.
• The four primary pump types include:
  • Volume - Flow 🌊
  • Depth – Flow 📏
  • Head – Flow 📌
  • Depth - Flow 📊

Step 3: Define the Pump Curve 📈

• Under the Operation Tab, outline the desired pump curve to ensure efficient pump functioning.

Step 3:  Define the Pump Curve in the Operation Tab 

Step 4: Set a Surcharge or Pressure Depth 🌡️

• By setting a positive Surcharge Depth at the Downstream node, you ensure that during the simulation, the node remains pressurized, driving the flow through the Force Main.

• This plot offers a visual representation of the hydraulic gradient line (HGL) for the Force Main System, showcasing the pressure changes within the system.

• Define the downstream conduits emerging from the pump as Force Mains.
• Choose either the Hazen Williams or Darcy-Weisbach coefficient based on your requirements. (This is typically set in SWMM 5 options or InfoSWMM's Run Manager.)

Step 5: Force Main Data 🛤️

Step 6: HGL Plot of the Force Main System 📊

  

Step 7: Pump Summary 📑

• Refer to the RPT File to get a comprehensive summary of the pump's performance and other related parameters.

Conclusion: 🌟 Setting up the Pump/Force Main system in InfoSWMM and SWMM 5 is a meticulous process but ensures efficient and effective wastewater management. Following these steps will ensure a robust system in place! 🚀🌊🛠️

SWMM 5 Pump Curve Head/Flow Curves (1)

Subject:  The Pump flow is based on the lookup table you enter for the pump (Figure 1).  At each iteration during each time step of the solution SWMM 5 will look up the flow for thepump based on the current control variable across the pump.  The control variable for the pump can be one of four variables:

1.   The volume of the upstream wet well,

2.   The depth of water at the upstream node or inlet node without interpolation between data points,

3.   The downstream water surface elevation across the pump minus the upstream water surface elevation, and

4.   The depth of water at the upstream node or inlet node with interpolation between data points.

The pump summary table in the rpt file will tell you how often the pump was used, the maximum flow, the average flow, the total volume of the pump, the power usage and the percent of the time off the entered pump curve.  You can also plot the pump flow versus the inlet depth to see how often the pump was off the pump curve (Figure 2).

Figure 1:  Plot of Head and Flow for Pump PUMP1@82309e-15009e over time along with the input and output table for the pump.

Figure 2:  Plot of Head versus Flow for Pump PUMP1@82309e-15009e

InfoSewer Inflow Control for a Pump with a Pump Curve

InfoSewer Inflow Control for a Pump with a Pump Curve

You can control the pumps in InfoSewer and H2OMap Sewer by using a Pump Control which will control the pump based on: 

1.       Volume

2.      Level

3.      Discharge

4.     Inflow

5.      Time 

If you use a By Inflow control the pump speed of the pump is increased or decreased to make the Upstream Wet Well Level Constant (Figure 1) for an exponential 3 point curve

Figure 1.  Inflow Control for  PUMP in InfoSewer and H2OMAP Sewer will change the Pump Speed of the pump to make the Wet Well level constant

Flow Units In InfoSWMM may be different then the Output Link Flow Units

Note:  Flow Units In InfoSWMM may be different then the Output Link Flow Units

The flows units selected in Run Manager determines the flow units of all incoming units including DWF, Inflow Time Series and other features in pump curves and other curves.  The output unit manager determines what you see when you make a graph of the link flow.  For example, you can have dry weather inflow of CFS and output units of GPM or MGD if you so request and set the correct flags in the interface.

 

Time Step Selection in InfoSWMM and SWMM5

1^st The time step you use in SWMM 5 is controlled from the top by the rainfall interval (Figure 1):

1.   All of your time steps should be less than the rainfall interval,

2.   The hydrology time step should be less than or equal to the smallest raingage rainfall interval in your network,

3.   The hydraulic time step should be less than or equal to the hydrology time step and should be based on the hydraulic needs of the your network.  Short length links, pump and weirs may require a smaller maximum hydraulic time step.

2^nd The report time step controls what you see in the graphics output of SWMM 5. If you see a large difference between that you see in the graphics output and the report text file it is because you have a large difference between the report time step and the average time step used during the simulation.

Solution: If there is a large discrepancy in the graphics and report text file then the best solution is to reduce the maximum time hydraulic time step so it is closer to the average time step and also to make the report time step closer to the Maximum time step (Figure 2).

Figure 1:  Relationship between the rainfall, hydrology and hydraulic time steps.

Figure 2:  Relationship between the minimum, average and maximum simulation time steps and the report time step.

InfoSewer Inflow Control for a PUMP

InfoSewer Inflow Control for a PUMP

You can control the pumps in InfoSewer and H2OMap Sewer by using a Pump Control which will control the pump based on:

1.       Volume

2.      Level

3.      Discharge

4.      Inflow

5.      Time

If you use a By Inflow control the pump speed of the pump is increased or decreased to make the Upstream Wet Well Level Constant (Figure 1).

Figure 1.  Inflow Control for  PUMP in InfoSewer and H2OMAP Sewer will change the Pump Speed of the pump to make the Wet Well level constant

Smoother Switching Between Pumps in SWMM 5 - A better simulation of a VSP?

Subject - Smoother Switching Between Pumps in SWMM 5 - A better simulation of a VSP?

An oft requested feature in SWMM 5 is the ability to better simulate a variable speed pump.   The basic feature we are trying to model is multiple pumps between two nodes, one pump curve for all of the pumps and the ability to turn on and turn off the pumps based on either the head or depth at a Wet Well (Figure 1).  You can turn on or off the pumps Pump1, Pump2 and Pump3 based on the depth at the Wet Well but this feature is stepwise linear and usually uses three pump curves.  A better way to simulate this feature is to use the SWMM 5 Real Time Rules (RTC) to simulate the Pump setting based on a control curve.  

The Pump flow at any time step is the Pump Flow estimated from the Pump Curve (Figure 2) * The Pump Setting (Figure 3)

Each of the three pumps has a different Control Curve (Figure's 4, 5 and 6, respectively) which turns on or turns off the Pump based on a range of Wet Well Depths.  The overall effect is that the total flow summing all three pumps together is smoother (Figure 7 and Figure 8) and the user can simulate different pump speeds based on the same pump curve depending on which pump is currently on.

Figure 1.   Example RTC Rules and VSP Pumps in a SWMM 5 model.

Figure 2.  The Pump Curve Used for all 3 Pumps

  

Figure 3.  The Pump Setting for all Three Pumps

Figure 4.   Pump Control Curve for Pump 1.  The Pump has a Setting of ¼ between 0.5 and 3 feet at the node Wet Well and zero otherwise.

Figure 5.   Pump Control Curve for Pump 2.  The Pump has a Setting of 1/2 between 3 and 5 feet at the node Wet Well and zero otherwise.

Figure 6.   Pump Control Curve for Pump 3.  The Pump has a Setting of 1 above 5 feet at the node Wet Well and zero otherwise.

Figure 7.  The Flow in all 3 Pumps.

  

Figure 8.  The total flow from all three Pumps to the downstream node.

Stopping Tolerance in InfoSWMM, H2OMAP SWMM and SWMM5 Internal Units

Stopping Tolerance in InfoSWMM, H2OMAP SWMM and SWMM5 Internal Units

InfoSWMM, H2OMAP SWMM and SWMM 5 share the same underlying dynamic engine code but one small difference is that InfoSWMM and H2OMAP SWMM allows the user to select the node stopping tolerance instead of always using the default SWMM 5 stopping tolerance of 0.0005  feet.  SWMM 5 uses internal units of feet and shows the output in meters if you are using SI units, as does InfoSWMM and H2OMAP SWMM.  The following table shows how the stopping tolerance translates to inches and millimeters in the engine of a US and SI model.   The smaller the tolerance the larger the number of iterations used during the simulation but using a very small tolerance does not always mean a better simulation.  If possible, for example, with pumps it is better to use a small time step and a medium level tolerance – for example 1 millimeter is a good starting  value, but maybe 2 or 3 millimeters may help if you have a continuity error at a pump node. 

The nodes are considered converged if the depths between successive iterations is less than the stop tolerance of the program (the default stop tolerance is less than the stopping tolerance (Figure 1)

Stopping Tolerance	Inches	Millimeters
0.1000000	1.2000000	30.4800000
0.0500000	0.6000000	15.2400000
0.0100000	0.1200000	3.0480000
0.0050000	0.0600000	1.5240000
0.0001000	0.0012000	0.0304800
0.0005000	0.0060000	0.1524000
0.0000100	0.0001200	0.0030480
0.0000500	0.0006000	0.0152400
0.0000010	0.0000120	0.0003048
0.0000050	0.0000600	0.0015240
0.0000001	0.0000012	0.0000305

Figure 1  If the node depths between successive iterations are less than the stopping tolerance then the node is considered to be converged.