A pump is a type of rotating equipment designed to add energy to a fluid. For a given flow rate, pumps add a specific amount of energy, or total dynamic head (TDH), to the fluid’s energy head at the pump’s suction flange.

WaterGEMS CONNECT automatically imports pump information from WaterCAD or WaterGEMS using WaterObjects technology. You may need to enter additional data to model dynamic effects. WaterGEMS CONNECT can represent virtually any pump using one of these five hydraulic elements:

• Shut Down After Time Delay—four-quadrant pump curve built in: A pump between two pipe segments which shuts down after a user-specified time delay. Useful to simulate a power failure.
• Constant Speed - No Pump Curves—no pump curve: A simplified constant-speed pump element between two pipe segments.
• Constant Speed - Pump Curve: constant-speed pump between two pipes, which supports user-defined pump curves.
• Variable Speed/Torque—four-quadrant pump curve built in: A variable-speed (or torque) pump between two pipes. Also known as a variable-frequency drive or VFD.
  Note: When defining the properties of a Variable Speed/Torque pump, one of the attributes is Time (for valve to operate). This value should be the time from the start of the simulation for the valve to close (or open if initial flow is zero).
• Pump Start - Variable Speed/Torque— four-quadrant pump curve built in: A variable-speed (or torque) pump between two pipes. Also known as a variable-frequency drive or VFD. This variable speed pump type always displays the nominal head and flow values, allowing the user to change them.

Only the last two allow you to change the speed of the pump during a simulation. The information needed to describe a pump’s hydraulic characteristics depends on the type selected, but the following are common parameters:

• Duty or Design Point—Point at which the pump was designed to operate, defined as its Nominal Flow and Nominal Head (1, 1 in the Pump Curve table). It is typically at or near the best efficiency point (BEP). For flows above or below this point, the pump may not be operating under optimum hydraulic conditions. Other points on the pump curve are entered as a ratio of the nominal head and flow (e.g., 0.1 to 1.2 times these values). If a pump curve is not available, see First-Quadrant and Four-Quadrant Representations.
• Shutoff and Runout—Shutoff is the maximum head a pump can develop at zero flow. Runout is an operating point at the other extreme of the pump curve, where the pump is discharging at a high rate but is no longer able to add any energy (i.e., head) to the flow. WaterGEMS CONNECT will not automatically shut down a pump if it reaches shutoff head or runout flow; therefore, this information is not required for a WaterGEMS CONNECT run.
• Elevation—The pump elevation is required to calculate suction or discharge pressures and to display the pump at the correct location on profile plots.
• Efficiency—Efficiency is defined as the ratio of the hydraulic energy transferred to the water divided by the total electrical energy delivered to the motor. This parameter is only required for pumps whose speed changes during a simulation. It is used to determine the accelerating or decelerating torque, where required.
• Speed—Rotational speed in revolutions per minute (rpm) of the impeller. This is commonly the same as the motor’s rotational speed, unless a transmission is installed. It is fixed for constant-speed pumps but can vary for variable-frequency drives. This parameter is only required for pumps whose speed changes during a simulation.
• Inertia—Pump inertia is the resistance of the pump assembly to acceleration or deceleration. WaterGEMS CONNECT uses inertia and efficiency to track the rate at which a pump spins up or down when power is added or removed, respectively. It is a constant for a particular pump and motor combination. For more information, see Pump Inertia.
• Specific Speed—A pump’s specific speed is a function of its rotational speed, Nominal Flow, and Nominal Head. For more information, see Specific Speed.