Booster Pumps & B.F.Preventers

• On this screen, Booster Pumps and/or Back Flow Preventers may be entered. Booster Pumps and Back Flow Preventers are entered "in a pipe". A Back Flow Preventer is a double check detector assembly, or a reduced pressure detector assembly.

• For Booster pumps and Back Flow Preventers, water is always assumed to flow from node A to node B (as entered on the Pipes Tab Page). This is very important as it is the one time that the order of the nodes is relevant and if entered incorrectly, wildly erroneous results can be produced.

• The buttons on the Tool Bar for this page are:

  • Close - exits this screen.
  • Show Errors
  • Deletes the current line (booster pump or back flow preventer).
  • Help on the current tab page.

Booster Pumps

• The items of input for booster pumps are:

  • Pipe Number: The pipe number in which the booster pump is located. Note that the pipe that the booster pump is in must have the nodes entered in the direction of flow.

  • Pump - a selection for Booster Pump

  • Curve/Linear:

    • LINEAR signifies linear interpolation with a series of points on a curve of pressure vs flow (obtained from the supplier of the pump).
    • CURVE signifies a series of coefficients are to be calculated from the entered values of flow and pressure for a polynomial fit to the points. At least eight points must be entered. This is a slightly more accurate method of describing the curve than the LINEAR method.
    • The polynomial takes the form:
      p = a + bq + cq2 + dq3 + eq4
      where
      q is the flow
      a, b, c, d and e are the coefficients which are displayed on the screen and inserted in the input data file for use in the calculations.

  • Flow 1, Pressure 1, Flow 2, Pressure 2,..................Flow n, Pressure n:

    • A series of up to eight flow/pressure points on the pump or back flow preventer curve. The first value of flow must be zero. For a pump the first pressure is the shut off pressure whilst for a back flow preventer, it is the pressure below which flow is prevented. Above this pressure the pressure drop through the device is a function of flow, as defined by the other flow/pressure points.
    • If CURVE is being used the number of pairs of points must be eight, and after the first two flows are entered the remaining flows are extrapolated using the same increment for each pair. They may be changed as necessary.

Back Flow Preventers

• The items of input for back flow preventers are:
  • Pipe Number: The pipe number in which the back flow preventer is located. Note that the pipe that the back flow preventer is in must have the nodes entered in the direction of flow.
  • B.F.Prev – a selection for Back Flow Preventer
  • Linear: For a Back Flow Preventer the performance is entered as a linear curve, i.e. a series of (at least two) points on a curve of pressure vs. flow. The program linearly interpolates between the entered points.
  • Flow 1, Pressure 1, Flow 2, Pressure 2,..................Flow n, Pressure n:
    • A series of up to eight flow/pressure points on the pump or back flow preventer curve. The first value of flow must be zero. For a pump the first pressure is the shut off pressure whilst for a back flow preventer, it is the pressure below which flow is prevented. Above this pressure the pressure drop through the device is a function of flow, as defined by the other flow/pressure points.
    • If CURVE is being used the number of pairs of points must be eight, and after the first two flows are entered the remaining flows are extrapolated using the same increment for each pair. They may be changed as necessary.
• Once sufficient points are entered a graph appears in the lower portion of the screen displaying the points and the fitted curve. This is a useful check on the entered values and in the case of "curve" whether the curve fit is reasonable. At the right end of the graph, there is provision for extending the curve to check, in the case of curve, that the curve behaves acceptably past the last point on the graph.