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pump duty


    Pumping is a part of almost any production facility. The way to calculate the conditions for a pump is well known to engineers, but can be quite time consuming. Engineering Page does the hard work for you.

    Calculation Input

    The form for the Pump Conditions calculation asks for a lot of data. The sketch underneath provides an overview of the required data.

    Pump Conditions


    Please note that for many of the parameters a maximum and a minimum value is requested. These are used to calculate the maximum and minimum values of the pump operating window.

    The program will calculate the pressure at the discharge and suction flange of the pump. This is calculated using:

    pump suction pressure


  • p SuctionFlange = Pressure at the Suction Flange Pa
  • p SuctionVessel = Pressure in the Suction Vessel Pa
  • delta pSuctionLine = Pressure drop in the Suction Line Pa
  • rho hS g = static head Pa
  • rho = density kg/m3
  • hS = liquid column height at suction side m
  • g = gravitational constant m/s2 (appr 9.81)
  • To calculate hS:

    pump suction

    This will provide the pressure at the suction side. To calculate the pressure at the discharge side is almost the same formula, the difference is that the pressure drop through the line needs to be added to the pressure:

    pump discharge



    Note that the height at the suction flange is used to provide the differential pressure that the pump needs to deliver.

    The pressure drop calculations are valid for the full range of laminar and turbulent flow. The Moody diagram was used to provide the friction factors for straight pipe. For the fittings the 2-k method was used as this gives a good value for the full range. The 2-k method uses:

    pressure drop laminar turbulent

    The values for greek letters zêta (both zêta1 and zêtainfinity) are taken from a table that was published by William B. Hooper - see the reference list on Pressure Drop, When you read this bear in mind that the article uses inches as the unit for the internal diameter d. The first part of the equation will increase the friction factor at low Reynolds numbers, at high Reynolds numbers it will go to zero. The second part is a constant for a chosen fitting. Drawn in a graph this provides a Moody diagram shape look-a-like. The traditional approach would give a straight line, which is good enough at high Reynolds numbers, but inaccurate at low. The Reynolds number is calculated using:

    Pump conditions calculator


  • d = internal diameter in m
  • v = fluid velocity in m/s
  • rho = density in kg/m3
  • eta = dynamic viscosity in Pa.s (=Ns/m2)
  • We used this more elaborate method as it provides a good prediction of the pressure drop of fittings in both the laminar and turbulent flow region. Users that prefer the equivalent diameter or fixed k method can input their value in the fixed item section.

    The input is fairly straight forward. Two forms are available: one for ANSI piping and one for manual input of the piping diameter and wall thikness. For the number of fittings a choice needs to be made with a radio button. Using the correlation will give a good first guess for the number of fittings to be expected, in that case you can skip a large part of the input form as the fitting input will be ignored for that choice. The additional pressure drop items will be used in the calculation.

    Calculation Results

    The conditions for the pump are calculated and presented in an easy to read format. Line sizing, pump conditions etc. are checked and recommendations are given where appropriate. These are self explanatory.

    The recommendations are intended to aid engineers and give tips / hints for selection. They are not intended to select or exclude any commercial products or manufactures.

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