PUMP-SYSTEM-CURVE ESSENTIALS
Generation of a centrifugal pump flow-head characteristic curve requires a set flow/head test data . Then a suitable curve can be drawn fitting the points obtained from such tests. Theoretically centrifugal pump flow-head curve should generally follow a two degree polynomial curve since hydraulic resistance within the pump varies as square of the flow. But in real life the test data obtained varies, since various factors like manufacturing imperfections, internal/external leakages, bearing resistances and measurement errors causes the data to differ from the ideal curve. Depending upon the nature and reliability of the data set, various types of curves can be fitted to simulate the best possible scenario. Pump-system-curve software allows users to choose anyone from 2nd, 3rd, 4th degree polynomial and the cubic spline fit. If the data set is consistent and within the acceptable tolerance limits, a polynomial fit curve of suitable degree can be chosen after experimenting within the software itself. Highly reliable data set can be fitted with a cubic spline fit curve where the curve always passes through all the data points. Pump-system-curve software allows the generation of 1 pump, 2 parallel pumps and 3 parallel pumps operation curves as user options.
System resistance curve is more likely follow a two degree polynomial curve, since system head varies directly in proportion to the square of the system flow. However, here also the curve may not follow the ideal curve since factors like fixed losses in the system, control valve losses etc. may contribute to the departure from simple two degree polynomial curve. Pump-system-curve software, allows user to fit anyone of the 2nd, 3rd, 4th degree polynomial and the cubic spline fit for the system resistance curve and up to three different system resistance curves can be drawn on one pump curve.
Pump efficiency curve can also be plotted along with the pump curve by fitting anyone of the 2nd, 3rd, 4th degree polynomial and the cubic spline fit depending upon the nature of data. Here also the user can check the suitability of different type of fits to suit the dataset. Pump-system-curve software allows user to include or exclude the pump efficiency curve and subsequent efficiency related calculations as option.
Quite often at the initial stages of the project, pump curve data set is not made available by the manufacturers unless the order is placed. However, project progress can not be compromised for the lack of such data. Under such circumstances pump-system-curve software allows user to generate a centrifugal pump curve based on shut-off head and design point flow/head, calculated from pump system configuration, using the equation H = Hmax*(1-(Q/Qmax)^2). Similarly pump-system-curve software allows also to generate system resistance curve using static/fixed head at zero flow and the design point flow/head calculated from pump system configuration using the equation H = Static head + K*Q^2. This is a very handy tool go ahead with the preliminary designs.
The operating point, which is the meeting point of pump curve and the system curve is automatically determined by the software and corresponding flow, head and efficiency (if opted) are displayed in the output for each of the 1, 2, 3 pump operating cases as chosen by the user.
Pump-system-curve software allows users to calculate flow or head at any point on any plotted pump curve when one of the flow or head parameter is put in and it also calculates corresponding efficiency value (if opted). Similarly, the software allows user to calculate flow or head at any point on any of the maximum three allowed system resistance curves drawn by the user by inputting either flow or head.
The plotted graph with pump and system curves along with the input and output data can be exported to either Excel or Word for printing or Submission etc. Video demo can be run online or Tutorial video can be downloaded for use by new and seasoned users
In conclusion, it can be summarized that there is high potential of using pump-system-curve software in industry and academic world to conceptualize and record the pump operation. It can be conveniently used by engineers, designers and students in their day-to-day use for study, alternative selection, regular design and graphic records.
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