Pumps

Definition of a pump 

                       Generally a pump can be defined as an instrument or a device which can be used to transport the fluids. The fluid may be a liquid, slurry or a gas. As the fluid type the pump design and the method use for moving the fluid can be varied. (Michael W. Volk, Pump characteristics and applications, 01-05)

When we consider about a water or fluid controlling system, use of pumps is very effective method for it rather than control manually or mechanical system. Normally a pump is used to transport water from lower elevation to higher elevation. In the market there are various types of pumps are available as various requirements of the customers. And also there are pumps available as the various types of power supply methods. Pumps are used in various applications such as domestically as well as industrially.So we should consider various types of thing when we going to buy a pump.

Selecting a pump

         If we want to buy a pump for our application, we should select appropriate one as our requirement of the application. So we should think various types of factors depending on various situations. It can be listed as follows 

·      Amount of water body which have to be transported (Pumping rate)

·      Properties of the fluid (Density, viscosity, Solid content, Etc)

·      Type of flow (Laminar, Turbulent, Etc)

·      Pressure head variation (Suction, Discharge, Total)

·      Power supply (Electric, diesel, Pneumatic, Etc)

·      Cost compare to the efficiency

      One of the most important factors is pumping rate. It means the amount of fluid collected per unit time. So we need a pump which has a pumping rate more than the collecting rate. Or else we can’t remove the fluid effectively. In some cases we have limited time allocates for pumping so we have to pump within that limited time so we have to select a pump with that rate.

And also, when we going to select a pump, we should think about the properties of our transporting fluid such as density, viscosity, solid content, Etc. With the change of density of the fluid, power required for pumping is varied. And also the system of pumping is varied. So we should thin about the density of our fluid as well as the viscosity. And also the solid content of the fluid is very important to consider because the contaminant are caused to damages to the part of the pumps. So in those cases we have to select special types of pumps. So we should analyze the solid contaminant of the fluid. 

Another factor is the type of the flow of our fluid. It means the behavior of the fluid. It may be laminar, turbulent or another type. So we have to examine our flow type of the fluid because some pumps cannot be transport turbulent flowed fluids. So in that case we have to use special type of pump. 

 

And also the pressure head variation or the vertical height of the transportation of fluid is very essential when selecting a pump. So we should know the head of suction, discharge as well as total head. It is very important to select a pump and placing the pump (Paul N. Garay, Pump application desk book, 231-240). 

  

H1-Suction head

H2-Discharge head

(H1 + H2)-Total head 

                                     

            Power supplying method to the pump is also very important when we going to buy pumps because some powering methods cannot be used in every situation.  Now a day there are several method are used to supply the power to the pumps such as Electric, Diesel, Pneumatic and others So as our application we have to select appropriate method.

            Finally, we should thing about the cost we should spend for buying he pump. It’s depended on the scale of the application. For an example it is useless if we use a high cost pump for small scale application. So we should think about the cost with respect to the efficiency of the pump.