Pumps & Pumping systems

Fluid pumping systems

Fluid pumping systems have various applications varying from circulating water and pumping chemicals to maintaining pressure. Fluid pumping systems usually consist of multiple centrifugal pumps in a sequence, and variable speed pumps are utilized to pump variable flow rates.

To overcome system resistance or “head,” the pressure needs to be high enough. Static head occurs when there’s a height difference, while friction head exists when resistance to flow in a pumping system. A pump must transmit energy to transfer fluid from one point to another, and the energy required by the pump is based on the pump altitude, head, length, and diameter of the pipes.

The function of a pump

A pump is a device that moves fluids by mechanical action. Pumps can be classified into three major groups: direct lift, displacement, and gravity pumps. The function of a pump is not to generate pressure; it produces liquid movement or flow. Pumps produce the flow necessary for creating pressure, a function of resistance to fluid flow within a system.

Mechanical pumps can be utilized in various applications such as pumping water from wells, water cooling, pumping oil, and heating and cooling objects or systems. Hydraulic pumps are hydraulic systems that take mechanical energy and convert it into fluid energy. The primary function is to transfer energy; this is often achieved by transporting fluid by converting different types of energy.

The performance of a pump is measured by the function of the total head and the weight of the liquid pumped over some time.

Pump types

There are many pump designs, but most pump types can be classified under centrifugal and positive displacement pumps.

Centrifugal pump

Centrifugal pumps use impellers, curved blades that accelerate fluids when rotating. Centrifugal pumps can be classified into three sub-types: axial flow pumps, radial flow pumps, and mixed flow pumps. Centrifugal pumps are the most common type of pump. They’re easy to manufacture and are cheaper because they often are mass-produced.

Positive displacement pump

Positive displacement pumps use the regular interval to move a fixed amount of fluid. Displacement pumps can be reciprocating or rotary, depending on the required application. Reciprocating pumps have internal cavities that fill up to be discharged with higher pressure. Rotary pumps use rotors to trap water in cavities and discharge them later.

Selecting the right pump

The chances of buying exactly the right pump for your flow requirements without some research are minimal. The flow rate of your system depends on the physical characteristics of the system, such as friction, static head, and fluid viscosity if the fluid is different from water. Various fluids have their characteristics and are usually pumped under varying conditions; therefore, it's essential to know all the pump's relevant product and performance data before selecting the right one.

To select the right pump, some steps need to be considered. First, the flow rate should be determined. In industrial settings, the flow rate depends on the production level of the plant. Careful analysis of the interaction between processes is required to determine the exact flow rate required. Second, the static head and friction head should be determined.

The static head can be determined by measuring the different heights levels; friction head depends on the flow rate, pipe size, and pipe length. Third, the total head should be calculated by summing the static head and friction head. Finally, you are ready to select the right pump depending on your required flow rate, static head, and friction head.