Pumping

Pumping is a unit operation that is used to move fluid from one point to another. This chapter discusses various topics of this important unit operation relevant to the physical treatment of water and wastewater. These topics include pumping stations and various types of pumps; total developed head; pump scaling laws; pump characteristics; best operating efficiency; pump specific speed; pumping station heads; net positive suction head and deep-well pumps; and pumping station head analysis.

4.1 pumping stations and types of pumps

The location where pumps are installed is a pumping station. There may be only one pump, or several pumps. Depending on the desired results, the pumps may be connected in parallel or in series. In parallel connection, the discharges of all the pumps are combined into one. Thus, pumps connected in parallel increases the discharge from the pumping station. On the other hand, in series connection, the discharge of the first pump becomes the input of the second pump, and the discharge of the second pump becomes the input of the third pump and so on. Clearly, in this mode of operation, the head built up by the first pump is added to the head built up by the second pump, and the head built up by the second pump is added to the head built by the third pump and so on to obtain the total head developed in the system. Thus, pumps connected in series increase the total head output from a pumping station by adding the heads of all pumps. Although the total head output is increased, the total output discharge from the whole assembly is just the same input to the first pump.

Figure 4.1 shows section and plan views of a sewage pumping station, indicating the parallel type of connection. The discharges from each of the three pumps are conveyed into a common manifold pipe. In the manifold, the discharges are added. As indicated in the drawing, a manifold pipe has one or more pipes connected to it. Figure 4.2 shows a schematic of pumps connected in series. As indicated, the discharge flow introduced into the first pump is the same discharge flow coming out of the last pump.

The word pump is a general term used to designate the unit used to move a fluid from one point to another. The fluid may be contaminated by air conveying fugitive dusts or water conveying sludge solids. Pumps are separated into two general classes: the centrifugal and the positive-displacement pumps. Centrifugal pumps are those that move fluids by imparting the tangential force of a rotating blade called an impeller to the fluid. The motion of the fluid is a result of the indirect action of the impeller. Displacement pumps, on the other hand, literally push the fluid in order to move it. Thus, the action is direct, positively moving the fluid, thus the name positive-displacement pumps. In centrifugal pumps, flows are introduced into the

Reflux valve

Automatic

Motor starter j

Section A-A

Automatic

Motor starter j

Was this article helpful?

0 0
Healthy Chemistry For Optimal Health

Healthy Chemistry For Optimal Health

Thousands Have Used Chemicals To Improve Their Medical Condition. This Book Is one Of The Most Valuable Resources In The World When It Comes To Chemicals. Not All Chemicals Are Harmful For Your Body – Find Out Those That Helps To Maintain Your Health.

Get My Free Ebook


Post a comment