Irrigation Reference Manual (Peace Corps, 1994): Chapter 5 - Farm water delivery systems: 5.2 Pipeline hydraulics and design: 5.2.3 Factors influencing head loss

Irrigation Reference Manual (Peace Corps, 1994)

Chapter 5 - Farm water delivery systems

5.2 Pipeline hydraulics and design

		(introduction...)
		5.2.1 Continuity equation
		5.2.2 Pressure, head, and friction losses
		5.2.3 Factors influencing head loss
		5.2.4 Pine design
		5.2.5 The hydraulic gradient line (HGL)
		5.2.6 Pipeline design sample problems
		5.2.7 Pipes and pipeworking
		5.2.8 Working with pipes
		5.2.9 Water hammer
		5.2.10 Air relief. Vacuum relief, and pressure relief
		5.2.11 Other pipeline structures and accessories
		5.2.12 Pipeline materials

5.2.3 Factors influencing head loss

The amount of head loss is influenced by the following factors:

a. The length of pipe.

The longer the pipeline, the greater the head loss. This loss is directly proportional to the length; i.e., the head loss for 200 meters of pipe would be twice that for 100 meters under the same conditions.

b. The diameter of the pipe.
The smaller the diameter of the pipeline, the greater the friction will be for the same flow of water. The differences are not proportional.
c. The velocity of water in the pipe.
The higher the flow rate of water in a given pipe, the greater the head loss due to friction. Friction increases as the square of the velocity.
d. The nine material.
The smoother the inner surface of the pipe, the lower the head loss. Thus, since PVC pipe is smoother than steel or cast iron, it has a lower head loss for identical conditions.
e. The number of fittings or bends in the pipeline.
A straight pipeline would have a lower head loss than one of the same length with fittings or bends.