Friction Losses & Pump Cavitation

This one simple equation can significantly resolve many pumping issues and improve pump performance, especially when friction losses are impacting performance. ?

Cavitation problems, in particular, can sometimes be solved by merely increasing the diameter of the suction pipe diameter by one size. For example, let’s compare the head loss in a 3-inch suction pipe versus a 2-inch suction pipe, assuming all other factors remain constant.

If the flow rate “Q” is unchanged, then the velocity (v) of the liquid is equal to (Q/A), where A is the cross sectional area of the pipe.

First, comparing the areas of both pipes gives us:

So comparing fluid velocity, and noting that it is squared in the equation, this leads to:

So if we eliminate the constants in the equation to focus on comparing the friction losses in a 3-inch pipe to the friction losses from a 2-inch pipe in the same application, we get:

Substituting with the ratios we just established, this leads to:

This demonstrates that increasing the suction pipe size from 2 inches to 3 inches can reduce the friction losses by over 85% - allowing your pump to operate more efficiently.