Factors that affect Head Loss and determine the need for additional pumps along the line.
1) Flow Rate
When the flow rate (GPM) increases, the velocity of the liquid increases at the same rate. The friction or resistance to flow (due to viscosity) also increases. The head loss is related to the square of the velocity so the increase in loss is very quick.
2) Inside diameter of the pipe
When the inside diameter is made larger, the flow area increases and the velocity of the liquid at a given flow rate is reduced. When the velocity is reduced there is lower head loss due to friction in the pipe. On the other hand, if the inside diameter of the pipe is reduced, the flow area decreases, the velocity of the liquid increases and the head loss due to friction increases.
3) Roughness of the pipe wall
As the roughness of the inside pipe wall increases so does the thickness of the slow or non-moving boundary layer of liquid. The resulting reduction in flow area increases the velocity of the liquid and increases the head loss due to friction.
4) Corrosion and Scale Deposits
Scale deposits and corrosion both increase the roughness of the inside pipe wall. Scale buildup has the added disadvantage of reducing the inside diameter of the pipe. All of these add up to a reduction in flow area, an increase of the velocity of the liquid, and an increase in head loss due to friction.
5) Viscosity of the liquid
The higher the viscosity of the liquid is, the higher the friction is from moving the liquid. More energy is required to move a high viscosity liquid than for a lower viscosity liquid.
6) Length of the pipe
Head loss due to friction occurs all along a pipe. It will be constant for each foot of pipe at a given flow rate. That constant (head loss value) must be multiplied by the total length of pipe. This is one of the main reasons why they need to put a pump station every 40 to 60 miles
7) Fittings
Elbows, tees, valves, and other fittings are necessary to a piping system for a pump. It must be remembered that fittings disrupt the smooth flow of the liquid being pumped. When the disruption occurs, head loss due to friction occurs.
8) Straightness of the pipe
Because of momentum, liquid wants to travel in a straight line. If it is disturbed due to crooked pipe, the liquid will bounce off of the pipe walls and the head loss due to friction will increase. There is no accurate way to predict the effects since “crooked” can mean a lot of things.
Here's what has been nagging me lately:
Will each of these pumps following an AOT (50 miles or so down line) actually create a bottleneck to the increased flow? This bottleneck would be the result of bends and fittings in and around the pump, and turbulence caused by the pumping action which would no doubt break down those short chains along the flow direction and increase viscosity. They may have to run the pumps harder in order to maintain the increased flow through the pump. The bottleneck would occur between the pump and the next AOT.
