Solved: Pressure Drop in Industrial Pipe Systems


Pump systems play a major role in transporting fluids for industrial applications. Being subjected to different fluids, temperatures, and pressures, they are bound to undergo degradation.

Pressure drop is a common issue plaguing industrial pumps with many possible causes. Below we'll dive into some of the main reasons why pressure drop occurs as well as how to fix it.

What Causes Pressure Drop?

A pressure drop is a loss in pressure within a pipe when the fluid moves from one section to another. Outside of proper sizing according to pump curves, some of the common causes for pressure drop are:

  • The rise of internal friction: Friction is a major cause of pressure drop. Friction occurs within the wall of the pipe. When fluid moves within these pipes, the irregular surface of the pipe restricts the fluid flow. A brand new pipe has its interior coated, giving a smooth surface finish. However, particles within the fluid can act as abrasives and scratch this internal coating. Over time, these interior irregularities increase and contribute to more friction and pressure drop.  
  • Sharp turns or intermediary valves: A fluid travels much more efficiently within a straight line than pipelines with sharp turns or valves in between. Sharp turns offer much more resistance to fluids since there is an abrupt change in the flow direction. This type of pressure drop is commonly referred to as pressure loss at bends. The magnitude of pressure loss primarily depends on the bend angle.
  • Pipe length: The longer the fluid has to travel, the more friction it needs to overcome. Therefore, pressure drop has a positive correlation with length; if length is the only variable between two otherwise identical pipes, pressure drop will be higher in the longer one.
  • Pipe diameter: The larger the diameter, the better the flow. The pipe diameter should be selected based on a pump's capacity. Increasing the pipe diameter beyond a point will create a considerable pressure drop.
  • Scaling: Pipes that carry mineral-rich fluids can develop scaling, which is mineral build-up on the pipe walls. Scaling obstructs the fluid flow and reduces the fluid pressure.
  • Gravity: With each increment in pipe elevation, the pump has to work to overpower the pull of gravity. Hence, the increase in height adversely affects pressure output regardless of pump lift or head

How to Calculate Pressure Drop?

Calculating pressure drop requires factoring in many variables. Everything from the diameter of the pipe and the bends to elbows and valves contribute to pressure drop. Another critical factor is the fluid itself. Each type of fluid behaves differently within pipes since they possess different viscosities and internal friction.

Let's have a look at how you can calculate pressure drop within a few different scenarios:

Pressure Drop in Circular Pipes:

ΔP = Pressure drop (Pa or Kg/ms2)

λ = Pipe friction coefficient

L = Length of pipe (m)

D = Pipe diameter (m)

ρ = Density of fluid (Kg/m3)

ω = Flow velocity (m/s)

Pressure Drop with Components:

Often the pipes carrying the fluid may have attachments like valves and meters that induce pressure loss. The manufacturer will provide the respective resistance coefficient of the component, which is used to calculate pressure drop. You can find the pressure loss for such components using:

ΔP = Pressure drop (Pa or Kg/ms2)

Cj = Resistance coefficient

ρ = Density of fluid (Kg/m3)

ω = Flow velocity (m/s)

Pressure Drop Due to Gravity

ΔP = Pressure drop (Pa or Kg/ms2)

ρ = Density of fluid (Kg/m3)

g = Acceleration of Gravity (m/s)

ΔH = Vertical elevation or drop

How to Prevent Pressure Drop?

There are several ways to reduce pressure drop in flowing fluids. The first step is to understand the specific cause of pressure drop in your application. Keeping in mind the factors we discussed earlier, let's look at some of the potential fixes:

  • Use a clean and polished pipe: Ensure that you use pipes that have a smooth internal finish.
  • Increase the pipe diameter if required: If the pipe diameter is the issue, use larger pipes for easier flow.
  • Reduce bends and obstructions to a minimum: Bends and elbows reduce the flow pressure. Therefore, minimizing the number of bends and obstructions is a great way to prevent pressure drop.
  • Minimize height if possible: Avoid adding unnecessary elevations to your piping system.
  • Improve the pump if required: If your piping layout is correct and you still don't get the desired fluid pressure, you most likely need to increase the pump output.

Need Help Troubleshooting a Pump System Issue?

Hayes Pump distributes the broadest line of pump products in the industry to suit virtually every fluid handling need. Contact our experts today for help with your application.Contact Us