Pressure Drop

Definition - What does Pressure Drop mean?

Pressure Drop is the difference in pressure between two points in a pipeline. It is a common phenomenon examined in the oil and gas industry, be it in the wellbore while extracting oil and gas or while transporting crude oil, natural gas or any petroleum product in a pipeline. The pressure drop in the equipment or in the production process needs to be calculated initially and necessary measures to be taken upfront in order to maintain the necessary operating pressures in the equipment.

Petropedia explains Pressure Drop

In fluid mechanics, when fluid is transported through a given length of pipeline, it generally tends to slow down because of pressure drop, head loss, frictions and other parameters within a pipeline. Thus, all the parameters need to be calculated based on certain phenomenological equations such as Darcy Weisbach Equation. This equation helps in calculating all the parameters such as pressure loss, head loss, frictional losses in the pipeline which ultimately leads to pressure drop inside the pipe.

Pressure drop = Pressure Loss + Head Loss + Frictional losses

The equation for pressure loss is:


= fluid density in kg per cubic meter

L = Length of pipe (m)

D = Pipe diameter (m)

V = Mean flow velocity (m/s)

fD = Darcy Friction Factor

The equation for head loss is:

Where, Delta h is fluid head loss due to friction (m) and g is the acceleration due to gravity (m/s2)

Equation for Darcy Frictional Factor is based on Laminar, Critical or Turbulent flow regime. For laminar flow, the Reynold’s number (Re) is less than 2000, for critical flow, Re is greater than 2000 but less than 4000 and for turbulent flow, Re is greater than 4000. Equation for Darcy frictional factor is:

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