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Understanding Erosional Velocity Calculations for Separator Inlets and Outlets

Updated: Sep 9, 2023


In the world of fluid dynamics and process engineering, maintaining the integrity and efficiency of separators is of paramount importance. Whether it's in the oil and gas industry or other chemical processes, separators play a vital role in isolating different components of a fluid mixture. However, one critical factor that often goes overlooked is erosional velocity, which can have a significant impact on the lifespan and safety of separators.

What is Erosional Velocity?

Erosional velocity is the maximum velocity at which a fluid can flow through a pipe or vessel without causing excessive erosion or wear on the internal surfaces. This erosion occurs due to the abrasive nature of the fluid and the impact it has on the separator's walls. Erosion can compromise the structural integrity of the equipment, leading to costly repairs and safety hazards.

Calculating Erosional Velocity

To ensure that your separators are operating within safe limits, it's crucial to calculate erosional velocity at both the inlet and outlet. The formula for calculating erosional velocity is as follows:

Erosional Velocity (ft/sec) = C / √ρ


  • C is the empiral constant (in lb/s/ft^2)

  • ρ is the fluid density (in lb/ft³).

In practice, you can assume

C=80 for vessel inlet and outlets

C=100 for continuous flow C=125 for non-continuous flow in a pipe.

Why is Erosional Velocity Important?

Exceeding the erosional velocity limit can have several adverse effects:

  • Equipment Damage: High-velocity flows can lead to rapid erosion of separator components, such as piping, nozzles, and baffles, ultimately causing equipment failure

  • Reduced Efficiency: As erosion progresses, the separator's efficiency diminishes. This can result in reduced separation of fluid components and increased operational costs.

  • Safety Concerns: Erosion can create leaks and weaken structural integrity, posing safety risks to personnel and the environment.

Noise Concerns and Velocity Limits

In addition to the mechanical risks posed by exceeding erosional velocity, noise concerns can also arise. When fluid flows at high velocities, it can produce significant noise levels, which can be disruptive to operations and harmful to employees' hearing.

To mitigate noise concerns, it is generally recommended to keep fluid velocities within the range of 70-80 ft/sec. This not only helps reduce noise but also serves as a practical guideline to prevent excessive erosion.


Erosional velocity calculations are a critical aspect of separator design and operation. By understanding and applying these calculations at the inlet and outlet of separators, you can ensure the longevity, efficiency, and safety of your equipment. Remember to consult industry standards and empirical data to determine the appropriate erosional velocity limits for your specific application, and always aim to keep velocities within the 70-80 ft/sec range to address noise concerns while maintaining separator integrity.

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