Durand's curves should be used when 2% ≤ Cv ≤ 15%, and Cave's curves should be used when 5% ≤ Cv ≤ 30%.

Durand's curves are more suitable for narrowly graded slurries, while Cave's curves are more suitable for broadly graded slurries.

Particle Size (d50)
Volume Concentration (Cv) %
- FL

Optional: Specific gravity of solids in suspension (SGs). Input a value (SGs > 1) to create a plot of minimum slurry velocity for pipe size.


FL Factor Graph

Durand's Limiting Settling Velocity (for STD. SCH.)

What is the Limit Settling Velocity?

For Durand's and Cave's set of curves, the Limit Settling Velocity (LSV, also known as Limit Deposit Velocity LDV) is defined as the line speed above which there is no stationary bed or sliding bed in a slurry. Below the LDV there may be either a stationary or fixed bed, or a sliding bed.

And what about Wilson's model?

It is very important to note that in the models he developed, Wilson defines the LSV as the velocity at which the bottom solids layer (or bed) starts to move, i.e., stops being stationary and starts sliding. Many authors differenciate this velocity by naming it Limit of Stationary Deposit Velocity, or LSDV.

Why are these velocities important?

If a slurry is pumped under the LDV, depositions might be formed in the pipe which would result in an increase of the hydraulic gradient, and therefore a loss of efficiency in the system. Blockages in the system are also a possibility if the slurry velocity is too low.

Read more:

Find more information in our Slurry Settling Velocity - How to calculate and which model to choose article.