Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

Slurry Transport - Minimum Flow Velocity

Flow velocities in slurry transport systems to avoid settling of solids.

Sponsored Links

Pipeline slurry transport

A suspension of solid particles in a liquid, as in a mixture of cement, clay, coal dust, manure, meat, etc. - with water is often called a slurry.

In transport systems for slurries it's important to avoid settling of solids by keeping the fluid velocities in the pipe lines above certain levels. The levels depends primary on the type and size of the solid in the slurry:

Type of SolidsSize of Solids
(Mesh No)
Minimum Flow Velocity
Fine over 200 1 – 1.5 3 – 5
Sand 200 – 20 1.5 – 2 5 – 7
Coarse 20 – 4 2 – 3.25 7 – 11
Sludge 0.6 - 3 2 - 9

Particle Sizes

A pipeline transport system may under certain circumstances be nearly self cleaning. When a solid settle the pipe area decrease - and fluid speed increase - until a state of equilibrium where the speed is so high that settling is avoided.

Sludges with solid content less than 2 percent have hydraulic characteristics similar to water. For solids contents greater than 2 percent the friction losses are from 1.5 - 4 times the friction losses for water.

The speed should be increased in lifting lines by decreasing the piping diameter. At the end of a pipeline the speed should be slowed down by increasing the pipeline diameter.

Mesh definition

  • Mesh is the number of openings per inch of a screen - "a 100 mesh screen"
  • Mesh is often used to measures the size of particles - "100 mesh powdered sand"
  • Sieve size and mesh designation

Slope and Self Cleaning 

The required slope for self cleaning of sludge pipe lines can be estimated as

Smin = τmin / (ρ Rh)                             (1)


Smin = minimum slope for self cleaning (m/m)

τmin = required shear stress for self cleaning (kg/m2) - (0.25 kg/m2 for slugde waste water, 0.15 kg/m2 for rain water)

ρ = density of fluid (kg/m3)

Rh = hydraulic diameter at maximum flow (m)

Sponsored Links

Related Topics

Fluid Flow and Pressure Loss

Pipe lines - fluid flow and pressure loss - water, sewer, steel pipes, pvc pipes, copper tubes and more.

Piping Systems

Dimensions of pipes and tubes, materials and capacities, pressure drop calculations and charts, insulation and heat loss diagrams.

Related Documents

Pneumatic Powder and Solid Transport Systems

Pneumatic transport systems used to move powder and other solid products.

Pneumatic Transport and Conveying - Carrying Velocities

Recommended air velocity for pneumatic transport of products like cement, coal, flour and more.

Pneumatics - Transport of Solids and Separator Types

Separators used in pneumatic solids transport systems and their minimum particle size.

Valves Selection Guide

Applications guide for selecting valves.

Sponsored Links

Engineering ToolBox - SketchUp Extension - Online 3D modeling!

3D Engineering ToolBox Extension to SketchUp - add parametric components to your SketchUp model

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp from the SketchUp Pro Sketchup Extension Warehouse!

About the Engineering ToolBox!


We don't collect information from our users. Only emails and answers are saved in our archive. Cookies are only used in the browser to improve user experience.

Some of our calculators and applications let you save application data to your local computer. These applications will - due to browser restrictions - send data between your browser and our server. We don't save this data.

Google use cookies for serving our ads and handling visitor statistics. Please read Google Privacy & Terms for more information about how you can control adserving and the information collected.

AddThis use cookies for handling links to social media. Please read AddThis Privacy for more information.


This page can be cited as

  • The Engineering ToolBox (2003). Slurry Transport - Minimum Flow Velocity. [online] Available at: [Accessed Day Month Year].

Modify access date.

. .


3D Engineering ToolBox - draw and model technical applications! 2D Engineering ToolBox - create and share online diagram drawing templates! Engineering ToolBox Apps - mobile online and offline engineering applications!

6 6

Sponsored Links