SLURRY AND SLUDGE PIPING
Ramesh L. Gandhi
San Francisco, CA
DEFINITION AND BACKGROUND
Slurry is a mixture of solids and liquid. A sludge denotes a mud or a concentrated
slurry having a considerable amount of fine material that imparts high viscosity.
Typical examples of slurries are the solid-liquid mixtures encountered in mineral
processing plants and dredged material from waterways and dams. Most of the
slurries are made up with water. However, industrial paints, rocket fuel, coal-oil
mixture, and coal-methanol slurries are made up with liquids other than water.
River sediment in the form of slurry appears to have been handled since ancient
times.1 All ancient civilizations arose on river banks. Maintenance of waterways
requires periodic dredging which results in a sand and silt water slurry. Today
dredging represents the largest volume of solids handled in slurry form. Slurry
transport is also used for dam construction.
Blatch2 reported the first hydraulic test results for a sand-water slurry flowing
through NPS 1 (DN 25) pipe. Gregory,3 O’Brien and Folsom,4 and Howard5 reported
results of tests of clay, sand, and gravel slurries. The flow of muds and sludges
through pipes was first examined by Caldwell and Babbit.6 The first large-scale
experimental program on the flow of slurries through pipes was reported by Durand.7
The correlations proposed by Durand and his coworkers serve as a basis for the
present-day design methods.
Design of a slurry piping system involves
● Selection of pipe diameter
● Estimate of friction loss and pumping requirements
● Selection of pipe material, valves, and fittings
● Selection of pumps
● Selection of instruments and control system for safe and reliable operation
Pipelines transporting liquids such as oil and water can be operated at any
velocity up to their design limits. In most slurry applications, a certain minimum
velocity needs to be maintained, to keep solids from settling out in horizontal