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Hat Bhosdike

This document describes an experiment to determine the effectiveness of a screen. The effectiveness (E) of a screen is a measure of its ability to separate particles into oversize and undersize fractions with minimal contamination between fractions. Samples are screened and the mass fractions of various particle sizes are measured in the feed, oversize, and undersize. These mass fraction values (XF, XD, XB) are used to calculate the screen's effectiveness E according to the given equation. Graphs of cumulative mass fraction versus particle size are made to determine XF, XD, XB from. The experiment aims to find the effectiveness of a given screen using this analysis method.

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181 views3 pages

Hat Bhosdike

This document describes an experiment to determine the effectiveness of a screen. The effectiveness (E) of a screen is a measure of its ability to separate particles into oversize and undersize fractions with minimal contamination between fractions. Samples are screened and the mass fractions of various particle sizes are measured in the feed, oversize, and undersize. These mass fraction values (XF, XD, XB) are used to calculate the screen's effectiveness E according to the given equation. Graphs of cumulative mass fraction versus particle size are made to determine XF, XD, XB from. The experiment aims to find the effectiveness of a given screen using this analysis method.

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CHE1022: Mechanical Operation Lab

Experiment No :1
Date :

EFFECTIVENESS OF SCREEN
AIM:

To determine the effectiveness of a given screen by analysis of the given sample.

APPARATUS:

Standard sieves, sample material, balance with weight and sieve shaker.

THEORY:

The effectiveness of a screen E is a measure of its ability to separate the oversize and
undersize as effectively as possible. An ideal screen will separate the feed into oversize and
undersize in such a way that there will be no oversize particle in the underflow and no
undersized particle in the overflow.
The effectiveness of a screen is given by the expression
E = (Xf Xb) (XD XF) (1-XB) XD / (XD XB)2 (1-XF) XF
Where,
Xf mass fraction of material A in feed
XD- mass fraction of material A in oversize
XB mass fraction of material A in undersize

PROCEDURE:

Weight about 500g of given sample accurately and analyze using a set of sieves in a sieve
shaker. Measure the weight of sample retained on each mesh and calculate the weight fractions.
Further, mix the different fractions and take the entire sample on a screen whose effectiveness is
to be found. Now, manually screen the sample and record the mass of oversize fraction and
undersize fraction. Again, separately analyze oversize and undersize fraction using the same set
of sieves by using sieve shaker for 5 minutes. Weight the sample on each mesh carefully and
calculate the weight fraction.

1
CHE1022: Mechanical Operation Lab
Sl. No. Feed Analysis Oversize Analysis Undersize Analysis
Mass
Mesh DP Mass Mass Cumulative Mass Cumulative Mass Mass Cumulative
retained
Number mm retained Fraction Mass Fraction Mass retained Fraction Mass
(w), gm xi fraction, xi fraction, (w), gm xi fraction,
(w), gm

2
CHE1022: Mechanical Operation Lab

Draw a plot of vs. Dp for feed, overflow and underflow. Calculate the effectiveness
of the selected screen by taking the value of Xf, XD and XB from the graph corresponding to
mesh opening of the screen.
Assumption: The cut diameter is assumed to be mesh opening.

OBSERVATION:

Sample material =
Total weight of sample =
W= weight retained on each mesh g
xi = Weight fraction; = cumulative weight fraction

Draw a graph of Vs DP

CALCULATION:

From graph,
XF = ; XD= ; XB=

The effectiveness ( E) of ____________ mesh screen is

E = (XF XB) (XD XF) (1 - XB) XD / XD XB)2 (1-XF) XF

RESULT:

The effectiveness of __________mesh screen by analysis of the feed, oversize and under is
found to be_________.

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