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Allowances
Practice Problems
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Example 1
Suppose you have a fine assembly task Standing
Requires approximately 300 kCal / hr (based on
HR measurement) NT = 90 cmin.
Additional Considerations include Illumination25 fc in work area
Noisefairly continuous 91 dBA in work area
HeatFirst hot day of the year, WBGT = 80 F No significant mental strain, monotony, or
repetitiveness.
What is the Standard Time?
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Example 1 (contd)
ST = NT (1+ allowances)
2 ways to find allowances
Quick & Dirty way Table 11-2 (ILO Recommendations)
More thorough way
Calculate individual relaxation allowances,RA, for each variable and special allowance
factor.
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ILO Recommendations
Table 11-2, Niebel & Frievalds p. 437
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Example 1 (contd)
More thorough method Use Table 11-11, p. 453.
Some factors can be found directlyfrom the table
Constant
Posture
Visual Strain
Others must be calculated.
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Example 1 (contd)
Personal needs = 5% (always constant)
Basic Fatigue = 4% (always constant
Posturestanding = 2% Why isnt there an option for seated?
Visual StrainFine assembly = 2%
Mental Stress, Monotony, Repetitiveness =
0%.
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Example 1 (contd)
Illumination
Looks like a chart lookup, but what are
IES subcategories? Refer to Ch. 6, p. 237, Table 6-2.
Our illumination = 25 fc, or CAT D.
What should our illumination category be?
Do you see fine assembly listed? Should be between medium & extra-fine
assembly.
Should be CAT F, but we are 2 categories below.
From Table 11-11, illumination allowance = 3%
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Example 1 (contd)
Atmospheric Conditions (HEAT)
Workload, W = 300 kcal/hr
WBGT = 80 F
How do you determine WBGT?
RA = e (-41.5 + 0.0161W + 0.497WBGT)
= e (-41.5 + 0.0161x300 + 0.497x80)
= e(3.09)
= 22% Can also lookup RAL from Fig 6-11, p. 253.
RAL for 300 kcal/hr & WBGT = 80 F is 48 min/hr
12 min rest / 48 min work = 25% allowance.
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Example 1(contd)
Noise SPL = 91 dBA
What is SPL
Need to calculate dose for 8 hour day. If 90 dBA is 8 hour-100% dose, what about 91dBA?
Must find time for 100% dose T = 8 / 2 [(L-90)/5]
T = 8 / 2 [(91-90)/5].
T = 6.96 hours is a 100% dose for 91 dBA.
D = 8/6.96 = 1.15.
RA = 100 x (D1)
= 100 x (1.15-1)
RA = 15%
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Example 1 (contd)
Find Standard Time
ST = NT x (1 + allowances)
ST = 90 cmin x (1+0.05+0.04+0.02+0.03+0.02+0.22+0.15)
ST = 90 cmin x (1 + 0.16 + 0.22 + 0.15) HEAT NOISE
ST = 90 x (1.53)
ST = 137.7 cmin
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Example 1 - Redesign
As a process engineer, what would be
the first things you would want to do
to bring the standard time closer tothe NT?
The heat allowance is the largest?
It can be reduced to eliminate extra heat
fatigue.
How?
The noise allowance is the next largest
What would you do about that one?
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Measurement
How do you measure Illumination?
Heat?
Noise? For the next 3 labs, you will practice
measuring these three environmental factors This week, we will begin with noise.
You will write one report that considers theimpact of these three factors on workperformance based on the data you will collect
AND, based on some homework problems you
will receive in lab.
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Homework
Work the following problems
Ch. 11Prob #1, 2, 3, 5 & 7.
Due one week from today.
This is in addition to the homework
you will receive in lab today!! But, theres no report due next week.