Allowances
Practice Problems
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
•
•
•
•
Illumination – 25 fc in work area
Noise – fairly continuous 91 dBA in work area
Heat – First hot day of the year, WBGT = 80 °F
No significant mental strain, monotony, or
repetitiveness.
• What is the Standard Time?
Example 1 (cont’d)
• 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.
ILO Recommendations
Table 11-2, Niebel & Frievalds p. 437
Example 1 (cont’d)
• More thorough method
– Use Table 11-11, p. 453.
• Some factors can be found directly
from the table
– Constant
– Posture
– Visual Strain
• Others must be calculated.
Example 1 (cont’d)
• Personal needs = 5% (always constant)
• Basic Fatigue = 4% (always constant
• Posture – standing = 2%
– Why isn’t there an option for seated?
• Visual Strain – Fine assembly = 2%
• Mental Stress, Monotony, Repetitiveness =
0%.
Example 1 (cont’d)
• 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%
Example 1 (cont’d)
• 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.
Example 1 – (cont’d)
• 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 (D – 1)
–
= 100 x (1.15-1)
– RA = 15%
Example 1 (cont’d)
• Find Standard Time
– ST = NT x (1 + Σ 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)
»
– ST = 90 x (1.53)
– ST = 137.7 cmin
HEAT
NOISE
Example 1 - Redesign
• As a process engineer, what would be
the first things you would want to do
to bring the standard time closer to
the 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?
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 the
impact of these three factors on work
performance
– based on the data you will collect
– AND, based on some homework problems you
will receive in lab.
Homework
• Work the following problems
– Ch. 11 – Prob #1, 2, 3, 5 & 7.
• Due one week from today.
• This is in addition to the homework
you will receive in lab today!!
– But, there’s no report due next week. 