Figure 2-2.--Estimating time required for a gangway repair job.
F. Drying time (8 hours). This must be counted in
24 man-hours
STEP C
the total estimate even though no work can be
done on the gangway during this period.
4 man-hours
STEP D
G. Giving the second coat of varnish. This step
STEP E
1 man-hour
might take one person about 1 hour.
STEP F
0 man-hour
H. Drying time (8 hours).
1 man-hour
STEP G
I. Putting on the metal fittings. This step might
0 man-hour
take one person about 1 hour.
STEP H
STEP I
Notice that, although there are four people available
1 man-hour
to work on this job, it is not possible for all four to be
33 man-hours
working on it at all times. Most of the work must be
TOTAL
=
done in sequence; for example, you can't finish the
So you find that the total job requires 33 man-hours
surface before you have renewed the stringer and treads,
of work. But what does this mean? Does the number of
and you can`t make the new stringer and treads before
you have made the template. Step A (obtaining the
man-hours tell you how long the job is going to take?
metal fittings) could be performed at any convenient
Is it safe to assume that a job requiring 33 man-hours
time before step I (putting on the metal fittings). The
can be done in 8 1/4 hours if you put four people to
advantage of using a diagram such as the one shown in
work on it? Obviously not, since there is a limit to the
figure 2-2 is that it shows at a glance the total number
number of people who can work on the job at any
of hours that must be allowed for the work-in this
given time.
case, 28 hours.
The unit MAN-HOURS, then, is a measure of
The diagram shows you something else, too: the
amount of work but not of total length of time. You
number of man-hours required for each step. Let's add
should be very cautious about using man-hours when
these up:
estimating how long a job will take, since this measure
does not allow for the sequence in which the work must
STEP A
1 man-hour
be performed, the number of steps required, or the
number of people who can work on the job at each
STEP B
1 man-hour
step.
2-15