Chemical Engineering July 2010 - 59

Starting day
Starting day
6/7 Mon
6/8 Tue
6/9 Wed
6/10 Thu
6/11 Fri
6/12 Sat
6/13 Sun
6/14 Mon
6/15 Tue
6/16 Wed
6/17 Thu
6/18 Fri
6/19 Sat
6/20 Sun
6/21 Mon
6/22 Tue
6/23 Wed
6/24 Thu
6/25 Fri
Source-composite curve
Sink-composite curve
Task 4
-5 -4 -3 -2 -1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Duration, days
1 2 3 4 5 6
Duration, days
1 2 3 4 5 6
Duration, days
FIGURE 4. The time-grand-composite curve is plotted to graphically illustrate the horizontal gaps between source- and sinkcomposite
curves
Starting day (Engineer 1)
Extra work days
5/3 Mon
5/4 Tue
5/5 Wed
5/6 Thu
5/7 Fri
5/8 Sat
5/9 Sun
5/10 Mon
5/11 Tue
5/12 Wed
5/13 Thu
5/14 Fri
5/15 Sat
5/16 Sun
5/17 Mon
5/18 Tue
5/19 Wed
5/20 Thu
5/21 Fri
5/22 Sat
5/23 Sun
5/24 Mon
5/25 Tue
5/26 Wed
Duration, days
Task 3
Task 3
Move 2 days
2 excess work days
Task 7
Task 1
Task 5
Task 2
Pinch = Mon, May 10th
2 excess work days
Task 6
Pinch = Thu, May 20th
Starting day (Engineer 2)
Extra work days
Source-composite curve
Sink-composite curve
Task 2
Pinch = Fri, June 18th
Task 3
Pinch = Fri, June 18th
2 days
Task 1
Starting day
2 days
1 day
3 days
Task 4
Task 4
Move 4 days
Task 8
-3 -2 -1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
-4 -3 -2 -1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Excess work days
Duration, days
FIGURE 5. When plotting the composite curves for two individual engineers separately, but side by side, it becomes readily apparent
that Engineer 1 has an earlier pinch day, so he may be available to assist Engineer 2 after this date
Starting day (Engineer 1)
Extra work days
5/3 Mon
5/4 Tue
5/5 Wed
5/6 Thu
5/7 Fri
5/8 Sat
5/9 Sun
5/10 Mon
5/11 Tue
5/12 Wed
5/13 Thu
5/14 Fri
5/15 Sat
5/16 Sun
5/17 Mon
5/18 Tue
5/19 Wed
5/20 Thu
5/21 Fri
5/22 Sat
5/23 Sun
5/24 Mon
5/25 Tue
5/26 Wed
Duration, days
Task 3
Off days
Task 7
Task 2
Pinch = Mon, May 10th
Task 6
New pinches
Task 1
Task 5
Starting day (Engineer 2)
Extra work day
New pinch = Fri, May 7th
Supported by
Engineer 1
Source-composite curve
Sink-composite curve
Task 4
Task 8
-3 -2 -1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
-1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
Duration, days
FIGURE 6. Task integration between 2 engineers can be accomplished by removing excess workdays from the source-composite
curve of Engineer 1 and transferring them to the source-composite curve of Engineer 2. Note how this generates a new (and
earlier) pinch point for Engineer 2
point (such as waste heat, wastewater
and so on), the region above the pinch
is experiencing a resource deficit. We
then disconnect the sink-composite
curve of Engineer 1, and shift the
available tasks below the pinch as far
to the right as possible. As a result,
Engineer 1 has two excess work days
upon the completion of Tasks 2 (May
10th, 11th) and 3 (May 17th and 18th),
respectively. These excess work days
may be utilized to assist Engineer 2 in
completing Tasks 6 and 7.
One could logically expect that the
availability of four excess work days of
Engineer 1 will completely remove the
four extra work days needed by Engineer
2. However, this is not the case.
As shown in Figure 6, a new pinch
day forms for Engineer 2 on May 7th,
which creates a new bottleneck for this
case. Thus, this pinch analysis reveals
that Engineer 1 will only need to contribute
three of the excess workdays
to Engineer 2. For this case, any three
of the four excess days that Engineer
1 can contribute will help Engineer 2
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Chemical Engineering July 2010

Table of Contents for the Digital Edition of Chemical Engineering July 2010
