pm line of balance
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Line of Balance
Also sometimes called also called the LinearScheduling Method , Sloping Bar Chart, Linear
Sloping Method (LSM) or Vertical Production
Method (VPM)
Used in projects that require a number of identical
units (each unit involves a number of identical or
similar steps)
The method enables tracking progress of the units
and identifying situations where progress is behind or
ahead of schedule.
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Example from bookPage 186
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Example from bookPage 187
This schedule is to be repeated for every crane
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Example from bookPage 187
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Example from bookPage 188
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Line of BalanceSecond Example
Example: a project requires 80 units of an item.
Each unit involves 4 steps: it must be produced,tested, installed, than tested again. It takes 8weeks to complete all the steps.
The completion of each unit is marked by amilestone
A = production
B = testC= installation
D = final test
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As shown, completion of each unit is marked by a milestoneA = production
B = test
C= installation
D = final test
Based on other requirements and available resources, the project schedule specifies that thefollowing number of units must be completed (i.e., reached milestone D) by the following dates:
units completed week
20 10
30 11
10 12
20 13
Production = 4 weeksTest =
1 weekInstallation
= 2 weeks
Finaltest =
1 week
A B C D
Line of BalanceSecond Example
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Looking only at the first 20 units to be completed in week 10, the time by when these
units should have reached the other milestones is shown below
Production = 4 weeks
Test =
1 week Installation
= 2 weeks
Final
test =
1 week
A B C D
initial 20 units: week 6 7 9 10
The times by when the others should reach the milestones is:
A B C D30 7 8 10 11
10 8 9 11 12
20 9 10 12 13
Line of BalanceSecond Example
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The total number of units that should have passed milestone D as of week 13 is 80.
However, for tracking purposes, the number of units that should have passed any of the
milestones anytime before week 13 can be represented on a graph. The graph belowshows number of units that should have passed each milestone by the end ofweek 9.
Units A B C D
20 week 6 7 9 10
30 7 8 10 11
10 8 9 11 12
20 9 10 12 13
Milestone A B C D
80
70
60
50
40
30
20
10
0
80
60
20
LOB
Line of BalanceSecond Example
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This graph shows number of units that should have passed each milestone by the end of
week 10.
Units A B C D
20 week 6 7 9 10
30 7 8 10 11
10 8 9 11 12
20 9 10 12 13
Milestone A B C D
80
70
60
50
40
30
20
10
0
80 80
50
20
The LOB is used to track progress.
Each week the number of units that
actually passed each milestone is
compared to the LOB. Whenever
actual units that passed a milestone
falls belowthe LOB, the work is
behind schedule.
LOB
Line of BalanceSecond Example
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Line of Balance (LOB)
Discrete and Continuous Cases
Discrete steps
e.g. a multi-storey building
Time
F
loorlevel
Brickwork
Plastering
Continuous process
e.g. rail construction
(Slope = rate of progress)
Time
Distance
Lay track
Ballast
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Linear Scheduling Method (LSM)(Construction Extension to PMBOK term for LOB)
often utilized on linear projects
such as highways, pipelines, etc.
where station or mile-post
numbers depict the physical
location of the work.
allows activities to be visuallyrepresented at a physical location
Construction Extension to the PMBoK Guide
Time
Distance(km)
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LOB and Project Control
Consider the following two lines of planned
actual progress for an activity:
Time Axis
Progress
Planned
Actual
(behind
schedule)
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LOB and Project Control
Consider the following two lines of actual
progressfor constructing a road (two activities):
Time Axis
D
istanceA
xis
Compact
subbase
Final Paving
Final paving came to
standstilldelayed
by compacting of
subbase
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LOB and Project Control
The use of buffers in highway construction
Time Axis
D
istanceA
xis
Excavation
Final
pavingCompactsubbase
Time buffer
Distance buffer
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LOB and Project Control
Buffers are also used to provide alag
betweenthe start times of activities
(e.g. to allow time for curing of concrete)
Time buffer
(Lag)
Time
F
loorlevel Cast
concrete
slabs
Build walls
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Advantages of LOB
Rates of progress are shown (unlike Ganttcharts and network diagrams)
For repetitive work, problem areas are easilyspotted
Helpful in allocation of resources to eliminatebottlenecks
Helpful in determining minimum buffer sizes
Simplicity of illustrating work scheduleeasilyunderstood by field staff & management
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Disadvantage of LOB
Useful for repetitive work
(identical units or continuous operations)
Otherwise, less or not applicable