PM Line of Balance

8/11/2019 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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This schedule is to be repeated for every crane


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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



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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



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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



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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



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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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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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The use of buffers in highway construction

Time Axis

D

istanceA

xis

Excavation

Final

pavingCompactsubbase

Time buffer

Distance buffer


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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

PM Line of Balance

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