module 7 session 7.1 visual 1 module 7 planning and scheduling with the critical path method session...

Module 7 Session 7.1 Visual 1

Module 7

Planning and Scheduling with the Critical Path Method

Session 7.1: Planning tools and the critical path method (CPM)


Instructional Objective

To prepare a critical path networkplan for projects or subprojects


Overview

Planning activities

Scheduling resources and

Controlling progress


On-the-job tasks

Review the WBS, responsibility matrix, master summary schedule, and level of detail

Select the appropriate scheduling tool (typically time-scaled, precedence network diagram)

Disaggregate summary activities on the master summary schedule into activities and prepare activity list(s)

Assign responsibility and resource to each activity


On-the-job tasks (continued)

Estimate the duration of each activity

Establish the sequence of activities

Prepare the time-scaled precedence network diagram (or other form of schedule)

Determine the critical path

Calculate the activity float

Revise as required


What is planning ?

Who ?

Does what?

When ? and

How long will it take?

With what inter-relationships?


Why is planning important ?

Coordination

Control

Communication

Commitment


A cargo ship: an analogy

Start of journey

Destination

Course set in

itially


A cargo ship: an analogy

Externalinfluence

Res

et c

ours

e

Actual travelPosition surveyed

Start of journey

Destination

Course set in

itially


Planning tools

Activity lists

Bar chart (Gantt)

Network diagram family


Planning tools


Critical path method (CPM)

Precedence diagram (PDM)

Time-scaled precedence diagram

Arrow diagram

PERT diagram


Master summary schedule House deliverable

Plan (A)

Site (C)

Foundation (C)

Frame (C)

Roof (SC)

Systems(SC) Plumbing (P) Electrical (E) Telephone (T)

Project mgt (PM)

4 8 12 16 20 24

WEEKS

Prepare

Construct

Construct

Construct

Prepare

Install

Continuous activity

From WBS summary activities or sub-projects or work package

CODE RESP.

10

20

30

40

50

60

70


Rolling wave subnets

MastersummaryscheduleT

od

ay

Start Finish

Detailed network for next period

Each monthadd a month

Each monthdrop a month

3-6 months

Level of detailmonths or weeks

Level of detailweeks or days


Guidelines for creating activities Disaggregate summary activities into activities Use “rolling wave” approach for long projects Use unit of time based on and less than previously

established control period Use verb (action) and a noun (the thing affected), for

example, buy land Assign responsibility to only one organization or

individual Assign only one resource to each activity Code with a “family member” Do not disaggregate project management


Master summary schedule House deliverable

Plan (A)

Site (C)

Foundation (C)

Frame (C)

Roof (SC)

Systems(SC) Plumbing (P) Electrical (E) Telephone (T)

Project mgt (PM)

4 8 12 16 20 24

WEEKS

Prepare

Construct

Construct

Construct

Prepare

Install

Continuous activity

From WBS summary activities or sub-projects or work package

CODE RESP.

10

20

30

40

50

60

70


Summary activity Disaggregate into activities

Terminology: Activity or Task


Summary activity # 10—PLAN Disaggregate into activities

Buy land

Study site

Define requirements

Finalize drawings

Select contractor

Order utilities

Plan construction


Activity list for house projectSummary activity: Planning #10

100

# Activity Responsibility Duration Start Finish(weeks) (weeks)

Buy land Owner 1 0 1

102

Study site Architect 2 1 3

103

104

105

106

Define requirements

Finalize drawings

Select contractor

101

Order utilities

Plan construction

Architect

Architect

Owner

Architect

Contractor

2

2

1

1

1

1 3

3 4

4 6

4 5

6 7


Bar chart for house project Summary activity: Planning #10

100

# Activity Duration(weeks)

Buy land(Owner)

1

102

Study site(Architect)

2

103

104

105

106

Define requirements

Finalize drawings

Select contractor

101

Order utilities

Plan construction

(Architect)

(Architect)

(Owner)

(Architect)

(Contractor)

2

2

1

1

1

1 2 3 4 5 6 7

xxxx

xxxx xxxx

xxxx xxxx

xxxx

xxxx xxxx

xxxx

xxxx






Arrow diagram

PERT diagram


Precedence diagram method (PDM)House projectSummary activity: Planning #10

100 1

Buy land

Owner

103 1Finalize drawings

Architect

106 1

Plan construction

Contractor

101 2

Study site

Architect

102 2Define

requirements

Architect

104 2

Select contractor

Owner

105 1

Order utilities

Architect

DurationActivityident. no.

Activitydescription

Resource


Critical Path (thick lines)House projectSummary activity: Planning #10

100 1

Buy land

Owner


Architect

106 1

Plan construction

Contractor

101 2

Study site

Architect

102 2Define

requirements

Architect

104 2

Select contractor

Owner

105 1

Order utilities

Architect

DurationActivityident. no.

Activitydescription

Resource


Time-scaled precedence diagramHouse project

Activity Box


Architect

101 2

Study site

Architect

102 2

Define requirements

Architect

100 1Buy land

Owner

FenceSlack orfloat

1 2 3 4 5 6 7Time scale in weeks

105 1

Orderutilities

Architect

106 1

Plan construction

Contractor

104 2

Select contractor

Owner

Summary activity: Planning #10


Key concepts

Project duration

Critical path

Float or slack


Mathematical Analysis

Early start (ES)

Late start (LS)

Early finish (EF)

Late finish (LF)


Table printout House projectSummary activity: Planning #10

# Activity ResponsibilityDuration(weeks)

Early start

Early finish

Late Start

Late finish

Total float

100 Buy land Owner 1 0 1 0 1 0

101 Study site Architect 2 1 3 1 3 0

102Define requirements

Architect 2 1 3 1 3 0

103Finalize drawings

Architect 1 3 4 3 4 0

104Select contractor

Owner 2 4 6 4 6 0

105 Order utilities Architect 1 4 5 5 6 1

106 Plan Contractor 1 6 7 6 7 0


Tool comparison

Tool When to use Example

Bar chart

Network diagram

Simple sequentiallogic with few parallelactivities

Complex sequentiallogic with many parallelactivities

Road construction

Bridge constructionWater supply systemconstruction


Making a CPM network:The process

Create activity list form for summary activities

Disaggregate summary activities and complete activity forms

Conduct meeting with managers

Develop logical sequence

Create network diagram

Blackboard version

Computer version


Activity listProject no.________Title: _______________________________ Summary activity No._________Title _______________

Date prepared: ____________________ Responsible person: _______________________________

No. Description Organizationalunit

Individualresponsibility

Manpowernumber

Cost Duration Start Date* Finish date*

* To be filled in after CPM is completed.


Making a PDM network:The mechanics

1. Make activities flow from left to right

2. Have one start box and one finish box

3. Draw arrows as you go

4. Draw arrows to and from end of box and parallel to horizontal

5. Can show any logic

6. Try to avoid crossing lines

7. Leave no hanging activities (danglers)


Simple finish to start

Hire salesmen

1

Train salesmen

3

Sell to distributors

5

Source: Mulvaney, Analysis Bar Charting


Two predecessors

Agree on testspecification

16

Obtain testequipment

18

Test part X

20



Multiple starts after decision

Prepare contractors’ list

23

Start working drawings

25

Arrangeaccess road

27

Prepare engineering

subcontracts

29

Instructarchitects to

proceed (Approval)

21



Cross-relationships

Machine part I

143

Machine part II

145

Obtain rawmaterial

139

Issue jobcards

141



Making a PDM network:The mechanics

1. Make activities flow from left to right

2. Have one start box and one finish box

3. Draw arrows as you go

4. Draw arrows to and from end of box and parallel to horizontal

5. Can show any logic

6. Try to avoid crossing lines

7. Leave no hanging activities (danglers)


Hanging activities

Start Finish

A

B

C

D

E

F


CalculationsSolve for ES, EF, LS, and LF

0 2

LFLS

A2

B4

D1

C2

EFESES ES

ES

EF

EF

EF

LFLS LFLS

LFLS


CalculationsSolve for ES, EF, LS, and LF (continued)

0 2

LFLS

A2

B4

D1

C2

Critical path

2 6

62

6 7

76

2 4

64

0 2

EFES

Don’t take shortcuts.


Mechanics of calculations

Backward pass

0 3

0 3

33 7

3 7

47 9

7 9

2

From rightto left

Write onbottom

Finds criticalpath and float

When a choice is available, take the lowest.

Forward pass From leftto right

Write on top Finds duration

When a choice is available, take the highest.

A B C


Summary

Planning is essential

Tools facilitate planning

Critical path and float are key concepts

Calculating the network is an essential skill


“Sample” network calculations Problem

Start

Finish

0 0 4

A4

C2

D5

B2

E1

(Weeks)


“Sample” network calculations Solution

Start

Finish

0 0 4

A4

C2

D5

B2

E1

(Weeks)

4 6

0 4 4 6

2 3

6 11

6 11

0 2

8 10 10 11

11

11

Criticalpath

Path B - Efloat = 8


B : 2 E 1

A : : : 4 C : 2 : D : : 5

1 2 3 4 5 6 7 8

Start Finish

B and E share path float of 8 (Total)Depending on when B is done E could have less activity float (Free)

0 1 2 3 4 5 6 7 8 9 10 11

“Sample” time-scaled precedence diagram Solution


Two kinds of float or slack

Activity float (Free)

Path float (Total)


Module 7

Planning and Scheduling with the Critical Path Method

Session 7.1Planning Tools: Arrow Diagram and PERT Diagram






Arrow diagram

PERT diagram

Planning tools: Arrow diagram and PERT diagram


Restate history

Draw distinctions

Give reasons why precedence diagrams are recommended

Objectives


Arrow Kelly and Walker at Du Pont

How to solve scheduling problems

U.S.A., 1957

Precedence France

PERT Booz-Allen and Hamilton

Polaris Submarine (US Navy)

U.S.A.

History


Arrow diagram networkHouse project

1

2

3

4 5

6

7 8

Define102

Plan103

Select104

Plan construction

106

2 21 1

Permits101

Utilities102

12

Duration in weeksDotted lines are dummy activities.Dummies are zero time dependencies.

Buy land1001



PERT diagram

Completeplans

Landbought

Start0

Event on node 3 time estimates

Shortest 1.5Most likely 3.0Longest 5.0

Expected time 3.08

FormulaFormula

3.08

(1 x shortest) + (4 x most likely) + (1 x longest) = 1.5 + 12 + 5 = 18.56 6 6


Three types of network methods

4 5 Prepare plan3

3

Planprepared

3.08

Activity on arrow Activity on node Event on node

Arrow diagram Precedence diagram (PDM)

Original PERT3 time estimates


Time-scaled precedence diagramHouse project

Activity Box


Architect

101 2

Study site

Architect

102 2

Define requirements

Architect

100 1Buy land

Owner

FenceSlack orfloat

1 2 3 4 5 6 7Time scale in weeks

105 1

Orderutilities

Architect

106 1

Plan construction

Contractor

104 2

Select contractor

Owner



Prepare plan : 2W

Time-scaled precedence diagram(merging Arrow and Precedence diagrams)

2WPrepare plan

2W

or

Prepare Plan

Broadened arrow Lengthened box

Time-scaled bar

Node and arrow merge


PERT

Typically not worth the effort

Arrow

Can be complicated to learn

Precedence

Easiest to learn and use

Supported by PC software

Which diagram to use?


Summary: Key ideas

Planning – a process, not an event

Planning tools select – the right one

CPM – a powerful, focusing methodology

Time-scaled precedence diagram – recommended


Summary: Networking process

Create activity form for summary activities

Define objectives, deliverables, and summary activities

Disaggregate summary activities

List activities and responsibilities

Assign responsibility

Estimate duration for each activity

Sequence activities

Calculate the network (Critical path + float)


START

G

A

B

C

D

I

F

E

H

106 4

108 1

105 3

109 1

103 1

101 2

102 2 104 2

107 1

Precedence diagram

0

Activity 7.1.3: ABC, Network Analysis Exercise, Solution 1 of 6


START

C

D

I

F

E

H

106 4

108 1

105 3

109 1

103 1

104 2

Precedence diagram with critical path3 4

G

107 1

0 1

4 5

A

101 2

0 2

1 3

B

102 2

0 2

0 2

02 3

2 3

2 4

4 62 3

5 6

5 6

3 6

3 6

6 10

6 10

Critical path

0




Company: Scale: 4=1 Week Title: ABC, Network Plannning Exercise

Division: Unit of Time: Manager:

Approved: Prepared by: Date:

107 G 1108 H 1

101 A 2

102 B 2103 C 1

105 : E 3

109 I 1

104 D 2

106 : : F 4

1 2 3 4 5 6 7 8 9 10

Weeks

Number:



Arrow diagram

1

6

2

3 4

5

7

2-6 Constraint dummy5-4 Procedural dummny

4F

1I

2

D

E3

C1

B2

A2

G1

H1

0

0


module 7 session 7.1 visual 1 module 7 planning and scheduling with the critical path method session...

Documents

activity slide

required slide

days slide

progress slide

critical path method

project management slide

wbs summary activities

critical path method