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 ?

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

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

Prepare

Construct

Prepare

Install

Continuous activity

From WBS summary activities or sub-projects or work package

CODE RESP.

Rolling wave subnets

MastersummaryscheduleT

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

Prepare

Construct

Prepare

Install

Continuous activity

From WBS summary activities or sub-projects or work package

CODE RESP.

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

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

Buy land Owner 1 0 1

Study site Architect 2 1 3

Define requirements

Finalize drawings

Select contractor

Order utilities

Plan construction

Architect

Contractor

Bar chart for house project Summary activity: Planning #10

# Activity Duration(weeks)

Buy land(Owner)

Study site(Architect)

Define requirements

Finalize drawings

Select contractor

Order utilities

Plan construction

(Architect)

(Owner)

(Architect)

(Contractor)

1 2 3 4 5 6 7

xxxx xxxx

Arrow diagram

PERT diagram

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

Buy land

103 1Finalize drawings

Architect

Plan construction

Contractor

Study site

Architect

102 2Define

requirements

Architect

Select contractor

Order utilities

Architect

DurationActivityident. no.

Activitydescription

Resource

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

Buy land

Architect

Plan construction

Contractor

Study site

Architect

102 2Define

requirements

Architect

Select contractor

Order utilities

Architect

DurationActivityident. no.

Activitydescription

Resource

Time-scaled precedence diagramHouse project

Activity Box

Architect

Study site

Architect

Define requirements

Architect

100 1Buy land

FenceSlack orfloat

1 2 3 4 5 6 7Time scale in weeks

Orderutilities

Architect

Plan construction

Contractor

Select contractor

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

Train salesmen

Sell to distributors

Source: Mulvaney, Analysis Bar Charting

Two predecessors

Agree on testspecification

Obtain testequipment

Test part X

Multiple starts after decision

Prepare contractors’ list

Start working drawings

Arrangeaccess road

Prepare engineering

subcontracts

Instructarchitects to

proceed (Approval)

Cross-relationships

Machine part I

Machine part II

Obtain rawmaterial

Issue jobcards

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

CalculationsSolve for ES, EF, LS, and LF

EFESES ES

LFLS LFLS

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

Critical path

Don’t take shortcuts.

Mechanics of calculations

Backward pass

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.

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

Finish

(Weeks)

“Sample” network calculations Solution

Finish

(Weeks)

0 4 4 6

8 10 10 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

Define102

Plan103

Select104

Plan construction

2 21 1

Permits101

Utilities102

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

(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

Planprepared

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

Study site

Architect

Define requirements

Architect

100 1Buy land

FenceSlack orfloat

1 2 3 4 5 6 7Time scale in weeks

Orderutilities

Architect

Plan construction

Contractor

Select contractor

Prepare plan : 2W

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

2WPrepare plan

Prepare Plan

Broadened arrow Lengthened box

Time-scaled bar

Node and arrow merge

Typically not worth the effort

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)

102 2 104 2

Precedence diagram

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

Precedence diagram with critical path3 4

4 62 3

Critical path

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

Number:

Arrow diagram

2-6 Constraint dummy5-4 Procedural dummny

Module 7 Session 7.1 Visual 1 Module 7 Planning and Scheduling with the Critical Path Method Session...

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