Tài liệu Project Planning and Control Part 5 ppt

21

Subdivision of blocks

One major point which requires stressing covers

the composition of a string of activities. It has

already been mentioned that the site should be

divided into blocks which are compatible with

the design networks. However, each block could

in itself be a very large area and a complex

operational unit. It is necessary, therefore, to

subdivide each block into logical units. There are

various ways of doing this. The subdivision could

be by:

1 Similar items of equipment;

2 Trades and disciplines;

3 Geographical proximity;

4 Operational systems;

5 Stages of completion.

Each subdivision has its own merits and justifies

further examination.

1 Similar items of equipment

Here the network shows a series of strings which

collect together similar items of equipment, such

as pumps, tanks, vessels, boilers, and roads. This

is shown in Figure 21.1.

Set pump

Erect

tank bott.

Harden

Erect

roof

Insulate

Hardening

Construct

pad

Cast

pipes

Align

motor

Erect

shell

Erect

exchanger

Cast

founds.

Construct

base

Cast

founds.

Excavate

Excavate

Excavate

Pump A

Tank A

Exchanger A

Pump B

Tank B

Exchanger B

Pump C

Tank C

Exchanger C

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Advantages:

(a) Equipment items are quickly found;

(b) Interface with design network is easily established.

2 Trades and disciplines

This network groups the work according to type. It is shown in Figure

21.2.

Advantages:

(a) Suitable when it is desirable to clear a trade off the site as soon as

completed;

(b) Eases resource loading of individual trades.

3 Geographical proximity

It may be considered useful to group together activities which are

geographically close to each other without further segregation into types or

trades. This is shown in Figure 21.3.

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Figure 21.1 Similar items of equipment

Align

Align

Test

Test

Concrete

Lay

pipe

Connect

piping

Set

up

Set

up

Erect

exchanger

Erect

Lay

kerbs

Insulate

Connect

piping

Concrete

Concrete

Build

pier

Construct

base

Construct

base

Construct sleepers

Excavate

founds

Excavate

founds

Excavate

founds

Excavate

founds

Grade

area

Level

ground

Pumps A

Pumps B

Exchanger

Vessel

Roads

Piping

Subdivision of blocks

Advantages:

(a) Makes a specific area self-contained and eases control;

(b) Coincides frequently with natural subdivision on site for construction

management.

4 Operational systems

Here the network consists of all the activities associated with a particular

system such as the boiler plant, the crude oil loading and the quarry crushing

and screening. A typical system network is shown in Figure 21.4.

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Figure 21.2 Trades and disciplines

Figure 21.3 Geographical proximity

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Advantages:

(a) Easy to establish and monitor the essential interrelationships of a

particular system;

(b) Particularly useful when commissioning is carried out by system since a

complete ‘package’ can be programmed very easily;

(c) Ideal where stage completion is required.

5 Stages of completion

If particular parts of the site have to be completed earlier than others (i.e. if

the work has to be handed over to the client in well-defined stages), it is

essential that each stage is programmed separately. There will, of course, be

interfaces and links with preceding and succeeding stages, but within these

boundaries the network should be self-contained.

Advantages:

(a) Attention is drawn to activities requiring early completion;

(b) Predictions for completion of each stage are made more quickly;

(c) Resources can be deployed more efficiently;

(d) Temporary shut-off and blanking-off operations can be highlighted.

In most cases a site network is in fact a combination of a number of the above

subdivisions. For example, if the boiler plant and water treatment plant are

168

Figure 21.4 Operational system