Page 119 - Plant design and economics for chemical engineers

GENERAL DESIGN CONSIDERATIONS 95

inspected and appraised on the basis of all the factors influencing the final
decision. Many times, the advantages of locating a new plant on land or near
other facilities already owned by the concern that is building the new plant
outweigh the disadvantages of the particular location. In any case, however, the
final decision on selecting the plant site should take into consideration all the
factors that can affect the ultimate success of the overall operation.

PLANT LAYOUT
After the process flow diagrams are completed and before detailed piping,
structural, and electrical design can begin, the layout of process units in a plant
and the equipment within these process units must be planned. This layout can
play an important part in determining construction and manufacturing costs,
and thus must be planned carefully with attention being given to future
problems that may arise. Since each plant differs in many ways and no two plant
sites are exactly alike, there is no one ideal plant layout. However, proper layout
in each case will include arrangement of processing areas, storage areas, and
handling areas in efficient coordination and with regard to such factors as:

1. New site development or addition to previously developed site
2. Type and quantity of products to be produced
3. Type of process and product control
4. Operational convenience and accessibility
5. Economic distribution of utilities and services
6. Type of buildings and building-code requirements
7. Health and safety considerations
8. Waste-disposal requirements
9. Auxiliary equipment
10. Space available and space required
11. Roads and railroads
12. Possible future expansion

Preparation of the Layout

Scale drawings, complete with elevation indications can be used for determining
the best location for equipment and facilities. Elementary layouts are developed
first. These show the fundamental relationships between storage space and
operating equipment. The next step requires consideration of the safe opera-
tional sequence and gives a primary layout based on the flow of materials, unit
operations, storage, and future expansion. By analyzing all the factors that are
involved in plant layout, a detailed recommendation can be presented, and
drawings and elevations, including isometric drawings of the piping systems, can
be prepared.