Page 60 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

Process Planning, Scheduling and Flowsheet Design 45

to light for evaluation. By contrast it is easy to make a wig [19]. A general check list of factors which usually need
career of even a small assignment when the field of inter- reviewing for the proper layout considerations of chemical
est is narrow and the over-all project perspective is not and petrochemical plants is given in Table 1-11.
clearly in view. There are many other factors which affect project plan-
When the work load is low, it is important to have other ning as it is related to process engineering. However,
assignments for these men. This is the time to develop these are usually peculiar to the process or objective of
standards for: the project. On first glance some of the items listed in
Table 1-11 may appear to be unrelated to the process
1. Design of various types and items of equipment engineering requirements, and this can be the case for
2. Methods of practice and general details some types of projects. In these situations they become
3. Electronic computer programs for these design stan- more of a project engineering responsibility. However, in
dards many cases these have a relationship either to the process
4. Evaluation of field data. engineering requirements or to the decisions which must
take this into account.
These should all be viewed from the long range and
repetitive value to the group effort. The individuals who Cost Estimates
develop these standards in effect become specialists if
they handle the assignment in good detail. Although this chapter is not intended to present the
total details on preparation of capital or production/
Plant Layout operating/manufacturing cost estimates, it is worthwhile
and helpful to provide some usable current references for
The final plant layout combines the various engineer- the engineer who for many situations will be called on lo
ing considerations for soil conditions; drainage; railroad, provide total estimates or contribute to their develop-
truck and services access; raw materials receiving; waste ment. As a guide lo information, procedure and neces-
materials removal; climate effect on outdoor versus indoor sary data, references [10, 11, 12, 13, 14, 19, 21, 22, 23, 24,
operations and on types of structures; prevailing wind 25, 26, 27, 28, 29, 30, 33, 34] can be useful, but they are
direction for vent as well as climatic moisture; corrosion; not all-inclusive, nor do they take the place of a thorough
plant expansion and growth; access to public, and many book on cost estimating for chemical and petrochemical
other general evaluation points. From these broad consid- plants. One of the most difficult problems is locating reli-
erations the details are developed to suit the particular able up-to-date capital costs for equipment (see [ 43]). It
plant process and the combined effects of the location. is not "safe" to escalate or update by indexes [ 42] for costs
The process engineer has an important responsibility that are more than six years old, and certainly not over
in site selection as well as plant layout, since many of the ten years old.
decisions regarding physical location of buildings and The details of the preparation of cost estimates will not
associated equipment require a knowledge of what is tak- be covered. However, it is important to recognize that the
ing place in the operation as well as the hazardous factors process engineer plays a key role in estimate develop-
of explosion, fire, toxicity, etc. The process engineer is ment. From a first draft flowsheet and a preliminary plot
usually called upon to describe the process requirements plan, a preliminary cost estimate can be prepared by the
and limitation to the other engineers-civil, structural, "factoring" or equivalent method. This basically accumu-
mechanical, electrical, and instrument. By progressively lates the individual costs of each item of major equipment
discussing the process each of the others can note the and then multiplies by an experience factor to produce
requirements which might affect the normal or routine one or all of (1) total plant cost installed with or without
design approach to each phase of the project. This review overhead costs (2) piping installed (3) equipment
must not be limited ta the design aspects of the engi- installed. For accuracy, these factors must be developed
neering but rather must describe how the plant is to oper- from actual plant costs, and are often peculiar to a specif-
ate and how product is to be shipped, stored. etc. ic type of construction or engineering approach to the
After the project begins to take shape and preliminary project. That is, they may be a function of a "poor-boy"
layouts of the over-all as well as sections of the plant are par- job, turn-key job, middle-of-the road, or "gold-plated" job.
tially complete, design work by the other phases of engi- These types are peculiar to either the engineering con-
neering will require the answering of questions as well as tractor, the customer or to both. The factor of 2.5 to 6.0
evaluating details of a particular phase as they are related usually covers most petrochemical processing plants. This
to the process performance. Some useful considerations factor times the costs of major equipment (pumps, com-
for selected details are given by Thompson [ 17] and Luci- pressors, tanks, columns, exchangers) but not instru-