Page 45 - Applied Process Design for Chemical and Petrochemical Plants Volume I

Process Planning, Scheduling and Flowsheet Design 33

4.1 Uniform Face-to-Face Dimensions for Flanged this conversion has been slow. This is primarily due to the
ntrol ‘Valve Bodies fact that engineers are more familiar with the “more prac-
6) W4.2 Standard Control Valve Manifold Designs tical” engineering units and also few text books using SI
0 S5.1 Instrumentation Flow Plan Symbols units are available. The conversion in the industry is awk-
0 lRP7.1 Pneumatic Control Circuit Pressure Test ward and confusing because there is no “feel” for the
6) W7.2 C~OP Code for Panel Tubing practical meaning of the SI terms.
0 W8.1 Instrument Enclosures for Industrial Environ-
System Design Pressures
.I Electxical Instruments in Hazardous Atmos-
In order to coordinate the design pressures for the var-
ious vessels in a given process system, it is necessary to
Intrinsically Safe and Non-Incendive Electri-
establish the relationship between the operating and
design conditions. Figure 1-33 and Tables 1-5 and 1-6 are
11) 312.4 Instrument Purging fior Reduction of Haz- guides to setting the percentage for the design pressure
ardous kea Chssifncation over the operating pressure. This type of relationship can
8.1 Specifications and Guides for the Use of Gen- be established according to the preferences of the respon-
Purpose Annunciators sible engineer or company policy. In the range near
8.1, and 20.2 Specification! Forms for Instruments
atmospheric pressure the preferences vary, however, for
Federal Safety Standards for Pipelines; Part 195Trans-
portation of liquids by Pipelines.
Often the process design cngineer will become Table 1-5
involved in managing a project, especially if he/she
designed the specifications for fabrication and purchase
of the equipment for the project. It is necessary that the
process engineer participate in equipment layout/
arrangement decisions for the e,arly stages of the plant Freon - 11 (or equivalent) 50
development. With all this backgy ound, the process engi- Freon - 12 (or equivalent) 200
neer is the logical person to handle or coordinate the Freon - 22 (or equivalent) 300
interrelationships of the various engineering disciplines Ammonia 250
and to review and (evaluate the equipment purchase pro- Chlorine 300
posals from the purchasing department. The role of a
project engineer often grows from the process design
engineer’s responsibilities (see [ 191 ) . Table 4-6
The process engineer should be responsible for under- Suggested Maximum Operating Pressure
standing the following regulations: Usual Condition of Maxbnum
System Opterating Pressure
Occupational Safety and Health Administration reg- Refrigeration Systems Refrigerant vapor pressure at
ulations as they relate to (a) safety of design related temperature 10”-15” F. above
to injury to personnel (includes such matters as lat- condensing water.
est vessel design [53], noise level from operating Storage Vessels Vapor pressure of liquid at maxi-
equipment, etc., [20, 21, 22, 23, 24, 25, 26, 27, 281. mum ambient temperature plus
30°F. (usually 110” to 140” F.)
(b) safety of the plant layout environment which
might influeme the safety of the plant facilities. Process Vessels Depends upon operating condi-
Environmental Protection Agency regulations relat- tions, surge conditions, insulation.
toxicity, explosion hazard, etc.
ed to air, water, solid waste, and land contamination
with toxic substances that a plant might emit/release A. In a compressor or pump
system:
into immediate plant area, or discharge as waste into
public streams, or inject into underground aquafiers, ( 1 ) Centrifugal Type Shut-off pressure plus 5 psi
or dump or store [29, 30, 311. (2) Reciprocating Type Normal operating pressure plus
15 psi for low pressures to plus
50 psi for 200-3000 psi system.
Although the 7J.S chemical industry is committed to B. Direct Injection of Steam, Supply line pressure plus 5 psi
converting from American Engineering Standard units to Air, Methane, Cooling to 15 psi.
Water, etc.
the metric standards, or SI units, the actual progress in