Page 48 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

Process Planning, Scheduling and Flowsheet Design 33

• RP4.l Uniform Face-to-Face Dimensions for Flanged this conversion has been slow. This is primarily due to the
Control Valve Bodies fact that engineers are more familiar with the "more prac-
• RP4.2 Standard Control Valve Manifold Designs tical" engineering units and also few text books using SI
• S5.1 Instrumentation Flow Plan Symbols units are available. The conversion in the industry is awk-
• RP7. l Pneumatic Control Circuit Pressure Test ward and confusing because there is no "feel" for the
• RP7.2 Color Code for Panel Tubing practical meaning of the SI terms.
• RP8. l Instrument Enclosures for Industrial Environ-
ments System Design Pressures
• RPI 2.1 Electrical Instruments in Hazardous Atmos-
pheres In order to coordinate the design pressures for the var-
• RP12.2 Intrinsically Safe and Non-Incendive Electri- ious vessels in a given process system, it is necessary to
cal Instruments establish the relationship between the operating and
• Sl2.4 Instrument Purging for Reduction of Haz- design conditions. Figure 1-33 and Tables 1-5 and 1-6 are
ardous Area Classification guides to setting the percentage for the design pressure
over the operating pressure. This type of relationship can
• RP18.1 Specifications and Guides for the Use of Gen- be established according to the preferences of the respon-
eral Purpose Annunciators sible engineer or company policy. In the range near
• RP20.l, and 20.2 Specification Forms for Instruments
atmospheric pressure the preferences vary, however, for
Federal Safety Standards for Pipelines; Part 195-Trans-
portation of liquids by Pipelines.
Often the process design engineer will become Table 1-5
involved in managing a project, especially if he/she Suggested System Design Pressures
designed the specifications for fabrication and purchase (Based upon condensation at l00°F with 10°F approach)
of the equipment for the project. It is necessary that the System Design Pressure, psig
process engineer participate in equipment layout/
arrangement decisions for the early stages of the plant Freon-!! (or equivalent) 50
development. With all this background, 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 fl9]). Table 1-6
The process engineer should be responsible for under- Suggested Maximum Operating Pressure
standing the following regulations: Usual Condition of Maximum
System Operating Pressure
l. 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, 28]. mum ambient temperature plus
30° F. ( usually 110° to 140° F.)
(b) safety of the plant layout environment which
might influence the safety of the plant facilities. Process Vessels Depends upon operating condi-
2. 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, 31]. (2) Reciprocating Type Normal operating pressure plus
15 psi for low pressures to plus
50 psi for 200-3000 psi system.
Although the U.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.
the metric standards, or SI units, the actual progress in Water, etc.