Page 37 - Analysis, Synthesis and Design of Chemical Processes, Third Edition

Table 1.2 Conventions Used for Identifying Process Equipment

Table 1.2 provides the information necessary for the identification of the process equipment icons shown
in a PFD. As an example of how to use this information, consider the unit operation P-101A/B and what
each number or letter means.
P-101A/B identifies the equipment as a pump.
P-101A/B indicates that the pump is located in area 100 of the plant.
P-101A/B indicates that this specific pump is number 01 in unit 100.
P-101A/B indicates that a backup pump is installed. Thus, there are two identical pumps P-101A
and P-101B. One pump will be operating while the other is idle.

The 100 area designation will be used for the benzene process throughout this text. Other processes
presented in the text will carry other area designations. Along the top of the PFD, each piece of process
equipment is assigned a descriptive name. From Figure 1.3 it can be seen that Pump P-101 is called the
“toluene feed pump.” This name will be commonly used in discussions about the process and is
synonymous with P-101.

During the life of the plant, many modifications will be made to the process; often it will be necessary to
replace or eliminate process equipment. When a piece of equipment wears out and is replaced by a new
unit that provides essentially the same process function as the old unit, then it is not uncommon for the

new piece of equipment to inherit the old equipment’s name and number (often an additional letter suffix
will be used, e.g., H-101 might become H-101A). On the other hand, if a significant process modification
takes place, then it is usual to use new equipment numbers and names. Example 1.1, taken from Figure
1.3, illustrates this concept.

Example 1.1

Operators report frequent problems with E-102, which are to be investigated. The PFD for the plant’s
100 area is reviewed, and E-102 is identified as the “Reactor Effluent Cooler.” The process stream
entering the cooler is a mixture of condensable and noncondensable gases at 654°C that are partially
condensed to form a two-phase mixture. The coolant is water at 30°C. These conditions characterize a

complex heat transfer problem. In addition, operators have noticed that the pressure drop across E-102