Читать книгу Petroleum Refining Design and Applications Handbook - A. Kayode Coker - Страница 46

Although the working role of the process design engineer may include all of the technical requirements listed above, it is very important to recognize what this entails in some detail. The process design engineer, in addition to being capable of participating in evaluation of research and pilot plant data and the conversion of this data into a proposed commercial process scheme, must also perform the following functions:

1 1. Prepare heat and mass balance studies for a proposed process, both “by hand” and by use of computer programs. The use of a spreadsheet package (e.g., Excel) is now prevalent in accomplishing these calculations. Simulation software products from vendors are now apt in performing these tasks.

2 2. Prepare rough cost economics, including preliminary sizing and important details of equipment, factor to an order of magnitude capital cost estimate [3] (see also [2]), prepare a production cost estimate and work with economic evaluation representatives to establish a payout and the financial economics of the proposed process.

3 3. Participate in layout planning for the proposed plant (see [4, 5]).

4 4. Prepare final detailed heat and material balances.

5 5. Prepare detailed sizing of all process equipment and possibly some utility systems. It is important that the process engineer visualizes the flow and processing of the fluids through the system and inside the various items of equipment in order to adequately recognize what will take place during the process.

6 6. Prepare/supervise preparation of draft of process flowsheets for review by others.

7 7. Prepare/supervise preparation of piping or mechanical flow diagram or piping and instrumentation diagram (P&ID), with necessary preliminary sizing of all pipe lines, distillation equipment, pumps, compressors, and so on, and representation of all instrumentation for detailing by instrument engineers.

8 8. Prepare mechanical and process specifications for all equipment, tanks, pumps, compressors, separators, drying systems, and refrigeration systems. This must include the selection of materials of construction and safety systems and the coordination of specifications with instrumentation and electrical requirements.

9 9. Determine size and specifications for all safety relief valves and/or rupture disks for process safety relief (including runaway reactions) and relief in case of external fire.

10 10. Prepare valve code specifications for incorporation on item 7 above, or select from existing company standards for the fluids and their operating conditions (see Figures 14.21 and 14.22).

11 11. Select from company insulation standards (or prepare, if necessary) the insulation codes to be applied to each hot or cold pipe or equipment. Note that insulation must be applied in some cases only to prevent operating personnel from contacting the base equipment. Table 14.1 for typical insulation thickness from which code numbers can be established.

12 12. Establish field construction hydraulic test pressures for each process equipment. Sometimes the equipment is blanked or blocked off, and no test pressure is applied in the field, because all pressure equipment must be tested in the fabricators’ or manufacturers’ shop as per American Society of Mechanical Engineers (ASME) Code.

13 13. Prepare drafts of line schedule and/or summary sheets (Figures 14.20a–14.20d), and equipment summary schedules (Figures 14.23–14.28), plus summary schedules for safety relief valves and rupture disks, compressors and other major equipment. Some of the process data sheets and equipment schedules (over 30) are readily available for downloading from the companion website.

14 14. Prepare detailed process and mechanical specifications for developing proposals for purchase by the purchasing department.

15 15. Participate and possibly lead the process hazard reviews (i.e., hazard and operability studies, (HAZOP) (Chapter 24).

Table 14.1 Typical thickness chart—insulation for services 70°F through 1200°F piping, vessels, and equipment 36” diameter and smaller.

Insulation thickness
Pipe size	1”	1½”	2”	2½”	3”
≤2½”	700°F	1000°F	1200°F
≤3”	700	900	1100	1200°F
≤4”	700	900	1100	1200
≤6”	600	800	1000	1200
≤8”	–	800	1000	1200
≤10”	–	800	1000	1200
≤12”	–	800	1000	1200
≤14”	–	800	1000	1100	1200°F
≤16”	–	800	900	1100	1200
≤18”	–	800	900	1100	1200
≤20”	–	800	900	1100	1200
≤24”	–	800	900	1100	1200
≤30”	–	800	900	1100	1200
≤36”	–	800	900	1000	1200

Notes: 1. Temperatures in chart are maximum operating temperatures in degrees Fahrenheit for given thickness.

2. All hot insulated piping shall be coded, including piping insulated for personnel protection. Thickness is a function of insulation composition.

The process design engineer actually interprets the process into appropriate hardware (equipment) to accomplish the process requirements. Therefore, the engineer must be interested in and conversant with the layout of the plant; the relationship of equipment for maintenance; the safety relationships of equipment in the plant; the possibilities for fire and/or explosion; the possibilities for external fire on the equipment areas of the plant; the existence of hazardous conditions, including toxic materials and pollution, that could arise; and, in general the overall picture.

The engineer’s ability to recognize the interrelationships of the various engineering disciplines with the process requirements is essential to thorough design. For example, the recognition of metallurgy and certain metallurgical testing requirements as they relate to the corrosion in the process environment is absolutely necessary to obtain a reliable process design and equipment specification. An example of the importance of this is hydrogen brittlement (see latest charts [6]). Another important area is water service (see [7]). The engineer selecting the materials of construction should recognize the importance of plastics and plastic composites in the design of industrial equipment and appreciate that plastics often serve as better corrosive resistant materials than do metals.