Process Control Diagram

Figure 7-2. Portion of typical Process Flow Diagram. Figure 7-3. Portion of typical Process Control Diagram.

To do this, the piping analyst decides on the valves required to meet the process and specification requirements including all the instruments shown on the process control diagrams. He then... 

Figure 16.8 Aspen Dynamics process control diagram with pressure-compensated temperature control.

FIGURE Process control diagram for (a) SVE, (b) air sparging, (c) direct chemicai injection, (d) geochemical enhancement tor bioremediation. [Reprinted with permission from Alternatvies for Groundwater Cleanup, 1994, by the National Academy of Sciences. Courtesy of the National Academy Press, V feishington, D.C.]... 

Classification of Process Control Strategies 1.3.1 Process Control Diagrams... 

The second area, the implementation of a modem process monitoring and control system, is the most dramatic current appHcation of CAD/CAM technology to the chemical process industry. The state of the art is the use of computer graphics to display the process flow diagram for sections of the process, current operating conditions, and controUer-set points. The process operator can interact directly with the control algorithms through the... 

Fig. 1. Process flow diagram for the selection of an exhaust control system.

Q7 PROCESS CHART. PARETO ANALYSIS, CAUSE AND EFFECT DIAGRAM, HISTOGRAM, CORRELATION DIAGRAMS, PROCESS CONTROL CHARTS, CHECK SHEETS... 

Fig. 4.27 Block diagram for liquid-level process control system.

Process flow diagrams are more complex and show all main flow streams including valves to enhance the understanding of the process as well as pressures and temperatures on all feed and product lines within all major vessels and in and out of headers and heat exchangers, and points of pressure and temperature control. Also, information on construction materials, pump capacities and pressure heads, compressor horsepower, and vessel design pressures and temperatures are shown when necessary for clarity. In addition, process flow diagrams usually show major components of control loops along with key utilities. 

You can quickly identify these plant sections by reviewing process flow diagrams and valving arrangements. Isolation points are defined by control valves or powered block valves that can be remotely activated. Process hazard analysis techniques help you identify the maximum credible accident scenarios. (Note that manual valves should not be considered reliable isolation points unless they are located to be accessible following a major accident. However, remotely-activated valves can only be considered reliable isolation points if there are adequate reliability engineering and maintenance programs in place.)... 

The process flow diagram, or PP D. is a pictorial description of the process. It gives the basic processing scheme, the basic control concept, and the process information from which equipment can be specified and designed. It pror ides the basis for the der elopment of the P l diagram and also serves as a guide for the plant operator. The process flow diagram usiuilly includes... 

Figure 6-33 diagrams vacuum system arrangements for process systems. It is important to examine the plant economics for each system plus the performance reliability for maintaining the desired vacuum for process control. 

Once the evidence has heen collected and a timeline or sequence diagram developed, the next phase of the investigation involves identifying the causal factors. These causal factors are the negative occurrences and actions that made a major contrihution to the incident. Causal factors involve human errors and equipment failures that led to the incident, hut can also he undesirable conditions, failed harriers (layers of protection, such as process controls or operating procedures), and energy flows. Causal factors point to the key areas that need to he examined to determine what caused that factor to exist. 

In 1989, the NDF Company opened a facility in Georgetown, South Carolina to produce low density polyethylene. Manufacturing of the polyethylene is done in two 50-ton reactors that are encased individually within their own 8-story-high process unit. The main raw materials for the manufacturing operations include ethylene, hexane, and hutene. The polymerization is completed in the presence of a catalyst. The hase chemicals for the catalyst are aluminum alkyl and isopentane. The reactor and catalyst preparation areas are on a distributed control system (DCS). A simplihed process flow diagram is attached. 

A basic process flow diagram for the SNCR TDN process is shown in Figure 17.3. Anhydrous or aqueous ammonia is vaporized and mixed with a carrier gas of air or steam for transport to injection/distribution modules. The injection distribution modules distribute ammonia and/or hydrogen reagent and carrier gas to proprietary spray nozzles or injection lances. Reagent flow control can be controlled and trimmed by outlet NOx signals or ammonia slip measurements. 

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