System design troubleshooting

This section is designed to assist in troubleshooting system problems. It is not a systematic approach as described in Chapter 10, which always yields better results. Keeping this in mind, I have listed a series of commonly seen problems, possible causes, and suggested treatments. 

Data collection and analysis is critical for monitoring system performance. As a minimum the data must be entered in Table 4.7. Mathematical relations for converting field data to performance data are given in Chapter 2. Normalised data must be plotted to study the performance trends, for example RO membrane rejection vs. time and RO productivity vs. time. The key performance parameters in Tables 4.8 and 4.9 should be used in conjunction with normahsed data to evaluate system output. The data along with RO systems design guidelines provided in Chapter 2, and RO projections given in Table 4.1 should be used to monitor and troubleshoot the performance over time. 

General troubleshooting guidelines are provided for chemical dosage systems including tanks, pumps and tank mixers. Not aU problems may be relevant to a particular system. Problems depend on system design and process conditions. 

Process optimization, process management, trend analysis, alarm processing, control-system design, and adaptive control Enhancement of classical controller performance by sensor failure identification, valve saturation, and process constrains Fault detection, diagnosis, and troubleshooting Supervisory control of simple PID-like controller and startup or shutdown procedures... 

How to Design Overhead Condensing Systems, Chem. Eng., Series beginning August 15, 1977. Lieberman, N. P, Troubleshooting Refinery Processes, Pennwell, 1981. 

Expert systems can also be used off-line as advisory systems. If some leeway is left in the process specifications, operators can even be instructed to make simple variations in the process. Hajicek developed an expert system for troubleshooting injection molding, which was designed to be used by operators to adjust controls as needed whenever part quality suffered [20], These expert systems do not necessarily plan an entire cycle. As we will see in the section on in-process control, however, they can be used to do so. There are even specifications that include rules for altering the cure cycle in response to the results of quality acceptance tests such as flow and volatiles, a primitive set of heuristics. 

E.A. Knight, M.G. Jones, P. Marjanovic, On-site measurement for troubleshooting pneumatic conveying systems, Proceedings of die Bulk Design Seminar, Sutton Coldfield, UK, December 1998. 

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