Problem diagnostic/troubleshooting

Diagnostic/Troubleshooting Problems If a change in process output (process disturbance or upset) is observed, the cause (change in process input, change in equipment performance) must be identified. 

The first item we re going to discuss isn t really a hardware problem, but a hardware troubleshooting aid. Every computer has a diagnostic program built into its BIOS called the power on self-test (POST). When you turn on the computer, it executes this set of diagnostics. These tests go by pretty quickly, so we ll detail them here. 

Luckily, most sound card vendors are quite aware of the problems and ship very good diagnostic utilities to help resolve them. Use your PC troubleshooting skills to determine the conflict, and then reconfigure until you have found an acceptable set of resources that are not in use. 

When you troubleshoot laser printers, there are three tests you can perform to narrow down which assembly is causing the problem. (These tests are internal diagnostics for the printers and are included with most laser printers.) The three tests are the engine self-test, the engine half self-test, and the secret seif-test. 

Referring to the maintenance and troubleshooting sections of an instrument s manual is highly recommended. Many individuals consult manuals only after a catastrophic failure and then only when all other problem-solving approaches have been exhausted. Modern HPLC systems often have self-diagnostic capabilities that help isolate the problem area within the instrument. 

Troubleshooting and Diagnostics (mechanical and non-mechanical problems, determination of probable problem cause, mechanic s responsibilities.)... 

This is already powerful information in troubleshooting. It can be used as a diagnostic test to monitor what effect changes in reactor geometry or baffles positioning or mixing rate, etc. might have on the tracer response curve. That is the approach used in industrial practice. Frequently the problem is solved by trial and error when conditions are found that yield an RTD close to the one of the desired ideal reactor. What quantitative conclusions can we derive on a model-free basis from these tracer experiments ... 

If a control loop is not performing satisfactorily, then troubleshooting is necessary to identify the source of the problem. This diagnostic activity should be based on a systems approach that considers the overall performance of the control loop as well as the performance of individual components. Retuning the controller is not a cure-all, especially if a sensor or a control valve is the source of the problem. Automated monitoring techniques for control loops are currently being developed and are commercially available (see Chapter 21). 

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