Current, troubleshooting

To accomplish troubleshooting at the node and gate level, both stimulus (Pulser) and response (Probe, Tracer, Clip and Comparator) Instruments are needed. Moreover, instruments with both voltage and current troubleshooting capability help isolate electrical faults where the precise physical location is hard to identify. 

Because of its small size and portabiHty, the hot-wire anemometer is ideally suited to measure gas velocities either continuously or on a troubleshooting basis in systems where excess pressure drop cannot be tolerated. Furnaces, smokestacks, electrostatic precipitators, and air ducts are typical areas of appHcation. Its fast response to velocity or temperature fluctuations in the surrounding gas makes it particularly useful in studying the turbulence characteristics and rapidity of mixing in gas streams. The constant current mode of operation has a wide frequency response and relatively lower noise level, provided a sufficiently small wire can be used. Where a more mgged wire is required, the constant temperature mode is employed because of its insensitivity to sensor heat capacity. In Hquids, hot-film sensors are employed instead of wires. The sensor consists of a thin metallic film mounted on the surface of a thermally and electrically insulated probe. 

Impressed Current Equipment and Transformer-Rectifiers 239 Table 8-2 Troubleshooting at cathodic protection stations... 

If no significant problems are found other than feedstock changes, verify that the refinery LP team has current data on unit yields and product quality with this feedstock. The result of troubleshooting may be that increasing diy gas may be a necessary price for changes in the feed. 

Record the current during the runs, as this is a valuable tool for troubleshooting. It is recommended to avoid current flows higher than 100 pA since the resulting amount of Joule heating may generate system failures. 

The results of the 4D-QSAR case study are interesting and provide large amounts of data about the system of interest, and, unlike static 3D-QSAR methods (CoMFA and SOMFA), 4D-QSAR is able to provide the exact locations of statistically important interaction pharmacophore elements. The ability of this method to overcome the question of What conformation to use and predict the bioactive conformation is impressive and a major reason to use the software. Yet it is the ability to construct manifold models and examine several models for the same alignment that is the true benefit of this method. Add to the list the ability to determine the best alignment scheme (based on statistical and experimental results) and this method will provide more information than one could imagine. This abundance of information is key when troubleshooting results that are not in agreement with current beliefs. 

Norman P. Lieberman is a chemical engineer with more than three decades of experience in process design and plant operations supervision. Currently an independent consultant, he troubleshoots refinery process problems for such companies as Chevron, Olin, and Texaco. 

Elizabeth T. Lieberman is a chemical engineer holding a B.Sc. in Chemical Engineering from the University of Wales, and an LIRC. in Chemistry. Elizabeth has two decades of experience in the process industries, and is currently working as a consultant troubleshooting refinery process problems and assisting Mr. Lieberman with the presentation of his seminars. 

Because of the high level of automation and instrument control, many modem analytical LC/UV/MS instmments have open-access software that enables non-trained users to use the system. In essence, such software needs only to be developed by expert users but once complete, will allow inexperienced personnel to operate the instmment and generate their own data reports without any intervention by trained operators. Trained operators/expert users are only required for system maintenance, troubleshooting, etc. This software gives the appearance that the system is easy to use and also does not require the user to set any operating parameters. Although not fully developed in either case yet, we are currently working on such software for both the autoprep and MS-prep systems. 

Design a piece of equipment Propose and design new equipment or a new process Evaluate a current piece of equipment or a process Suggest changes for equipment or a process Debottleneck by increasing the limiting capacity in a process Troubleshoot to correct faulty operation... 

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