Normal troubleshooting

The above assumes that the measurement statistics are known. This is rarely the case. Typically a normal distribution is assumed for the plant and the measurements. Since these distributions are used in the analysis of the data, an incorrect assumption will lead to further bias in the resultant troubleshooting, model, and parameter estimation conclusions. 

While working in a plant, a troubleshooter read a pressure gauge daily for several weeks and only realized it was inaccurate when one day the blower was down. The gauge still read about normal operating pressure. Had this have been a distillation unit, it could have been more serious. In distillation service, pressure is a more important variable than in many other unit operations. Relative volatility is a function of pressure. Pressure, or more accurately delta-P, is the best indication of the tower hydraulics. 

As previously noted, the troubleshooter will normally be under pressure to get the column lined out and operating properly. There are a few things which can be tried (safely and slowly) to perhaps alleviate the problem. These include ... 

Bulk density can be used to troubleshoot catalyst flow problems. A too-high ABD can restrict fluidization, and a too-low ABD can result in excessive catalyst loss. Normally, the ABD of the equilibrium catalyst is higher than the fresh catalyst ABD due to thermal and hydrothermal changes in pore structure that occur in the unit. 

Other aspects of sample preparation to consider, depending on the objective of the CZE method, are sample denaturation, reduction and/or derivatization, and the use of an IS. IS are widely used in CE separations to aid in normalization of slight inter-assay variability and in method troubleshooting. 

Control can be exercised by the operator in the control roam on the well chokes and manifold divert valves (although this is normally handled by the HOC), start/atop of the oil shipping pumps, utility equipment, switching valves, gas plant feed valves, gas compressor start/stop and emergency shutdown of any production train or the entire GC. Since the closed loop process control is performed by local pneumatic instruments, all set point changes and controller troubleshooting must be accomplished locally. 

There are numerous papers that refer to the quantification of tocopherols and tocotrienols using HPLC methods. Normal-phase HPLC methods with a silica column as well as reversed-phase HPLC methods with a C18 column are commonly used. A silica normal-phase column is able to separate all eight tocopherols and tocotrienols in a typical chromatographic procedure. Because plant tissues possess most forms of tocopherol and tocotrienol, it is recommended that the normal-phase HPLC method be applied to food samples from plants. In the reversed-phase HPLC method, [3- and y-tocopherol and (3-and y-tocotrienol are not usually completely separated. This method can be used in animal tissues, which either lack or have reduced levels of [3- and y-tocopherol and (3- and y-tocotrienol. The resolution of the normal-phase HPLC method is higher than that of reversed-phase HPLC method however, the reversed-phase HPLC column is more long-lasting than the normal-phase HPLC column (see Critical Parameters and Troubleshooting). 

Baseline drift is a normal effect of gradient delivery (see Critical Parameters and Troubleshooting) and therefore a blank (100% HPLC-grade acetone) should be run and subtracted from the sample, if desired. 

An area that provides time for troubleshooting so that operations personnel can make adjustments which cause the COP to return to the normal operating range. Process response time generally indicates zone size. 

Troubleshooting Actions on Reaching "Maximum Normal Operation" Limit WK WK U u U... 

Most of the mentioned troubleshooting tools will work with other silica-based columns. With normal-phase columns, you obviously need not worry about bonded-phase removal, but silica still dissolved at high pH and high salt concentrations. Polar materials like some proteins adhere very tightly and require... 

Table 14.1 is a troubleshooting matrix that shows trends in normalized performance and possible causes. The table lists different sets of performance parameters and possible causes for each. Some symptoms are the same, such as items one through three in the table, but each occurs in a different place in the RO system, and thus, each has a different cause. 

Before a technician can install or upgrade a component, he or she must determine which component needs to be replaced. A technician will normally use the skills addressed by the diagnosing and troubleshooting content areas to make that determination. Questions about these two topics together make up 30 percent of the exam. 

With nonaqueous samples (part B of Fig. 3.8), the decisions for sorbents are somewhat reversed. For example, an analyte that is polar and ionic is best recovered with ion exchange. This example is similar to that of an aqueous sample. If the analyte is polar but nonionic, then the sorbent choice could be reversed phase or normal phase. The choice depends on the organic solvent, either polar or nonpolar, respectively. Finally, if the analyte is nonpolar, the sorbent choice is reversed phase. The second step in methods development is to execute the SPE experiment. Lastly, one has to optimize and troubleshoot the SPE method. 

The key to effective troubleshooting is expressed in the old adage, divide and conquer. It is important to locate the portion of the control loop hardware that is causing the poor performance the hnal control element, the sensor system, the controller, or the process. The place to start is to test each system separately to determine whether that portion of the control loop is operating properly. The hnal control element can be evalnated by applying a series of input step tests. That is, the input to the hnal control element, which is normally set by the controller, can be manually adjusted. The test allows the determination of the dynamic response and deadband of the actuator system. If the performance in these two areas is satisfactory, there is no need to evaluate the actuator system further. 

Troubleshoot what temperatures are normal and what are different and what the... 

An oscilloscope camera is a useful but not an essential accessory. When the instrument is operating normally, a photograph of the waveform characteristics after each stage in the receiver and transmitter should be taken, to be used later in troubleshooting. In the absence of a scope camera, sketches of the waveform characteristics will have to do. 

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