Troubleshooting

Troubleshooting in CE is not as well defined as it is in HPLC, and, in general, the instrumentation is not readily serviced by the user. Neverthe- 

Confirm voltage setting. Ensure capillary ends are immersed in buffer. 

Confirm sample in vial. Be sure capillary extends into sample. Confirm injection time. 

Confirm wavelength setting. Confirm wavelength accuracy. 

Purge capillary with a syringe. Trim capillary ends. Replace capillary. 

Use of troubleshooting methods allows the user to systematically analyse a large number of compounding problems. There are many problems that can potentially occur during compounding which makes it difficult to develop a troubleshooting method that can be used for all compounding problems. 

While one is engaged in troubleshooting, it is necessary to consider the source of the problem and to examine how the problem might have arisen. Additional problems might arise from the sample composition and the mobile phase, and these also need to be considered. It should be noted that problems can present themselves in many different ways, and what might appear to be a pump-related problem can quite easily be a result of something else entirely. 

Different authors approach troubleshooting in different ways. Some prefer to present symptoms and solutions and others prefer to look at component-related problems and provide solutions. It is difficult to know which way is better, but we have always felt that the best source of information in relation to what is going on is the chromatogram. The chromatogram is the pictorial representation of what has happened in the system and therefore is a measure of what is right and what is wrong—for example  

Are the retention times as expected and within established tolerance limits  

Does the baseline look unusual for example, is there a lot of baseline noise  

With all types of plastic processes, troubleshooting guides are set up to take fast, corrective action when products do not meet their performance requirements. This problem-solving approach fits into the overall fabricating-design interface. One brief example of troubleshooting an RP/composite is in Table 8-44. 

A simplified approach to troubleshooting is to develop a checklist that incorporates the basic rules of problem solving such as 1) have a plan, and keep updating it, based on 

Nonfills Air entrapment Gel and/or resin time too short Additional air vents and/or vacuum required Adjust resin mix to lengthen time cycle 

Excessive thickness Improper clamping Check weight and lay-up and/or check 

Blistering Demolded too soon Improper catalytic action Extend molding cycle Check resin mix for accurate catalyst content and dispersion 

Design and operations are separated in this book for clarity, and so troubleshooting for all types of equipment is included in this section. 

Lieberman, N, P, Process Design for Reliable Operations, Gulf Professional Publishing, 1983. 

GPSA Engineering Data Book, Vols. 1 and 2, Gas Processors Suppliers Association, 10th Ed., 1987. 

France, John J., Sulzer Chemtech USA Inc., Troubleshooting Distillation Columns, presented to Rio Grande Chapter of AIChE, April 20, 1999. 

Most of the immunocytochemistry problems seen in a shared use microscope facility are problems with the immunocytochemical procedure. In immunocytochemistry problems will frequently occur and need to be solved by troubleshooting. Most of the method problems come from three sources (1) modified immunocytochemistry protocol that was not totally re-evaluated after being modified (2) protocol designed without sufficient thought, generally by a novice and (3) procedure errors where the protocol was not followed. 

Immunocytochemistry, DOI 10.1007/978-l-4419-1304-3 14, Springer Science+Business Media, LLC 2010 

Blocking inappropriate (too little or the blocking binds to antibodies) 

Use of inappropriate filter sets and/or laser lines in microscopy 

Attempts to overcome problems with image collection methods (increased 

The cat cracker plays a key role in the overall profitability of the refinery. It must operate reliably and efficiently. It must also operate safely and comply with federal, state, and local environmental requirements. A typical FCC unit circulates tons of catalyst per minute, processes various types of feedstock and uses hundreds of control loops, any of which can make operation difficult. Proper troubleshooting will ensure that the unit operates at maximum reliability and efficiency while complying with environmental concerns. 

Troubleshooting deals with identifying and solving problems. Problems can be immediate or long term and can be associated with off-spec products, poor efficiency, process improvements, capacity increases, or potential shutdown items. Problems can be related to management, operation, hardware and equipment, or process issues. Solutions can include improved operating procedures and training, preventative maintenance, or installation of new equipment or controls. 

Catalyst Circulation Catalyst Loss Coking/Fouling Flow Reversal 

This chapter is written with the unit process engineer in mind. No matter where the problem originates, the unit process engineer will be the point person for solving it. 

Problems with the mechanics of a procedure can involve an improperly diluted sample (perhaps manifested by an absorbance reading that is greater than specified or expected), an obstruction in the sample or reference beam, an improperly aligned source or mirror, the incomplete programming of a scan, or improper or inappropriate software entry. In these cases, the operator will need to carefully examine his or her technique or procedure, or instrumental parameters, such as the optical path, perhaps with the help of the instrument troubleshooting guide, to solve the problem. 

Contamination, as indicated previously, can manifest itself in the absorption spectrum. If a sample is contaminated with a chemical that has its own absorption spectrum in the range studied, the absorption pattern (spectrum) of the analyte will not match the expected pattern. If a contaminant is suspected, it may originate from any of the chemicals used in the procedure, including the solvent, the analyte used to prepare standards, or any other chemical added to the solutions tested. In that case, repeating the solution preparation using chemicals from fresh, unopened containers may help solve the problem. 

During the implementation, numerous problems may arise. Many of those can be readily solved in a straightforward manner. A few issues will be fisted here. 

While baseline offsets are usually not a problem in a laboratory cuvette, they can be a significant issue in on-line measurements. There are several sources of such offsets. 

Particles also cause the scattering of light in a process sample. Filtering probes and cells are available, which can eliminate most particles and bubbles from the optical path and make reliable process measurements possible for difhcult sample matrices (see e.g. Section 4.7). If particle formation is inherent, like insoluble excipients in dissolution studies of tablets, an ATR UV probe may be considered. 

In some cases, the sample will deposit a film onto the optical surfaces of a probe or cell. This film might lead to a bias in the analytical results, and eventually could reduce hght transmission to make the analysis impossible. Film buildup requires some action be taken to clean the cell or the probe, either cleaning in place or by removing the probe or cell for cleaning by hand. 

The movement of a fiber-optic probe and/or the hbers leading to/from a probe or cell can also induce baseline shifts in the recorded spectra. These shifts are usually minor and can be eliminated with proper preprocessing of the data (e.g. derivatives). (A detailed description of preprocessing techniques can be found in Chapter 12) 

Specific steps that can go wrong have already been discussed in the related sections. Here, some more general problems are mentioned. 

RNA is also nonenzymatically degraded by hydroxyl ions and, at high temperatures, by divalent cations. Hence, solutions that contain RNA should not exceed a pH value of 9 and should not be heated for too long periods of time if divalent cations are present. 

To prevent the selection of aptamers with low affinity to the target molecule, the target concentration has to be decreased and the washing procedure has to be done with increased stringency. This enhances the discrimination between aptamers with high affinity and aptamers with lower affinity [6]. 

Despite a preselection procedure, aptamers may be selected that bind to the bare selection matrix, the cellulose filter, or any other component of the selection setup, because the possible binding sites are presented in a large number (compared to 

Cellular actin is also modified by non-enzymatic ADP-ribosylation. This modification occurs at cysteine residues and depends on the presence of free ADP-ribose. Thus, cleavage of NAD by endogenous NAD glycohydrolases or release of ADP-ribose from poly-ADP-ribosylated proteins can increase the amount of ADP-ribose and may induce non-enzymatic modification of actin. Non-enzymatic labeling of actin in the presence of [ C]/[ P]NAD can be identified because this reaction is quenched by unlabelled ADP-ribose at rather high concentrations (1 mM), whereas enzymatically-catalyzed [ C]/pP]-ADP-ribosylation is not influenced by ADP-ribose. 

At some point during operation of a crystallizer, difficulties are going to occur. A list of some of the more common difficulties along with probable causes and recommended remedies is given below. 

Note The bandwidth and current capability of the current probes used for noise measurements are important. Popular choices for such probes are from Pearson Electronics and Fischer Custom Communications at www.pearsonelectronics.com and www.fischercc.com, respectively. For very high currents (up to thousands of amperes if necessary), a possible choice are current probes based on the Rogowski principle. This type of probe is available from several manufacturers, for example Power 

Ensure this current probe in particular, does not saturate (because the operating supply current also adds to the flux in this) 

Electronic Measurements Ltd. at www.pemuk.com. These probes are not the usual current transformer type. The output from a Rogowski probe depends not on the instantaneous current enclosed, but on the rate of change of current. So, instead of just placing several turns around the wire to be sensed, as in a typical current transformer, the Rogowski probe effectively takes an air-cored solenoid and then bends that in a circle around the sensed wire (like a doughnut). Such probes are also considered virtually noninvasive. 

The usual lab active current probes (which also measure dc, and therefore include a Hall sensor) are usually just not suited for these high-bandwidth noise measurements. 

Note A quick diagnostic test for understanding a particular high-frequency conducted EMI problem (measured by a LISN at the inputs of the power supply) is to twist the output cables of the power supply tightly together (along with their respective return wires). This induces field cancellation (also called flux containment), thus reducing the radiation from the output cables (if present). 

Throughout this chapter and the book there are discussions of why problems develop and how they can be eliminated or kept to a controllable minimum. To do the best job of eliminating or reducing problems, one must understand the complete process, and there is no substitute for experience. Only through hands-on problem solving can an operator, or even management, really begin to understand the complexity of extrusion and know how to handle the wide variety of problems that invariably occur. (See Chapter 

under Troubleshooting, for an approach that includes screw wear and inspection, and is applicable to extrusion.) 

Much useful information on problems and solutions in extrusion is available from material and equipment suppliers. Trade journals publish special issues on this subject with very useful tables, and industrial literature includes practical guides with helpful details (see reference 2 and Chapter 18). The size of this book does not permit such treatment, but an excellent summary of troubleshooting is given in Table 3-11, from Plastics World (185). 

Gels (Contaminants that look like small specks or bubbles) Melt temperature too high Not enough progression in screw Bad resin Melt temperature too high Lower melt temperature Use new screw Check resin quality Check melt temperature 

Melt fracture (Rough surface finish. Also called sharkskin. ) Melt temperature too low Die gaps too narrow Increase melt temperature Heat die lips Increase die gaps Use processing aids 

The chapter is divided into two main categories related to blown him production extruder and him problems. The main sections covered in this chapter are  

Thermo Scientifc (AppsLab Library) https //appslab.thermoscientific.com/ 

Chromatography Forum http //www.chromforum.org Google Group sci.chem.analytical  

Waters HPLC Troubleshooting Guide (registration required) http //www.waters.com/waters/library.htm cid=511436 lid=1528445 

Processing of RP is an art of detail. The more you pay attention to details, the fewer problems/faults develop in the process. If it has been running, it will continue running well unless a change occurs. Correct the problem and do not compensate. It may not be an easy task, but understanding what you have equipment wise, material wise, processing wise, environment wise, and/or people wise can help. In order to understand potential problems/faults and solutions of fabrication, it is 

Nonfills Air entrapment Additional air vents and/or vacuum required 

Excessive thickness Improper clamping and/ Check weight and layup and/or 

Blistering Demolded too soon Extend molding cycle 

Extended curing cycie Improper catalytic action Check equipment, if used, for proper catalyst metering Remix resin and contents agitate mix to provide even dispersion 

In spite of precautions taken during the design of evaporator systems, problems do arise during startup and operation. Parameters which cannot always be precisely determined make it nearly impossible to define all the problems during the design stage. These parameters include  

Discrepancies in performance may be caused by deviations in physical properties of fluids, flow rates, inlet temperatures, mechanical construction of the equipment. The troubleshooter should first check to see that compositions, flows, temperatures, and physical properties agree with those specified for design. He 

Problems encountered in evaporators fall into four major categories  

These difficulties can often be traced to faulty operation, mechanical wear, or improper design. 

Problems arising in one or more of the system components will result in problems in other areas as well. 

Worn blast media is the most likely cause of insufficient metal preparation. Time windows will be reduced in humid climates. 

Inadequate stirring is probably the greatest single cause of bond failure. 

Cryogenic deflashing should be controlled so that only the flash is embrittled. If the polymer in the component becomes brittle the bond could fracture. 

Contamination with mould release agents or substances that will prevent bonding mnst be avoided. 

To achieve a bond the rubber must be stationary in the monld. Leaking moulds keep the rubber moving and lead to bond failure. 

Less frequently, local infections, scar tissue, or fluid around the receiver can impair pacing effectiveness. If receiver migration has occurred or if the internal components require repair or replacement, then surgical exploration may be required. Dysfunctional phrenic nerve conduction or diaphragmatic responses are sometimes reversible. 

In this chapter the failure modes of adhesives are discussed and some practical hints and tips are included to help identify and rectify the reason for the failure mode. 

There are a whole host of reasons as to why an adhesive might fail for a particular joint and the list below is not necessarily complete and in many applications it may be a combination of factors that lead to a failure. 

The failures can often be categorised into one of four main areas  

---

Troubleshooting Trouton constant Troxerutin [7085-55-4] Troysan 174 Troysan 192 True color holograms TrueType Truex process Truncatella sp. Truscottite [12425-42-2] Truxal Trycol... 

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. 

A.ccessibility. AccessibiUty means having sufficient working space around a component to diagnose, troubleshoot, and complete maintenance activities safely and effectively. 

Stand-alone computer systems, usually based on a personal computer (PC) or programmable logic controller (PLC), provide a separate computer system for each pilot plant. This allows for economical expansion for new units, separates pilot plants completely for maintenance and troubleshooting, and often has the lowest initial cost. Standardization can be a problem and software control, data gathering, and storage packages can be limited in size, scope, and capabiUty these are usually acceptable trade-offs. 

Another option is the dry-pit design (Fig. 7c). This pump is installed in a dry pit and coimected to a weU via a pipe. Because the dry pit is usually dug out wider than the wet pit, Tenough room is available for pump maintenance, troubleshooting, and repair without pulling the pump to the surface for servicing. 

The need for weU-trained technical service professionals is expected to continue as an essential aspect of the chemical industry, despite the phenomenal growth ia electronic methods of information storage, retrieval, and transmission. Advanced troubleshooting of complex customer processes and accelerated accurate product development and market introductions should continue to be principal elements of technical service personnel duties. Increased levels of integration, perhaps blurring the lines between suppHer and customer, may come to pass. There are already instances of personnel swapping between customers and suppHers for extended periods to allow cross-fertilization of ideas and provide more accurate perspectives for the companies involved in these efforts. Technical service and research personnel have been those persons most directly involved in such efforts. 

A silver stain is used when proteins exist in a very small quantity or when analysis of as many bands as possible created by separation techniques is desired. One positive apphcation of silver stain is its sensitivity. A drawback of the silver stain, however, is that it is more complex and often requires more troubleshooting to obtain the desired results. 

Gans, M., Systematize Troubleshooting Techniques, Chemical Engineeiing Piogiess, April 1991, 25-29. (Equipment malfunction examples)... 

Hasbrouck, J.F, J.G. Kunesh, and VC. Smith, Successfully Troubleshoot Distillation Towers, Chemical Engineeiing Piogiess, 199.3, 6.3-72. 

The three vertices are the operating plant, the plant data, and the plant model. The plant produces a product. The data and their uncertainties provide the histoiy of plant operation. The model along with values of the model parameters can be used for troubleshooting, fault detection, design, and/or plant control. 

The vertices are connected with hues indicating information flow. Measurements from the plant flow to plant data, where raw measurements are converted to typical engineering units. The plant data information flows via reconciliation, rec tification, and interpretation to the plant model. The results of the model (i.e., troubleshooting, model building, or parameter estimation) are then used to improve plant operation through remedial action, control, and design. 

Extended Plant-Performance Triangle The historical representation of plant-performance analysis in Fig. 30-1 misses one of the principal a ects identification. Identification establishes troubleshooting hypotheses and measurements that will support the level of confidence required in the resultant model (i.e., which measurements will be most beneficial). Unfortunately, the relative impact of the measurements on the desired end use of the analysis is frequently overlooked. The most important technical step in the analysis procedures is to identify which measurements should be made. This is one of the roles of the plant-performance engineer. Figure 30-3 includes identification in the plant-performance triangle. 

Plant Operation The purpose is to maintain and improve performance (i.e., product quality, rate, efficiency, safety, and profits). Examples include identification of plant conditions that limit performance (troubleshooting, debottlenecking) and exploration of new operating regions. 

Design In this context, design embodies all aspec ts requiring a model of the plant operations. Examples can include troubleshooting, fault detection, control corrections, and design development. 

Data Acquisition As part or the understanding, the measurements that can be taken must be understood. A useful procedure to prepare for this is to develop a tag sheet for the process (Lieberman, N.P., Troubleshooting Refinery Processes, PennWell Books, Tulsa, 1981, 360 pp). An example of a simplified sheet is given in Fig. 30-5. 

Focus For the purposes of this discussion, a model is a mathematical representation of the unit. The purpose of the model is to tie operating specifications and unit input to the products. A model can be used for troubleshooting, fault detection, control, and design. Development and refinement of the unit model is one of the principal results of analysis of plant performance. There are two broad model classifications. 

Plant-performance analysis reqmres the proper analysis of limited, uncertain plant measurements to develop a model of plant operations for troubleshooting, design, and control. 

The purpose of the plant-performance analysis is to operate on the set of measurements obtained, subject to the equipment constraints to troubleshoot to develop models or to estimate values for model parameters. 

Measurement Selection The identification of which measurements to make is an often overlooked aspect of plant-performance analysis. The end use of the data interpretation must be understood (i.e., the purpose for which the data, the parameters, or the resultant model will be used). For example, building a mathematical model of the process to explore other regions of operation is an end use. Another is to use the data to troubleshoot an operating problem. The level of data accuracy, the amount of data, and the sophistication of the interpretation depends upon the accuracy with which the result of the analysis needs to oe known. Daily measurements to a great extent and special plant measurements to a lesser extent are rarelv planned with the end use in mind. The result is typically too little data of too low accuracy or an inordinate amount with the resultant misuse in resources. 

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. 

Limitations Identifying the appropriate test to troubleshoot a unit problem requires hypothesis development and testing. Hypothe-... 

---