Analyzer Maintenance

Based on manufacturers recommendations and experience, laboratories perform regular preventative maintenance procedures on the analyzers, with some additional maintenance procedures initiated in response to internal quality control performance or analyzer malfunctions. Calibration and quality control performances should always be checked after maintenance visits because replacement parts and disturbances of the optical and hydraulic systems sometimes adversely affect subsequent analyzer performance (sometimes called PMT—postmaintenance visit trauma). These procedures form part of good laboratory practice. 

---

Assign a special team of instrument technicians to process analyzer maintenance. Having this specialized maintenance done by every instrument technician in the plant is simply not satisfactory, as demonstrated over the years at many plants. 

The real-time process analyzer is significantly different from conventional instrumental measurements in combining analytical chemistry with instrumentation. Typically, there is a sample transportation and conditioning system associated with the analysis, as well as some form of data presentation for human or automatic interface. It is also different from the laboratory analytical instrument. While laboratory analysis occurs within environmentally controlled conditions, the process analyzer is typically installed in a harsh environment and the analyses are taking place around the clock. Because of these unusual characteristics, the technicians responsible for analyzer maintenance must be thoroughly familiar with the entire analyzer system (analyzer as well as sample conditioning system). Analyzer technicians are typically well trained and highly skilled, and dedicated solely to analyzer system maintenance. Occasionally, analyzer technicians work side by side with laboratory technicians. 

Depending on the size of the plant, the number of analyzers, the culture of the location, and, to some extent, precedents in maintenance practice, the analyzer maintenance organization may be of any variety. Smaller plants may have a few analyzers that require only one person to maintain. A large plant may need to have a well-structured and staffed department to maintain the analyzers throughout the plant. Some plants may choose to have some analyzer technicians assigned to a certain production area, while others may assign technicians based on their skill levels. The analyzer maintenance organization may be localized or centralized. 

Spare Parts evaluation The analyzer maintenance expeditor should maintain close ties with the plant warehouse and the purchasing department to optimize parts availability and its location. Spare parts should be readily available when needed. Vendor information should be used as a guide to determine the parts to be included in stores. We have to be careful to avoid over-stocking of parts to control the cost. If the expensive parts can be readily obtained from vendors in a timely manner, then it need not be in the warehouse. 

The Z-spray inlet/ion source is a particularly efficient adaptation of the normal in-line electrospray source and gets its name from the approximate shape of the trajectory taken by the ions between their formation and their entrance into the analyzer region of the mass spectrometer. A Z-spray source requires much less maintenance downtime for cleaning. 

Selecting the Sampling Point The selection of the sampling point is based primarily on supplying the analyzer with a sample whose composition or physical properties are pertinent to the control function to be performed. Other considerations include selecting locations that provide representative homogeneous samples with minimum transport delay, locations that cohect a minimum of contaminating material, and locations that are accessible for test and maintenance procedures. 

Questions of the analytic control of maintenance of the bivalent metals cations to their joint presence in materials of diverse fixing always were actual. A simultaneous presence in their composition of two cations with like descriptions makes analysis by sufficiently complicated process. Determination of composition still more complicates, if analyzed object is a solid solution, in which side by side with pair of cations (for example, Mg " -Co ", Mn -Co, Zn -Co ) attends diphosphate anion. Their analysis demands for individual approach to working of methods using to each concrete cations pair. 

It is neeessary to understand the TDH and it s eomponents in order to make eorreet deeisions when parts of the system are changed, replaced, or modified (valves, heat exchangers, elbows, pipe diameter, probes, filters, strainers, ete.) It s neces.sary to know these TDH values at the moment of specifying the new pump, or to analyze a problem with an existing pump. In order to have proper pump operation with low maintenance over the long haul, the BF P of the pump must be approximately equal to the TDH of the system. 

In the event of failures due to lubrication problems, the failures should be thoroughly analyzed to determine if they were indeed caused by lubricant failure or incorrect maintenance procedures. Once the problem has been isolated, corrective action can be initiated to prevent subsequent similar failures—whether it requires changing lubricants or procedures. 

List of the maintenance tasks analyzed iicin this method,... 

Plant Availability. A detailed PSA (2) may be used to analyze the effects of test and maintenance on plant jperability through improved scheduling, component reliability improvement, and improved procedures Hie eost-beiiefit of stocking vs warehousing of feed materials and spare parts may be done to find an optimum ... 

Regarding service reports, these should be collected from the servicing or maintenance personnel and analyzed for repetitive problems. The data can also be used to compute the actual reliability, maintainability, and many other characteristics of the products. 

Data from an existing collection system were analyzed for failure modes and distribution. The results of Pareto analyses indicate the principal causes of failure. A few values of mean times to maintenance action (MTBM) are given for ethylene plant pumps (85 electric driven centrifugal pumps over a 19-month period), and ethylbenzene-styrene monomer plant equipment from 10 months data 4 gas compressors, 3 screw conveyors, 121 pumps, and 235 other items... 

Repair and maintenance records were analyzed to determine failure rates and distribution of failure modes. Preliminary findings are reported which include the Weibull distribution characteristics. Failure mode distributions are approximate. Overall mean-time-between-failure is given for the kiln, leach tank, screwfeeder, tank pump, tank gearbox, and kiln gearbox. The study was confined to an analysis of unscheduled repairs and failures. 

The fact that vibration profiles can be obtained for all machinery having rotating or moving elements allows vibration-based analysis techniques to be used for predictive maintenance. Vibration analysis is one of several predictive maintenance techniques used to monitor and analyze critical machines, equipment, and systems in a typical plant. However, as indicated before, the use of vibration analysis to monitor rotating machinery to detect budding problems and to head off catastrophic failure is the dominant predictive maintenance technique used with maintenance management programs. 

This limitation prohibits the use of most microprocessor-based vibration analyzers for complex machinery or machines with variable speeds. Single-channel data-acquisition technology assumes the vibration profile generated by a machine-train remains constant throughout the data-acquisition process. This is generally true in applications where machine speed remains relatively constant (i.e., within 5 to fO rpm). In this case, its use does not severely limit diagnostic accuracy and can be effectively used in a predictive-maintenance program. 

Most predictive-maintenance programs rely almost exclusively on frequency-domain vibration data. The microprocessor-based analyzers gather time-domain data and automatically convert it using Fast Fourier Transform (FFT) to frequency-domain data. A frequency-domain signature shows the machine s individual frequency components, or peaks. 

Boundary conditions and resolution The frequency boundary conditions and resolution for the full FFT signature depends on the specific system being used. Typically, the full-signature capability of various predictive-maintenance systems has a lower frequency limit of 10 Hz and an upper limit of 10 to 30 kHz. A few special low-frequency analyzers have a lower limit of 0.1 Hz, but retain the upper limit of 30 kHz. Typical resolutions are 100 to 12,800 lines. 

---