Repair, detectors

Radiation-damaged detectors can be repaired in-house, but some of the manufacturers and independent companies do provide a repair service. Such services are certainly worth taking advantage of. Apart from the loss of efficiency in p-type detectors, the performance of repaired detectors is likely to be almost as good as new. Perhaps surprisingly, there appears to be no limit to the number of times a detector can be aimealed in this way. 

With a new, or repaired, detector it may be worthwhile to check whether you agree with the manufacturer s suggestion. You may wish, in any case, to select a shorter time constant in order to cope with particularly high count rates, accepting a small resolution penalty in return. 

Periodical verification" enables, by annual measurements on the particular flaw detector itself, to detect any non acceptable deviation of characteristics. These verifications are also performed at the delivery of the flaw detector, or at the occasion of repair. 

The tank had contained a light naphtha and had not been thoroughly cleaned before repairs started. It had been filled with water and then emptied, but some naphtha remained in various nooks and crannies. (It might, for example, have gotten into the hollow roof supports through pinholes or cracks and then drained out when the tank was emptied.) No tests were carried out with combustible gas detectors. 

A. The filter system shall include a- series redundant-parallel Chemical Biological Radiological (CBR) filter assembly with a capability of placing a detector between the adsorber banks to warn of "breakthrough". The system shall provide accessibility to filters for repairs, maintenance and leak testing. 

Early detection is essential. The placement of detectors inside cabinets can significantly reduce the time to detection. An early warning high sensitivity smoke detector (HSSD) smoke detection system can be used to detect incipient stage fires and allow planned repairs prior to equipment failure. Hence, fire suppression may not be required. 

Figure 5.14 A control chart showing a steady change from low to high values. Such a control chart can result from a steady drift in the calibration of a spectrophotometric detector, for example, indicating that the detector may need to be repaired or replaced.

Service, major and minor repairs, and parts replacement that will necessitate a requalification of the instrument. For example, the replacement of a UV lamp in a UV detector does not require a full requalification, whereas a replacement of circuitry board will warrant full requalification. 

The operation instruction, maintenance, and calibration should be included in the SOP. It is not necessary to copy the entire operation manually into the SOP. Writing simple instructions with references to the related sections in the manual is a better way. The frequency and tasks to be performed during maintenance should be stated in the maintenance section. The tests required to calibrate the instrument, the acceptance criteria, and the frequency for each test should be included in the calibration section of the SOP. Definitions of major and minor repairs which necessitate partial or full system requalification should be included as well. For example, the replacement of a UV lamp in a UV detector does not require full requalification whereas replacement of a circuitry board will. 

Nuclear track detectors are very simple and very efficient detectors of rare events that produce highly ionizing radiation. Carefully prepared and scanned track detectors have been used to identify individual rare decays. The detectors are integrating in that the damage caused by a track is not spontaneously repaired. The drawback to track detectors is that the tracks are small and can only be observed with a microscope. In the past, scanning by eye was extremely labor intensive and prone to error. Modern computer-controlled scanning has improved the speed and reliability of the analysis. Plastic track detectors that are sensitive to a particles are used extensively in commercial radon detectors. 

The hardware of an automated solid-phase synthesizer consists of all the electromechanical components of the system (reaction vessel, tubing, valves, pumps, detectors, power supplies, circuit boards, sensors, etc.). It is imperative that all these components are reliable and can operate without failure for many synthesis cycles before repair or replacement. Before using any component in an automated system, it should undergo compatibility and lifetime testing with the reagents that would be in contact during the synthesis. 

One of the advantages of this automatic system is that the state-of-health data recorded for the numerous subsystems, including blowers, component states, temperatures, and other critical information, allow remote failure detection, diagnosis, and possibly prevention. As an example, variation in detector temperature may show the onset of failure of a mechanical cooler. Remote diagnostics are used to schedule repair trips and minimize down time. 

An adequate maintenance program should also include a consideration of the auxiliary and safety equipment. Periodic inspections should be made of release diaphragms, safety equipment (fire-fighting equipment, gas detectors, alarm systems, flame detectors, respirators, etc.), ventilation systems, compressors, electrical equipment, etc. Detailed records should be kept of all inspections. These should show the condition of equipment, any malfunctions noted, and repairs made. All repairs should be inspected and approved by authorized personnel... 

The apparatus test includes a protocol about pump, injector and detector functions and includes the requirements listed in Table 19.1 Usually they are easily fulfilled by today s HPLC instrumentation, especially when new. The apparatus test should be performed routinely in adequate time intervals and after each repair. It is a prerequisite for method validation. A proposal can be found in Chapter 24. 

No, this may only help when old instruments and single-beam diode array detectors are in use. With modem detectors, the common cause comes from the electronics which can only be repaired by the manufacturer. 

Most electronic repairs consist of replacing entire printed circuit boards, as opposed to individual electronic components and wiring, which was required in early instrumentation. Cam timers have disappeared, to be replaced by digital electronics. Analog electronics have been minimized in order to preserve the integrity of the signal by digitizing as close as possible to the detector. 

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