Instrument Maintenance 1. Introduction Scientific equipment is like anything that is used regularly – it needs attention to keep going properly and consistently, and occasionally it will break down and either stop working completely, or at least not work properly. Part of a laboratory technician’s job is to keep the instrument working properly as long as possible – maintenance – and to recognise when something is going wrong and determine what might be the cause – troubleshooting. Rarely will it be the technician’s task to fix the problem (repair). while working Maintenance after breakdown
Troubleshooting Repair 2. Routine maintenance Routine or preventative maintenance is a set of planned and systematic actions intended to prevent known problems from disrupting device operation. If maintenance isn’t being done properly, then problems will arise that are beyond the list of usual wear and tear, and are likely to be costly and cause considerable downtime. Maintenance is a key aspect of laboratory work that directly impacts of the quality of results. Unfortunately, it tends to be the first thing that is cut back or put aside when time or money becomes tight. Some problems will occur even though the instrument is being used correctly and being maintained appropriately. These include the need to replace consumable items, such as electrode membranes, injection port septums and water filters. Consumables are what the name indicates – they are designed to degrade with use, and be replaced. There are three basic types of maintenance tasks: 
housekeeping – ensuring the device is clean; ensuring any services are operational 
instrument‐specific operations – actions that vary from one instrument to the next 
performance checks – running a standard substance through the instrument to monitor if the response is changing Maintenance procedures can be time‐based – carried out at set times intervals – or need‐based – carried out when required. 2.1 Housekeeping Dusting and cleaning may seem a bit menial for a laboratory technician, but in these days of economic belt tightening, the lab may choose not to afford a cleaner, and it then becomes the responsibility of the lab staff. Electronic components and optics do not like dust or liquids, and at the very least, degrade instrument performance. At the very worst, permanent damage (e.g. component burn out) can occur. It is also necessary that water filters, gas bottles and contaminant traps (e.g. desiccants) are fully functional. Filters and traps tend to be changed at specific time intervals, since they are rarely designed to be obvious when they need changing. Some desiccants have an indicator in them (e.g. silica gel) to indicate when they need changing. Instrument Maintenance 2.2 Instrument‐specific maintenance tasks
The majority of tasks will be instrument‐specific, where the different components and operation of different instruments requires totally different actions. They can even vary from one brand/model of the same device to another. This is where you need the manufacturer to supply a comprehensive and well‐written manual. Alas, it is not always the case. EXERCISE 1 (a) What are the good & bad points of the extracts from three manuals for different brands of fluoride ISEs below and on the next page? (b) Summarise the maintenance procedures for a fluoride ISE, based on the three information sources. (a) Hanna The HI 4010 sensor can be stored in standards near measured values for short periods of time and should be stored dry with the protective cap on when not in use for long periods of time. The model HI 4110 combination electrode can be left in standards that were used for calibration for short time periods. If the electrode will be used frequently and needs to be ready for use, take measures to prevent evaporation of fill solution. Top off fill solution, and replace o‐ring and plug on fill hole opening. Place sensor tip in a dilute fluoride standard, positioned upright. Prior to use, drain electrolyte chamber and refill with fresh fill solution. For long term storage, the electrode should be drained, disassembled and washed of salts with deionised water. Wrap the ceramic junction in Parafilm or other sealing wrap. Unscrew the fluoride module and store dry in the shipping vial. Store disassembled electrode in storage box provided with electrode. IM p2 Instrument Maintenance (b) Pasco Scientific (c) EDT After use rinse with deionised water, wipe clean with a tissue or lint free cloth, replace protective cap and store dry in its box. If performance becomes sluggish rinse with dilute detergent, rinse with deionised water and immerse the tip in a 1000 ppm Fluoride solution for 1 hour. Should further conditioning be requires rub down the crystal surface with a very fine polishing strip. 2.3 Maintenance operations for laboratory instruments It is not realistic here to provide detailed descriptions of the common maintenance tasks for the instrumentation you are familiar with, because the actual means of performing the task will vary from one model to the next. However, you should be aware of what is done – see Table 1. 2.4 Maintenance logs It is essential that these operations be recorded, for quality assurance reasons, but also so that instrument problems can be identified more easily, based on the length of time since a certain task had been performed. IM p3 Instrument Maintenance TABLE 1 Common maintenance tasks Flame AAS/photometer  clean burner slot  empty drainage bottle (if not directly linked to waste)  clean drain hose  monitor hollow cathode lamp voltage (AAS) pH electrode  general cleaning: soak in 0.1 M HCl for 20 minutes  removal of deposits and bacteria: soak in 1% domestic bleach solution for 10 minutes  removing oil and grease: a mild detergent or methanol  removing protein deposits: soak in 1% pepsin and 0.1 M HCl for 5 minutes Electrothermal AAS 
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replace graphite tube clean optical windows replace electrodes check autosampler syringe operation replace argon supply ICP emission spectrophotometer 
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clean torch clean nebuliser replace pump tubing empty drainage bottle (if not directly linked to waste water) clean drain hose HPLC  replace guard column  replace suppressor cartridge (ion chromatograph only) Gas chromatograph  replace injection port septum  replace oxygen trap (if used) Fourier transform IR  replace desiccant in gas line Polarograph 
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replace mercury if “dirty” clean electrode capillary keep reference electrode filled replace nitrogen supply In case you are wondering why the XRF and UV/VIS spectrophotometers and fluorimeter aren’t included here, it is because there is essentially nothing to do other than keep them clean. 3. Performance tests It is not enough to assume that the routine maintenance tasks will keep the instrument running properly. Plenty of other things can go wrong, and it isn’t always obvious that there are problems on the horizon. One way of keeping a check on the instrument is to regularly run a performance check. Sometimes it is referred to, rather confusingly, as instrument calibration but it has absolutely nothing to do with calibration graphs. This is intended to establish how the instrument is performing over its lifetime, showing variations by the repeated measurement of the same material. This material does not have to be a standard of known composition, but it needs to be unchanging, so that any variation in the measured value from one run to the next is due to the instrument, not the material. These tests are not intended to occupy large amounts of laboratory time, so they should be relatively simple to perform. They should cover the key measurements made by the instrument, and test a range of responses, if possible. IM p4 Instrument Maintenance EXAMPLE 1 What would be a suitable performance check for a pH electrode? The starter question is really: what instrument performance characteristics should be tested? For a pH electrode, it is simply the pH value it reports. To test this, you need a solution of consistent pH. You don’t actually need to know the exact value for the pH, just that it must be the same each time we make the solution (assuming it won’t last “forever”). The pH buffers that you use for the calibration – 7 & either 4 or 9 – aren’t appropriate, since you adjust the instrument’s setup with them. Another solution in the calibration range (4‐7 or 7‐9) would be suitable. There are numerous other pH standards available. EXERCISE 2 What performance characteristics of the following instruments could be routinely tested? (a) UV‐VIS absorption spectrophotometer (b) gas chromatograph EXERCISE 3 How would you know what an acceptable value for a performance check test is? 3.1 When to do performance checks The timing for doing these tests may be based on time (calendar or usage hours) intervals or instrument‐related events. It will be partly based on practicality – quick & simple tests can be performed often – and the likelihood or past history of performance problems. If there is a change in the instrument, such as location, repair, maintenance, upgrade, then a full set of performance check should be done before using it for serious analysis. 3.2 Results Once the performance check has been run, the results MUST ALWAYS be kept in the instrument log, in a clearly marked section. This is vital for detection of components that are about to fail, and to provide information to auditors checking on quality assurance procedures. In some situations (such as in the case of certain accredited laboratories) it may be a legal requirement to maintain all qualification records. In many cases, the results will be graphed on a run chart for easy recognition of trends. IM p5 Instrument Maintenance 4. Troubleshooting No matter how well maintained your instrument is, things will go wrong, meaning that it won’t work as well as it should, or it won't work at all! There are some problems that an experienced laboratory technician will be able to fix themselves, but many others than will need specialist assistance because of the complexity of the device. He/she is unlikely to be an electronics engineer, and so will not be able to fix faults associated with the electronic functions and controls of the instrument. This is the same as with modern cars: thirty years ago, a keen interested person could do most mechanical car work themselves, now almost nothing is within the range of the keen amateur. However, this is not to say that when something goes wrong, you can throw your hands up and "it's not working – ring the service technician"! With experience, you can what is the most likely cause of a particular problem. This is known as troubleshooting. EXERCISE 4 What is the difference between troubleshooting and maintenance? Unfortunately, having the ability to identify what is causing the problem is not the same as having the ability to fix it – sometimes a specialist is necessary. However, if you have found the cause or eliminated a number of possible causes, it will reduce the time spent by the specialist service engineer, who will be able to bring the correct part or know exactly where to look first, reducing the repair bill substantially (they charge typically $200/hour). And there is something even more fundamental that this: you need to realise that the instrument isn’t working properly in the first place. 4.1 Basic principles Troubleshooting, by its name, means that you start the process after trouble arises, not before. This will result from the observation that something isn’t right. You are observing a symptom of the problem, but not the problem itself, and definitely not its cause. The process of troubleshooting is the process of working out the (most likely) cause of the problem from an analysis of the symptom. This will often involve some checks/tests which help in pinpointing the cause. IM SYMPTOM CAUSE The observable “incorrect behaviour”
The fault that has led to the “incorrect behaviour” Checks/tests
p6 Instrument Maintenance Knowing what might cause a particular symptom means:  being very familiar with the correct operation of the device,  knowing what can go wrong with it  knowing what incorrect behaviour results from various faults Unfortunately, in complex equipment, this isn’t easy. 4.2 Symptoms A symptom is the physical appearance of the problem. For example, when you have a cold, the symptoms are often a runny nose and a cough. These are the result of the problem, and can be a problem themselves, but trying to deal with the symptoms doesn’t fix the underlying cause. To be able to recognise the cause of the fault requires a good description of the symptom. “It’s not working (properly)” simply isn’t good enough! The description of the symptom needs to be specific, because it will allow a more efficient analysis of what is the cause. Some useful descriptions are: 
“the power light isn’t on” 
“the absorbance value is zero for a standard” 
“the readings are very inconsistent” 
“the software is showing error code 1234” EXERCISE 5 For the following pieces of equipment, suggest some common symptoms: Electric kettle MP3 player Analytical balance Any competent technician should be able to describe the symptoms of a malfunctioning device, regardless of who might be doing the troubleshooting. Generally, when a major problem arises, requiring a service technician from the supplier, there will be a phone/email conversation first where the service person will ask what the problem is. They will often make some suggestions about what you can do to help identify the problem. This will save your company money, because hourly rates for service technicians make plumbers seem cheap! IM p7 Instrument Maintenance 4.3 Causes Many equipment symptoms can have a number of causes, even for a simple device. These can be due to a failure of some part of the device, or from an external source. External External causes are those which are not due to a problem with the device itself, but rather:  errors in how it is used ‐ operator error  “supply” problems – conditions required for the device to work properly, such as power, gas, water, temperature etc are not correct Electrical power in the laboratory For power to be useful in a home or business, its voltage has to be stepped‐down from hundreds of thousands volts to 240. Once the power arrives at the end‐user, it is split off the main distribution line – the power lines running along the streets – and supplied to domestic, commercial and light industrial users as a single phase. Users requiring higher power will get what is known as three phase power, which is 415V. The typical maximum current for a normal laboratory circuit is 15 amps. This means that all energy‐
consuming items connected to this circuit should not demand more than a total of 15A at any one time, without potentially exceeding the safe limit for the wiring. Since high power‐consuming appliances such as ovens can typically require the whole 15A, it is usual that each building will have multiple connections to the grid, each supplying 240V/15A. Thus, lighting is often in circuits on its own, the air conditioner and the oven may also have their own circuit, and then there will be general purpose circuits for items that are less power‐hungry or not on all the time, e.g. TV, computer. Just because a circuit has a limit of 15A doesn’t mean that this couldn’t be exceeded if enough devices were requiring power at the same time. Fuses (originally) and circuit breakers (now – see right) are used to avoid this situation. They are designed to cut the circuit if a certain current is reached. Circuit breakers simply trip an internal switch which breaks the circuit, and can simply be reversed by flipping the switch back, as long as the problem, e,g, too many devices, has been dealt with. Instruments also have current protection if something goes wrong and the device tries to draw too much current, causing internal components to burn out. Rather than circuit breakers, they have fuses, which are constructed of a metal wire or strip that melts when too much current flows. Different current cutout values are achieved by different thicknesses of the metal. Some fuses are metal‐capped glass tubes with the wire visible, others coated in ceramic to make them more electrically safe (see right). EXERCISE 6 Examine the fuse used in each of the instruments in the laboratory where the rear of the device is accessible. IM p8 Instrument Maintenance DEVICE‐RELATED Knowing specific causes of particular symptoms does require some familiarity with a device, but some of the basic ones should be possible to work out for anyone let loose on the instrument. There is nothing more embarrassing than contacting your supervisor or even worse a service person with an equipment problem, only to find that a lead had fallen out or the switch wasn’t on etc. EXERCISE 7 (a) Suggest possible device‐related causes of the specified symptoms. Kettle Symptom – doesn’t heat at all Causes MP3 player Symptom – poor sound quality Causes Balance Symptom – inconsistent readings Causes (b) In each case, which is the most likely cause of the symptom. (c) How would you test whether this was the cause? IM p9 Instrument Maintenance MAKING LIFE EASIER Fortunately, life is sometimes made easier for the technician by the instruction manual that comes with the device. Often this will have common symptoms/faults/checks (look at home at the manual for your DVD player or TV). Unfortunately, not all manufacturers take this trouble, and sometimes when they do, it can be more worrying than anything. For example, the GC symptom No Peaks has eleven possible causes at least (see Figure 1)!! FIGURE 1 Possible causes of no peaks in a gas chromatogram (from Supelco Bulletin 853A) IM p10 Instrument Maintenance EXERCISE 8 For the eleven causes for no GC peaks in Figure 1, identify which you think are: (i) most likely (ii) easiest to check If you are lucky, you can not only identify the cause but correct it. Sometimes it might only be the identify part, and someone else will have to fix it. Sometimes, it will be beyond your capability to even diagnose the exact cause, let alone fix it. At that point, you get back on the phone/email to the service technician and break out the cheque book! At least you will eliminated the obvious, reducing the service technician’s time, your cost and also your potential embarrassment. EXERCISE 9 Listen to two extracts from a talkback radio program dealing with car problems (they can be downloaded from the theory notes webpage (mp3 files), along with transcripts if you found the American accents hard to understand). Extract 1 (a) What is the basic symptom? (b) What further information was provided about the symptom? (c) How did the “experts” attempt to clarify (check) the problem? (d) IM What was the likely cause? p11 Instrument Maintenance EXERCISE 9 (CONT’D) Extract 2 (a) What is the basic symptom? (b) What further information was provided about the symptom? (c) How did the “experts” attempt to clarify (check) the problem? (d) What were the likely causes? (e) How could this be checked? 4.4 Common instrument problems (& their solutions) Modern instrumentation is far too complicated for there to be a complete list of problems and solutions drawn up. Electronics‐based problems will almost certainly be beyond the ability of a normal laboratory technician to diagnose, let alone fix. However, most instruments do have a set of problems producing recognisable symptoms, which can be diagnosed and possibly fixed by experienced technicians. Interfaced instruments have two units that can cause problems: the instrument and the PC. Many interfaced instruments have absolutely no manual control at all – think about the Cary UV/VIS – which obviously reduces their price, but seriously reduces their usefulness, if PC problems occur. It also makes troubleshooting that much harder, since they are essentially “black” (or more commonly beige) boxes, which only trained service technicians can open and work on. However, the controlling influence of the computer software can be a positive when the problem occurs in the instrument, as the better software produces an error message to indicate that there is a problem, and what it might be. Sometimes, these messages are intelligible without looking in the manual, and sometimes even reading the manual doesn’t help (but it should help the service technician, so always record the exact message when documenting the problem!) IM p12 Instrument Maintenance EXERCISE 10 Complete the following tables. Where there is a ? in the left hand (cause) column, you are expected to make suggestions. General Symptom No power (switches are on and there is power to other instruments) Causes & ? ? Internal power supply problem Tests Symptom Computer loses control over instrument; PC still works normally otherwise Causes & ? ? Tests Ion‐selective & pH electrodes Symptom Will not calibrate/poor sensitivity Causes & Membrane has dried out Membrane is coated in something Reference electrode out of solution Tests HPLC Symptom High back pressure Causes & Guard column blocked Tests Symptom Pump stops or will not start Causes & Blockage in check valves Tests Symptom Spikes in the chromatogram Causes & Air bubbles in the system (most likely the detector) Tests Symptom Rising baseline (ion chromatography) Causes & Suppressor cartridge exhausted Tests IM p13 Instrument Maintenance Flame AAS & flame photometer Symptom Readings suddenly drop to zero Causes & ? Tests Symptom Flame has gaps in it Causes & Blockage in burner Tests Symptom Flame changes colour even with no solution being aspirated Causes & Outlet drain has blocked up and solution has backed up into flame Tests Polarograph Symptom No peaks Causes & Matrix problems ? Tests Symptom Poorly shaped peaks Causes & Mercury not dropping Tests Symptom “High resistance” error message Causes & Reference electrode out of electrolyte Tests Electrothermal AAS Symptom Very inconsistent readings (but not zero) for replicates Causes & Graphite tube worn out Tests Symptom Tube catches fire Causes & ? Tests IM p14 Instrument Maintenance Symptom Occasional zero readings from non‐blanks Causes & Sample delivery not working consistently Tests ICP Symptom Readings suddenly drop to zero Causes & ? Spray chamber not draining Tests Symptom Plasma doesn’t start or goes out mid‐run Causes & Argon pressure is too low Tests Symptom Plasma starts but loud clicking noises and bright flashes come from plasma chamber Causes & Torch is not aligned properly Tests Gas chromatograph Symptom Drifting baseline Causes & Leaking injection port septum Tests Symptom Very long retention times Causes & Blockage in column Leaking septum Tests Symptom Poor separation Causes & Column overload Tests Symptom Poor sensitivity Causes & ? ? Tests IM p15