Slide1 : total time: 9:38 Welcome to our 3 tutorials series on how to keep a laser particle size analyzer's cell clean, clean it if you have to, and helpful solutions when cleaning fails. This is the first of 3 tutorials. Please enjoy these tutorials brought to you by Granuloshop. Pictures in this tutorial have been taken on our lab's Microtrac (tm) 3500. This tutorial should apply to the vast majority of other fine instruments on the market Slide : 2 time: 0:38 As on many other instruments, a blank is acquired. In Laser particle size analyzers this is called set-zero. The set zero is the signal that the diffractometer receives when no sample is present. This signal will be subtracted from that received by the diffractometer when sample is introduced. If the set zero is too high, then, a warning pops up. Possible causes are : - failure in the electro-optic device, this is extremely rare, - liquid is turbid due to bubbles, contamination, or pollution, - or, noise is generated by the cell itself, caused by stains or scratches. If needed, have a look at the set-zero. If the warning was triggered by a small margin, you may disregard it. Slide : 3 time: 1:45 Your particle size analyzer is built to serve you many many years, therefore it should be adjusted on a regular basis to correct for detector aging. You should perform this array calibration every month or every 3 months. Sometimes more often. Calibration is fast and lasts only 42 seconds. In Service menu, click on "Calibration", then OK. Do also Align the laser. We recommend that you check the laser auto align option. This detector calibration applies to the optical path past the sample cell. This may be enough to get the set zero to pass. Yet, if the set zero alarm keeps being triggered, we can suspect a problem upstream, and most likely: the sample cell. No matter what, do not forget to perform the array calibration on a regular basis Slide : 4 time: 2:56 If the liquid is not clear, then obviously, the set zero will be too high. Possible causes are easy to observe. There may, for example, be some of your previous measurement sample left in the unit. Rince several times, then try a new set zero. If you are seeing bubbles: they are often caused by some surfactant left behind by a previous measurement or rince. Rince again. Liquid may contain hard to see micro-bubbles, sometimes due to a temperature difference between the liquid, such as tap water, and the instrument or to a micro leak in the circuit. Retighten nuts and check for leaks. In the very rare case where you use several non-miscible liquids, make sure to use well mixing liquids for rincing between runs. Two non-miscible liquids will emulsify. We recommand that you check that the liquid tank is clean, scrub the circulator reservoir with a swab or scraper, and, from time to time, wipe underneath the teflon detector to remove pollution. Slide : 5 time: 4:22 If, despite these simple steps, the set zero remains bad, then most likely the problem lies with the sample cell. These problems can be of various types and, simple procedures can prevent them. Those procedures are simple, fast and efficient. Next slide reviews these simple steps that can help prevent, slow down, or even solve cell fouling or deposits related issues Slide : 6 time: 4:58 Always rince right after each run Add a drop, just one only drop, of surfactant during each rince. If your water is hard, top up with household acid on a regular basis and circulate for a few minutes to disolve any calcium film deposition on the cell windows. You should also rince several times with some surfactant before taking action on the cell itself. In the very rare case where you rince with non-standard liquids, do not forget that liquids should be well mixing. If liquid A does not mix with B, do rince thoroughly with an intermediate liquid that mixes well with both. If the instrument will be left unused for an extended period, we recommend that you leave enough liquid in the unit to kept the cell wetted. You may want to use a protective film to avoid evaporation. To prevent particles to enter the unit a sixty micron filter is mounted at the rear of the circulator; this filter should be cleaned up every 2 to 3 years to avoid clogging. Using wrenches, disassemble the filter set up, clean the metal frit with sonication and or compressed air. Reassemble in the same order: an arrow shows how to place the filter. on nifty twick: you may want to place the filter, not at the very rear of the unit, but at the other end of the tubing. It will thus act as a weight to keep the tubing at the bottom of your liquid tank Slide : 7 time: 7:02 Two pollutions are possible, inside or outside. External pollution is much more of a problem. Remember this: laser protective coatings are deposited on the external surfaces and not on the inside, since internal surfaces come in contact with the potentially abrasive sample. If external surfaces are stained, scratched or damage, repairing the cell will be extremely difficult: this will be lesson 3. Never forget: never touch the cell's outside windows! Do not attempt to clean the outside windows yourself. Whenever you are putting the sample cell back in its location make sure that the 2 O'rings are well in place and tighten firmly to waterproof the circulation circuit. If there is a leak there, liquid will circulate and spill outside the cell. The cell ouside windows will thus be severly stained and damaged. If such a leak ever occurs, the enclosure should be left open to dry for 24 h, avoiding dust, as this area must be perfectly dry : mist resulting from humidity may diffract light and add to the noise; mist may also migrate to other optical components. Never attempt to disassemble the sample cell. Pay extra attention to what you are doing whenever you switch an instrument from wet to dry modes. Obviously, you should not attempt to clean the cell in a sonicated bath or washing machine. Slide : 8 time: 9:07 Our lesson 1 on preventive maintenance of a laser particle size analyzer is over. If you still can not get a valid setzero, you will have to manually clean the inside of the cell: this will be our lesson 2. Do not miss our other tutorials, our main web site granuloshop.com, our on-line shop, tutorials series and lab services. Thank you.