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Smoke Spots

Without a doubt one of the most important things we can do for oil heat’s image and our environment is to set all of the oil burners we work on for true zero smoke. This setting will not only make our life easier at the next tune-up, but goes a long way to enhance the image of oil heat with consumers. Even a trace of smoke is smoke, but zero smoke is no smoke at all, right?

I bet you’re wondering, ‘Hasn’t he pretty much beaten this subject to death?” Well as it turns out even with all of with my articles and books on combustion, combustion testing, the Lanthier Scale, and even more on testing and maintenance of the instruments, you would think so, right? Wrong.

It turns out, with all of the words written, I keep making the simple assumption that people read OEM instructions. So, in this article we’re going to take the smoke tester apart, literally, and go through it and solve some mysteries of the wet-kit. Even that is a misnomer because although electronic testers are slowly winning the combustion testing game, the manual smoke tester still can’t be beat and there is supposed to be nothing wet in a typical oil burner’s combustion gases.

The reason why the smoke tester should and will continue to remain one of our most important tools is simply its ease of use and accuracy, if used correctly. In addition, the use of a smoke tester external from today’s electronic analyzers promotes longer life of the sensors in the analyzers and better overall cleanliness of the pathways within the analyzer, and that’s just better for everyone.

Today, there are several smoke testers that are commonly being used including those produced by Bacharach, Mitco, Testo, Westwood and Wohler. Although they all perform the same job and pretty much work the same, each should be maintained according to the respective manufacturer’s instructions and that’s where I made my assumptions. Since you may assume you’re using the tester correctly and may not be, let’s review the procedure for taking a test as a review and then take the tester apart and service it. The following is taken from my book Advanced Residential Oilburners.

Using Figure 1 for reference, insert a clean piece of filter paper into the holding slot of the tester, A. After the burner has achieved steady-state condition, insert the sampling tube into the open test hole in the flue pipe, B. Pull the smoke tester handle through 10 full pump strokes. Make sure that the tester is not driven by taking the strokes too quickly. Allow a few seconds at the end of each pumping stroke. Remove the tester from the flue pipe and then remove the paper from the holding slot.

Compare the smoke spot on the paper by placing it under the spot on the scale that comes the closest to matching it, C.

That’s the one and only correct way to use the tester, but what about those full strokes? Try this little trick the next smoke test you do. Simply take a test as you normally do and then move the test paper and do another test taking 20 full strokes. If you get a different reading, you’re drawing the sample too quickly and need to slow down ‘ we’re looking for accuracy in smoke testing, not speed. Next, let’s check the tester for correct maintenance by using another excerpt from my book. By the way, you can’t pull too many strokes, but you can pull not enough.

Check the smoke tester by first inserting a clean test paper into the instrument. Block off the end of the sampling tube. Pull the plunger handle about one inch and release. The handle should return to about the original position. If no resistance is met or if the instrument handle does not return to the original position, the instrument should be checked for leakage. If leakage occurs, the short piece of rubber tubing under the spring and between the tester and sampling tube should be checked first. It may have become disconnected, or it may have deteriorated due to age and may need to be replaced. An atmospheric test should be made of the instrument. Do a standard test on room air. If after 10 full strokes a smoke reading is observed that can be measured on the chart, another test with a clean test paper should be performed. If after this the instrument still measures smoke, the instrument should be disassembled and cleaned with warm water and detergent. Be sure to lubricate the cylinder of the plunger-type with the proper material after servicing.

Now, that’s where I made my biggest assumption that people would refer to the manufacturer’s instructions for proper servicing. So, without any further fanfare, let’s get to it. I’m first of all going to have to explain the use of two things that many people have always wondered about. When you first got your wet-kit or analyzer, either new or as a hand-me-down, you found a small T shaped wrench attached to the side of your smoke tester or in the carry case. Also in the carry case, I hope, was a small bottle of clear fluid. We need to look at those two items first.

The first is that T wrench. It’s available from Bacharach as their part number 21-0078 and can be used on Bacharach and Testo smoke testers. It’s used for removing the nose pieces at the front of the instrument, Figure 2. The nose pieces hold the test paper tight and dry when in use, essentially making these pieces a moisture filter. Brigon uses another type of wrench, so you’ll have to contact them, and the Mitco and Westwood testers can be easily taken apart with a screwdriver. Although the Wohler smoke tester can be easily taken apart and stripped down, I’m not too concerned with the servicing of these testers, Figure 3. The Wohler has four filter elements and if they are replaced on a regular basis, I doubt if you’ll ever have to clean it, but you can check with them on this point.

Using the T wrench, or whatever the OEM recommends, take the smoke tester completely apart. The nose pieces should be removed from the hose piece and body and the rod and cup removed from the tester body. Then either clean all of the parts in an approved solvent or a bath of soapy water. Do not damage or remove the rubber cup from the rod unless it is necessary and follow the OEM’s guidelines. If the rod is dirty, clean it with a light abrasive. After cleaning, thoroughly dry off all of the components and reassemble the nose pieces to the tester body. The tester’s sampling cup should be lubricated with the proper fluid and reinserted into the body. The fluid in that small bottle mentioned earlier is for this purpose. Finally, check to make sure any hoses on the instrument are connected and have not deteriorated, which will cause air leakage when used. If the hoses are damaged, replace them and retest the tester using a new piece of test paper.

George Lanthier is the owner of Firedragon Enterprises, a teaching, publishing and consulting firm. His website is www.FiredragonEnt.com

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