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www.fueloilnews.com | FUEL OIL NEWS | MARCH 2016 45 Checking the wet-type draft gauge—check to be sure that gauge is level and zeroed, Figure 3. Check out the same as dry-type gauge. However, if this instrument does not return to zero after a couple of samples, thoroughly clean the instrument and recharge with clean gauge oil. It has also been found that when draft gauges respond slowly or are sluggish, the following components should be checked: Leads and probes may be plugged or leaking Pointer may be touching scale Shut-off rings on wet-type are leaking air With the electronic testers of today, it is merely a matter of turning it on, Figure 4, and following the directions. Checking the smoke tester—insert clean test paper into instrument. Block off end of sampling tube. Pull plunger handle about 1 inch and release. Handle should return to about the original position. If no resistance is met or if instrument does not return to origi- nal position, the instrument should be checked for leakage. An atmospheric test should be made of the instrument, Figure 5. If, after ten full strokes, a smoke reading is observed which 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. Be sure to lubricate the cylin- der of the plunger-type with the proper material after servicing. Checking the CO analyzer, Figure 6. Testing of this instru- ment should be done after about 200 samples have been taken, following long storage periods, or after coming from extreme temperatures, such as cold service vans or hot service and sales car trunks. If the CO, scale is down, two or three drops of water or fresh fluid added to the instrument should bring up the scale fluid to the zero point. If water has been added more than a few times, a test should be performed to establish fluid strength. There are two ways to obtain CO2 to establish fluid strength and only one way to confirm this strength: After taking a sample in the usual way, which requires 18 full depres- sions of the aspirator bulb, the instrument, is inverted twice and the test result is recorded. Then the instru- ment is inverted or tipped t w i c e m o r e . I f t h e C O , percent reading rises more than 1/2%, the fluid is becom- ing weak and should be replaced. The second method is as follows, and is called t h e e x h a l e d b r e a t h t e s t . This should only be done when no equipment sample is available. Disconnect tubing so that connector and short piece of hose, less check valve, can be attached to instrument. Take deep breath, hold for 3 or 4 seconds, depress inlet valve and exhale into instrument. Release inlet plunger at same time while exhaling. Perform double inversion test as in example #l. Do not perform two tests on exhaled breath for establishing CO2 content. It is an increase in percent CO2, on the one-and-the- same sample that indicates weak fluid. The sampling hose and pump, Figure 6, should also be checked. The filter yarn in the sampling hose should be replaced when- ever noticeable discoloration takes place. This will also provide easier pump operation. The entire hose assembly should be checked periodically. The easiest way is as follows: With finger placed over inlet side or filter side, depress pump. Pump should remain depressed until vacuum is released. With finger over out- let or instrument side, apply moderate pressure to the bulb. If it cannot be depressed, the bulb and hose are all right. For greatest accuracy when using CO2, indicators, allow them to reach room temperature. If they are cold, experience has shown that readings will be slightly high. Also, when servicing C02 indicators be cau- tious with the red absorbent solution. It is potassium hydroxide, which is a poison and acidic and can cause severe burns. Always avoid contact with skin, eyes and clothing. Checking the stack thermometer: The thermometer should be checked for obvious damage and/or a bent stem. If the instru- ment appears in good condition, the following tests can be performed to check accuracy: Boiling water test; insert thermometer in boiling water. If instrument reads 210-215°F, instrument is okay. Thermotest; check thermometer against a thermocouple or good mercury thermom- eter. Another good test is comparing temperature in a warm air furnace plenum against either of these two instruments. If, when using a Bacharach thermometer, Figure 7, it is found that the instrument has wandered, it can be recalibrated by securing the hex-shaped nut on the back of the "Tempoint" and by rotating the black dial to correspond to the correct tempera- ture setting. checked for leakage. An atmospheric test should be made of the instrument, 5 is observed which can be measured on the chart, another test with a clean test percent reading rises more than This should only be done when no equipment sample is available. Disconnect tubing so that connector and short piece of hose, less check instrument reads 210-215°F, instrument is okay. Thermotest; check thermometer against a thermocouple or good mercury thermom- eter. Another good test is comparing the hex-shaped nut on the back of the "Tempoint" and by rotating the black dial to correspond to the correct tempera- Figure 3 Figure 5 Figure 7 Figure 6 Figure 4