1. I live in a very dry climate. Do I really need an engine dehydrator?
YES you do. Since water is a byproduct of combustion, it is present in the winter and summer. For every pound of fuel burned about 1 pound of water is produced. Most of this water goes out the exhaust, but some gets past the piston rings and enters the crankcase as blow by. The crankcase has only one outlet, the crankcase breather tube. This allows the hot moist air that gets by the piston rings to escape without blowing out the front crankshaft oil seal. Consequently, the air is going out the breather tube but the only thing that is pushing it out is more hot moist air.
2. I fly frequently, at least once a week. I would think that my engine parts are always coated in oil. Why would I need an engine dehydrator?
You probably don’t if you are truly flying once a week or more. Most of us would like to fly that often but sometimes weeks can pass by between flights. As time goes on, the oil will thin and make internal engine parts more susceptible to rust. Some oils do cling to the shiny metal surfaces and protect better and longer than others. It all gets down to the question – “how long will the oil protection last”? If in doubt, the best practice is to use the dehydrator between flights. Or for extended storage, “pickle” the engine per the manufacturers recommendations. Tanis sells a pickling kit for that purpose.
3. Once the humidity has dropped to its lowest level, should I turn the dehumidifier off or should I let it run continuously?
From our tests we recommend continuous operation of the dehydrator until all of the moisture is removed from the engine crankcase. After the dehydrator has been connected for a short period of time you will see a significant drop in the indicated humidity level. But the humidity will quickly rise again after the dehydrator is removed if any moisture remains in the engine. Once all of the moisture has been removed, the engine will stay dry for days or weeks depending on the outside humidity.
4. I live in a damp climate where the humidity is almost always high. Will the humidity level in my engine increase to the outside humidity soon after the dehydrator is shut off?
If you have left the dehydrator on long enough to get all the water out and leave the hoses connected it will come up again very slowly depending on the saturation level of the desiccant. If you disconnect the dehydrator on a dry engine the humidity will very slowly move toward the outside humidity but not as fast as you would think. The engine “breathes” with temperature and barometer changes. However, with that long breather tube, a dry engine can take a couple weeks to make an appreciable swing.
5. Do I need to connect the dehydrator to the engine as soon as I am done flying or can I wait for a while?
Either way works. Ideally we recommend connecting the Dehydrator soon after flight but not before you can touch the engine without burning your hand. While the engine is hot, more of the moisture is in vapor form and will be removed more easily and quickly before it drops below the dew point. However, some engines operate extremely hot and are still cooking oil vapors off the oil for a long time after the aircraft is parked. If the dehydrator is connected at this point, the oil vapors will condense in the dehydrator, coating the drying desiccant granules with oil. The performance degenerates quickly if this happens.
6. I have an engine preheat system on my plane. If I have the engine heater on, does it speed up dehydration of the engine?
Yes, greatly. The heat helps turn the water to vapor allowing it to move out of the crankcase and get trapped in the desiccant. I’ve removed a cup of water from our test crankcase in less than 3 hours with the heater on, where as it took several days (nearly a week) at room temperature.
7. How long does it take to saturate the desiccant in the dehydrator?
We have taken up to 1 cup of water out of a hot simulated crankcase without reactivating the desiccant. At that point it would not pull the relative humidity below 27% and the desiccant was pink indicating it was time to reactivate.
8. What is the life of the desiccant in the dryer? Will I need to replace it someday? The life expectancy of the desiccant should be unlimited if cared for properly. Two things that will destroy the product are immersion in water and exposure to some chemicals. The absorbency of the desiccant will be reduced if the granules become covered in oil film. The desiccant would need to be replaced if oil coating occurs. Purging the crankcase for 5 to 15 minutes with the dehydrator should dramatically reduce the possibility of this happening. We have done field tests for over 10 months without significant oil contamination.
*Note- we have found that ‘turbo’ aircraft are more subject to oil vaporization / contamination due to their high operating temperatures and should be cooled down prior to connecting the breather tube side of the dehydrator.
9. How long does it usually take to dry out/ reactivate the desiccant once it is saturated?
When fully saturated, the desiccant will take about four hours to dry out. Naturally, it will take less time to reactivate if only partially saturated.
10. How is the Tanis dehydrator any different or better than other dryers on the market?
Aircraft crankcases are sealed boxes except for the crankcase breather tube. The Tanis dehydrator circulates the engine crankcase air through a desiccant and returns the dry air to the crankcase. Other units on the market pump outside air through the desiccant then into the crankcase breather. This may look fine and bring the humidity level down slightly, but this does not provide enough air movement or air exchange to dry the crankcase completely. The Tanis unit exchanges the approximately 2 cubic feet of crankcase air in about 2 minutes.
11. Can the dehydrator remove rust from my engine?
NO! The Tanis dehydrator removes moisture from the engine crankcase creating an environment that is not conducive to rust, but it will not remove rust that was present prior to its use.
12. Is there any fire concern with the desiccant regeneration?
No, the desiccant is in a metal box and nonflammable. Before the desiccant leaves the manufacturer it is heated to 1750°, so flames or over heating is not an issue.
13. Are there health issues connected with the desiccant?
Mild potential. The Material Safety Data Sheet (MSDS) recommends: Do not breathe the dust and do not handle with bare hands. The desiccant dries the skin and the dust is a potential carcinogen on some scales. Wear a dust mask and gloves when changing the desiccant granules.
14. I have a Continental 0-200 engine with a kidney oil tank (dry sump). Will the Dehydrator work on this engine?
YES the dehydrator will work with your engine and other small block Continentals such as the A65, C85, and C90. In these engines, the oil filler standpipe in the kidney tank protrudes down below the oil level when the oil tank is filled to the full mark. This prevents dry air from moving through the tank into the crankcase and out the vent. Any method that drops the oil below the standpipe in the tank will allow dry air to circulate. A couple of possibilities that owners have used are: rolling the appropriate main gear wheel up onto a small ramp to lift the stand pipe out of the oil, or dropping the oil level a quart low, or a combination of above. If you look down the pipe with a flashlight you can see if the standpipe is above the oil level. If it is, air can circulate, and the dehydrator can be used. Just be sure to return oil to the proper level before flight.
15. On some of the Cont 520 & 550 engines the crankcase breather tube comes out the side of the oil fill pipe. Can I still use the Tanis
Engine Dehydrator?
YES, Tanis has an optional adaptor that feeds a 12" hose into the oil fill tube, turns 90 degrees and goes into the crankcase. Moist air exits around the tube. It works great.
16. I am building an airplane and have already purchased the engine. But, I will not be ready to fly for at least a year. Is the Dehydrator a good option to protect my engine during that time?
The Tanis Dehydrator is not intended to be a long-term storage device. For long-term storage follow the engine manufacturer’s recommendations. This normally includes coating the inside of the crankcase and cylinders with pickle oil and placing desiccant absorbers in the intake, exhaust, and spark plug openings in each cylinder. Tanis has a pickle kit that includes all of the above in one package.
rev 07-09-2007