Closed-loop engine dehydrator

Overview

Corrosion is one of the most common causes of early engine overhaul or repair. An important protection against corrosion is to maintain levels of moisture and acids in the engine oil as low as possible. Frequently flying the aircraft until achieving operating temperatures for 60+ minutes, plus performing oil changes every 40 hours or four months help reduce contaminants in the oil. Reducing relative humidity levels to below 15% inside the engine case also helps to reduce corrosion.

Description

This engine dehydrator uses a closed-loop system, wherein an vacuum pump pulls air from inside the engine through a slip-on adapter on the oil dipstick tube. The air is then pumped to an airtight case of desiccant, where the air is dehumidified. The dried air is then pumped back into the engine through the engine’s breather at the bottom of the engine.

Two identical gauges in each chamber measure temperature and relative humidity. When first starting the pump after a flight, the relative humidity of untreated engine air jumps to 70% or more, while treated, dry air is pumped back to the engine at 10% to 12% (assuming fresh desiccant is used).

After several hours of operation, humidity levels on both gauges reach equilibrium, at about 12% relative humidity. The pump can then be turned off, followed by infrequent, brief periods of running the pump to confirm continued low relative humidity within the engine. When preheating the engine in winter, the dehydrator is used to keep humidity levels low while cold internal engine parts are warmed.