Flushing and purification of AT details

Characterization of contamination. During operation various kinds of pollution are formed on the details of the aircraft and engine.The most widespread contaminants are:

– external sediments based on water;

–external sediments based on lubricants and special fluids;

– carbon-hydrogen sediments;

– products of metal corrosiondestruction;

– remnants of oldpaintwork(varnish/paint)coatings(PWC).

These contaminations are different in nature, so they have different opportunities and methods for their removal from surfaces.

External deposits can be divided into dusty-mud and oily-mud.Aerodrome zone always contains a certain amount of dust in the air.When ingested dust particles on the wet surface increases their coagulation and sedimentation on the surface.Strength retention of particles on the surface depends on the surface roughness, the size of the particles and humidity.

Lubricant-mud deposits are formed when the dust fall on the surface of details, which are contaminated by lubricants, fuel remains and special liquids. It is possible reverse phenomenon - falling these liquids on the surface contaminated by dust.

Carbon-hydrogen contaminations are divided on soot-formed, varnish sediments, tar sediments and residues.

Soot-formations are mainly formed on the walls of the combustion chambers, nozzles, valves, candlelight, the upper parts pistons of internal combustion engines and other parts, operating at high temperatures, where the combustion is proceed. Thickness of the carbon layer reaches 3 mm. The condition for soot formation is the high temperature on details surface.

Varnish sediments is the product of lubricantstransformation. Firstly, lubricant gets on the hot wall parts of the detail and under high temperature it will evaporate, forming a varnish film.

Varnish film increases under action of oxygen of high temperature and catalytic activity of metal. External varnish sediment is a thin and durable film with a smooth surface.The film is formed mainly on the details surface in the absence of conditions for the combustion of lubricant, but at a high temperature that activates the process of thin layer oxidation.

Tar sediments are low melting substance from dark brown to blackcolour.They are often postponed on the surfaces of the fuel system components of gasoline engines, especially in the cavity of supercharger, in the suction pipes and inlet valves.Tars are formed and during storage of fuel due to oxidation and polymerization of unsaturated hydrocarbons.

Residues aredeposited in the internal oil channels of engine, on filters, oil coolers and other details where the lubricant passes under the pressure.Externally, they are thick sticky mass of gray-brown or black colour.

Corrosion products are formed as a result of chemical or electrochemical destruction of metals and alloys during their interaction with the environment.

Remnants of the old PWC during operationalby the period of overhaul resource significantly damages due to the influence of solar radiation, temperature changes, moisture, mechanical damages, and other factors, that’s whyduring the overhaul all PWCon the aircraft and engine, details and aggregates should be removed and replaced with new ones. Process of PWC deleting is time-consuming, which is difficult for mechanization and automation,it requires specialized equipment and technology.

Дата добавления: 2014-01-05