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Physicochemical fundamentals of purification and characteristic of detergents




Estimation of surface cleanness during pollution extraction

Surface purification is an extraction of liquid and solid pollutions from the surface till definite level its cleanness. Cleanness is a state, under which there is allowable amount of pollution for given manufacturing or given process.

In relation to repair production, we may select 3 equal purification: macro purification, micro purification and activation purification.

Macro purification is a process of the biggest pollution extraction from the surface, which obstructs dismantling, detection and tooling.

During micro purification pollution traces are extracted, traces, which are still on the surface after macro purification and light pollutions of production. Even after micro purification on surface are active remains of substances and protective films.

Activation purification doesn’t play role in manufacturing repair. This kind of purification is an intermediate operation of etching metal layer with thickness 2-15mkm during electrolyte causing.

Pollutions, which are remained on the surface after purification, may be determined by different methods: weighable, luminescent, water damping and comparison with measure.

In the process of weighable method, pollution remain is determined by weighing. For this surface is cleaned by filter paper, paper napkin, white cloth or cotton swab. Pollution amount is determined by weighing of purification material before and after purification.

Luminescent method is based on oil property to glow under action of UV rays. Area and intensity of the surface define the surface pollution level.

Water damping method is based on metal surface ability to hold continuous water film, if this surface is free from oil pollutions. After purification specimen, which is under control, is immersed into cold distilled water, then it is taken out. Surface should be in vertical position. If the surface is free from oil pollutions, water film would distribute equally and covers whole surface.

Comparison with measure method. Cleaned surface is compared with specimen, that has some pollution. There is special ten-point scale, that estimates surface pollution level. During comparison cleaned specimens with measure, we may rapidly and exactly estimate wash ability of different means.

 

Purification surface of detail is connected with expansion of energy which is directed for overcome of adhesion forces of pollution and surface. During this work for purification Ао consists of work Aphch, which is done by detergents due to its physicochemical activity and work АМ, connected with mechanical influence of detergents on destruction of bonds of pollution with surface:

A0=Aphch+Am

There are methods of purification where some of the type of energy loss is absent. For example while degreasing the surface by immersion into solvent Am =0, and while purification the surface by blowing with drupaceous cap Aphch=0. Given examples are rare cases. Practically in most cases there are losses of both types of energy.

The problem of intensification of purification process due to increasing of value of work Aphch or Am is solved with the help of technological and economical analysis. At the same time we should take into account that work Aphch depends on action of detergent (its content, application of solvents, surfactants, alkaline etc.) and temperature. Detergents can differ from each other by its activity in 10-50 times, and increasing in temperature on 10-15 °С increases rate of purification in twice.

Work Am depends on view of mechanical intensification process (flow of high or low pressure, propellers, vibration, ultrasound oscillations, bubbling of air etc.). Methods of mechanical irritation by its intensity differ from each other in 10-20 times.

The right choice of activity of the detergent and corresponding mechanical irritator of process fastens purification in 10 times.

According to methods of purification the surface from pollution in aircraft repair manufacturing different types of purification machines are used: jets, with immersion, combined, special and automatic lines. Characteristics of such machines are given below.




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