RU2172218C1 - Method of cleaning cavities of articles - Google Patents

Abstract

FIELD: mechanical engineering; methods of cleaning inner cavities of articles. SUBSTANCE: method consists in evacuation of atmosphere air from cavities, treatment of surfaces with volatile solvent, in liquid or vapor phases. Upon completion of cleaning process, solvent is drained from article and it is connected to evacuated system without admitting atmospheric air; evacuation system is provided with solvent vapor cooled condenser; then system is heated. Condensate formed during heating is discharge to special reservoir till condensation is completed. Removal of solvent vapor is effected at temperature T_o and vapor condensation is effected at temperature T_con which are found from the following formula:

, where

is coefficient of reduction of losses of solvent in the course of cleaning process, (n>1); T is temperature of solvent in the course of cleaning, K; ρ_l(T) and ρ_v(T) are densities of liquid and vapor phases of solvent at temperature T, kg/cu.m; ρ_v(T_con) is density of solvent vapor at condensation point, kg/cu.m; γ_v is volume fraction of article occupied by solvent residue. EFFECT: saving of solvent. 1 dwg, 3 tbl

Description

 The invention relates to the field of technological methods for cleaning parts and assembly units of products from oils, fats and mechanical particles using volatile solvents and can find application in general engineering, aircraft manufacturing, rocket science, instrument making, electronic and other technical fields.

Volatile solvents are used to clean the internal cavities of products. The product cavities are filled with solvent and the cleaning process is carried out either by pumping the solvent, or by rinsing the internal surfaces. After the cleaning process, the solvent is drained from the cavities, and its residues are removed by any of the following methods:
blowing cold or hot air,
heating in a vacuum thermal furnace,
pumping the cavity with a vacuum pump, etc. [12].

 The disadvantage of this cleaning method is the large loss of solvent: in particular for products with a large volume of the internal cavity, as well as with a complex configuration of this cavity.

 The proposed method allows you to collect and dispose of most of the remaining in the cavities of the product after the process of cleaning the solvent.

 Closest to the proposed solution [3], is a method that involves filling the chamber with washing liquid with the formation of free space above its surface, mixing the layers of liquid by rotating it, characterized in that, in order to improve the quality of washing, to ensure better mixing of the layers of washing liquid in the chamber in the space formed above the washing liquid creates a vacuum. The disadvantage of this method is the loss of solvent during washing and when removing products from the washing chamber.

The aim of the invention is to develop a method for the economical use of a solvent when performing technological operations for cleaning-degreasing cavities of products. This goal is achieved by the fact that the cleaning process is carried out after sealing the cavity of the product and removing air from it, and in order to eliminate the loss of solvent with vapor phase and non-sludge residues at the end of the cleaning process and draining the solvent, the product is connected to the previously evacuated air without letting in atmospheric air in its cavity to a system having a cold condenser, the product heats up to a certain temperature T _о , and the resulting vapors condense on cold surfaces in the condenser (temp The temperature T _k ) and the condensate are collected in a special collector, moreover, the condensation process is continued until the vapor condensation ceases, after that the product is disconnected from the system with a condenser and its cavities are filled with dry, neutral gas to atmospheric pressure.

где

- коэффициент снижения потерь растворителя, ед.;
m₁, m₂ - соответственно потери растворителя в каждом цикле очистки при использовании традиционных и предлагаемого способов очистки, кг;
ρ_ж(T), ρ_п(T) - соответственно плотность жидкой и паровой фаз растворителя при температуре технологического процесса обезжиривания-очистки, T, K, кг/м³;
ρ_п(T_к) - плотность паровой фазы растворителя при температуре охлаждаемых поверхностей конденсатора, T, K, кг/м³;
T_о - температура изделия при выпаривании остатков растворителя K;
γ_v - доля объема полости изделия, занимаемая удаляемым несливаемым остатком растворителя, ед.The heating temperature of the product T _o for evaporation of the residual solvent and the temperature of the cooling surfaces of the condenser T _to determine from the ratio:

Where

- coefficient of reduction of solvent losses, units;
m ₁ , m ₂ - respectively, the loss of solvent in each cleaning cycle using traditional and proposed cleaning methods, kg;
ρ _W (T), ρ _p (T) - respectively, the density of the liquid and vapor phases of the solvent at the temperature of the technological process of degreasing, cleaning, T, K, kg / m ³ ;
ρ _p (T _to ) - the density of the vapor phase of the solvent at a temperature of the cooled surfaces of the condenser, T, K, kg / m ³ ;
T _about - the temperature of the product during evaporation of the residual solvent K;
γ _v is the fraction of the volume of the cavity of the product occupied by the removable non-leaking solvent residue, units

Table 1 shows estimates of the value of n depending on the values of T _to and T _about for the use of freon 113 as a solvent, the cleaning-degreasing process is performed at a temperature of T = 293 K, and the value of γ _v = 0.01.

Table 2 shows the estimates of n for the cases T = 323 K, γ = 0.01
Table 3 gives estimates of the value of n for the case T = 293 K, γ = 0
As can be seen, even with a small amount of unsoluble residues, the proposed method allows to achieve a significant reduction in the loss of HFC 113. It follows from relation (1) that the benefit from its implementation will be even greater if the technological process of degreasing-cleaning is performed at elevated temperature (see table 2) solvent, if the proportion of unsoluble solvent residues is higher than 0.01.

 A significant reduction in losses can be achieved even in the absence of non-leaking residues in the cavity, γ = 0 (see table 3).

 The method is as follows. From relation (1), the value of the indicators of the mode of evaporation and condensation of solvent vapor is estimated, satisfying the value of its desired savings in each cleaning cycle of the product - n.

 The invention is illustrated in the drawing, which shows a schematic diagram of the installation.

The cavity of the product 1 is pumped out by a vacuum pump 2. By the pump 3 from the evacuated tank 4, pure solvent is fed into the cavity of the product 1 to carry out the cleaning process. The cleaning-degreasing process is performed at a temperature of T. At the end of the cleaning process, the contaminated solvent is discharged into a previously evacuated container 5, from which it is taken for regeneration for the purpose of cleaning. The removal of unsolvable solvent residues and its vapors from the cavity of the product is carried out by heating the product with a heater 7 to a temperature T _о and condensing them on a cooled condenser 6 having a temperature T _k , condensed vapors are collected in a tank 4. The process of removing solvent vapor at given temperatures T _o and T _k lead to the complete termination of the condensation process. After the process is completed, the contaminated solvent is transferred to the regeneration unit (not shown in the diagram) and, after cleaning and regeneration, is supplied to the tank 4.

. Экспериментально показано, что при изменении температуры изделия в пределах 50-100^oC, температуры конденсатора в пределах -10...-20^oC достигаемые значения η изменяются в пределах η = 0,96...0,98. Таким образом показано, что предлагаемый способ очистки позволяет использовать растворитель в достаточной мере эффективно.Experiments to refine the proposed cleaning method were performed using the product model with internal cavity volumes of ≈ 100 l. Freon 113 was used as a solvent. A vacuum system equipped with a solvent vapor condenser was previously pumped out by a vacuum mechanical pump to a residual pressure of 10 ^-1 mm RT. Art. The condenser was cooled using an industrial refrigeration unit, the refrigerant was freon 22. The temperature of the cold surfaces of the condenser was maintained within the range of -10 ...- 20 ^o C. The temperature of the product heated by evaporation of vapor rose to 50-100 ^o C. In the cavity of the layout after evacuation control doses of the solvent were introduced in amounts ensuring the formation of vapor and liquid phases of the solvent. The efficiency of the capture by the condenser of the solvent vapor evaporated from the cavity of the prototype was controlled by comparing the amount of condensate formed in the volume of the condenser - M _k , with the amount of solvent introduced into the cavity of the product - M _p ,

. It was experimentally shown that when the temperature of the product varies between 50-100 ^o C, the temperature of the capacitor within -10 ...- 20 ^o C, the achieved values of η change within the range of η = 0.96 ... 0.98. Thus, it is shown that the proposed cleaning method allows the use of a solvent sufficiently effectively.

Использованная информация
1. П.Н. Белянин и др. "Промышленная чистота машин". М., Маш., 1982 г.

Information used
1. P.N. Belyanin et al. Industrial Cleanliness of Machines. M., Mash., 1982

 2. V.F. Tomanovskaya et al. "Freons", "Chemistry", Leningrad, 1970.

 3. RF patent N 977374, B 67 C 1/00 BI N 44-82, p. 82

Claims (1)

A method for cleaning product cavities, which involves removing atmospheric air from them by evacuation, treating the internal surfaces with a volatile solvent in the liquid or vapor phases, characterized in that after the process of cleaning and draining the solvent, the product is connected to a previously evacuated system equipped with a cooled condenser without letting in atmospheric air solvent vapor, the product is heated, and the condensate of solvent vapor formed in the cooled condenser is taken to a special capacity until the condensation process ceases, moreover, the removal of solvent vapor from the product cavities is carried out at the product temperature T _о , and the vapor condensation is performed at the condenser temperature T _k , and the value of Т _о , Т _к is determined by the ratio

Where

- coefficient of reduction of solvent losses during the cleaning process, (n>1);
m ₁ - loss of solvent in each cleaning cycle of the product using traditional cleaning methods, kg;
m ₂ - loss of solvent in each cleaning cycle of the product when using the proposed cleaning method, kg;
T is the temperature of the solvent during the cleaning-degreasing process, K;
ρ _W (T), ρ _p (T) is the density of the liquid and vapor phase of the solvent at a temperature of T, kg / m ³ ;
ρ _p (T _to ) is the vapor density of the solvent at the condensation temperature, kg / m ³ ;
γ _v is the fraction of the volume of the cavity of the product occupied by the indelible residue of the solvent.

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