Kulik A. V., Kriachunenko.O. L., Zevako A. V.

Oles Honchar Dnipropetrovsk National University


Relevance of the chosen topic is caused by the needs of Ukrainian space rocket industry to fulfill international orders and projects. The transition to international standards enhances cleanness of tank cavities, pipelines and other pneumo and hydro systems.

Analysis of the assembly – welding operations revealed possible sources of contamination and its character. During the assembly-disassembly operations and machining work using hand electrical equipment, brush, scraper, etc. according to the technological process different sorts of dust, abrasive particles, chips and other things on the surface of structural elements can get on the parts surface. Welding operation goes after edges preparation – removal of the oxide film (mechanical, chemical methods), degreasing. These methods of preparation before welding are also sources of pollution. Test work such as endurance test and calibration tank leave behind residue in the form of dust and dirt on the inner walls. Workshop walls, floor, ceiling and equipment may also be sources of pollution. Poor ventilation in the room provides a basis for the emergence of fine dust. Exploring the nature and sources of pollution shows ways to reduce and prevent them. There are mechanical, physical, chemical, physico-chemical, and thermal methods of cleaning the surface from contamination. Not all existing cleaning methods can be used in removing dirt from the tank inner cavity. This is due to the specific design and difficulty getting inside. Usually the only way to get inside is manholes and technological holes for chokes and valves. To clean the inside cavity of the fuel compartment hydrodynamic cleaning method is used. The cleaning process takes place on a vertical hydraulic testing bench using washing head. There is a hydro­motor inside of the washing head body that allows it to rotate around its axis and transform the kinetic energy of translational motion into the kinetic energy of rotational motion. Jet washout quality depends on the physical properties of the fluid and the environment, their viscosity and surface tension. To achieve the required level of tanks internal cavities purity and high quality of surface preparation before test for leaks in the design documentation in degreasing and cleaning surfaces from mechanical impurities introduced using 0.0 -0.02% aqueous solution of potassium dichromate in distilled water. Explosion safety, incombusti­bility and chemical inertness of this solution allows it to be used in devices for mechanized cleaning due to hydrodynamic jet effects.

To achieve the required surface purity the following must be considered:

- specific consumption of washer fluid for 1m2;

- fluid heating temperature;

- nozzle device inlet pressure;

- the distance from the nozzle to the surface to be cleaned;

- area of ​​effective action;

- an indicator of purity;

As a result of experimental studies it has been revealed that compatibility and range of jets depends on the diameter of the nozzle, turbulent flow stabilizer design in the flume and fluid pressure. Nozzle with “z-element + mesh" flow stabilizer type, hole diameter of 4 mm has better performance in comparison with nozzles with outlets diameters 1.5 mm,2.0 mm, 3.0 mm, 5 mm. For nozzle with d0 = 4 mm optimal pressure is P0 = 0,5 ÷ 0,6 MPa, and for the nozzle with a diameter d0 = 2 mm – pressure P0 = 0.2 ÷ 0.3 MPa. Effective action range for liquid jet is 40-85mm. The most effective treatment is during the first few seconds. This guarantee removal of 92–93% of contaminants, following treatment increases the purity of the sample not more than for 3–5%. When cleaning with hot water (40-50C) with pressure P0 = 0,5 ÷ 0,6 MPa and specific consumption of 80 – 90 l / m 2 over 98% of contaminants can be removed, while with specific consumption of more than    450 l / m 2 almost 100 % of impurities may be deleted. However, during the organization of regular spacecraft parts jet cleaning it is necessary in each case to perform technical and economic assessment of feasibility of increasing the cost of heating washer fluid to reduce the duration of treatment cavities.