SELECTION OF MATERIALS USED FOR MANUFACTURING DIAPHRAGMS OF DIAPHRAGM-PISTON PUMPS IN AGGRESSIVE ENVIRONMENT

Wear of the diaphragm-piston pump may occur due to a reduction in the cross-section of the suction circuit (caused by an unsuitable pipe diameter, a dirty filter, pumping of high-viscosity liquids, etc.), the use of very aggressive chemicals, high operating temperature, abrasive particles, and high pressure in the pneumatic line. The paper considers various types of materials used for the manufacture of diaphragm piston pumps: rubbers, thermoplastic elastomers, thermoplastics and thermoset materials. The physical and mechanical, technological and operational characteristics of materials and the corresponding requirements for chemical resistance, temperature range of operation and abrasiveness were taken into account using an example of soybean cultivation. It was found that the optimal material that meets the above criteria is cast polyurethane. It has high physical and mechanical characteristics, a wide range of hardness (from 30 A to 90 D by Shore), low shrinkage, which implies long-term use of the material. Polyurethane products are manufactured by free casting, in which the liquid polymer composition is cured in a form that does not require complex and expensive injection molding rigs, unlike thermoplastics and elastomers. Injection polyurethane has sufficient chemical resistance in contact with the pump's working fluids and features wear resistance when pumping abrasive media. Therefore it is suitable for working in the climatic conditions of the Central region of Russia, and is also affordable, cheap and technologically advanced.

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