Identifying the causes of the two-part engine piston destruction in a gas-diesel mining dump truck

Abstract

Introduction. The paper considers the relevance and prospects of using liquefied natural gas in BelAZ 75131 mining dump trucks. It is an alternative fuel source which allows reducing greenhouse gas emissions. Accidents occurring in the course of such gas-diesel dump trucks operation are associated with the destruction of one two-part piston from the entire KTA 50-C engine piston group. Research objective is to find the cause of the KTA 50-C engine two-part piston destruction during its gas-diesel operation by studying its microstructural characteristics. Methods of research. Тhree prototypes from different parts of a two-piece piston are sampled for research. The microstructural characteristics of the prototypes were studied using a JEOL JSM-6390 LV scanning electron microscope with a JED 2300 energy-dispersive X-ray detector under certain regulated conditions. Research results. The results of the microstructure studies showed the difference in the elemental mass composition of the aluminum alloy of the piston’s upper and lower parts, as well as the presence of more developed caverns and microcracks in the upper part of the piston than in the lower one. Analysis and discussion. At high operating temperatures and variable high-frequency pressures, the presence of cavities in the upper part of the piston contributed to the formation and propagation of large microcracks, which subsequently led to its destruction. There is a hypothesis that liquefied natural gas used as motor fuel may lead to the destruction of the two-part piston aluminum alloy upper part as it increases the operating temperature in the cylinder by 3–3.5%. This hypothesis has been proved invalid. Conclusions. The cause of the two-part piston destruction was found and revealed no interconnection with the conversion of BelAZ 75131 mining dump truck to dual-fuel (gas-diesel) operation using liquefied natural gas as motor fuel. A recommendation was given to enterprises operating and repairing mining equipment.