Drilling mud pumps operate under harsh conditions and are a weak link in drilling equipment. In actual production, it is almost a daily occurrence to stop drilling due to mud pump accidents or damage. Statistics in oil drilling show that when the drill length is 2500M, 28.4% of daily expenses are spent on drilling mud pumps, and 49.3% of the drilling downtime for repairs is used to fix the drilling pumps. The vast majority of mud pump failures are caused by damage to wear parts. According to statistics, in 1970 the Soviet Union drilled a total of 13.82 million meters, consuming 89,200 cylinder liners, 175,000 pistons, and 238,000 valve sets. In the Shengli Oilfield in 1972, among 73 drilling rigs, the total consumption cost of seven wear parts of drilling pumps was 1.57 million yuan, including 580,000 yuan for valves, 270,000 yuan for pistons, 300,000 yuan for cylinder liners, and 420,000 yuan for tie rods and packing. This shows that studying the failure mechanisms of wear parts and the factors affecting their lifespan, thereby improving their durability and operational reliability, is of great significance for reducing labor and material consumption, improving drilling efficiency, and lowering costs.

This is also a key issue in the design of drilling equipment. Practice shows that even for the same type of wear parts, their service life varies with different models of drilling pumps; even for the same pump and the same wear parts, the lifespan differs between improved and unimproved versions. This indicates that after fully understanding the factors affecting the lifespan of wear parts, improvements in structure, materials, and processing technology can enhance their durability. The main wear parts of reciprocating mud pumps include cylinder liners, pistons (or plungers and their packing), valves and valve seats, piston rods and their packing, etc. These are reciprocating parts and their sealing friction pairs' mating parts, sharing two common characteristics: first, the mating parts are elastomers capable of deformation; second, they bear a certain pressure difference during operation. Therefore, unlike friction pairs formed by two rigid parts, studying their friction and wear patterns is more challenging.

The flushing fluid conveyed by the mud pump often contains a large amount of abrasive particles, sometimes as high as 5-10%, with particle diameters reaching 1.5-2.0mm and microscopic hardness of 180-230. During reciprocating motion, due to pressure differences, wedge-shaped fluid flow carries particles into the friction contact surfaces, causing scratches or grooves on sealing or rigid parts. Over time, this results in wear parts losing their normal functionality. Therefore, normal wear of wear parts generally forms grooves along the circumference of the friction pair parts consistent with the reciprocating motion direction, and some areas show signs of fluid erosion. The grooves on the elastic parts and rigid parts of the friction pair often correspond in convex and concave shapes. For the elastic parts in the friction pair, due to imperfect surface finish and intrusion of abrasive particles, friction resistance arises during reciprocating motion, increasing with working pressure. Part of the energy converts to heat, raising the temperature of the friction pair contact surfaces. Since elastic rubber has a very low thermal conductivity, heat concentrates on the rubber surface layer, accelerating rubber aging until it loses elasticity and sealing performance.

Damage to valves and valve seats: Extensive analysis shows that valve lifespan mainly depends on the working performance of valve seals. Valve damage and scrapping are primarily due to premature failure of rubber seals, causing tiny gaps on the working surfaces of valves and valve seats. At this time, high-pressure fluid containing abrasive particles erodes the valve working surfaces through these small gaps, leading to damage. The process can be described as follows: when the mud pump operates, dynamic loads repeatedly act on the valve, firmly embedding abrasive particles into the working surfaces of the valve disc and valve seat. The metal layer on these surfaces undergoes localized plastic deformation, forming varying degrees of dents. When the valve disc and valve seat contact again, abrasive particles deepen and enlarge these dents. Repeated cycles cause local tearing and elastic spalling of the metal surface, ultimately damaging the valve and valve seat. Actual statistics show that 85% of scrapped valve discs are due to rubber seal ring failure, all showing grooves; 70% of scrapped valve seats are due to abrasive wear under impact dynamic loads, with annular wear marks on the working surfaces.