The progressive cavity pump (PCP) is a positive displacement pump, consisting of a polished helical-shaped rod (rotor) turning inside a helical elastomer (stator). PCP has many advantages, but the pump durability is manly limited by elastomer behavior. At piston pumps (PP) used for drilling mud piston has an elastomer sleeve that also limit the durability. Standards like ISO 15136.1 & 2 for pumps developed by manufactures and users’ committees provides requirements for design, quality design verification etc., but do not define specifically the elastomer for the stator or the metal used for the rotor. Each PCP and PP manufacturer used specific materials at pump construction. The aim of this study was to evaluate the tribological behavior of some elastomers such polybutadiene rubber (BR), polybutadiene acrylonitrile rubber (NBR), polybutadiene acrylonitrile carboxylate (XNBR) and polyamide (PA 6) in couples with hard chromium coated steel, nitride steel and cast iron. Were determined friction coefficients and wear on 2 types of friction couples (plane to plane and shoe to plane) on two tribometers and some mechanical proprieties (Young’s modulus, ultimate tensile strength, elongation, hardness).
Abstract. Progressive cavitation pumps are designed to work in aggressive environments thus their wear is inevitable. The specific tribological coupling of these pumps is composed of a helical rotor with a single outward helix and a stator with a double inside helix. These elements are in relative motion and direct contact to each other and also in direct contact with the pumped oil. Therefore the main forms of wear of rotor-stator coupling elements are the abrasive wear and the erosion wear. In this paper is presented the analysis of erosion with Bitter and Hutchings models. The results are useful for estimation of progressive cavity pumps specific abrasive-erosive wear.
IntroductionThe researchers attention was focused on the study of the influence factors from the abrasive erosion models relations, to specify the share of their influence, the precision in describing the erosive processes, the generalization degree and the limits of applicability.The main assumptions on which erosion models were developed are as following [1-3]: a -the erosive wear particle occurs due to the mechanical action of abrasive particles on the surfaces that cause microcracking and microcutting of the incident material layer (the microcutting component of erosion); b -the kinetic energy of the abrasive particles is generated by their impact with the target surface causing the deformation of the material, initiation and propagation of crack and detachement of wear particle when the cracks have reached a critical length (the localized plastic deformation component associated with the mechanical fatigue process).The first case is typical to ductile material and the second one to fragile material. The assumptions made are based on Johnson, Cook and Holmquist studies [4][5] and analyzed by Wang [6].
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