Tribological Characterization of Some Elastomers Used at Progressive Cavity and Piston Pumps

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).

Cryogenic Pumps Monitoring, Diagnostics and Expert Systems Using Motor Current Signature Analyses and Vibration Analyses

The paper discusses the Cryogenic Pumps Condition Monitoring and Machinery Diagnostics Systems, including the automated Expert Diagnostics Systems. The Cryogenic Pump construction differs by design, failure modes and criticality and no single solution will suit all designs. Therefore, two approaches are discussed: Motor Current Signature Analyses and Vibration Analyses. The paper further shows the real case studies, diagnostics and findings on Cryogenic Pumps using both analyses. The article addresses common failure types and proposes applicable solutions. The Cryogenic Pumps mechanical and electrical malfunctions are discussed, their reflection on the dynamic current spectrum using improved Motor Current Signature Analysis (MCSA), aka. Model-Based Voltage and Current (MBVI) Analyses and vibration spectrum using Vibration Analyses (VA). The article contrasts the similarities vs. differences and advantages vs. disadvantages of both methods and may be of value for field engineers to understand the pros. and cons. of each technology. The paper outlines the Expert Diagnostics System based on MBVI, able to distinguish automatically among different malfunctions. The Expert System uses the power spectral density of the difference between the expected current obtained from the model and the actual current. These differences include only abnormalities generated by the motor anomaly. Therefore, they are immune to the noise or harmonics present in the supply voltages. The presented results, using both approaches: Model-Based Voltage and Current Analyses and Vibration Analyses, prove the potential of both techniques and the advantages of their combined use for reaching a maximum reliable Condition Monitoring and Diagnostics of Cryogenic Pumps.

Methodology based on best practice rules to design a new-born trochoidal gear pump

The trochoidal gear pump, also known as gerotor, owing to its remarkable advantages compared to other hydraulic pumps is chosen for many engineering applications. As each application is unique, the designer ought to be knowledgeable of the required specifications as a first task but need not be an expert in the hydraulic pump design. The review of the existing research reveals significant gaps to develop a new-born project and the work presented in this paper, drawn on existing research work and the authors’ own experience and know-how, aims to overcome them. The objective of the paper is then to provide a summary of the best practice rules to design a trochoidal gear pump from scratch achieving a thorough understanding. In the conceptual stage, making decisions come according to a predetermined set of four parameters known by the designer that will lead to the complete development of the trochoidal gear set. Afterwards, in the design process, the most important characteristics of the pump such as the porting, the pump construction, and the limitations are presented based on the significant explanations, with regard to each feature, selection, effects, and good practices. As a result, the methodology presented compiles the process of engineering in designing a new trochoidal gear pump as a catalogue of guidelines aiming to overcome a vague design due to a lack of knowledge. This collection of best practice rules intends to guide the designer to take good decisions early in the design process that limit design change later in the final stage—the prototype.

Effects of Materials on Cracking of Pumping Concrete

The constituents of concrete have a crucial effect on early age cracks of pumping concrete. Based on early age cracking mechanism of pumping concrete, the influence of raw materials, which includes cement, coarse and fine aggregates, mix ratio, admixtures, mineral additives and fibers on cracks are analyzed. The results show that the extent of early age cracking varies with constituents of concrete. It is advised that the appropriate concrete materials should be selected in terms of specific engineering features, not only by the requirements of strength and slump. With regards to the projects that are required crack control strictly, the characteristics of pump construction should be considered and the appropriate composition of concrete, especially the types and dosage of admixtures, mineral additives and fibers, should be determined by experiments.

Multiphase Transport With Conventional and Newly Designed Twin Screw Pumps in a Pipeline Network

Twin screw pumps are displacement pumps, working with two axially parallel and countercurrently rotating screws. They are experimentally and theoretically investigated by variation of the boundary conditions at the suction and discharge side of the pump. These are defined by the multi-phase flow patterns in the pipeline system of the closed loop test facility which is operated with oil, gas and water. Because of the efficient continuously operated phase separation, the plant is suited for the experimental investigation of the delivery characteristics in dependence of different flow patterns as well as modifications of the pump construction. A newly designed pair of screws (fig.1) with declining pitch is proposed for operation. The delivery of the pump depends on the declining volumes of the chambers, formed by the intermeshing screws moving from the suction to the discharge side. The improved performance of gas compression gives advantages in the efficiency of power consumption especially for multiphase pumping of mixtures with increasing gas volume flow fractions. By comparison with non-declining screws, the isothermal efficiency for declining screws is increased.

Applicability of Pump Models for Varying Operational Conditions

It is commonly known that the characteristics of a fluid power pump depend on pump type, pressure, rotational speed and displacement. But in addition to these, also all the other parameters or factors associated with the operating conditions may have a significant effect on the characteristics. The most important of these are the pump construction and size, operating point temperature and the characteristics of the oil, which also depend on temperature and pressure. The aim of this study is to show the effects that the varying operational conditions have on the characteristics of a axial piston pump, to compare the measured characteristics with other published characteristics of axial piston pumps and to study the capability of pump models to represent these characteristics. The results include information of the effects of fluid temperature, type of fluid and the setting value of the displacement on the pump characteristics along with the effects of pressure and rotational speed. The sensitivity of the pump to each of the parameters is discussed. The effect of limited information of pump characteristics on the reliability of simulation results is studied using the Schlo¨sser models.