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(a) Valve seat recess tilted, (b) erosion in orifice bore, (c) valve A operating pin, (d) SEM image of valve A operating pin, erosion at tip.
Contexts in source publication
Context 1
... particle, material appeared to have been lost in a pattern that suggested flow, consistent with an erosion process, around the particle in the direction of the orifice, as indicated by the arrows on Fig. 1d. The scalloping pattern of flow indicated that the particle contact area with the valve seat recess was of the order of 20 mm in diameter. Fig. 2a shows the valve seat tilted to observe the bore of the orifice and Fig. 2b shows the seat rotated with the particle remnant towards the bottom of the image. There was an area within the bore of the orifice, diametrically opposite the remnant of the particle, where loss of material or pitting had occurred. The pitting was smooth with ...Context 2
... flow, consistent with an erosion process, around the particle in the direction of the orifice, as indicated by the arrows on Fig. 1d. The scalloping pattern of flow indicated that the particle contact area with the valve seat recess was of the order of 20 mm in diameter. Fig. 2a shows the valve seat tilted to observe the bore of the orifice and Fig. 2b shows the seat rotated with the particle remnant towards the bottom of the image. There was an area within the bore of the orifice, diametrically opposite the remnant of the particle, where loss of material or pitting had occurred. The pitting was smooth with defined peaks and consistent with an erosion process. The position of the ...Context 3
... examination of the operating pin, shown in Fig. 2c, suggested that one end was essentially undamaged and the other had undergone some metal loss. The damaged end is shown in Fig. 2d and in more detail in Fig. 3a. Metal had apparently been removed in various locations around the circumference leaving generally smooth, scalloped areas, consistent with an erosion mechanism. In some ...Context 4
... examination of the operating pin, shown in Fig. 2c, suggested that one end was essentially undamaged and the other had undergone some metal loss. The damaged end is shown in Fig. 2d and in more detail in Fig. 3a. Metal had apparently been removed in various locations around the circumference leaving generally smooth, scalloped areas, consistent with an erosion mechanism. In some locations, a rough, pitted surface was apparent, shown in Fig. 3b, which was more consistent with a corrosion mechanism. ...Citations
... And this is the most common problem which has occurred in China (Wang et al., 2017). An excessive impact load causes serious damage to the hydraulic support, leading to its instability and hydraulic cylinder rupture (Geary, 2013). Once the hydraulic support has problems in the supporting process, it will directly threaten life safety of the miners and the routine operation of the mining equipment, causing enormous economic losses. ...
A two-stage linkage safety valve for hydraulic support is presented. Considering the hydraulic support is impacted, dynamic simulation of the column circuit with the two-stage safety valve subject impact loading was carried out, and the dynamic characteristics of the two- -stage safety valve with different impact forms were studied. A rapid impact loading test rig was built to test the two-stage safety valve sample under impact loading. Simulation and experimental results indicate that the two-stage safety valve has high sensitivity and good unloading performance, it can realize fast and large flow unloading of the hydraulic support under different impact forms and pressures. © 2020 Polish Society of Theoretical and Allied Mechanics. All rights reserved.
... However, reference is made here of generic types as found in Refs. [72][73][74]. Valves used in hydraulic systems, such as a WEC to control behaviour of the hydraulic fluid, are of three types; Pressure valve, Flow valve and Directional valve. Valve faults such as abrasion and wear usually have, as a causal factor, improper assembly which creates uneven loading and tilting of the valve-plate. ...
Experts’ judgement is employed in offshore risk assessment because reliable failure data for quantitative risk analysis are scarce. The challenges with this practice lies with knowledge-based uncertainties which renders risk expression and estimation, hence components’ risk-based prioritisation, subjective to the assessor – even for the same case study. In this paper, a new risk assessment framework is developed to improve the fidelity and consistency of prioritisation of components of complex offshore engineering systems based on expert judgement. Unlike other frameworks, such as the Failure Mode and Effect Criticality Analysis, it introduces two additional dimensions: variables and parameters, to allow more effective scoring. These additional dimensions provide the much needed and uniform information that will assist experts with the estimation of probability of occurrence, severity of consequence and safeguards, herein referred to as 3-D methodology. In so doing, it achieves a more systematic approach to risk description and estimation compared to the conventional Risk Priority Number (RPN) of FMECA. Finally, the framework is demonstrated on a real case study of a wave energy converter (WEC) and conclusions of the assessment proved well in comparison and prioritization.
Booker et al. [3] stated that “in many engineering defect investigations, the choice of forensic analysis methodology is rarely questioned, and the forensic analysis methodology is chosen by the analyst without due diligence, resulting in a methodology that may not be the most accurate or expedient. This in turn has the potential to increase the risk and cost of the decision-making process.” Therefore, a need was identified to identify and analyse the variables that influence practitioners’ selection of an appropriate forensic analysis methodology. A review of current literature highlighted the fact that there was no definitive correlation identifying the primary variables that affect the selection of forensic analysis methodology. Noting that the determination of the correct methodology for a specific instance is not within scope of this paper, the first stage of the analysis was to apply previously collated methodology taxonomy, and then apply Principal Component Analysis (PCA) to determine which variables had the highest significance of influence on the selection of Forensic Analysis Methodology from 132 case studies selected from Case Studies in Engineering Failure Analysis [2] (Annex A.). The analysis has determined that the methodology selected to conduct forensic analysis is primarily influenced by the geographical culture and industry of the analyst. Therefore, there is a requirement to acknowledge and understand the role of cultural and industry biases when choosing an appropriate methodology, and subsequently, when evaluating a forensic analysis case study.
Although the mere recognition of the existence of cultural and industry bias does not guarantee that the right decisions will be made, it does, however, facilitate an objective rigour to the process of the selection of the forensic analysis methodology to be applied, which in turn, will mitigate subjective reasoning and potentially reduce the risk and cost of the decision-making process. Without an international standard for forensic analysis, or universally acknowledged guidelines for the selection of forensic analysis methodology, analysts will continue to be susceptible to methodology selection bias, which will increase the probability of choosing the wrong methodology, which, in turn, can prolong the investigation and adversely affect the accuracy of the analysis.
The large flow electro-hydraulic directional valves are the key operating components for automation of the hydraulic roof supports in the coal mine. Cracking is a common failure mode of the valve. Effects of the buffer damp diameter, the valve type and the static pressure on the stress of the valve were researched. The valve dynamic behavior was investigated by AMESim. The transient collision stresses of the inlet valve sleeve of the main control valve under different buffer damp diameters and different valve types were investigated by ANSYS/LS-DYNA. The static stress analysis was conducted in ANSYS too. Results show that the valve failure is due to the fatigue of the inlet valve sleeve when suffered from the collision stress wave in the valve opening process, rather than the lack of component strength. The buffer damp diameter, the key parameter of the valve, has a significant effect on the collision stress of the inlet valve sleeve. The integrated type valve has a better stress state compared to the separated type valve. This paper provides an effective method to solve the fracture problems of hydraulic directional valves. It is also significant for the design and optimization of hydraulic components.
