Reliability Of Valves Research Articles

Relationship between Some Design Characteristics and Wear in the Bicarbon Heart Valve Prosthesis

The hinge design of a new bileaflet valve (Bicarbon) is presented in relation to the long-term durability characteristics. Theoretical considerations supported by experimental findings, lead to the identification of two different wear mechanisms acting in bileaflet valves, i.e. impact and friction wear. Impact wear, caused by the collision between the hinge stops and inflow surface of the leaflet pivots, is the predominant phenomenon; it is mostly influenced by the design of the coupling elements. The wear due friction is significantly less important, given a proper kinematic coupling and a thorough washout. These different mechanisms can significantly affect the wear resistance and long-term reliability of bileaflet valves; therefore, they have been properly taken into account in designing the new valve model. The safety of the overall material and design solutions adopted in the Bicarbon valve has been confirmed by extensive accelerated durability tests resulting in no mechanical failure or loss of functionality.

Current Developments in High-Power Thyristors

AbstractOne way of increasing the reliability of thyristor valves is to reduce the number of devices required for a high blocking voltage. An essential precondition for this is the introduction of new technologies which allow the total power loss of high-blocking thyristors to be kept within reasonable limits. The drive circuitry can be further simplified by directly integrating light triggering and overvoltage protection into the thyristor.

Studies on Low-Erosion Butterfly Valves. Suppression of Erosive Vortex Cavitation.

In order to improve the reliability of butterfly valves, it is absolutely imperative to prevent fatal cavitation erosion and to control the flow rates precisely. In our previous studies, erosive vortex cavitation, which takes place within a limited part of the high-shear region, was found to play an important role in the erosion. This fact suggests to us a useful method for overcoming erosion. To date, many types of modified valves have been proposed, in which very uniquely-shaped buffers are attached on the orifice and nozzle sides of the valve disc, although data on the results of their practical use are unavailable. In this paper, therefore, the erosive shock-pressure distributions on the inner pipe-wall surface downstream from the valve disc and the corresponding cavitation-flow pattern are precisely measured in the typical bounded flow around butterfly valves by means of pressure-sensitive films and high-speed photography. It is found that the erosive pulses and the range of their occurrence in the shear regions can be significantly attenuated by introducing simple buffers.

Functional tests of French safety valves, type SEBIM, for their fitness for use in the primary system of German pressurized water reactors

Several safety requirements are made to the operativeness of the relief and safety valves of the pressurizer of German pressurized water reactors. Reliable pressure limitation and - if necessary - reduction to the required pressure must be warranted by them under any transient plant conditions, in case of operational transients and accidents. In addition, the valves must reliably close again if there are requirements for opening and in the event of malfunction in order to avoid loss of coolant accidents. These different requirements result in the fact that the valves must be able to discharge different media such as hydrogen, steam and water. To enable the valves of the pressurizer to meet all specific requirements made to them, retrofittings and modifications to a different extent are required for German pressurized water reactors. In doing so it must be warranted that the valves used will neither show any instable behaviour due to the different discharge media nor cause any relevant strain produced by pressure waves on the adjacent conduits. For retrofitting of the safety valves of the pressurizer, the French company SEBIM, too, proposes a concept for the protection of the primary circuit against exceeding pressure. To prove the functional reliability of safety valves, type SEBIM, under the thermohydraulic conditions prevailing in German pressurized water reactors, an extensive test programme was carried out on the CUMULUS test facility (true scale [1:1] of the real plant) of Eléctricité de France. Due to the positive results obtained in these tests it is to be stated that the safety valves, type SEBIM, stand for an interesting solution for the protection devices of the primary system of German pressurized water reactors (DWR) against exceeding pressure.

Suppression of Cavitation Erosion on a Low-Erosion Butterfly Valve with a Tunnel-Type Buffer.

In order to improve the reliability of butterfly valves, it is absolutely imperative to prevent fatal cavitation erosion. In our previous studies, we developed a new butterfly valve with a tunnel-type buffer, and showed that it was effective in suppressing cavitation erosion on a specific valve opening when the erosive vortex cavitation occurred predominantly on a typical valve. Practically speaking, when the valve is operated near valve closure, erosion is an especially big problem. In this paper, therefore, the cavitation shock pressures and the highly erosive vortex cavitation arising around the butterfly valve with the tunnel-type buffer are compared with a typical valve counterpart by means of pressure-sensitive films and high-speed photography. It is found that the tunnel-type buffer is also useful in preventing erosion near valve closure.

Limit switches key to valve reliability

Limit switches key to valve reliability

The Reliability of Artificial Heart Valves ‐ A Case Study for the Proportional Hazards Model

Investigates the medical factors affecting the reliability of artificial heart valves using the proportional hazards model. The data, from a database which is still being assembled at Killingbeck Hospital, Leeds, refer to patients who have had artificial heart valves implanted. The analysis of the data has been carried out using a suite of programs not specifically designed with this application in mind. Illustrates the exploratory analysis, the parameter estimation for the model and the validation of the model, being a preliminary study to assess the value of the proportional hazards model for this area. Follow‐up work, as the database is revised and augmented, is intended.

Studies on Low-Erosion Butterfly Valves. Suppression of Erosive Vortex Cavitation.

In order to improve the reliability of butterfly valves, it is absolutely imperative to prevent fatal cavitation erosion and to control the flow rates precisely. In our previous studies, the erosive vortex cavitation, which takes place within the limited part of high-shear region, was found to play an important role in the erosion. This fact suggests to us a useful method for overcoming erosion. To date, many types of modified valves have been proposed, in which very singular shaped buffers are attached to the orifice- and the nozzle-side of the valve disc, although data on the results of their practical use are unavailable. In this paper, therefore, the erosive shock-pressure distributions on the inner pipe-wall surface downstream from the valve disc and the corresponding cavitation-flow pattern are precisely measured in the typical bounded flow around butterfly valves by means of pressure-sensitive films and high-speed photography. It is found that the erosive pulses and the range of their occurrence in the shear regions can be significantly attenuated by introducing simple buffers.

Reliability Management of Surface-Controlled Subsurface Safety Valves for the TOGI Project

Summary This paper describes Norsk Hydro and SINTEF's efforts to obtain higher reliability of surface-controlled subsurface safety valves (SCSSV's) for the Troll-Oseberg gas-injection (TOGI) project. Because of the severe consequence of system failures, reliability management was fully implemented on the TOGI subsea production system. The methodology used combines reliability theory with operating experience. Data bases with relevant field data, design review techniques, valve prototype testing, and review of test results are other elements of the reliability management program. Although this specific application was for SCSSV's, the methodology presented in this paper can easily be applied to systems where the consequence of failure is severe.

Commercial external ventricular drainage sets: Unsolved safety and handling problems

Twelve commercially available sets for drainage of cerebrospinal fluid were tested for handling, design, features for fixation of the ventricular catheter, reliability of the anti-reflux valve, obstruction, efficiency of the air ventilation filter caps, accuracy of flow measurement and adjustment of flow, quality of material, adjustment, and cost. All systems showed considerable deficiencies in their reliability and handling. None of them can be recommended without certain restrictions and they should all be revised.

Valve testing and development in the laboratories of the kwu group of siemens ag

In nuclear power plants, valves make up the largest number of active components. Valve failures contribute to safety-related events and to nuclear power plant downtime. KWU together with plant operators and valve manufacturers have therefore made increasing efforts to improve valve performance, particularly through experimental qualification at valve test facilities. Newly-developed valves are qualified by type tests. Hypothetical accidents such as ATWS and main steam pipe breaks have been modeled at full-scale test facilities, and the as-specified performance of safety valves and main steam isolation valves has been demonstrated experimentally. In-service testing and maintenance using a valve service system developed by KWU, which is conducted in close cooperation with the power plant operators and the valve manufacturers during plant operation and scheduled outages, further improve valve reliability and safety over the entire service life of the plant.

Analysis of the initial temperature data for evaluating the reliability of a shut-off valve

Analysis of the initial temperature data for evaluating the reliability of a shut-off valve

Calculation of design reliability of suction valve of a diaphragm compressor

Calculation of design reliability of suction valve of a diaphragm compressor

Increasing the reliability of lever-spring type slide valves

Increasing the reliability of lever-spring type slide valves

The Application of Two-Out-of-Three Logic for the Control of Electric Motor Operated Valves in Candu safety Systems

Traditionally, the operation of electric motor operated (EMO) valves has been controlled by a position limit switch and a torque limit switch which are part of the actuator. A malfunction or improper maintenance of either of these switches has resulted in numerous actuator failures. The reliability of EMO valves and, in the case of nuclear power plants, the frequency of forced shutdowns could be significantly improved by using two-out-of-three logic in the control circuits. The feasibility of mounting additional switches on the valve and the control circuits was verified in tests and has been assessed as suitable for both new and existing nuclear installations.

The reliability of safety valves

The reliability of safety valves

An Assessment of Diesel Engine Poppet Valves

The paper reviews an assessment of the factors affecting the reliability and durability of poppet valves of highly rated medium speed diesels burning standard or residual oils. Detailed analysis demonstrated that an undercut (tuliped) profile is preferable. Optimum dimensional proportions are derived. The valve behaviour under operating conditions was such as to suggest that it plays a passive part in the phenomenon of ‘valve sinkage’. The adoption of ‘differentially angled seats’ appears to have little meaning in practice. Cylinder head deflection was a governing feature of seat ‘guttering’. A review of material properties suggested that the often quoted Eichelberg quality factor is inadequate and an alternative parameter for assessing the suitability of materials is derived. All materials suitable for valve manufacture possess poor resistance to corrosion attack. A number of possible palliatives are examined.

An Assessment of Diesel Engine Poppet Valves

The paper reviews an assessment of the factors affecting the reliability and durability of poppet valves of highly rated medium speed diesels burning standard or residual oils. Detailed analysis demonstrated that an undercut (tuliped) profile is preferable. Optimum dimensional proportions are derived. The valve behaviour under operating conditions was such as to suggest that it plays a passive part in the phenomenon of ‘valve sinkage’. The adoption of ‘differentially angled seats’ appears to have little meaning in practice. Cylinder head deflection was a governing feature of seat ‘guttering’. A review of material properties suggested that the often quoted Eichelberg quality factor is inadequate and an alternative parameter for assessing the suitability of materials is derived. All materials suitable for valve manufacture possess poor resistance to corrosion attack. A number of possible palliatives are examined.

Factors affecting the reliability of thyristor valves

Electrical Engineering in JapanVolume 93, Issue 6 p. 66-72 Article Factors affecting the reliability of thyristor valves Y. Sekine, Y. Sekine member Faculty of Engineering, University of TokyoSearch for more papers by this authorT. Miki, T. Miki member Faculty of Engineering, University of TokyoSearch for more papers by this authorT. Sakurai, T. Sakurai member Tokyo Electric Power Co., Inc.Search for more papers by this authorM. Iwasaki, M. Iwasaki member Tokyo Electric Power Co., Inc.Search for more papers by this authorO. Nagasaki, O. Nagasaki member Tokyo Electric Power Co., Inc.Search for more papers by this author Y. Sekine, Y. Sekine member Faculty of Engineering, University of TokyoSearch for more papers by this authorT. Miki, T. Miki member Faculty of Engineering, University of TokyoSearch for more papers by this authorT. Sakurai, T. Sakurai member Tokyo Electric Power Co., Inc.Search for more papers by this authorM. Iwasaki, M. Iwasaki member Tokyo Electric Power Co., Inc.Search for more papers by this authorO. Nagasaki, O. Nagasaki member Tokyo Electric Power Co., Inc.Search for more papers by this author First published: 1973 https://doi.org/10.1002/eej.4390930611Citations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume93, Issue61973Pages 66-72 RelatedInformation

A method for calculating the reliability of hvdc thyristor valves

A method for calculating the reliability of hvdc thyristor valves