Journal articles: 'Pressure Valve'

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Odend'hal, C. J. "MODIFIED BACK PRESSURE VALVE." Journal of the American Society for Naval Engineers 39, no. 4 (March 18, 2009): 702–6. http://dx.doi.org/10.1111/j.1559-3584.1927.tb04234.x.

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Bergsneider, Marvin, Isaac Yang, Xiao Hu, David L. McArthur, Shon W. Cook, and W. J. Boscardin. "Relationship between Valve Opening Pressure, Body Position, and Intracranial Pressure in Normal Pressure Hydrocephalus: Paradigm for Selection of Programmable Valve Pressure Setting." Neurosurgery 55, no. 4 (October 1, 2004): 851–59. http://dx.doi.org/10.1227/01.neu.0000137631.42164.b8.

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Abstract OBJECTIVE: There is little scientific basis for guidance in selecting the optimal valve for the treatment of normal pressure hydrocephalus. The aim of this study was to determine the programmable valve opening pressure setting that would result in a slight reduction in intracranial pressure (ICP) after a ventriculoperitoneal shunt is implanted. We also assessed whether shunt-induced ICP could be predicted on the basis of a simple hydrodynamic equation. METHODS: In this prospective study of 11 patients with normal pressure hydrocephalus, ICP was measured before and after implantation of a shunt incorporating a programmable valve without an antisiphon device. Pressure measurements, including intraperitoneal pressure, were recorded at body angles ranging from 0 to 55 degrees and at valve settings ranging from 30 to 200 mm H2O. Measured ICP values were compared with values computed using a simple hydrodynamic equation. RESULTS: Even at a valve setting greater than the mean baseline ICP (200 mm H2O), the supine ICP was significantly lower than the baseline value (baseline ICP, 164 ± 64 mm H2O; postoperative ICP, 125 ± 69 mm H2O, P = 0.04). Valve pressure did not equate 1:1 with the measured postoperative ICP. Comprehensive ICP measurements at upright body positions demonstrated a stepwise reduction in ICP rather than a precipitous decline as a result of so-called siphoning. CONCLUSION: This study indicates that very high valve opening pressure settings may be optimal for the initial treatment of normal pressure hydrocephalus. The relationship between ICP and opening pressure valves is linear but not predicted by simple hydrodynamics.

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Horton, Donald, and Michael Pollay. "Fluid flow performance of a new siphon-control device for ventricular shunts." Journal of Neurosurgery 72, no. 6 (June 1990): 926–32. http://dx.doi.org/10.3171/jns.1990.72.6.0926.

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✓ Most available cerebrospinal fluid diversion systems utilize differential-pressure valves that often induce overshunting, resulting in complications due to the siphoning of fluid from the ventricular system when the patient is in the erect position. A new siphon-control device (SCD) was tested alone and in combination with four types of differential-pressure valves with low, medium, and high opening pressures (namely PS Medical, Heyer-Schulte, Cordis-Hakim, and Codman valves). The valve inlet and outlet pressures were measured at several fluid inflow rates between 2.0 and 50.0 ml/hr. Inlet pressure and valve resistance were determined when the outlet pressures of the differential-pressure valve or SCD were varied between 0 and −60 cm H2O. Of the differential-pressures valves tested, none provided protection against siphoning without the distal connection of the SCD. The SCD allowed all differential-pressure valves tested to maintain atmospheric pressure regardless of the outlet pressure. The SCD performs in a manner similar to the older anti-siphon device, but with some improvements in design and construction. The results of this investigation suggest that the increased resistance due to the inline SCD is not functionally significant when added to the conventional valve systems with low opening pressure.

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Chaurasiya, Kanhaiya Lal, Bishakh Bhattacharya, AK Varma, and Sarthak Rastogi. "Dynamic modeling of a cabin pressure control system." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 234, no. 2 (August 9, 2019): 401–15. http://dx.doi.org/10.1177/0954410019867578.

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Cabin pressure control system of an aircraft maintains cabin pressure in all flight modes as per the aircraft cabin pressurization characteristics by controlling the air flow from the cabin through the outflow valve of the cabin pressure control valve. The movement of outflow valve in turn depends on the air flow from the control chamber of cabin pressure control valve, which is controlled by the clapper and the poppet valves. These valves are actuated by absolute pressure and the differential pressure capsules, respectively depending upon the operating flight conditions. Mathematical models have been developed to simulate the air outflow rates from the cabin and the control chamber of cabin pressure control valve during steady-state and transient flight conditions. These mathematical models have then been translated into a MATLAB program to obtain plots of cabin pressures as a function of aircraft altitudes. The mathematical models are validated for standard cabin pressurization characteristics of a multirole light fighter/trainer aircraft. The model developed, thus can be used to produce a number of variants of cabin pressure control valve to suit different cabin pressurization characteristics.

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Zhang, Katherine Qinfen, Bryan W. Karney, and David L. McPherson. "Pressure-relief valve selection and transient pressure control." Journal - American Water Works Association 100, no. 8 (August 2008): 62–69. http://dx.doi.org/10.1002/j.1551-8833.2008.tb09700.x.

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Chakravarty, Tarun, Justin Cox, Yigal Abramowitz, Sharjeel Israr, Abhimanyu Uberoi, Sunghan Yoon, Damini Dey, Paya Zadeh, Wen Cheng, and Raj R. Makkar. "High-pressure post-dilation following transcatheter valve-in-valve implantation in small surgical valves." EuroIntervention 14, no. 2 (June 2018): 158–65. http://dx.doi.org/10.4244/eij-d-17-00563.

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Lee, Candice Y., Joshua K. Wong, Ronald E. Ross, David C. Liu, Kamal R. Khabbaz, Angelo J. Martellaro, Heather R. Gorea, Jude S. Sauer, and Peter A. Knight. "Prosthetic Aortic Valve Fixation Study: 48 Replacement Valves Analyzed Using Digital Pressure Mapping." Innovations: Technology and Techniques in Cardiothoracic and Vascular Surgery 11, no. 5 (September 2016): 327–36. http://dx.doi.org/10.1097/imi.0000000000000286.

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Objective Prostheses attachment is critical in aortic valve replacement surgery, yet reliable prosthetic security remains a challenge. Accurate techniques to analyze prosthetic fixation pressures may enable the use of fewer sutures while reducing the risk of paravalvular leaks (PVL). Methods Customized digital thin film pressure transducers were sutured between aortic annulus models and 21-mm bioprosthetic valves with 15 × 4-mm, 12 × 4-mm, or 9 × 6-mm-wide pledgeted mattress sutures. Simulating open and minimally invasive access, 4 surgeons, blinded to data acquisition, each secured 12 valves using manual knot-tying (hand-tied [HT] or knot-pusher [KP]) or automated titanium fasteners (TFs). Real-time pressure measurements and times were recorded. Two-dimensional (2D) and 3D pressure maps were generated for all valves. Pressures less than 80 mm Hg were considered at risk for PVL. Results Pressures under each knot (intrasuture) fell less than 80 mm Hg for 12 of 144 manual knots (5/144 HT, 7/144 KP) versus 0 of 288 TF (P < 0.001). Pressures outside adjacent sutures (extrasuture) were less than 80 mm Hg in 10 of 60 HT, zero of 60 KP, and zero of 120 TF sites for 15 × 4-mm valves; 17 of 48 HT, 25 of 48 KP, and 12 of 96 TF for 12 × 4-mm valves; and 15 of 36 HT, 17 of 36 KP and 9 and 72 TF for 9 × 6-mm valves; P < 0.001 all manual versus TF. Annular areas with pressures less than 80 mm Hg ranged from 0% of the sewing-ring area (all open TF) to 31% (12 × 4 mm, KP). The average time per manual knot, 46 seconds (HT, 31 seconds; KP, 61 seconds), was greater than TF, 14 seconds (P < 0.005). Conclusions Reduced operative times and PVL risk would fortify the advantages of surgical aortic valve replacement. This research encourages continued exploration of technical factors in optimizing prosthetic valve security.

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Suzuki, Katsuya, Ikuo Nakamura, and J. U. Thoma. "Pressure regulator valve by Bondgraph." Simulation Practice and Theory 7, no. 5-6 (December 1999): 603–11. http://dx.doi.org/10.1016/s0928-4869(99)00024-5.

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Gassmann, Stefan, and Lienhard Pagel. "Magnetic actuated pressure relief valve." Sensors and Actuators A: Physical 194 (May 2013): 106–11. http://dx.doi.org/10.1016/j.sna.2012.12.033.

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Stewart, J. T., H. H. Gray, and D. R. Redwood. "MITRAL VALVE AND WEDGE PRESSURE." Lancet 334, no. 8665 (September 1989): 742. http://dx.doi.org/10.1016/s0140-6736(89)90802-7.

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Ruan, J., R. Burton, P. Ukrainetz, and Y. M. Xu. "Two-dimensional pressure control valve." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 215, no. 9 (September 1, 2001): 1031–38. http://dx.doi.org/10.1177/095440620121500903.

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The two-dimensional pressure control valve is a piloted control valve which functions by using both linear and rotary motions of a single spool. A groove on the spool land, incorporating a sensing channel, forms the pilot stage to control the pressure of a spool chamber, while the load pressure is fed to the other spool chamber. To sustain the balance of the force across the spool, the load pressure must follow the change of pressure variation along the groove while the spool is in rotary motion. The geometric parameters of the groove and the spool-to-sleeve clearance have significant effects on both the static and dynamic characteristics of the valve. Increasing the sectional size of the groove results in a large Reynolds number and the static property of the valve thus changes from that of linearity owing to the entrance effect. The linearity of the static property is also affected by the leakage through the spool-to-sleeve clearance. The dynamic characteristics of the valve are dependent upon both the structural parameters and the tune constant of the load. The stability and dynamic response were investigated under different structural parameters and time constants of the load using both linear theory and simulation methods. Experiments were designed to obtain the static and dynamic characteristics of the valve and the leakage through the pilot. A balance should be made between the linearity of the static property and the response speed; it was found that both fairly linear static and desired dynamic characteristics could be simultaneously maintained for the two-dimensional pressure control valve.

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Ruan, J., R. Burton, P. Ukrainetz, and Y. M. Xu. "Two-dimensional pressure control valve." Proceedings of the I MECH E Part C Journal of Mechanical Engineering Scienc 215, no. 9 (September 18, 2001): 1031–39. http://dx.doi.org/10.1243/0954406011524397.

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Trotta, Thiago, Charles Kashou, and Nancy Faulk. "Pressure relief valve inspection interval." Process Safety Progress 37, no. 1 (April 20, 2017): 37–41. http://dx.doi.org/10.1002/prs.11892.

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Bernard, Y., and A. Razek. "Low pressure piezoelectric valve design." Smart Materials and Structures 21, no. 6 (May 30, 2012): 064009. http://dx.doi.org/10.1088/0964-1726/21/6/064009.

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Primiano, Frank P. "Open Adjustable Pressure Limiter Valve." Anesthesiology 88, no. 2 (February 1, 1998): 552. http://dx.doi.org/10.1097/00000542-199802000-00047.

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Kiyachenko, Yu F., and V. E. Podnek. "Miniature high pressure needle valve." Actual Problems of Oil and Gas, no. 30 (December 21, 2020): 86–92. http://dx.doi.org/10.29222/ipng.2078-5712.2020-30.art8.

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A simple and miniature high pressure needle valve has been designed and tested. The valve has shown reliable and stable operation at the temperature range 0–110 °C and pressure up to 30 MPa. This valve design will be useful for devices and setups when small size and small weight are needed.

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Opalić, Milan, Ivica Galić, and Krešimir Vučković. "Influence of the Wall Thickness on the Allowable and Failure Pressures of Two- and Tree-Way Globe Valve Bodies." Key Engineering Materials 488-489 (September 2011): 646–49. http://dx.doi.org/10.4028/www.scientific.net/kem.488-489.646.

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A globe valve is a linear motion valve used to shut off and regulate fluid flow in pipelines. Depending on the number of process connections, they are produced as two‑ or three-way valves. The main valve component carrying the internal pressure is the valve body. For safe exploitation, the valves are designed with the allowable internal pressure taken into consideration. The aim of this paper is to investigate the influence of the wall thickness on the allowable and failure pressures of two- and tree-way globe valve bodies, DN50 and DN100 respectively. Twice-elastic-slope (TES) and the tangent‑intersection (TI) methods are used to obtain the plastic collapse pressures at the critical location which was determined (Fig. 1a and 1b) at the location where maximum equivalent plastic strain throughout the valve body thickness reaches the outer surface. Obtained values are used afterwards to calculate corresponding allowable pressures according to the limit design method, while the failure pressure at the same location was determined as the highest point from the load-maximal principal strain curve. Calculated allowable pressure values, for both valve bodies, are compared with the corresponding ones obtained using the EN standard.

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Aihara, Yasuo, Ichiro Shoji, and Yoshikazu Okada. "In vitro experiment for verification of the tandem shunt valve system: a novel method for treating hydrocephalus by flexibly controlling cerebrospinal fluid flow and intracranial pressure." Journal of Neurosurgery: Pediatrics 11, no. 1 (January 2013): 43–47. http://dx.doi.org/10.3171/2012.10.peds12226.

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Object The CSF shunt valve is a medical device whose main function is to regulate intracranial pressure and drain excess CSF. The authors have developed a new therapeutic method for treating hydrocephalus, namely the tandem shunt valve system, which has the potential of flexibly controlling the CSF flow rate and intracranial pressure in patients. Methods The properties of the tandem system were verified by performing in vitro experiments. An in vitro system with a manometer was built to measure pressure and flow rates of water in open systems using the Codman Hakim Programmable Valve and the Strata adjustable pressure programmable valve. A single valve and 2 single shunt valves connected in series (the tandem shunt valve system) were connected to the manometer to check the final pressure. Results Conventional single shunt valve systems require valve pressures to be set higher to slow down the CSF flow rate, which inevitably results in a higher final pressure. On the other hand, the tandem shunt valve system uses the combination of 2 valves to slow the CSF flow rate without increasing the final pressure. Conclusions The authors succeeded in experimentally demonstrating in vitro results of tandem systems and their effectiveness by applying a model to show that the valve with the higher pressure setting determined the final pressure of the entire system and the flow rate became slower than single shunt valve systems.

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Patel, Krishan, Soraya Sadeghi, and Jamil Aboulhosn. "Invasive Hemodynamic Characteristics in Patients Undergoing Transcatheter Tricuspid Valve-In-Valve Implantation for Treatment of Tricuspid Stenosis." World Journal for Pediatric and Congenital Heart Surgery 11, no. 4 (July 2020): 411–16. http://dx.doi.org/10.1177/2150135120910366.

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Background: We sought to describe invasive hemodynamic measurements in patients with tricuspid stenosis (TS) undergoing transcatheter tricuspid valve-in-valve (TVIV) implantation immediately pre- and postimplantation. Development of TS in patients who have undergone surgical tricuspid valve replacement with a bioprosthetic valve is a serious complication that leads to elevated right atrial (RA) pressures and decreased cardiac output. Transcatheter TVIV implantation is a viable alternative to surgical tricuspid valve replacement, but data on the hemodynamic consequences of TVIV for the treatment of severe TS are currently limited to echocardiographic assessment of Doppler-derived gradients. Methods: Eleven patients undergoing transcatheter TVIV implantation with moderate to severe bioprosthetic valve stenosis were selected for retrospective review. Right atrial mean pressure, right ventricular (RV) systolic and end-diastolic pressure, mean diastolic RA-RV pressure gradient, pulmonary artery capillary wedge pressure, pulmonary artery systolic, end-diastolic and mean pressures, and pulmonary artery pulsatility index (PAPi) both before and after transcatheter valve placement were collected from catheterization reports. Results: After transcatheter TVIV implantation, the mean TS gradient decreased significantly ( P < .01), while the mean RV end-diastolic pressure increased ( P = .046). Pulmonary artery pulsatility index also increased as the TS was relieved ( P = .039). Conclusions: Tricuspid valve-in-valve implantation results in immediate relief of TS, leading to increased RV preload with resultant augmentation of RV and pulmonary pressures. Increased PAPi following the procedure demonstrates acute improvement in RV output but remains low due to the failure of the RA pressure to decline significantly immediately following intervention.

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Ma, Xiu Hua. "Research on the Best Autofrettage Pressure of Ultra-High Pressure Valve Body." Key Engineering Materials 667 (October 2015): 524–29. http://dx.doi.org/10.4028/www.scientific.net/kem.667.524.

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This paper takes the ultra-high pressure (103.5MPa) valve body as the research object and adopts the finite element method to perform simulation analysis on the three bearing conditions involved with the valve body, i.e., autofrettage pressure, discharge and working pressure. The simulation shows identical results with the theoretical calculation. The relationship between the maximum equivalent stress and autofrettage pressure during the operation of the valve is obtained from the simulation results; therefore the best autofrettage pressure is determined. When determining the maximum value of autofrettage pressure, the maximum pressure, at which reverse yield does not happen, and the complete yield pressure shall be taken into consideration, with the smaller value of the two taken after comparison and analysis. When the size of the valve body is fixed at certain value, the best autofrettage pressure is not a fixed value, but it varies with the change of working pressure.

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Zhang, Jian. "Flow characteristics of a hydraulic cone-throttle valve during cavitation." Industrial Lubrication and Tribology 71, no. 10 (December 2, 2019): 1186–93. http://dx.doi.org/10.1108/ilt-10-2018-0394.

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Purpose This paper aims to resolve the cavitation problem encountered in cone throttle valves concerning fluid flow performance and pitting from cavitation luminescence, the author studied the flow field within a cone throttle valve set with various valve openings, inlet pressures and outlet back pressures. Design/methodology/approach The flow and cavitation distribution in the valve under different pressure conditions were obtained in simulations. To confirm these results experimentally, a hydraulic cavitation platform was constructed. The valve was made of polymethyl methacrylate material with high transparency to observe the cavitation directly, as well as cavitation luminescence. The flow characteristics of this valve were measured under various working conditions. Findings With increasing cavitation strength, a reduction in cavitation on the throttle capacity was more evident. Increasing the back pressure and reducing the working pressure of the valve appropriately improves the flow capacity of the valve, which subsequently improves the performance of the valve. The cavitation luminescence is also linearly related to cavitation intensity. That is, the stronger the flow capacity of the valve, the less likely the luminescence is produced. Moreover, a stronger luminescence intensity worsens the flow performance of the valve. Research limitations/implications Owing to the limitation of experimental means and lack of research on bubble shape, the subsequent research will complement this aspect. Practical implications With a view to providing theoretical and experimental support, cavitation luminescence is also studied to gain a deeper understanding of the cavitation mechanism in hydraulic valves. Originality/value The innovation of this paper is to study the cavitation luminescence in the hydraulic system.

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Davis, Michael J., Elaheh Rahbar, Anatoliy A. Gashev, David C. Zawieja, and James E. Moore. "Determinants of valve gating in collecting lymphatic vessels from rat mesentery." American Journal of Physiology-Heart and Circulatory Physiology 301, no. 1 (July 2011): H48—H60. http://dx.doi.org/10.1152/ajpheart.00133.2011.

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Secondary lymphatic valves are essential for minimizing backflow of lymph and are presumed to gate passively according to the instantaneous trans-valve pressure gradient. We hypothesized that valve gating is also modulated by vessel distention, which could alter leaflet stiffness and coaptation. To test this hypothesis, we devised protocols to measure the small pressure gradients required to open or close lymphatic valves and determine if the gradients varied as a function of vessel diameter. Lymphatic vessels were isolated from rat mesentery, cannulated, and pressurized using a servo-control system. Detection of valve leaflet position simultaneously with diameter and intraluminal pressure changes in two-valve segments revealed the detailed temporal relationships between these parameters during the lymphatic contraction cycle. The timing of valve movements was similar to that of cardiac valves, but only when lymphatic vessel afterload was elevated. The pressure gradients required to open or close a valve were determined in one-valve segments during slow, ramp-wise pressure elevation, either from the input or output side of the valve. Tests were conducted over a wide range of baseline pressures (and thus diameters) in passive vessels as well as in vessels with two levels of imposed tone. Surprisingly, the pressure gradient required for valve closure varied >20-fold (0.1–2.2 cmH2O) as a passive vessel progressively distended. Similarly, the pressure gradient required for valve opening varied sixfold with vessel distention. Finally, our functional evidence supports the concept that lymphatic muscle tone exerts an indirect effect on valve gating.

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Elansary, A. S., and D. N. Contractor. "Valve Closure: Method for Controlling Transients." Journal of Pressure Vessel Technology 116, no. 4 (November 1, 1994): 437–42. http://dx.doi.org/10.1115/1.2929613.

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One of the objectives of this study was to reduce the undesirable dynamic pressure oscillation that occurs in a simple pipeline due to valve closure and to prevent the occurrence of column separation. This is accomplished by maximizing the minimum pressure in the pipeline. The second objective was to minimize the maximum dynamic pressure, and the third objective was to estimate the best (minimum) time of closure, T*c, that results in a pipe stress equal to the maximum allowable stress. The method of characteristics with the time-line interpolation technique was used to solve the transient stresses and pressures in a liquid-filled piping system. Frequency-dependent friction was used in the equation of motion for the fluid and the pipe wall. A nonlinear optimization technique was utilized to generate the optimum valve closure policy. Maximum and minimum pressure heads resulting from the optimal policy were calculated and compared with those resulting from a uniform valve closure. Plots of pressure variation at the valve for these two valve closure policies were also generated. Examples are presented to demonstrate the advantage of the optimum valve closure policy over the uniform valve closure policy. The reduction in the maximum dynamic pressure and stress at the valve for different Tc is also presented.

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Francel, Paul C., F. Alan Stevens, Paul Tompkins, and Michael Pollay. "The importance of shunt valve position in flow characteristics of the Medtronic PS Medical Delta valve." Neurosurgical Focus 7, no. 5 (November 1999): E9. http://dx.doi.org/10.3171/foc.1999.7.5.10.

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This study was conducted to document the extent to which flow depends on valve position in relation to head-pressure reference. Medtronic PS Medical Delta valves (contour model, performance levels 0.5, 1.0, 1.5, and 2.0) were studied in a bench test designed to evaluate flow rates with respect to valve position in relation to the head-pressure reference postion. The valves were connected to an “infinite” reservoir by the standard inlet catheter. An initial head (proximal) pressure was selected for each valve based on package insert data. The position of the inlet catheter tip was fixed at this starting head pressure, thus making the inlet catheter tip position the reference for relative head pressures on the valve assembly. When the valve body is positioned above this level, the effective head pressure is lowered, and when the valve body is positioned below this level, the effective head pressure is raised. Flow was established with the siphon control portion of the valve body located on the same horizontal level as the inlet catheter tip (the reference head pressure or “0” position). A standard silastic catheter was attached to the outlet of the valve, and its length was fixed at 50 cm for all valves (-50 cm H20). The distal end of the outlet catheter was connected to a fraction collector, and 1-minute samples (five replicates) were collected for gravimetric determination of flow rate. The valve assembly was then moved in 1-cm increments through the range of 4 cm above to 8 cm below the head-pressure reference position. Samples were collected from each position (4 cm to -8 cm) relative to the inlet catheter tip. Flow rate, in milliliters/hour, was plotted against both relative position (4 cm to -8 cm) and absolute head pressure (in centimeters of water). Each of the valves tested was shown to have a linear relationship between flow and position relative to the inlet catheter tip (or absolute head pressure). The average increase in flow per centimeter of displacement of valve from catheter tip was 16.5 ml/hr/cm (range 14.4-17.6 ml/hr/cm). Once the inlet catheter tip is fixed in position, it serves as a pressure reference. Movement of the valve above this level results in a net decrease in effective head pressure, and movement below this position results in a net increase in effective head pressure. Thus, the positioning of shunt valves in locations different from this pressure reference position should be performed only with the knowledge that significant increases in outflow rate may occur when the valve body is positioned lower than the inlet catheter tip. This increase in outflow rate is not the result of siphoning or a defect in the antisiphon device but instead the result of a net increase in effective head pressure.

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Shi, Rui, Chuanli Wang, Tao He, and Tian Xie. "Analysis of Dynamic Characteristics of Pressure-Regulating and Pressure-Limiting Combined Relief Valve." Mathematical Problems in Engineering 2021 (March 29, 2021): 1–13. http://dx.doi.org/10.1155/2021/3486143.

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Aiming at the problem of the lack of a cooperation mechanism of combined relief valves, this paper proposes a new pressure-regulating and pressure-limiting combined relief valve. Combined with the ordinary relief valve dynamic characteristic analysis method, the dynamic model of the combined relief valve under normal working conditions was established, and its dynamic characteristics were simulated using Simulink. The results showed that the multi-pressure stabilization design of the combined relief valve improves its usability and stability. Under the same structural parameters, the overshoot of the combined relief valve was 5.7%, and the response time was 12 ms, which is better than the ordinary relief valve. Besides, it effectively improves the instability problems, such as the vibration and the large pressure fluctuation of the ordinary relief valve under high pressure and large flow conditions. When the sum of the effective force area on the upper side of the flange of the pressure-regulating valve core and the area of the tail vertebra is equal to the effective force area of the lower side of the flange of the pressure-regulating valve core, the dynamic performance of the relief valve is optimal. For example, if the effective force area under the flange is 1.8 cm2, then the inlet pressure overshoot is 2.8%, and the response time is 10 ms. An appropriate volume of the sensitive cavity, the quality of the valve core, and the fluid resistance of the pressure relief valve are factors that can effectively improve the dynamic performance of the pressure-regulating and pressure-limiting combined relief valve.

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Koroliov, A. V., P. Y. Pavlyshyn, and I. V. Bandurko. "Experimental Research of Valve Tightness at Different Closure Forces." Nuclear and Radiation Safety, no. 4(80) (December 3, 2018): 14–17. http://dx.doi.org/10.32918/nrs.2018.4(80).03.

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Power valves are installed on almost all the pipelines of nuclear power plants performing the functions of regulation and shutting off the flow, so its failure often leads to emergencies. A particularly large number of failures is observed in motor-operated valves. Incorrect setting of the limiting clutch leads either to incomplete closure of the valve or to rod failure. Therefore, the valves are equipment of a nuclear power plant, which often falls into repair shops. Failures leading to an increase of valve leakage are especially dangerous for nuclear power plants. In this case, leakage of high-pressure valves leads to erosion of the sealing surfaces, which only increases the leakage. Thus, it is very important to determine the optimum rotational value when the valve is closed. The lack of conditions for closure force in the standards for valve leakage complicates the issue. A bench that allows working in the air with a pressure up to 3.5 MPa was developed on valve rod to study dependence of valve leakage on the rotational moment. Four independent parameters were measured: air pressure in front of the valve under study, closure force of the valve, volume of air loss through the valve and leakage time. A standard stop valve with a nominal diameter of 15 mm and a nominal pressure of 64 atm was used for the study. The determined dependence of the leakage on torque value allows recommending a gentler mode of valve closure without significantly reducing its tightness. As a result of experimental data processing, a criterial equation is obtained linking a leakage rate, pressure drop on the valve and a rotational moment value. The received criterial equation will allow defining the compromise between valve closure force and permissible leak level according to regulatory requirements. The analysis of the “leakage/rotational moment” diagram showed the possibility to reveal the damaged valves. This possibility may be used during the incoming inspection of the valves supplied to NPP, which should significantly improve the reliability of their operation.

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Andrenko, Pavlo, Olha Dmytriienko, Viktor Klitnoy, and Vadym Myronov. "DEVELOPMENT OF DIFFERENTIAL PRESSURE CONTROL VALVE." Bulletin of the National Technical University "KhPI". Series: Hydraulic machines and hydraulic units, no. 1 (November 13, 2019): 77–82. http://dx.doi.org/10.20998/2411-3441.2019.1.12.

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Jha, DeepakK, AbhijeetS Barath, OmP Thakur, Mayank Garg, and Suryanarayanan Bhaskar. "Suction Pressure Control Valve for Microneurosurgery." Neurology India 68, no. 3 (2020): 652. http://dx.doi.org/10.4103/0028-3886.288977.

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M. Patil, Shradha. "Lean Manufacturing of Pressure Valve Plate." IOSR Journal of Engineering 4, no. 2 (February 2014): 01–11. http://dx.doi.org/10.9790/3021-04220111.

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Nagtilak, Ashwini, and Siddaram Biradar. "Design of Flow Regulating Pressure valve." International Journal of Engineering Trends and Technology 39, no. 2 (September 25, 2016): 78–81. http://dx.doi.org/10.14445/22315381/ijett-v39p214.

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Vykoukal, Ondřej, Lumír Hružík, and Adam Bureček. "Static Characteristics of Pressure Control Valve." Strojnícky casopis – Journal of Mechanical Engineering 67, no. 1 (April 1, 2017): 119–24. http://dx.doi.org/10.1515/scjme-2017-0012.

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Abstract The article deals with the measurement of static characteristics of a pressure control valve. The pressure, at which the valve starts to leak oil, is adjusted by a spring. The measurement is performed on a hydraulic system that consists of tank, hydraulic pump, check valve, relief valve and pressure control valve which is measured. The results of this experimental measurement are Δp - Q characteristics of the pressure control valve for various pressure settings.

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Eng, Marvin H., and Paul S. Teirstein. "Ballooning the aortic valve under pressure." Catheterization and Cardiovascular Interventions 83, no. 5 (March 18, 2014): 789–90. http://dx.doi.org/10.1002/ccd.25446.

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Laskey, W. K., and W. G. Kussmaul. "Pressure recovery in aortic valve stenosis." Circulation 89, no. 1 (January 1994): 116–21. http://dx.doi.org/10.1161/01.cir.89.1.116.

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Bram, J., and Amsel. "Pressure Recovery Across The Aortic Valve." Acta Clinica Belgica 52, no. 4 (January 1997): 219–25. http://dx.doi.org/10.1080/17843286.1997.11718580.

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Kurshin, A. P., and B. �. Kanishchev. "Safety valve for high-pressure systems." Chemical and Petroleum Engineering 21, no. 1 (January 1985): 3–4. http://dx.doi.org/10.1007/bf01148288.

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Bergsneider, Marvin, Isaac Yang, Shon Cook, and Donald P. Becker. "811 Relationship between Valve Opening Pressure, Body Position, and Intracranial Pressure in Normal-pressure Hydrocephalus: Paradigm for Selection of Programmable Valve Pressure Setting." Neurosurgery 55, no. 2 (August 1, 2004): 490. http://dx.doi.org/10.1227/00006123-200408000-00147.

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Chang, Te-I., Kang-Hong Hsu, Chi-Wen Luo, Jen-Hong Yen, Po-Chien Lu, and Chung-I. Chang. "In vitro study of trileaflet polytetrafluoroethylene conduit and its valve-in-valve transformation." Interactive CardioVascular and Thoracic Surgery 30, no. 3 (January 3, 2020): 408–16. http://dx.doi.org/10.1093/icvts/ivz274.

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Abstract OBJECTIVES Handmade trileaflet expanded polytetrafluoroethylene valved conduit developed using the flip-over method has been tailored for pulmonary valve reconstruction with satisfactory outcomes. We investigated the in vitro performance of the valve design in a mock circulatory system with various conduit sizes. In our study, the design was transformed into a transcatheter stent graft system which could fit in original valved conduits in a valve-in-valve fashion. METHODS Five different sizes of valved polytetrafluoroethylene vascular grafts (16, 18, 20, 22 and 24 mm) were mounted onto a mock circulatory system with a prism window for direct leaflets motion observation. Transvalvular pressure gradients were recorded using pressure transducers. Mean and instant flows were determined via a rotameter and a flowmeter. Similar flip-over trileaflet valve design was then carried out in 3 available stent graft sizes (23, 26 and 28.5 mm, Gore aortic extender), which were deployed inside the valved conduits. RESULTS Peak pressure gradient across 5 different sized graft valves, in their appropriate flow setting (2.0, 2.5 and 5.0 l/min), ranged from 4.7 to 13.2 mmHg. No significant valve regurgitation was noted (regurgitant fraction: 1.6–4.9%) in all valve sizes and combinations. Three sizes of the trileaflet-valved stent grafts were implanted in the 4 sizes of valved conduits except for the 16-mm conduit. Peak pressure gradient increase after valved-stent graft-in-valved-conduit setting was <10 mmHg in all 4 conduits. CONCLUSIONS The study showed excellent in vitro performance of trileaflet polytetrafluoroethylene valved conduits. Its valved stent graft transformation provided data which may serve as a reference for transcatheter valve-in-valve research in the future.

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Hassan, Mahmood, Sotaro Higashi, and Junkoh Yamashita. "Risks in using siphon-reducing devices in adult patients with normal-pressure hydrocephalus: bench test investigations with Delta valves." Journal of Neurosurgery 84, no. 4 (April 1996): 634–41. http://dx.doi.org/10.3171/jns.1996.84.4.0634.

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✓ To elucidate the reason for malfunction of Delta valves in patients with normal-pressure hydrocephalus, the authors applied a new concept of the bench test and simulated intracranial pressure (ICP) to measure the resultant flow with a complete shunt system. Subcutaneous pressure on the valve, valve implantation site, and postural hydrostatic differentialpressure changes were simulated in this bench test designed for adult patients with normal-pressure hydrocephalus. Subcutaneous pressure ranged within 6.4 ± 0.9 cm H2O (mean ± standard deviation) on the 7th day after the implantation of the valve in rats. A linear correlation between valve closing pressures and the external pressure was observed: gradual increase of the latter resulted in an approximately equal rise in the closing pressure. Closing pressure ranged within the physiological variation of ICP (10 ± 5 cm H2O) in the supine position. In the erect position it was higher than the physiological variation (+5 to −5 cm H2O) when the valve was placed at the level of the foramen of Monro and lower when placed at the level of the clavicle. This observation indicates that the subcutaneous pressure around the Delta valve significantly affects its closing pressure. An excessive reduction of flow or a functional obstruction occurs when the patient with a Delta valve implanted at the foramen of Monro assumes an erect posture. The authors conclude that Delta valves are not recommended for implantation at the level of the foramen of Monro in patients with normal-pressure hydrocephalus because of the risk of underdrainage. The mastoid process or clavicle may be the alternative levels for its implantation to prevent underdrainage; however, the possibility of shunt malfunction should be kept in mind because subcutaneous pressure is variable among patients and that might affect the performance characteristics of these valves.

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Spinney, S., K. A. Sprigge, and T. Lawson. "Flow-pressure characteristics of an Intersurgical adjustable pressure-limiting valve." Anaesthesia 72, no. 4 (March 13, 2017): 539–40. http://dx.doi.org/10.1111/anae.13846.

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Nguyen, Quang Khai, Kwang Hyo Jung, Gang Nam Lee, Sung Bu Suh, and Peter To. "Experimental Study on Pressure Distribution and Flow Coefficient of Globe Valve." Processes 8, no. 7 (July 20, 2020): 875. http://dx.doi.org/10.3390/pr8070875.

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In this study, the pressure distribution and flow coefficient of a globe valve are investigated with a series of experiments conducted in a flow test loop. The experiments are performed on a three-inch model test valve from an eight-inch ANSI (American National Standards Institute) B16.11—Class 2500# prototype globe valve with various pump speeds and full range of valve openings. Both inherent and installed flow characteristics are measured, and the results show that the flow coefficient depends not only on the valve geometry and valve opening but also on the Reynolds number. When the Reynolds number exceeds a certain value, the flow coefficients are stable. In addition, the pressures at different positions in the upstream and the downstream of the valve are measured and compared with recommendation per ANSI/ISA-75.01 standard. The results show that, in single-phase flow, the discrepancies in pressure between different measurement locations within close range of 10 nominal diameter from the valve are inconsiderable.

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Wu, Wan Rong, and Zhi Xu. "Mechanical Mechanics and Application of High Speed On/Off Valve to Feeding System of Hydraulic Drilling Rig." Advanced Materials Research 908 (March 2014): 330–34. http://dx.doi.org/10.4028/www.scientific.net/amr.908.330.

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Feeding pressures control of hydraulic drilling rig is a critical technology of drilling quality. In order to control feeding pressure accurately during hydraulic drilling rigs working, A new feeding system was proposed, based on the cartridge valve controlled by high speed on/off valve. Feeding pressure was exported proportionally via control of high speed on/off valves input PWM signal. Its model was built by AMESim software, to analyze characteristics of the cartridge valve and research the feeding systems response to pressure-commanded signal. The results show that the feeding pressure can be regulated proportionally and the control performance of the feeding pressure can be improved by increasing moderately PWM signals frequency, which provides a reliable reference for further optimization of hydraulic system of drilling rig.

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Xiangyang, Zhao, Xu Wen-bo, and Gang Liu. "Pressure Estimation and Pressure Control of Hydraulic Control Unit in Electric-Wheel Vehicle." Mathematical Problems in Engineering 2020 (July 14, 2020): 1–14. http://dx.doi.org/10.1155/2020/6576297.

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In order to improve the braking performance and safety performance of electric vehicles driven by a hub motor, the cylinder pressure estimation and pressure control of its hydraulic braking system are studied. In this paper, a mathematical model is established for the solenoid valve, a key component of the hydraulic actuator, and the hydraulic and electrical characteristics of the solenoid valve are studied. A state equation is established for the solenoid valve, and the square root volume Kalman filter (SRCKF) algorithm is used to estimate the solenoid valve spool position. The brake fluid flow and brake wheel cylinder pressure are calculated based on the spool position. Finally, a solenoid valve spool position control algorithm based on sliding mode variable structure algorithm is designed, and the brake pressure in the brake wheel cylinder is controlled by adjusting the spool position. Matlab/Simulink-AMESim software simulation and hardware-in-the-loop were used to verify the algorithm. Simulation results show that the brake cylinder pressure can be estimated accurately, and the pressure control algorithm can accurately follow the control target value.

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Abdullayev, V. J. "New approach for two-phase flow calcuation of artifical lift." SOCAR Proceedings, no. 1 (March 30, 2021): 49–55. http://dx.doi.org/10.5510/ogp20210100479.

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The article develops a method for adjusting design pressure of bellows gas lift valves in deviated gas lift wells based on research and calculations and provides a method for the arrangement of gas lift valves along tubing. As a result of the calculations, the valve opening pressure of the first gas lift valve was taken equal to the initial gas pressure, the valve opening pressure of the following valves was 0.05-0.175 MPa lower than that of the previous gas lift valve, and the pressure difference between the last valve and the second from the last valve was 0.28-0.35 MPa.

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Kim, Gi-Heon, Allan Kirkpatrick, and Charles Mitchell. "Computational Modeling of Natural Gas Injection in a Large Bore Engine." Journal of Engineering for Gas Turbines and Power 126, no. 3 (July 1, 2004): 656–64. http://dx.doi.org/10.1115/1.1762906.

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The topic of this paper is the computational modeling of gas injection through various poppet valve geometries in a large bore engine. The objective of the paper is to contribute to a better understanding of the significance of the poppet valve and the piston top in controlling the mixing of the injected fuel with the air in the cylinder. In this paper, the flow past the poppet valve into the engine cylinder is computed for both a low (4 bar) and a high pressure (35 bar) injection process using unshrouded and shrouded valves. Experiments using PLIF (planar laser induced fluorescence) are used to visualize the actual fluid flow for the valve geometries considered. The results indicate that for low injection pressures the gas flow around a typical poppet valve collapses to the axis of symmetry of the valve downstream of the poppet. At high pressure, the gas flow from this simple poppet valve does not collapse, but rather expands outward and flows along the cylinder wall. At high pressures, addition of a shroud around the poppet valve was effective in directing the supersonic flow toward the center of the cylinder. Additional computations with a moving piston show that at top dead center, the flammable volume fraction and turbulence intensity with high pressure shrouded injection are larger than for low pressure injection.

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Zhang, Yang, Rongjun Li, and Linhai Zou. "The Pressure Control of High-Pressure Tubing Based on Difference Equation." Mathematical Problems in Engineering 2020 (May 15, 2020): 1–9. http://dx.doi.org/10.1155/2020/3436298.

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The situation where fuel enters and exits the high-pressure tubing is one of the important factors that affect the working efficiency of the engine. Based on the simplified high-pressure tubing model, this paper studies the control problems of high-pressure tubing injection and fuel supply under certain circumstances. According to the idea of the difference equation, the paper obtains the opening time of the one-way valve when the pressure value of the high-pressure tubing is kept constant or rises to a specific value by enumerating the opening time of the one-way valve. By establishing the physical model of the high-pressure tubing and the fuel injection nozzle, and then using the enumeration method, the angular velocity of the high-pressure oil pump cam when the pressure of the high-pressure fuel pipe is kept constant can be obtained. Under the more complicated injector model, the control method of the injector is solved by the double enumeration method. The results show that the above model can quickly calculate the optimal working time of the high-pressure fuel pump and needle valve when the accuracy meets the requirements.

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Sainte-Rose, Christian, Michael D. Hooven, and Jean-François Hirsch. "A new approach in the treatment of hydrocephalus." Journal of Neurosurgery 66, no. 2 (February 1987): 213–26. http://dx.doi.org/10.3171/jns.1987.66.2.0213.

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✓ To date, most patients suffering from hydrocephalus have been treated by insertion of differential-pressure valves that have fairly constant resistance. Since intracranial pressure (ICP) is a variable parameter (depending on such factors as patient's position and rapid eye movement sleep) and since cerebrospinal fluid (CSF) secretion is almost constant, it may be assumed that some shunt complications are related to too much or too little CSF drainage. The authors suggest a new approach to treating hydrocephalus, the aim of which is to provide CSF drainage at or below the CSF secretion rate within a physiological ICP range. This concept has led the authors to develop a three-stage valve system. The first stage consists of a medium-pressure low-resistance valve that operates as a conventional differential-pressure valve until the flow through the shunt reaches a mean value of 20 ml/hr. A second stage consists of a variable-resistance flow regulator that maintains flow between 20 and 30 ml/hr at differential pressures of 80 to 350 mm H2O. The third stage is a safety device that operates at differential pressures above 350 mm H2O (inducing a rapid increase in CSF flow rate) and therefore prevents hyper-elevated ICP. An in vitro study is described that demonstrates the capability of this system to maintain flow rates close to CSF production under a range of pressures similar to those observed under various human physiological and postural conditions. Promising clinical results in 19 patients shunted with this valve are summarized.

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Frim, David M., and Lilliana C. Goumnerova. "In vivo intracranial pressure dynamics in patients with hydrocephalus treated by shunt placement." Journal of Neurosurgery 92, no. 6 (June 2000): 927–32. http://dx.doi.org/10.3171/jns.2000.92.6.0927.

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Object. With the commercial availability of a variety of shunt systems, there is considerable controversy over the choice of the most appropriate shunt valve for each individual with hydrocephalus. Although the performance characteristics of all shunt systems are well documented in the laboratory setting, there is little description of the in vivo dynamics of intracranial pressure (ICP) after implantation of commonly used shunt systems in humans. The authors coupled telemonitoring devices to several different shunt systems to measure the performance characteristics of these valve systems with respect to intraventricular pressure (IVP) at increments of head elevation.Methods. Twenty-five patients with different shunt systems and three control patients without shunts were studied for IVP at 0°, 15°, 30°, 45°, 60°, 75°, and 90° of head elevation, and the resultant curves were analyzed for the best-fit regression coefficient. For purposes of analysis the authors grouped shunt valve systems by design characteristics into three groups: differential-pressure valves (r = −0.321 ± 0.061; 11 patients), nonsiphoning systems (r = −0.158 ± 0.027; 10 patients), and flow-regulated valves (r = −0.16 ± 0.056; four patients); there were three control patients without shunts (r = −0.112 ± 0.037).Conclusions. The authors found that differential-pressure valves always caused ICP to drop to 0 by 30° of head elevation, whereas all other valve systems caused a more gradual drop in ICP, more consistent with pressures observed in the control patients without shunts. Not surprisingly, the differential-pressure valve group was found to have a significant difference in mean regression coefficient when compared with those in whom nonsiphoning shunts (p < 0.023) or no shunts were placed (p < 0.049). These data provide a basis for evaluating shunt valve performance and for predicting valve appropriateness in patients in whom characteristics such as pressure and flow dynamics are weighed in the choice of a specific valve for implantation.

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Gölz, Leonie, Johannes Lemcke, and Ullrich Meier. "Indications for valve-pressure adjustments of gravitational assisted valves in patients with idiopathic normal pressure hydrocephalus." Surgical Neurology International 4, no. 1 (2013): 140. http://dx.doi.org/10.4103/2152-7806.119879.

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Xiong, Xiaoyan, and Jiahai Huang. "Performance of a flow control valve with pilot switching valve." Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering 232, no. 2 (December 14, 2017): 178–94. http://dx.doi.org/10.1177/0959651817743889.

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In digital fluid power, fast switching valve is a potential digital hydraulic component because of less throttling loss, reliability, low price, and so on. But its outlet flow is usually small and discontinuous. In this article, a two-stage proportional flow control valve is presented, in which the main stage is a flow amplifying valve, and the pilot stage consists of several switching valves with pulse width modulation control strategy. Peak and hold technique is adopted to improve the dynamic performance of the pilot stage. Benefits of the proposed configuration are continuous outlet flow and large flow capacity. The valve performance is investigated by theoretical analysis, simulation, and test. It is shown that both poppet displacement and outlet flow fluctuate around a stable value because of the discontinuous pilot flow, but the average outlet flow as well as poppet displacement of the main stage can be approximately proportionally regulated by changing pulse width modulation duty ratio. Average outlet flow of the main stage is an amplification of that of pilot stage. Increasing the average pressure drop not only increases outlet flow but also increases the severity of flow pulsations because pressure fluctuation becomes more serious as the average pressure difference increases. In theory, higher carrier frequency leads to smoother outflow; however, tested outflow profile of the proposed valve at 50 Hz is not significantly smoother than that at 30 Hz. This phenomenon may be due to the asynchrony of the four switching valves and the pressure fluctuations during the testing process.

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Francis, J., and P. L. Betts. "Modelling incompressible flow in a pressure relief valve." Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering 211, no. 2 (May 1, 1997): 83–93. http://dx.doi.org/10.1243/0954408971529575.

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Lift, blowdown and discharge of pressure relief valves depend ultimately on the flow structures generated within those valves. A report is made of an enquiry into the incompressible flow structure within such a valve. Commercial software is used to predict axisymmetric flow patterns inside a model of a real valve, and comparisons are made with the pressure distribution and force imposed on the real valve disc. The reliability of the simulation is further assessed using the oil-film technique to record reattachment lengths of separated shear layers. Results of the simulation are encouraging and have enabled flow regimes visible in the valve flow characteristic to be identified with the transition between separated flow patterns inside the valve.

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Journal articles on the topic 'Pressure Valve'

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