We report the results and techniques developed to find a small helium leak in a valve developed for use at cryogenic temperatures. The leak was found during testing of NASA's XRISM/Resolve Instrument ...after it was integrated into the Flight Dewar that would later be installed onto the spacecraft. This leak was determined to be on the order of ▪. Initial testing in the Dewar showed the leak disappeared when the valve was cooled below ▪. The rate and temperature behavior was verified by testing the valve in a controlled environment within a range of temperatures that span from room temperature to below the superfluid transition of helium-4. The techniques employed to minimize the detection of helium external to the measurement as well as the analysis necessary to tease the weak signal from the leak in the presence of a small helium background signal will be discussed.
•Highly-sensitive leak check of a device from room to superfluid helium temperatures.•Discovery and elimination of a small helium leak in a cryogenic fluid valve.•Resolution of a leak on the order of ▪ in the presence of a small helium background.
There have been few improvements in cerebrospinal fluid (CSF) shunt technology since John Holter introduced the silicon valve, with overdrainage remaining a major source of complications.
To better ...understand why valves are afflicted by supra-normal CSF flow rates. We present in Vitro benchtop analyses of flow through a differential pressure valve under simulated physiological conditions.
The pseudo-ventricle benchtop valve testing platform that comprises a rigid pseudo-ventricle, compliance chamber, pulsation generator, and pressure sensors was used to measure flow rates through a differential pressure shunt valve under the following simulated physiological conditions: orientation (horizontal/vertical), compliance (low/medium/high), and pulsation generator force (low/medium/high).
Our data show that pulse pressures are faithfully transmitted from the ventricle to the valve, that lower compliance and higher pulse generator forces lead to higher pulse pressures in the pseudo-ventricle, and that both gravity and higher pulse pressure lead to higher flow rates. The presence of a valve mitigates but does not eliminate these higher flow rates.
Shunt valves are prone to gravity-dependent overdrainage, which has motivated the development of gravitational valves and antisiphon devices. This study shows that overdrainage is not limited to the vertical position but that pulse pressures that simulate rhythmic (eg, cardiac) and provoked (eg, Valsalva) physiological CSF pulsations increase outflow in both the horizontal and vertical positions and are dependent on compliance. A deeper understanding of the physiological parameters that affect intracranial pressure and flow through shunt systems is prerequisite to the development of novel valves.
Safety valves are widely used as the safety device in pressure systems, such as boilers and pressure pipes, to ensure the safe operation of pressure systems. At present, the inspection of safety ...valves is mainly carried out by manual operation or semi-automatic operation, and it requires a lot of manpower operation costs. Moreover, the measurement of different pressure ranges is performed using only a single pressure sensor such that the test precision is insufficient. In this study, a high-precision safety valve test architecture with three testing channels was proposed, and an automated testing system was developed. In this system, the user can define the test specifications through parameter setting. The system can automatically execute the complete test control process and judge whether the test was passed based on the measured data. In this article, for the low, middle, and high test pressures, the safety valves of four different states were tested respectively and the test reports were automatically generated. Finally, it statistically analyzed the test results for the diagnosis of the safety valve failure. Therefore, the results of this research may effectively solve the problems of current safety valve testing and improve its operational efficiency and test quality.
Introduction
The advanced design techniques used in modern prosthetic heart valve (PHV) development require accurate replication of the entire cardiac cycle. While cardiac pulse duplicator (CPD) ...design has a direct impact on the PHV test data generated, no clear guidelines exist to evaluate the CPD’s performance. In response to this, we present a method to quantitatively assess CPD performance.
Materials and Methods
A method to establish the fidelity of CPDs was formulated based on the pressure/time relationship and the error related to this relationship’s target. This method was applied to assess the performance of a custom-made CPD. The performance evaluation included the assessment of the motion control system and overall repeatability of pressure measurements using a St Jude Epic 21 mm aortic valve.
Results
The CPD’s motion control system had an average root mean square error (RMSE) beat-to-beat tracking accuracy of 0.046 ± 0.008 mm. Assessment of the pressure measurements yielded a repeatability of < 2.4 ± 0.9 mmHg RMSE beat-to-beat differential pressure. The combination of pressure and its location within a heartbeat (fidelity) was within 5.0% of the individual targets for at least 95% of heartbeats.
Conclusion
Fidelity can be used to objectively quantify the performance of various aspects of CPDs and to identify the cause of unexpected PHV or CPD behaviour. It also enables comparisons to be made among various CPDs in terms of overall performance. This approach may enable standardization of the assessment of CPD performance in the future.
Die zunehmende Entwicklung und Herstellung künstlicher Organe, die nach Implantation von Blut durchströmt werden (Gefäß- und Herklappenprothesen, Herzassist-Systeme), erfordern umfangreiche ...In-vitro-Testungen in Modellkreisläufen. Humanblut steht für derartige Untersuchungen nicht in ausreichendem Maße zur Verfügung, so daß charakteristische Strömungsparameter mit anderen Fluiden (Wasser, physiologische NaCl-Lösung, Glycerinlösung) gemessen werden. Hierbei bleiben die nicht-Newtonschen Fließeigenschaften von Blut unberücksichtigt, ebenso kann keine Aussage über eine mögliche Blutschädigung gemacht werden. Verdünnte Lösungen langkettiger Polymere, z. B. mit Polyacrylamid (PAA), haben derartige Fließeigenschaften und werden zudem von den in der Strömung auftretenden Scherspannungen degradiert. Sie könnten deshalb als Modellfluide für Blut bei In-vitro-Testungen verwendet werden.
Anhand charakteristischer Parameter der Herzklappentestung wurden unterschiedlichste Lösungen mit Blut verglichen, ebenso wurde die scherinduzierte Schädigung von Erythrozyten der Polymerdegradation gegenübergestellt. Es konnte gezeigt werden, daß Polymerlösungen mit bestimmten Konzentrationen geeignete Modellfluide für Blut sowohl hinsichtlich der nicht-Newtonschen Fließeigenschaften als auch hinsichtlich der Abschätzung des Hämolyse-Potentials künstlicher Herzklappen sind.
The increasing development and implantation of artificial organs subject to perfusion with human blood once implanted (grafts, heart-valve prostheses and assist systems) require extensive testing of hydrodynamic performance in mock circulation models. As human blood ist not always available in the necessary quantities, different fluids (water, saline or glycerine solutions) are employed for measurements of flow characteristics. However, these model fluids do not possess the non-Newtonian rheological properties of blood. In addition, they do not allow estimation of possible blood damage.
Aqueous solutions of high molecular weight polyacrylamides (PAA) have rheological properties similar to blood, displaying also molecular degradation due to shear stress in the flow. Therefore, they were used as model fluid for blood.
Different model solutions were compared to blood with regard to their influence on characteristic flow parameters of mechanical heart valves. Likewise, the shear damage of erythrocytes could be compared to flowinduced polymer degradation. It was shown that PAA solutions in definite concentrations are suitable models for blood, not only in terms of non-Newtonian rheology, but also in terms of estimation of hemolytic potential of artificial heart valves.
This chapter deals with the procedures available for the analysis of the operation of sucker-rod pumping wells. The first topic discusses the special well testing procedures required in rod-pumped ...wells and includes the acoustic determination of annular liquid levels. Calculation of the well's liquid production potential is detailed, including inferred production tests as well. The hardware used and the procedures followed when conducting dynamometer surveys is fully described. The use of hydraulic and electronic dynamometers to take surface dynamometer cards as well as testing the downhole pump's valves is detailed. Interpretation of surface and downhole dynamometer cards is also presented, with an emphasis on the evaluation of pump cards calculated from surface data using the solution of the damped wave equation.
The auther carried out a comparative study of the behaviour of mechanical valves (tilting disc valves) and porcine xenograft valves experimentally and clinically. The experimental study revealed a ...significant difference between these two types of valves in resistance and regurgitation. Hemodynamic paramoters were examined in isolated mitral valve replacement cases pre and postoperatively. Cardiac index, pulmonary artery wedge pressure, pulmonary artery systolic pressure, left ventricular endodiastolic volume index, left ventricular endosystolic volume index, left ventricular ejection fraction were almost same for both types of valves. The postoperative valve area was determined 1.8cm2 for tilting disc valve and 1.1cm2 for porcine xenograft. Carpentier-Edwards valve which was obtained from a pt on re-operation was examined using our valve testing apparatus. The result showed that the biological material was not homogenous. We concluded therefore that xenograft prosthesis are at present not ideal valve prosthesis.
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