Spring-loaded Valve Research Articles

Dynamic response of spring valve subjected to underwater pressure pulse

Spring-loaded valves are widely used to protect sealed containers filled with liquid against sudden excessive overpressure; however, the unstable vibration of a valve spool under dynamic loading may lead to safety incidents. This study aims to investigate the nonlinear vibration processes of a valve spool subjected to an underwater pressure pulse. To achieve this objective, the spring-loaded valve was simplified to an air-back mass spring with a constraint boundary (AMSCB). A modified split Hopkinson pressure bar (SHPB) was adopted to generate a controllable pressure pulse to establish the relationship between the specific impulse and the discharged water mass. Following the experimental verification, the influences of the pressure pulse parameters and dimensionless time on the motion characteristics of the mass block and flow rate were studied based on finite element (FE) simulations. Five motion modes were identified according to the number of collisions with the constraint boundary and changes in movement direction: (i) no collision, (ii) single collision, (iii) chatter, (iv) single collision with direction change, (v) multiple collisions. Moreover, a theoretical model for predicting the movement of a mass block was developed and validated against numerical results. The classification phase diagram of the motion mode is presented in a two-dimensional plane composed of specific strength coefficient ϕ and fluid-structure interaction coefficient ψ, and the influence of the geometrical parameters of the AMSCB on the classification boundary of motion modes is presented. The results indicate that, when subjected to underwater pressure pulse loading, the mass block repeatedly collides with the constraint boundary and undergoes non-periodic motion. With higher loading pressure amplitude and duration, the mass block is more likely to collide with the back boundary, leading to a transition in movement modes from mode (i), mode (ii), mode (iv) to mode (v). Increasing the stiffness coefficient and areal density will increase the threshold of ϕ and ψ for the transition from mode (i) to mode (v), while the maximum allowable displacement has little effect on the classification boundaries. These research findings are valuable for analysing the motion response of mass spring with various constraint boundaries under dynamic loading, and for guiding the design of spring-loaded valves.

Analysis of the positive expiratory pressure valves of coupled oronasal mask

Positive expiratory pressure (PEP) is a technique used in respiratory physiotherapy to treat diseases related to the respiratory system through spontaneous breathing. This equipment consists of an oronasal mask coupled to a T connector with a unidirectional valve. Studies that evaluate whether the pressure level in the one-way valve corresponds to the actual pressure level provided are scarce in the scientific literature. In order to investigate the failures, bench tests were carried out on the spring-loaded valves, using a U-tube manometer. This pressure was exerted on the valve using a syringe that generated air flow inside the U-tube, allowing analysis numerical value of the measured pressure and the specified values of the valve, thus verifying the disparity of these measured values in relation to the PEP values operated by valves (0 to 20 cmH2O) from the three manufacturers under study. PEPs generated by spring-loaded valves from all three manufacturers were higher than pressures in the range of 2.5 to 20 cmH2O, with significant differences between manufacturers. This bench study showed inaccurate operation of all spring-loaded PEP valves of the three manufactures. The results obtained and the performance of the valves require a reevaluation of manufacturing procedures to preserve product quality and efficacy in clinical application.

Hydromechanical vibrator-pulsator for restoring the injectivity of injection wells

The article presents a bench model of a vibrator pulsator with a hydromechanical principle of operation designed for processing the bottom-hole zone of the reservoir of injection and production wells, columns of tubing, field pipelines.The design uses a spring-loaded rotary valve. The design of the test bench is described. According to the results of bench tests, the parameters of the pulsator’s stable operation were revealed: at a liquid flow rate of 0.012 m3/s, the oscillation amplitude of the pulsator body was 300 microns, the amplitude of liquid pressure fluctuations was 1.8 MPa at a frequency of 8 Hz. The results of field tests for cleaning columns of pumping and compressor pipes, field pipelines of oil collection are presented.

Damping Effect on Instability of Pressure Relief Valve Used for Cargo Venting System

A mathematical model for predicting an unstable working condition called cycling of a pressure relief valve controlled by weight and spring is proposed. The valve is connected to a reservoir used to store liquid cargo by a long pipe. A transient, compressible and one-dimensional fluid dynamic equation in the pipe is numerically solved, with boundary conditions given by the valve and reservoir dynamics. The effect of valve moving part damping coefficient is analysed, which can be changed by adding dampers. Installing a damper may solve the cycling problem for weight-loaded and spring-loaded pressure relief valves. The damping coefficient of the installed damper should be carefully selected, especially for spring-loaded valves. Too large damping coefficient may cause overpressure in the reservoir when the valve opens and too low pressure when the valve closes. After all, installing damper is a theoretically possible way to prevent cycling occurrence when the pipe length is too long in some practical situations.

Research on stability and control strategies for a spring-loaded valve with bypass outlet

The stability and control strategies of a spring-loaded valve with bypass outlet have been studied by combining numerical and theoretical analysis. First, a nonlinear dynamical model and a CFD model of a spring-loaded valve with bypass outlet are developed. The theoretical analysis requires parameters such as discharge coefficients and fluid forces obtained from CFD simulations. The equivalent area of the fluid forces and discharge coefficients are similar at different pressure differences, leading to a reduced-order formulation that serves the theoretical analysis of nonlinear dynamics. Second, the valve disc oscillates at small constant flow rates by nonlinear dynamical analysis. The oscillation frequency is a superposition of the Helmholtz cavity and the mass spring system, which increases as the valve disc impacts the seat or the upper limiter. More importantly, there is a frequency lock-in phenomenon at small fluctuating flow rates, which vanishes at large flow rates. The oscillations are not symmetric during the opening and closing processes, and the oscillations are more severe during the opening processes. Finally, the bypass outlet has a great effect on the stability of valve disc, which can appropriately kill the nonlinear component in the dynamic equation. A reasonable bypass sleeve design can reduce the unstable flow range and oscillation amplitude. This paper provides a reference for the design of spring-loaded valves.

Research on stability characteristics of a spring-loaded valve with two outlets

The stability characteristics of a spring-loaded valve with two outlets are studied by numerical simulation. The domain decomposition method is used to discrete the numerical model, and one degree-of-freedom system is established to study the disc motion. First, the internal flow structures and opening process are studied at constant flow rates. The results indicate that the flow coefficient is nonlinear with lifts at the main outlet and positively related to the lifts at the bypass outlet. More importantly, the fluid force acts as the driving and the damping force during the opening process. Second, the fluid damping effect and dynamic stability of the valve are studied by amplitude frequency characteristic analysis. The results show that the fluid force depends on the upstream oscillation frequency, and the fluid damping coefficient can be obtained through the fluctuation amplitude of fluid force and displacement. The amplitude of the disc displacement fluctuation is large for low-frequency excitation. Finally, the amplitude frequency characteristics are further analyzed by increasing the spring stiffness. The results show that increasing the spring stiffness can increase the fluid damping coefficient, thereby increasing the stability of the valve. This paper provides a reference for accurately establishing a valve dynamics model considering the fluid damping effect.

Manipulators adapted for automatic milking

The paper provides a rationale for the relevance of automation in machine milking. It deals with the design and control algorithm of a mobile manipulator adapted for milking machines. The manipulator allows for a change in the milking routine, thus making it possible to regulate the amount of vacuum in a tea cup, subject to a current flow rate separately for each pair of mammary glands. The paper presents the results of theoretical and experimental studies that indicate the way vacuum variations depend on the diameter of a metering orifice of a non-return valve, and how vacuum fluctuations in a teatcup chamber, as a spring-loaded valve opens, depend on the number of coils on a spring and its diameter. The results of a production check on a mobile milking manipulator are presented in the paper.

Auxiliary equipment for downhole fittings of injection wells and water supply lines used to improve their performance in winter

The article deals with two methods for eliminating freezing of injection wellhead fittings. The first method involves removing injected water from the well fitting under long well operation stoppage at negative ambient temperatures. Water is removed and air is supplied through the system of valves (a spring loaded valve and a float valve). When pumping water into the injection well, the float valve closes the access to the environment, and the spring-loaded valve is open for injected water. When the injection process stops, the spring-loaded valve supplies remaining water into the well fittings and the surface part of the water supply line and closes; the float valve opens. Air into the free space of the well fittings is supplied through the float valve thereby preventing the wellhead and the surface part of the water supply line from freezing. The second method is used to prevent the mouth of the injection well from freezing. A device is installed inside the casing, which allows heat to be accumulated in summer and winter. Accumulated heat is used to heat up the mouth when the water injection process stops.

Acoustic methods to suppress self-excited oscillations in spring-loaded valves

Spring-loaded valves have been reported to experience self-excited vibration in reciprocating compressor installations as well as in safety relief devices of pressurized systems. Prior work by the authors has provided an experimental characterization (El Bouzidi et al., 2018a) and a theoretical model (El Bouzidi et al., 2018b) of the flow–sound-interaction mechanism which causes the self-excited vibration. It was found that the vibration occurred only when the fluid–structure interaction at the valve is coupled with acoustic reflections in the associated piping system. In other words, coupling with the pipe acoustics was essential for the initiation of the self-excited valve vibration.This investigation evaluates the effectiveness of three acoustic devices in suppressing the self-excited vibrations. The objective is to dampen the sound waves in the piping system and weaken its coupling with the valve oscillations. A concentric Helmholtz-type cavity resonator, an orifice plate, and an anechoic termination are placed at the downstream side of a model valve which exhibited strong self-excited vibration in previous investigations. The orifice plate was successful in eliminating the oscillation frequency, but its placement at the acoustic pressure node was critical. The concentric cavity resonator dampened the oscillations to very small amplitudes, but a knowledge of the oscillation frequency was necessary. Finally, the anechoic termination was also successful in suppressing the oscillation, but its practicality is rather limited in industrial pipelines.

Self-excited vibrations of spring-loaded valves operating at small pressure drops

Flow-induced vibration is a major issue for spring-loaded valves. However, their complex geometry, combined with their diversity of operational conditions, creates a significant challenge for modelling their dynamic response to potential excitation mechanisms. This paper proposes an analytical framework to describe flow–sound–structurecoupling in spring-loaded valves operating at subcritical conditions, therefore without the occurrence of choking at the vena contracta. The model consists of a single-degree of freedom model of the valve structure, a pseudo-force implicit algorithm to calculate impact forces, a one-dimensional unsteady Bernoulli model to describe the flow, and a one-dimensional wave propagation finite difference scheme to account for the acoustic feedback. The model has shown excellent agreement with experimental results as well as promising predictive capabilities for valve life and wear assessment.

Experimental characterisation of the self-excited vibrations of spring-loaded valves

Valves are omnipresent in industrial processes. As a result, they must perform reliably according to their specifications. Spring-loaded valves are particularly susceptible to vibrations, as they are inherently flexible, often operate at small openings, and therefore they are more likely to interact with the surrounding flow. The current study experimentally investigates the self-excitation mechanism of a model spring-loaded valve with an emphasis on the interaction between the system flow and sound fields, and the valve structure. Tests are performed for various values of valve stiffness and maximum allowable valve lift. In each case, the pressure drop across the valve is increased gradually until the valve becomes fully open. The valve was found to oscillate at the fully coupled resonance frequency resulting from the interaction of the valve vibration with the acoustic field of the piping system. The oscillation amplitude was found to be positively correlated to both the pipe length and spring stiffness value. Furthermore, initial spring compression was found to have only moderate effects on the range of static pressures that would cause instability.

Unusual manufacturing defect of the endotracheal tube: Problem revisited.

Sir, Manufacturing defects of endotracheal tube (ETT) are still encountered in routine anesthesia practice. Many such defects go unnoticed during routine inspection prior to their use. We report a case of manufacturing defect at the junction of pilot balloon and spring-loaded one-way valve in a prepacked, single use, cuffed ETT. This case highlights the significance of standard monitoring of ventilation and the role of a vigilant clinician in detecting such defects and avoiding critical events that can arise from the use of such defective ETTs. It also emphasizes the need for double-checking ETT prior to their use. Difficulty in ventilating a tracheally intubated patient as a result of ETT defect is known in anesthesia practice. Despite the common practice of visual inspection and testing of ETTs for physical defects prior to use, some manufacturing defects still go unnoticed.[1] The patient, 8-year-old female weighing 24 kg, posted for fistulectomy for internal fistula of the left eye under general anesthesia. Her trachea was intubated with a 6.0 mm ID cuffed ETT and was ventilated with tidal volume (Vt) of 200 ml with a rate of 15/min. The correct placement of the tube was ensured and after three to four machine delivered breaths exhaled Vt started decreasing by more than 60 ml at around 20 cm H2O of cuff pressure. The tube in question is a CE-certified product (Hansraj Nayyar, Mumbai, India). We initially thought that the cuff needs to be inflated but in spite of inflating it the exhaled Vt would increase but only to decrease after a few breaths. When the leak was significant and end-tidal carbon dioxide started building up, we removed the tube and inserted a new tube, and thereafter ventilation was satisfactory. When we inserted the cuff of the tube in a bowl of water to check its potency, we did not find any leak, but the cuff was not sustaining the pressure to which it was inflated as measured by the cuff manometer. To our surprise, when we dipped both the pilot balloon and the cuff, the leak was detected at the junction of spring-loaded one-way valve and the pilot balloon [Figure 1] [Video], which is first of its kind to be reported. Figure 1 Original photograph showing the leak at the junction between pilot balloon and spring-loaded one-way valve A manufacturing defect in an ETT can lead to difficulty in ventilation involving any part of the ETT. Cuff defects leading to herniation of the ETT cuff and intraluminal tracheal obstruction,[2,3] elliptical defects in the wall of the tube causing air leak,[4] and kinking of ETT [5] have been described. In conclusion, double-checking of ETTs before their use aids in avoiding unnecessary intraoperative problems that can arise from the use of defective ETT although the method is not full proof. Most of the ETT defects described in literature could not be identified during routine preoperative inspection at least of this nature. Thus, the role of a vigilant anesthetist as well as standard monitoring of ventilation is invaluable for patient safety in the presence of a defective ETT. Further, the report points to the manufacturing practice and the need for stringent quality control of the manufacturer concerned in the production of such lifesaving equipment. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

Inspiratory conductance: an alternative index of the relationship between inspiratory effort and airflow with potential for clinical use

There is a need for a measure of airway status that is easier for patients to use. If airflow is briefly occluded at the onset of inspiration, the maximum rate of pressure fall, dP/dtmax can be measured. After the occlusion is released, the maximum rate of change of inspiratory airflow (dF/dtmax) can be measured and expressed as a ratio of dP/dtmax to generate an index of inspiratory conductance (IC). We explored the characteristics of IC as a preliminary step towards developing it as an easy-to-use alternative. To measure IC, we constructed an apparatus consisting of a pneumotachograph, a low-resistance spring-loaded valve and a pressure transducer to measure airflow and pressure drop at the start of inspiration. We studied 30 healthy adults to define the values of the index, its stability and its response to external inspiratory resistive loads. Mean IC was 2.49 (SD 0.96) Ls(-1) kPa(-1) , with no significant difference between men and women. The index was stable with a mean long-term variation of 11.25% around the normalised mean, compared with 2.1% for forced expiratory volume in 1 s (FEV1) and within-test variation < 5%. In response to external resistive loading, IC fell in a non-linear but consistent manner from 3.96 (0.32) to 0.96 (0.10) Ls(-1) kPa(-1) across an added resistance range of 0-70 kPasL(-1) . We showed that IC was measurable with a minimal need for subject participation. It was stable and reproducible in normal individuals and responded to added inspiratory resistive loads in a way that suggested it could be of clinical utility.

New Method for Comparing Flow in Spring-Loaded Valves

Spring-loaded valves possesses a dynamic operating range, in which the moving element is balanced by the flow and the spring forces. This feature means that the valve performance, including the pressure drop coefficient and the valve gaps, cannot be fully described only by using the Reynolds number without considering the spring properties. In this article, the theoretical analysis of the flow in spring-loaded valves was made to unify the flow and the spring forces. A new dimensionless number named the Zhang number was defined, with which the valve gaps and thus the pressure drop coefficient in the dynamic operating range can be clearly described. The similarity of flows in the valve loaded by different spring sets is then ensured. The significance of this similarity has been excellently demonstrated by an industrial compressor valve. Specifically, once a valve loaded by a set of springs is characterized, the valve characteristics using other spring sets can be directly obtained from the existing characteristic. No additional calibration of valve flows is necessary.

Loose adhesive in anaesthetic circuit

During a routine anaesthetic machine check we found there was a leak between the common gas outlet and the patient end of the circuit (which included a circle absorber). All the connections were checked and tightened but the leak persisted and a test lung failed to inflate. On disconnecting the scavenging system attached to the APL valve we found that all the gases were exiting through it. Fully opening or closing the APL valve made no difference and we decided that the fault was with the APL valve. On inspecting the APL valve our Medical Physics staff found that there was some soft plastic material obstructing the diaphragm of the valve (Fig. 3) causing it to malfunction. It was suggested that the material was some excessive adhesive used to join the hard 22 mm plastic connector of the anaesthetic circuit tubing to the corrugated soft plastic. In this case the adhesive had broken free and become trapped in the APL valve. Further discussion with the Medical Physics staff revealed that a similar incident had occurred a few months previously, but they had been unable to identify the source of the plastic. A further incident came to light in a neighbouring hospital within NHS Highland, discovered by a service engineer during routine maintenance. Scottish Healthcare Supplies and the manufacturers of the anaesthetic circuit tubing (Armstrong Medical Ltd, Coleraine, N. Ireland) were contacted. All our stock of this particular type of circuit (A-100 anaesthetic circle absorber/breathing circuit) was withdrawn and replaced with non-bonded corrugated tubing as an interim measure, while further investigations and monitoring were undertaken by the company. However, customers outside the UK, constituting some 90% of total output, continue to be supplied with the suspect circuit. Loose adhesive trapped in APL valve. Thank you for the opportunity to reply to Dr Barker's observations. In the original hospital complaint, the debris found in the APL valve was referred to as a small piece of plastic and, indeed, this is how the material is described in Dr Barker's letter. The source of this debris could not be accurately determined due to the number of potential origins of such material, nor was the debris ever conclusively identified as adhesive from the Armstrong circuit. If the assumption is made that this debris was, indeed, a small, disc-shaped piece of adhesive, the likelihood of such a piece of material occluding gas flow must be considered to be low. In any event, inhalation or ingestion of this material would not be possible given the use of a patient-end bacterial and viral resistant breathing filter as per Association of Anaesthetists of Great Britain and Ireland guidelines. For such material to be present in the APL valve it would have to detach from the inner surface of the tubing or connector, negotiate a tortuous route through the head of the absorber without causing an obstruction and, presumably carried by the gas flow, become lodged in the APL valve. Its ability to cause a fully closed spring-loaded APL valve to remain open and vent gas should be further evaluated along with other possible reasons for valve malfunction. Despite the inconclusive nature of our findings, and the fact that many thousands of circuits of similar construction were sold globally by Armstrong Medical in the previous 12 months with no reports of similar occurrences, immediate preventative action was taken as described in Dr Barker's letter. In addition to this, due to the necessity of using adhesive in this particular design of circuit, an improved adhesive is now used on all such circuits. We have received no reports of any similar occurrences during the 10+ years of clinical use of our smooth bore circuits.

Vented gaseous deflagrations: Modelling of spring-loaded inertial vent covers

The model of vented explosion dynamics in an enclosure with inertial vent covers is advanced further by the option of a spring-loaded cover acting as venting device. The model and CINDY code are used to process by the inverse problem method the experiments by Wilson in a 1.7 m 3 vessel with spring-loaded valves with surface densities of up to 245 kg/m 2 at conditions of initially quiescent and turbulent mixtures. It is demonstrated that, similar to translating and hinged vent covers, modelling of the vent cover jet effect is crucial for reasonable prediction of interdependent explosion pressure–time and cover displacement–time transients. The spring constant k was determined through backfitting, and reflects not only the resistance of the cover springs to the internal vessel pressure, but also the cycling frequency of the cover during deflagration. The turbulence factor was found to rise during venting.

A Nanoscale Spring-Loaded Valve Actuated by Colloidal Forces

A Nanoscale Spring-Loaded Valve Actuated by Colloidal Forces

Development of an automated pressure-threshold loading device for evaluation of inspiratory muscle performance

In 1996 Johnson et al. (Medicine and Science in Sports and Exercise, 28, 1129–1137) concluded that respiratory muscle fatigue may limit human performance whereby the work done by the respiratory muscles to drive the ventilatory pump might significantly affect exercise tolerance. As a result of these and similar findings there is a growing interest in respiratory muscle performance. However, methods for appraising inspiratory muscle function which are relevant to exercise performance are limited. The purpose of the present paper is to describe the development and validation of an automated pressure-threshold loading device for use in evaluating the maximum incremental performance of the inspiratory muscles and other endurance-based measures of inspiratory muscle performance. The device utilizes a stepper motor to vary the resistance of a spring-loaded poppet valve arrangement, thereby permitting automatic selection of various inspiratory muscle loading profiles. The device is accurate to within 1.5% (0.1–1.5 cmH2O) of selected load across its range and permits continuous incremental loading with a resolution of 0.1 cmH2O·min–1. This apparatus allows an endurance-based measure of inspiratory muscle endurance to be obtained which is distinctly different from measures of inspiratory muscle strength such as peak inspiratory mouth pressure. Furthermore, reproducible measures can be attained without the need to regulate breathing pattern or to maintain isocapnia. In summary, the current device is useful when a simple yet reproducible endurance-based measure of inspiratory muscle performance is required.

Onset Time, Recovery Duration, and Drug Cost with Four Different Methods of Inducing General Anesthesia

We compared two conventional induction techniques (thiopental and propofol), an inhaled induction with sevoflurane using a circle system, and a rebreathing method.Fentanyl 1 [micro sign]g/kg was given to women undergoing 10- to 20-min procedures. Anesthesia was induced (n = 20 each) with one of the following: 1) sevoflurane and N2 O from a rebreathing bag (Sevo/Bag). A 5-L bag was prefilled with a mixture of sevoflurane 7% and N2 O 60% in oxygen. The bag was connected between the normal circle system, separated by a spring-loaded valve; 2) sevoflurane 8% and N (2) O 60% from a circle system on a conventional anesthesia machine with a total fresh gas flow of 6 L/min (Sevo/Circle); 3) propofol 3 mg/kg as an IV bolus; 4) thiopental sodium 5 mg/kg as an IV bolus. Postoperative nausea and vomiting was treated with ondansetron. Induction times were comparable with each method. Recovery duration was shortest with sevoflurane, intermediate with propofol, and longest with thiopental. Induction drug costs were lowest with Sevo/Bag and thiopental, intermediate with Sevo/Circle, and highest with propofol. However, sevoflurane (by either method) caused considerable nausea and vomiting that required treatment. Consequently, total drug cost was least with thiopental, intermediate with Sevo/Bag and propofol, and greatest with Sevo/Circle. Thus, no single technique was clearly superior. Implications: Anesthetic induction techniques influence awakening time, recovery duration, and drug costs. We tested two IV methods and two inhaled techniques. However, none of the four tested methods was clearly superior to the others. (Anesth Analg 1999;88:930-5)

Dynamic Analysis of a Double-Tube Shock Absorber for Robust Design.

In this study, a robust design approach is presented to determine the desired damper force characteristics of a double-tube shock absorber based on a dynamic analysis in which design constraints to prevent cavitation are derived. First, a nonlinear mathematical model of the shock absorber is developed based on fluid mechanics. Then, the design constraints to prevent cavitation are derived based on a dynamic analysis, and a design methodology of the desired damper force characteristics of a spring-loaded valve is determined. Finally, experimental verifications are performed to confirm the mathematical model and the design constraints, and computer simulations are performed for three design cases to verify the postulated design methodology.