Non-return Valve Research Articles

Modeling of Plasticating Injection Molding – Experimental Assessment

Abstract A computational model for the description of polymer flow during the plasticating phase of the injection molding process is proposed. The polymer behavior is determined during the dynamic and static phases of the process. The model takes into account the backwards movement of the screw, the presence of a non-return valve and the conduction of heat during the idle times. Results for the dynamic and static phases of the plasticization are presented. The model is also used to study the influence of some important operative process parameters, such as, screw speed, backpressure, barrel temperatures and injection chamber length. The assessment of the computational results is made experimentally by comparing the average temperature calculated with measurements made in front of the screw nozzle using both, an IR camera and an IR thermometer. The differences between the computational and the IR camera measurements are below 5%.

A Fuzzy Logic Based Model to Predict Weld Width – A Case Study of Hard Facing Process Using MIG Welding on Dual Plate Check Valve

Welding input parameters play a very significant role in determining the quality of a weld joint. The joint quality can be defined in terms of weld-bead geometry. The 23 replication with 4 center points experiments are performed on non-return valve material WCB by varying various MIG Welding process parameters. Here welding current, welding speed and gas flow rate are considered as input parameters with two levels. A fuzzy model is developed to predict the weld width in context of these input parameters. Fuzzy model uses fuzzy expert rules, triangular membership function and centroid area method for defuzzyfication process using MATLAB fuzzy logic tool box. The developed model is validated by performing experiments at center points. The result shows prediction may lie in the range of 95.18-100%.

G113(P) The effects of sleeping position and maternal smoking on the ventilatory response to hypoxia

AimsBoth prone sleeping and maternal antenatal smoking are known risk factors for Sudden Infant Death Syndrome (SIDS). The aim of this study was to determine whether the two factors could...

ANALYSIS OF DIFFERENT PROTECTION METHODS AGAINST WATER HAMMER ON WATER SUPPLY NETWORK (CASE STUDY-ASSIUT CITY NETWORK)

The effect of using different protection devices on water hammer phenomenon to provide an acceptable level of protection against system failure due to pipe collapse or bursting is presented. Water Hammer and Mass Oscillation (WHAMO) software is used in the analysis which uses the implicit finite difference scheme for solving the momentum and continuity equations at unsteady state case. Assiut city water supply network is used. The network is supplied from two points at pump No. 36 and pump No. 37. Flow of pipe network is studied under steady normal case, without any protection case against water hammer phenomenon, and the model under different operation cases; with a transient protection device(s) such as non-return valve, open surge tank, air chamber and pressure relief valve (PRV). The results are performed for three scenarios; the first is the normal operation of pump 36 and failure of pump 37, the second is the normal operation of pump 37 and failure of pump 36, and finally failure of pumps 36 and 37 together. The results showed that using of open surge tank or air chamber with non-return valve protects the pipe network effectively from the harm of water hammer. Also, using PRV with non-return valve protects the pipe network from extreme pressures. Although using non-return valve only doesn’t have a great effect on the maximum pressure head than the normal case, it protects the network from the more low pressures than without protection one. All protection cases safeguard the pipe network from the extremes of water hammer, but increase the water hammer wave period. Finally, the sudden shut down of the pumps 36 and 37 together has the large effect on the pressure heads than the shut down of any of them only.

STUDYING OF WATER HAMMER IN WATER SUPPLY PIPES NETWORK WITH DIFFERENT ABNORMAL OPERATION CONDITIONS (CASE STUDY - ASSIUT CITY NETWORK)

This research studies the effect of abnormal operation conditions on water hammer phenomenon in water supply pipe network in order to provide an acceptable level of protection against system failure due to pipes collapse or bursting. Water Hammer and Mass Oscillation WHAMO software is used in the analysis which uses the implicit finite difference scheme for solving the momentum and continuity equations at unsteady state case. Assiut city water supply network is used in the analysis. Flow of pipe network is studied due to; firstly, the sudden change in water demand at one or more junctions, secondly, the closing of some pipes of the network on the transient pressure and flow rates, and finally the failure in some network pipelines on intrusion or leakage due to transient pressure head fluctuations. The previous cases are studied in steady normal case, without any protection, and under different protection device(s) such as non-return valve and open surge tank. The results showed that rapidly change in demand increases the pressure head and flow rate fluctuations. Closing some pipelines increases pressure in a region and decreases it at another and also changes the direction of flow in the network. Also, failure of some pipelines can cause intrusion and leakage from outside the network to inside and inversely, which affects the values of minimum pressure heads more than the maximum ones. Finally, using of open surge tank with non-return valve protects the pipe network effectively from the harm water hammer.

The Effect of Non-Return Nalve on Micro Injection Molding Machine

The micro injection molding machine (MIMM) is used to produce precision plastic products. The non-return valve (NRV) on the screw head of injection machine plays the role of preventing the melt back discharge during injection process. The sensitivity of non-return valves opening and closing affects the quality of the product. In this paper, numerical simulation of three-dimensional flow field is generalized by the Newtonian isothermal fluid method. Then, five kinds of different structural parameters of NRV are designed, and the pressure field, the pressure difference is simulated by the Polyflow software. At last, the pressure field, and the pressure difference on both side of NRV are analyzed and compared. The best structure parameter of NRV is decided. The simulation results are useful for the NRV design.

Development of a model of a multi-lymphangion lymphatic vessel incorporating realistic and measured parameter values

Our published model of a lymphatic vessel consisting of multiple actively contracting segments between non-return valves has been further developed by the incorporation of properties derived from observations and measurements of rat mesenteric vessels. These included (1) a refractory period between contractions, (2) a highly nonlinear form for the passive part of the pressure-diameter relationship, (3) hysteretic and transmural-pressure-dependent valve opening and closing pressure thresholds and (4) dependence of active tension on muscle length as reflected in local diameter. Experimentally, lymphatic valves are known to be biased to stay open. In consequence, in the improved model, vessel pumping of fluid suffers losses by regurgitation, and valve closure is dependent on backflow first causing an adverse valve pressure drop sufficient to reach the closure threshold. The assumed resistance of an open valve therefore becomes a critical parameter, and experiments to measure this quantity are reported here. However, incorporating this parameter value, along with other parameter values based on existing measurements, led to ineffective pumping. It is argued that the published measurements of valve-closing pressure threshold overestimate this quantity owing to neglect of micro-pipette resistance. An estimate is made of the extent of the possible resulting error. Correcting by this amount, the pumping performance is improved, but still very inefficient unless the open-valve resistance is also increased beyond the measured level. Arguments are given as to why this is justified, and other areas where experimental data are lacking are identified. The model is capable of future adaptation as new experimental data appear.

Acoustic compressor coupled with fluidic diodes

Performance of an acoustic compressor coupled with a fluidic diode is studied. The acoustic compressor works on the idea of Resonant Macrosonic Synthesis (RMS) technology demonstrated by Lawrenson et al. The main idea is to replace non-return valves by no moving part fluidic device. Fluidic diode rectifies an oscillatory flow analogous to rectifying an electric AC to obtain DC output. Synthetic jets analogous to AC current falls in the category of jet-driven acoustic streaming, which has a zero mean mass flux. The synthetic jet can be combined with no-moving part fluidic device to generate Hybrid Synthetic Jets with non zero mean mass flux. Non-zero mass flow rate was achieved by coupling fluidic diode and the resonator. In the present study, better rectification is achieved by having number of fluidic diodes in series. Experiments were done for the case of 3 and 4 diodes in series. In the case of three diodes in series the mass flow was 4.6 l/min and in case of four diodes it was 4.9 l/min. Full paper will present the pressure and mass flow measurements for 1 to 5 diodes in series. Thus, RMS cavities with fluid diodes can work as a pump.

Anatomical modifications, viviparous reproduction and hydraulic expulsion of larvae byCephenemyianasopharyngeal bot flies of deer

Several specialized adaptations of the reproductive and respiratory systems associated with the retention and expulsion of larvae in ovoviviparous Cephenemyia species (Diptera: Oestridae) are described and illustrated. In these flies the anterior section of the common oviduct is modified into a large sac-like uterus that contains larvae, and the posterior section is modified into a larvipositor with a central tubular vagina. During larviposition, contraction of abdominal muscles forces haemolymph into a perivaginal sinus, causing a hydraulically driven exsertion of the larvipositor. A group of larvae and uterine fluid sealed off within the lumen of the vagina are then expelled from the vulva via hydraulic pressure as the stretched vagina is compressed. A one-way, non-return valve between the uterus and vagina prevents a reflux of larvae upward into the uterus during larviposition. All mutually dependent actions associated with larviposition occur almost simultaneously. All species have evolved a similar mechanism of expelling their larvae, but the shape of the non-return valve is different in each species studied.

Investigation of Water Hammer Effect Through Pipeline System

This paper we study the condition where the water hammer effect is occurs in pipe line. Water hammer can cause the pipe to break if the pressure is high enough. The experiment will be set-up to investigate the water hammer effect in order to avoid the water hammer effect happen. The prevention of water hammer effect will be propose and prove the prevention method is successfully reduce the water hammer effect. The prevention method using is installing the bypass pipe with non-return valve. The experiment is done by capture the vibration signal by using data acquisition device and accelerometer. The pressure signal is capture after a sudden shutoff for the valve. The signal is than analyze and convert to wave speed. The project is differentiating and compares the water hammer phenomenon with different pipe material, pipe length, inlet diameter of pipe, and pressure in pipeline. From the experiment, result shown that the lower strength material pipe, smaller inlet diameter pipe, and longer pipe will deal with lager water hammer effect. Besides, the prevention method by installing by pass pipe with non-return valve of water hammer effect is proved successfully reduce the water hammer phenomenon by 33.33% of pressure.

Devices For Displaying Modal Patterns

The present invention provides an acoustic display device for displaying modal patterns in response to sound from a sound source. The display device (10) has a substantially circular housing (12), which housing (12) includes a continuous curved side wall (13a), a substantially flat base wall (13b), and open end (13c). The open end (13c) is closed by diaphragm (14), thereby forming closed chamber (15). Excitation of the diaphragm can be effected by introducing vocal sounds to the underside of the diaphragm via one of a plurality of sound connecting means (22) that include a flexible tubular section (30), which terminates in a mouthpiece (32). A user can place the mouthpiece over their mouth and nose and make vocal sounds, which are delivered to the interior of the chamber (15). The mouthpiece (32) can be substituted with a sound collector (60) having a 'horn' shape and an annular flange for engagement with a loudspeaker. The other ends (24) of the sound connecting means (22), within the closed chamber (15), each contain a non-return valve so that pressure within the chamber is maintained. The device can also include weight locating means (21a, 21b, 21c) or magnetic tensioning means (80, 84) for tuning the diaphragm. Removable covers having different markings can assist in analysing the patterns produced. Two or more integral curved spirit levels (38) in conjunction with adjustable feet (40) enable accurate levelling of the diaphragm.

Artificial erection in Peyronie's disease surgery

Figure 1 Loose body in knee joint sited into either corporal body through the glans (Figs 1 and 2), taking care not to injure the penile urethra. Following adequate placement, the cannula is secured to the foreskin with a suture and a non-return valve with a Luer lock connector is attached (Fig 3). The penis is inflated using 50ml of normal saline. The syringe can then be detached, refilled and reattached without dismantling the cannula mechanism.

Flow accelerated corrosion: Experience from examination of components from nuclear power plants

Flow accelerated corrosion (FAC) has affected a large number of components made from carbon steel in the secondary as well as primary circuits of light water reactors worldwide. This is primarily a corrosion process enhanced by (electro) chemical dissolution and mass transfer, rather than a mechanical process. It has caused rupture of all sizes of pipelines as well as other components carrying either single phase water or two phase (wet steam) flow. It is reported to be the only mechanism that has significant potential for large leaks in the secondary circuit. This paper describes the observations from examination of a number of components that were affected by FAC in Pressurized Heavy Water Reactors in the past 5 years. Failure analysis done on the 10% feed water line, non-return valve (NRV) in the auxiliary feed water system and on the affected pipeline components from the secondary water system of various reactors has been described in this paper. The surface features observed (the signature pattern of FAC) on the inner surfaces of the pipelines affected by FAC in the primary and the secondary circuits of nuclear reactors have been described. Signature patterns of FAC, on components severely affected by single phase FAC (scallops) and on components affected by dual phase FAC (tiger striping) are recorded and reported. Components where FAC degradation had just initiated showed that the patterns were not well defined. The signature patterns became evident only after the degradation had occurred to a large extent. FAC like features were not seen in stainless steel components in the secondary side. Case studies showing that thinning of carbon steel components is not always attributable to FAC in the secondary circuit of the reactors are also described and reasons of these thinning illustrated to show the importance of establishing the cause of each thinning case. The paper also discusses if the size of the scallops is possible to be correlated to the FAC rate.

Non-return valves do not prevent backflow and bacterial contamination of intravenous infusions

Non-return valves (NRVs) are designed to avoid backflow of infusion fluid against the designated direction of flow (DDF) when more than one infusion is delivered via one venous access. We tested in vitro whether NRVs reliably prevent flow against the DDF at clinically relevant low flow rates. Since catheter-related infections caused by the infusion of contaminated fluids represent a relevant problem in patient care, we tested whether NRVs preclude bacterial contamination of infusions proximal to the NRVs and thus might play a role in preventing healthcare-associated infections. Additionally, the incidence of bacterial contamination of drips and infusion fluids in our intensive care unit (ICU) was quantified. In vitro, a low flow against the DDF of ten examples each of five different NRV models was applied and the integrity for fluid and transmigration of three different indicator micro-organisms was tested. Second, we investigated whether contamination of intravenous infusion tubing collected from patients treated on our ICU occurred. Largely independent from the model, 40% of the tested NRVs were not leak-tight for fluids when a pressure against the DDF was built up slowly. In 30%, bacteria migrated against the DDF and were detected proximal to the valve. In 6.7% of the tubing samples collected from ICU patients we detected bacterial contamination. In conclusion, contamination of drips is a relevant problem on ICU. NRVs neither reliably prevent backflow of fluids nor serve as micro-organism filters. Therefore they cannot be recommended as a way of reducing healthcare-associated infections.

Plate Loading Tests and Bearing Capacity Characteristics of Grouted Screw Pile Method

Environmental awareness leads to an increasing use of screw piles in construction because such piles generate low noise, low vibration and also generate no surplus soil. Also, such piling technique has practical benefit during construction. Such piles are also believed to provide relatively large compressive strength and pullout resistance capacity. In this study, a new kind of ground improving pile is developed wherein the surrounding soil around the pile is also improved by injecting compressed cement grout using non-return valves. Such piles provide larger resistance capacity than conventional screw piles. The ground is improved by injecting grout into the ground in three patterns. The improvement effect and bearing capacity characteristics of each pattern was compared and examined through field tests (plate loading test).

ANALYSIS OF TRANSIENT FLOW PHENOMENON IN PRESSURIZED PIPES SYSTEM AND METHODS OF PROTECTION

Water hammer phenomenon is an important consideration in designing of many hydraulic systems due to extreme variations in pressure it causes. For example, the dramatic pressure rise can cause pipes to rupture. Accompanying the high pressure wave, there is a negative wave that can cause very low pressures leading to the possibility of contaminant intrusion or column separation. This paper investigates the effect of different parameters such as fluid density, steady flow velocity, air entrainment, pipeline material type and pipeline friction factor on transient flow in pipeline system due to pump shut down, effect of protection devices on the transient pressure head along the pipeline and effect of existence of a crack in pipeline flow. WHAMO software was used in the analysis which uses the implicit finite difference scheme for solving the momentum and continuity equations at unsteady state case. The study was applied on a pipeline composed of six segments of different diameters and elevations with a total length of 2523 m. The flow is pumped in the pipeline by pumping station to a constant head reservoir at the end of the pipeline. The results showed that many parameters such as fluid density, steady flow velocity, air entrainment, pipeline material type and pipeline friction factor have significant effect on the water hammer phenomenon. Also, it was found that in spite of the non-return valve protects the pump from water hammer effect, increases the pressure head in the pipeline. Surge tank or air chamber fitted at the beginning of the pipeline can protect it effectively from the water hammer effect. At the end, it was found that a crack in pipeline can cause intrusion from outside the pipe to inside and inversely can cause leakage to outside or both.

ПРОМЫСЛОВЫЕ ИССЛЕДОВАНИЯ ПРОЦЕССА СЕПАРАЦИИ ГАЗА НА ПРИЕМЕ ПОГРУЖНЫХ НАСОСОВ

Introduction The problem of studying the process of gas separation in the design of artificial oil lift is sufficiently relevant. According to data of the separation, we can predict the actual pump flow and calculate the necessary depth of submersion under the dynamic level. Aims and Objectives Determination of the gas separation at the reception of submersible pumps as well as the link between the separation rate and GOR. Methods The method is based on measuring the amount of gas withdrawn from the annulus, and the amount of gas evolved from oil at the wellhead. Results Studies were conducted on the wells of some Lukoil-Komi deposits. It was shown that the coefficient of separation of gas at the pump intake varies widely: from 0,1 to 1,0, depending on the feed pumps and gas-oil ratio of oil. Conclusion The extraction of gas from the annulus directly into the gas line before the gas meter can improve the accuracy of gas-oil ratio by eliminating the pressure drop in the non-return valve and an additional mixing with the liquid to a gas separator.

Pressure drop across vortex diodes: Experiments and design guidelines

Vortex diodes are used as leaky non-return valves in applications where it is desirable to avoid valves with moving parts. Despite their use in practice for several decades, no clear guidelines for design and optimization of vortex diodes are available. Detailed experimental study on flow and pressure drop characteristics of vortex diodes was therefore carried out to evolve such guidelines. The study covered a wide range of vortex diodes. The variation of diodicity (ratio of pressure drop for reverse and forward flow for the same flow rate) with respect to diode geometry, diode size ( d C), aspect ratio ( d C/ h), nozzle configuration and Reynolds number ( Re) was studied. The experimental results were critically analyzed to develop a design methodology. The methodology is shown to be useful for obtaining the diode dimensions that would yield the desired diodicity for the required operating flow rate.

Instabilities of Nonreturn Valves in Low-Speed Air Systems

Practical observations of the nonreturn valve wear in aero-engine cabin-bleed systems suggest that such valves are subject to unstable behavior. A theoretical model for the prediction of nonreturn valve instabilities in air systems is proposed and a nonlinear state-space model of the nonreturn valve and air volume interaction is derived from first principles. Experimental work is used to identify both the dynamic characteristics and the flow properties of the valve, which are used to identify the coefficients within the model. Through frequency analysis of valve oscillatory behavior, the levels of damping within the system are identified. Finally, using a local linearization of the state-space model an explicit mathematical prediction of valve stability is derived based on system parameters. These predictions are used to generate a map of the transition from stable to unstable system behavior for low-speed air flow, which is in excellent agreement with experimental data.

On-chip liquid storage and dispensing for lab-on-a-chip applications

This work presents novel components for on-chip storage and dispensing inside a lab-on-a-chip (LOC) for applications in immunoassay point-of-care testing (POCT), where incubation and washing steps are essential. It involves easy-to-use on-chip solutions for the sequential thermo-hydraulic actuation of liquids. The novel concept of combining the use of a rubber plug, both as a non-return valve cap and as a liquid injection interface of a sealed reservoir, allows simple filling of a sterilized cavity, as well as the storage and dispensing of reagent and washing buffer liquids. Segmenting the flow with air spacers enables effective rinsing and the use of small volumes of on-chip stored liquids. The chip uses low-resistance resistors as heaters in the paraffin actuator, providing the low-voltage actuation that is preferred for handheld battery driven instruments.