Bellows Valves Research Articles

An experimental study of the influence of valve drive type on the dynamic loading and service life of valve seals of units

The article discusses an experimental study of the influence of the valve drive type on the dynamic loading and service life of valve seals of units. The results of research of the modes of closing of piston valves and bellows valves at different response speeds are presented. The differences in the amplitude characteristics of repeated impact, arising from the rapid return motion of the valves trim, in the piston and bellows versions of the valve are established. The influence of the operating mode on the service life in both versions of the valve design was assessed, and pressurized leakage tests were also carried out.

A new calibration technique for quantitative gas analyses of fluid inclusions using a quadrupole mass spectrometer.

Quantitative gas analysis by quadrupole mass spectrometry is used widely in the study of fluid inclusion volatiles, but the currently available instrument calibration techniques have a number of limitations. We describe a new method to overcome these by employing custom-machined stainless-steel calibration volumes that fit into modified bellows valves and can be filled on the high-vacuum prep line of the instrument. This allows the calibration gas to be introduced in a pulse-like fashion, replicating a burst of sample gas from a ruptured fluid inclusion. The modified bellows valves equipped with calibration volumes are loaded onto the high-vacuum inlet of a quadrupole mass spectrometer. Cobalt-based alloy stem tips are then used to seal calibration gases (dry air, in this case) at known pressures into the calibration volumes for analysis. Two volumes of different dimensions were used to produce a relationship between moles introduced and integrated beam area for m/z 14, 32, 40, and 44. A linear fit along with a 95% confidence band for the relationship of moles introduced and integrated beam area was determined for the purpose of quantitative gas analysis in fluid inclusions containing atmospheric air. The calibration curves for each m/z have R-squared (COD) values of 0.94 or better. For validation of this calibration technique, measurements were made using outside air as an unknown. A new calibration technique has been developed for measuring femto- to pico-mole quantities of atmospheric air that greatly reduces contamination and introduces calibration gas in a pulse similar to sample gas. This technique has reduced the error in quantifying these small aliquots of air to an uncertainty of ±1.5%.

Analysis of small bubbles in glass by glow discharge—Time-of-flight mass spectrometry

The chemical reactions occurring during the glass manufacturing processes can give rise to small bubbles, damaging the required glass properties. To avoid eventual bubbles formation, the chemical composition of the bubbles should be known to trace back the gas sources and take appropriate corrective actions. Mass spectrometry is a most adequate detection technique for such purpose due to its ability to provide the required information in a short time. Analysis of these small bubbles in glass requires a system incorporating a very small volume (for a fast evacuation of the entire line and low dilution of the analytes) and a fast mass analyser allowing the quasi-simultaneous detection of the whole spectral interval of interest, such as a time-of-flight mass spectrometer (TOFMS). In this work, the analytical potential of a radiofrequency glow discharge (rf-GD) coupled to a TOFMS was evaluated for the first time for the analysis of bubbles in glasses. The operating conditions of the rf-GD (pressure and applied power) were optimized by introducing into the system known volumes of air. Detection limits in the order of nL were obtained for molecular nitrogen, oxygen and carbon dioxide. Finally, a stainless steel bellows valve was modified to serve as glass breaker for the sampling process. This valve was connected on-line to the mass spectrometer inlet line and proved to be most appropriate for the analysis of the gaseous content of bubbles (with diameters below 0.5 mm) entrapped in industrial glasses.

A versatile computer-controlled valve

We have developed a computer-controlled valve based on the popular Nupro B-4HK bellows valve. The valve is actuated by a stepper motor. A modification to the Nupro valve necessary to achieve reproducible performance in setting the flow rate is described, and performance data on the coefficient of flow is presented. These valves have been cycled thousands of times without difficulties.

Spark combustion reactor for 13-carbon isotope enrichment analysis of gases

A novel spark combustion reactor was designed, built, and utilized for quantitative 13-carbon isotope determination of highly enriched permanent gases. The analytical methodology developed is straightforward and begins by loading the reactor with hydrocarbon and oxygen using a steel gas manifold. High voltage is applied to the platinum electrode spark plug incorporated into the reactor, which rapidly converts hydrocarbon to carbon dioxide (and other products). Carbon dioxide species are then quantitated by quadrupole mass spectrometry. The primary reactor consists of a three-way stainless steel tee, plus the following components connected to threaded ports: (1) a platinum electrode spark plug sealed with a Viton O ring, (2) a steel gas storage cylinder, and (3) a manual bellows valve terminated with a VCO type connector. Making use of the spark combustion reactor, the 13-carbon fraction of highly enriched CH413 was measured to be ⩾99.5 at. % 13C. This portable, static reactor permits determination of the C13/C12 isotope fraction for permanent gases utilizing mass spectrometric detection. The analytical system presented is relatively rapid (due to spark ignition), straightforward, and flexible (applicable to hydrocarbon gases using various gas detectors). Its limitation in performance for C13 isotope work is probably due to carbon embedded in the reactor interior.

Jet expansion module for liquid-sampled GC-discharge ionization detection of liquefied gases.

A rugged jet expansion module was designed, built, and utilized to sample liquefied gas for gas chromatography-discharge ionization detector (GC-DID) analysis. The module is inserted at an intermediate stage between a higher pressure sample cylinder and lower pressure gas injection manifold. The title jet module permits selection of liquid-phase or vapor-phase sampling by setting the valve-cylinder orientation up or down (relative to gravity). It consists of a four-way stainless steel cross, plus the following components connected to pipe thread ports: (1) mechanical pressure gauge, -15 to +30 psig; (2) threaded nut with 0.010-in. jet orifice (connect to sample cylinder valve); (3) bellows valve (connect to GC manifold); (4) bellows valve (connect to expansion cylinder). Making use of the jet module, measurement of air concentration in [15N]ammonia and sulfur hexafluoride (single-component) samples was found to be significantly lower in the liquid phase by GC-DID. This compact apparatus enables phase-selective sampling, reduces primary manifold contamination, and improves operator safety.

ＫＥＫＢ加速器初期運転時の真空特性

The commissioning of KEKB accelerator (KEKB-factory) started in December, 1998. The vacuum system is working almost satisfactorily although several troubles occurred near the interaction region. The photon stimulated gas desorption coefficient of copper beam chamber is decreasing steadily and reached to around 1×10-5 molecules photon-1 at the integrated linear photon flux of 1×1024 photons m-1. The beam lifetime is increasing with the integrated beam current but is shorter than that expected by the average pressure especially for the Low Energy Ring. A pressure burst was observed at a straight section of the positron ring. The Helicoflex vacuum sealing is stable. Bellows and gate valves with RF-shield structure showed no excess heating up to the storage current of 500 mA.

Resealable Superfluid Valve

Recently it has been shown that Torlon may be used to construct a resealable superfluid bellows valve with a “hard seat, soft stem” configuration. We present a modification on this design incorporating a thin BeCu diaphragm to produce a valve having a dead volume of 0.02 cm 3. The valve may be actuated using a high pressure gas handling system or electrically using a sealed expansion volume.

96/01988 Balanced bellows valves — A thing of the past?

96/01988 Balanced bellows valves — A thing of the past?

A Radon Generator/Delivery System

A radon-generating system is described in which 222Rn, emanating from 226Ra stored in an aluminum containment vessel, may be pumped into a syringe for subsequent injection into a standard spinner flask containing tissue culture medium. The radium-containment vessel is sealed by an indium gasket and three metal bellows valves, one of which was used to fracture the glass capsule that contained 2.9 GBq of radium salt. A rotating piston pump transfers radon-enriched air from the radium-containment vessel to a delivery loop that includes a transfer syringe. The flow of air and radon through the loop is manipulated by three crossover ball valves, one of which may be set to fill the syringe. A charcoal trap is provided to collect residual radon left in the delivery loop after the transfer syringe has been filled. The protocol used to expose cells to radon and its progeny is described as well as the dosimetry that is used to estimate the dose delivered to the cells. A description of safety precautions taken in fabricating the generator and in conducting radiobiological studies is also presented.

MOCVD manifold switching effects on growth and characterization

The components of metalorganic chemical vapor deposition (MOCVD) supply manifolds have significant effects on the ability to rapidly introduce and exhaust growth materials. This in turn has direct bearing on the achievable heterojunction interface abruptness for a given manifold design. Research to quantify the effects of various manifold components on the switching speed has been performed with a combined modeling and experimental approach. An overview of the experimental investigation is reported. Manifold switching sections were incorporated in a manifold line instrumented with an atmospheric pressure sampling mass spectrometer. A constant flow rate of nitrogen was established in the manifold line to serve as the carrier gas. Into this flow, controlled concentration pulses of argon were introduced from one switching section at a time to model the transport of source gases. A square-wave generator was used to control the on-time of the source for both single and multiple pulse experiments. The results of the single pulse experiments are reported here. The sudden displacement of the valve seats in the air-actuated bellows valves was found to introduce significant pressure and concentration spikes. These spikes demonstrate the need to carefully resolve the effects of pressure and concentration on the measurement technique. For the mass spectrometer system, measurement artifacts occur due to the pressure pulses increasing the rate at which gas enters the sampling orifice. Similar measurement artifacts would be expected in any concentration measurement system which measures number density or which employs a sampling orifice.

Sampling of organic volatiles in the atmosphere at moderate and low pollution levels

Several techniques are available for measuring organic volatiles in the atmosphere. For measurements at low and moderate pollution levels (between several μg m −3 and a fraction of a μg m −3), the existing methods can be adopted to a broad range of different compounds. Whole-air sampling in stainless-steel containers with metal bellows valves combined with subsequent gas chromatographic separation after preconcentration in the laboratory is probably the best procedure for low and medium molecular weight trace gases of moderate or low polarity and reasonable chemical stability (e.g., hydrocarbons and halocarbons). For organic compounds of lower volatility, adsorptive sampling on non-polar porous organic polymers (e.g., Tenax) and thermal desorption combined with cryotrapping and gas chromatographic separation of the sampled compounds is widely used. However, there are often substantial problems due to artefact formation or loss reactions. Owing to the generally larger sample volumes, these problems are even more pronounced for sorptive sampling techniques combined with sample recovery by solvent extraction. Unfortunately, the general understanding of the various processes of sample degradation due to chemical reactions of reactive components of the atmosphere with each other or with the sorbent is not yet sufficient to allow reasonable estimates of the extent of such interferences without elaborate test procedures.

Compact, rugged Monel Bellows valves

Compact, rugged Monel Bellows valves

Bellows valves for high vacuum

Bellows valves for high vacuum

100. Miniature high-pressure bellows valve: D I Vasil'ev,Pribory Tekh Eksper, No 1, 1966, 217 (in Russian)

100. Miniature high-pressure bellows valve: D I Vasil'ev,Pribory Tekh Eksper, No 1, 1966, 217 (in Russian)

The Flow of Gases in Pipes at Low Pressures

Data are presented on the flow of air at low pressures in copper pipes of radius 0.795 and 1.30 cm; iron pipes of radius 2.64, 5.12, and 10.1 cm; and for hydrogen in a copper pipe of radius 1.30 cm. Data are also given for the resistance to flow of air in 1½- and 3-inch nominal pipe size elbows, for 1½-inch Kinney bellows valves, and for short sections of 1-inch nominal pipe size iron pipe connecting large gas chambers. The data on straight iron and copper pipes, together with the data from the literature on glass capillaries, are correlated by the introduction of a correction factor F in Poiseuille's equation. F is correlated graphically in terms of a dimensionless group representing the ratio of mean free path to pipe radius, with separate curves for iron pipe and for copper and glass pipes or capillaries.