Vapor detectors

Acoustic Wave Sensors. Another emerging physical transduction technique involves the use of acoustic waves to detect the accumulation of species in or on a chemically sensitive film. This technique originated with the use of quartz resonators excited into thickness-shear resonance to monitor vacuum deposition of metals (11). The device is operated in an oscillator configuration. Changes in resonant frequency are simply related to the areal mass density accumulated on the crystal face. These sensors, often referred to as quartz crystal microbalances (QCMs), have been coated with chemically sensitive films to produce gas and vapor detectors (12), and have been operated in solution as Hquid-phase microbalances (13). A dual QCM that has one smooth surface and one textured surface can be used to measure both the density and viscosity of many Hquids in real time (14). 

Flammable Vapor Detectors These should be installed to warn of leaks, although such devices do not effectively control UVCEs with sudden, massive releases. 

Flevated or Remote Air Intakes Elevated or remote air intakes for control rooms will help in reducing ingress of dense, flammable vapors into those rooms. Ordinarily, elevating the tip of the air intake duct 9 m (30 ft) above the ground is sufficient. Installing flammable vapor detectors in the air intake ducts provides additional protection. Controls that automatically stop air to control rooms if vapor concentrations reach 25 percent of their LFL should also be considered. 

EMEC 1987. Gas and Vapor Detectors and Analysis Systems. Eoss Prevention Data Sheet No.5-49. Eactory Mutual Engineering Corporation, Norwood, MA. 

Probable causes of this accident include (1) installation of a fail-open valve instead of a fail-closed valve, (2) lack of vapor detectors, (3) lack of a block installed as a mitigating device, and (4) failure to eliminate ignition sources in this operating region. 

Lewis, N. S., Comparisons between mammalian and artificial olfaction based on arrays of carbon black polymer composite vapor detectors, Acc. Chem. Res. 2004, 37, 663 672... 

In an effort to address the problem of detection of low-metal-content mines, DARPA funded development of new sensor technologies that focused on detection of the single material unique to all landmines—the explosive. The Fido sensor was one of several explosives vapor detectors developed under this program. Unless specified otherwise, the data presented in this section was collected during field tests of this sensor. 

DNT would be present at slightly higher concentrations. Nevertheless, vapor detectors must be extremely sensitive in order to detect these low concentrations of signature compounds. 

Air None. Toxic gas vapor detector tube 0.05 ppm No data EPA1997... 

Laser systems have been applied to spectroscopic studies of expls (Ref 40). A novel expl vapor detector, based on photoacoustic measurements, has been used to characterize absorption coefficients of expl reaction products (Ref 63). Acoustic spectra from underwater TNT explns have also been measured and analyzed with respect to refracted pulse behavior (Ref 15)... 

Quantitative Detection of Vapors from Low Volatility Compounds , USP 3883739 (1975) 105) L. Elias M. Krzymien, Methods of Evaluating the Sensitivity of Explosives Vapor Detectors , Lab Tech Rept LTR-VA, Natl Res Council, Canada (1975) 106) T. Kraziejko,... 

P.A. Pella, Generator for Producing Trace Vapor Concentrations of TNT, 2,4-DNT and EGDN for Calibrating Explosive Vapor Detectors , AnalChem 48, 1632-37 (1976)... 

Microsensor Vapor Detectors Based on Coating Films of Phthalocyanine and Several of Its Metal Complexes... 

Safety features are essential to a microwave apparatus. An exhaust fan draws the air from the oven to a solvent vapor detector. Should solvent vapors be detected, the magnetron is shut off automatically while the fan keeps running. Each vessel has a rupture membrane that breaks if the pressure in the vessel exceeds the preset limit. In the case of a membrane rupture, solvent vapor escapes into an expansion chamber, which is connected to the vessels through vent tubing. To prevent excessive pressure buildup, some manufacturer use resealable vessels. A spring device allows the vessel to open and close quickly, releasing the excess pressure. 

G. A. Sotzing, J. N. Phend, R. H. Grubbs, and N. S. Lewis, Highly sensitive detection and discrimination of biogenic amines utilizing arrays of polyaniline/ carbon black composite vapor detectors , Chemistry of Materials 12, 593 (2000). 

R.F. Wernlund, M.J. Cohen and R.C. Kindel, The ion mobility spectrometer as an explosive or taggant vapor detector. Proceedings of the New Concept Symposium and Workshop on Detection Identification of Explosives, Reston, VA, USA, October/November 1978, pp. 185-189. 

At PPG Industries in Lake Charles, Louisiana, numerous instrument loops provide critical safety, alarm, and shutdown functions. These protective instruments are located on reactors, oil heaters, incinerators, cracking furnaces, compressors, steam-heated vaporizers, kettles, distillation columns, boilers, turbines, and other critical equipment. Process analyzers and flammable vapor detectors also enhance the overall process safety environment. [8]... 

Class 1 safety instrumentation loops include alarms and trips on storage tanks containing flammable or toxic liquids, devices to control high temperature and high pressure on exothermic-reaction vessels, and control mechanisms for low-flow, high-temperature fluids on fired heaters. Other Class 1 instruments include alarms that warn of flame failure on fired heaters, and vapor detectors for emergency valve isolation and sprinkler-system activation. All of these alarms, shutdown valves, and other critical instruments are regularly proof-tested to a well-defined schedule. 

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