Dry-air purge

An experiment was carried out where a sensor was exposed to H2 over a three-month period. The temporal sequence of the gas stream included a 24-hour dry air purge followed by a 10-minute exposure to 1% H2. Figure 5 shows the long-term test results. The sensor remains fully functional after approximately three months of repeated exposure to H2. This observation, while it does not directly provide a measure of sensor lifetime, is encouraging. 

MASTMAASIS test tind is used for exfoliation testing of aluminum. Annex 2 uses a 5 % sodium chloride solution that has been adjusted to a pH between 2.8 and 3.0 with acetic acid [4], The test cycle is a 6-h cycle of %-h spray, 2-h dry air purge, and 3 -h soak at high humidity. The... 

Spectral measurements in the NIR region are used for spectral analysis of trapped water in samples because water has many close absorption bands at approximately 1900 nm. Ambient moisture bands from the air must be factored out by calculation or by using a dry air purge system during the spectral run. 

A Fourier transform infrared spectrophotometer (Digilab FTS-14 )was used at a resolution of 3 cm throughout the spectral range (3800-450 cm ) and with a dry air purge. Coaddition of 300 scans was a common condition except for the fibers with very little silane. In this case, 600 scans with dry nitrogen purge were used in order to improve the slgnal-to-... 

In the case of heavier-than-air purge gas, there is no buoyancy mechanism causing air entry into the stack, and there is thus no incentive to include a dry seal. Unlike a water seal, a dry seal cannot prevent a flashback from traveling upstream if a combustible mixture has been formed by the entry of air into the safety valve or flare headers. It only protects against internal burning flashback... 

Applications PSA cycles are used primarily for purification of wet gases and of hydrogen. One of the earliest applications was the original Skarstrom two-bed cycle (adsorption, countercurrent blowdown, countercurrent purge, and cocurrent repressurization) to dry air stream to less than 1 ppm H20 [Skarstrom, ibid.]. Instrument-air dryers still use a PSA cycle similar to Skarstrom s with activated alumina or silica gel [Armond, in Townsend, The Properties and Applications of Zeolites, The Chemical Society, London, pp. 92-102 (1980)]. 

Liquid nitrogen cooled, photoconductive FIgCdTe detectors with peak sensitivities between 7 and 12 //m, and detectivities D between 5xl010 to 9xl010 [cm Hz W 1] are suitable. For operation at 6 /an, the instrument needs to be purged with dry air to reduce atmospheric water vib-rotational absorptions. 

This compressed air system had supplied air with undesirable moisture content for a number of years. For several years prior to this incident this small air system was idle. Innovators decided to use compressed, dry air to purge out the moisture and cool down the hot unit after it achieved the appropriate temperature. They first used hoses to connect to a dry air system, and this improvement led to better dew points and longer dryer cycles. The temporary hose system seemed so beneficial that it was replaced with piping. (See Figure 2—20.)... 

The task of purging pipelines for maintenance is almost second-nature to well-experienced operators in this unit. Typically, pipeline clearing is routine and is uneventful. This time, however, the utility dry air system was also being utilized as a source for instrument air in the operating area. Hence, this corrosive material was able to backflow throughout the instrument air system into monitoring and control systems. The backflow created expensive instrument damages. 

Center at Valley Forge, Pa. (9). It was the Library of Congress recommendation for the safety limits of cellulose-type materials which made possible the success of this project and others which have followed. After the St. Louis fire at the Military Records Center, the Library of Congress was again involved in vacuum—air purge drying operations, this time in collaboration with McDonnell Douglas Aircraft Corp. (7). 

Apparatus Use a Fourier transform infrared spectrometer (FTIR), with its associated computer and peripherals, capable of measuring from 4500 to 500 cm-1 and of acquiring data with a resolution of at least 2 cm-1. The optics of the instmment must be sealed and desiccated, or, like the sample chamber, must be under continuous dry air or nitrogen gas purge. The spectrometer is equipped with software capable of multicomponent analysis using the partial least squares method (PLS-1, or equivalent). This software is commercially available as an accessory to the spectrometer or as an external software package. 

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