Monitoring methods Pressure

Inspection for Types of Damage Modes of Deterioration and Failure General Types if Inspection and Surveillance Condition Monitoring Locations Condition Monitoring Methods Pressure Testing... 

This monitoring method should make it possible to decide wether to continue with the pressurization of the vessel or to stop it, based on real-time and reliable detection and location of any potentially hazardous defect which is evolving. 

The evaluation methods could be direct, e.g., measuring a containment index, or indirect, e.g., measuring pressure loss or velocity distribution. The direct methods are used to measure the performance of a hood or an inlet during periodic preventive maintenance. Indirect methods are used for verifying or checking on a daily basis (routine checks). How often each method is used depends on the availability of instrumentation and qualified personnel, since direct measurement of a hood s performance can be both expensive and difficult. On the other hand, indirect methods are usually easier to use and can sometimes include inexpensive, continuously monitoring instruments (pressure gauges or velocity indicators). 

This is the most common test method employed to qualify the leak characteristics of a new seal material. The test method involves applying the seal between two ceramic discs or between a ceramic and a metal disc, pressurizing the cavity formed by the seal and monitoring the pressure decay as a function of time.22 Alternatively, a metal tube and a ceramic disc can also be used [34], Typically, the cavity is pressurized to about 2 psi and the leak rate is determined by the pressure decay as a function of time. These tests can be done at room temperature or elevated temperatures. Similar test arrangement has also been used to test a plastically deformable brazed metal seal between fuel cell anode material and Haynes 214 washer [35], The cavity is pressurized to measure the rupture strength of the seal material. 

Other premeasured volume methods deliver a volume (or mass) by controlling the pressure and time of the delivery. Pressure is used to fill the container for higher viscosity products. Product is pumped under pressure through a filling valve and then via a product mbe transferred into the container. A sensing air mbe is built into the product mbe to monitor air pressure in the container. Low-pressure air... 

Application of SLMs provides a way to circumvent the equihbrium hmitations of other separation processes. Stabihty of SLM is, however, a major issue during operation. This results from the displacement of the membrane phase from the support pores due to osmotic pressure [138]. Nondestructive monitoring methods based on impedance spectroscopy have been reported for the monitoring of the carrier and/or diluent losses from the LM [139]. Ho and Wang [138] studied the apphcation of several alkylated phenylphosphonic acids as carrier for the removal of Sr and Sr from simulated groundwater. They also reported on a system that allowed for the stabilization of the SLM against leaking of the membrane phase from the pores due to osmotic pressure, that is, the so-called SLM with strip dispersion. 

The design and construction of high pressure containers or cells depend on the monitoring method and whether the reaction may be classified as conventional in its time range or is a fast reaction. The division between the two is not defined and in... 

Application of the hydrostatic pressure variable in a multitude of reaction kinetics studies leading to the volume of activation has been clearly demonstrated to be of inestimable value in mechanistic studies of organometallic chemistry reactions. Its relative simplicity of definition and precision of typical experimental values render the volume of activation to be of far superior mechanistic value than is the entropy of activation. The selection of reports described, a truly eclectic collection, illustrates that reactions of a wide range of metal-centred reactions have benefitted mechanistically from elevated pressure kinetics studies. Indeed in many cases the volume of activation adds that extra dimension to mechanistic elucidation. The breadth of techniques and variety of reaction monitoring methods described have added broader scope, interest and depth to this account. 

Pressure decay systems normally operate to a specified pressure (usually within the pack) which is then monitored for pressure drop. Leaks down to 10 3 cm3/s can be detected. There is also a pressure increase method where leakage from a pack under vacuum can be detected as a positive pressure change (assuming an excellent vacuum chamber seal is achieved). 

The flash filament experiment as first described by Becker and Hartman (14) has since been used extensively in studies of the adsorption of gases onto refractory metals, particularly in association with other techniques. The basic method is to allow gas introduced at a known input rate to adsorb for a measured time onto a previously cleaned wire or ribbon. The gas is then desorbed by heating the sample, and the resulting pressure bursts monitored. The pressure versus time curve is referred to as a desorption spectrum, as illustrated in Fig. 4 and 5. Sticking probabilities can then be obtained from the relative adsorption times and desorption quantities. Methods of analysis of these desorption spectra (15, 16) and of the variation in thermal resolution by different heating schedules such as linear or reciprocal increase in temperature with time, have been discussed extensively by a number of authors... 

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