Sintered metal elements

In addition to using an arrester element with greater flow capacity, it is common to use two arresters in parallel where frequent cleaning is required, with one arrester in standby. A three-way valve can be used to allow uninterrupted operation during changeover. Where elements have an intrinsically high pressure drop, suA as sintered metal elements used in acetylene sei vice, multiple parallel elements can be used. 

Decomposition Flame Arresters Above certain minimum pipe diameters, temperatures, and pressures, some gases may propagate decomposition flames in the absence of oxidant. Special in-line arresters have been developed (Fig. 26-27). Both deflagration and detonation flames of acetylene have been arrested by hydrauhc valve arresters, packed beds (which can be additionally water-wetted), and arrays of parallel sintered metal elements. Information on hydraulic and packed-bed arresters can be found in the Compressed Gas Association Pamphlet G1.3, Acetylene Transmission for Chemical Synthesis. Special arresters have also been used for ethylene in 1000- to 1500-psi transmission lines and for ethylene oxide in process units. Since ethylene is not known to detonate in the absence of oxidant, these arresters were designed for in-line deflagration application. 

The apertures in sintered metal elements can be made so small that this arrester is able to quench detonations provided that it has sufficient mechanical strength. Particular care is required to ensure a secure anchorage of the sintered element to prevent leakage around the element caused by the impact of the shockwave (HSE 1980). 

The determination of open porosity (or fluid permeability) as given in ISO Standard 4022 is not expensive, and by this way the permeability of a sintered metal element can be correlated with its effective gap indicating the grade of flameproofness. 

Sintered metal elements as a part of a flameproof enclosure are often used for gas warning detectors for combustible gases. As a cost effective gas sensor, an electrically heated platinum coil covered with a catalyst and as a part of a... 

A proprietary sintered metal arrester was made by the Linde Division of Union Carbide Corporation (now Praxair) for rise in processes handling acetylene, but is no longer made by Praxair (Dickerman 1999). A sintered metal flashback flame arrester for rise on an acetylene cylinder is made by Western Enterprises of Westlake, OH. Figure 5-4c shows a sintered metal flame-arresting element. 

Flame arresters for acetylene-air mixtures with a flame-arresting element of sintered metal are available from Western Enterprises of Westlake,... 

Static Flame Arrester A flame arrester designed to prevent flame transmission by qnenching gaps (apertnres). These are nsnally dry type flame arresters with elements snch as crimped metal ribbon, parallel plates, wire ganze (mesh), and sintered metal. 

Figure 4-77B. Porous sintered metal filter elements. By permission, Pall Process Filtration Co.

Brake horsepower, centrifugal pumps, 200 Driver horsepower, 201 Burst pressure, 405, 456 Cartridge filters, 274-278 Capture mechanism, 279 Edge filler, 278 Filter media, table, 278 Micron ratings, 277 Reusable elements, 281 Sintered metal, 280 Types, 276, 277, 279 Wound vs. pleated, 276, 277 Centrifugal pumps, operating characteristics, 177-180 Calculations, see hydraulic performance Capacity, 180... 

Most analyzer sampling systems require a filter with at least one wire mesh strainer (100 mesh or finer) to remove larger particles that might cause plugging. Available filter materials include cellulose, which should only be considered if it does not absorb the components of interest. Sintered metallic filters can remove particles as fine as 2 ym, cellulose filters can remove down to 3 /on, and ceramic or porous metallic elements can trap particles of 13 ym or larger. When the solids content is high, two filters can be installed in parallel with isolation valves on each. Motorized self-cleaning filters are also available for such services. 

The necessity to have more than one component in a catalyst arises from many needs those linked to the polyfunctionality often required for the different steps in a reaction, the need to enhance the rate of some reaction steps, inhibition of unwanted side reactions, provision of adequate thermal stability, to take advantage of observed synergetic effects. From a fundamental point of view, the presence of several metal elements in a common structure permits the adjustment of the local electronic properties, imposes well defined coordinations, limits the extent of oxidation-reduction phenomena, and may stabilize the whole catalyst by retarding sintering. Mixed oxide catalysts are used as such, or as precursors of active catalysts, for a whole range of important industrial processes, a representative selection of which is given in Table 1. 

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