Zones tests


The tests have been able to display the stresses distribution on the vessel surface (shell and heads) as well as characterize the most relevant zones for structural controls (weldings and so on).  [c.408]

In time, submicrometer particles will coagulate into chains or agglomerates through Brownian motion. Increasing turbulence during coagulation will increase the frequency of coUisions and coagulation rate. The addition of fans to stir the gas, or gas flow motion through tortuous passages such as those of a packed bed, will aid coagulation. Sonic energy is also known as an aid to the coagulation process. Production of standing waves in the confines of long narrow tubes can bring about concentration and coagulation of aerosols in band zones in the tube. The addition of water and oil mists to the treated aerosol can improve the effectiveness of sonic agglomeration by improving the tendency of the colliding particles to stick together. Sulfuric acid mist (302) and carbon black (303) have been sufficiently agglomerated so that the coagulated product can be collected in a cyclone. Sonic agglomeration has been tested in the past for many metallurgical fumes, but has generally been found too power intensive for practical consideration. One problem is the low energy efficiency of transforming other energy sources to sonic energy in available sonic generators. The development of more energy efficient sonic generators, coupled with improved knowledge of the phenomenon of sonic coagulation, might justify further investigation. The combination of sonic agglomeration and electrostatic precipitation could result in considerable reduction of precipitator size and perhaps capital cost (304). Coagulation techniques have been discussed in mathematical terms in references 272 and 276.  [c.411]

Electric current conduction tests, in which current is introduced into test materials by direct electric contacts and potential drops are measured across specific zones of the test surface using additional contact electrodes, are used to measure effects of corrosion wall-thinning, as in petroleum product storage tank roofs, or to detect cracks in welds, metallic sheets and plate, and railroad rails (1,6). Modifications of such systems measure the resultant magnetic field distributions created by the current conduction, as for Hall effect semiconductor devices, moving pick-up coils, and even by thermal effects resulting from resistance heating within the test materials (1). Difficulties in applying direct electric contact testing include the possibiHty of sparks or bums created by passing high current through poor electrode contact areas, and the thermoelectric and triboelectric effects that may produce false signal voltages owing to short-circuit paths that the current may find through touching crack surfaces. Alternatively, thermoelectric or triboelectric voltage signals can be used to identify and sort metals and alloys where surface contamination effects do not interfere.  [c.131]

Combined aerobic—anaerobic systems use sequenced aerobic and anaerobic conditions to degrade compounds that ate resistant to aerobic biodegradation. Ground water passes through the anaerobic zone first which partially degrades the resistant compounds. These degradation products are then further degraded in an aerobic zone. A two-zone, plume interception approach was tested under the U.S. EPA s Superfund Iimovative Technology Evaluation (SITE) Emerging Technologies Program to degrade chlorinated compounds (17). The first zone was anaerobic where methanogenic (methane producing) microorganisms were expected to promote reductive dechlorination of chlorinated solvents. The second zone was aerobic where the partially dechlorinated products were to be biodegraded. Combined systems do not necessarily have to be separate zones in the aquifer. Aerobic and anaerobic conditions can be alternated by eliminating the oxygen source at timed intervals.  [c.170]

For the safety of these circuits, therefore, the main consideration is defined by the level of this energy, which should always be less than that required to ignite explosive gases, chemical vapour or volatile liquids in the surrounding atmosphere, Accordingly, minimum safe ignition currents (MICs) have been established by labo-ratory tests for different control voltages and R, L, and C of the circuit, attd are the basis of testing ihe circuits of these devices and instruments tt such locations to determine their compliance for safe installation. Since such circuits would be required for other zones and groups of gases also with differetit limiting temperatures, lEC 60079-11 would also apply to all such zones and groups of gases. The test requirements, however, would vary for different locations, as stipulated.  [c.183]

Adsorption on granular activated carbon is a diffusion process consisting of the following steps (1) bulk diffusion of the adsorbate from the liquid to the film around the carbon particle (2) diffusion through the film and (3) internal pore diffusion to the adsorption sites. In multicomponent systems there is the added step of competition for site results in displacement of previously adsorbed, but less strongly held, components. Ideally, it would be desirable to be able to mathematically model the carbon performance from the equilibrium data. In studies used to develop models, one or more of the following elements is usually present in the study or assumed in the model uniform carbon particle size, ideal isotherm, dilute solutions,, single component, adsorbate molecule was too large to enter any pore, so there was no pore diffusion, thus film diffusion was controlling, the flow rate was high so pore diffusion was controlling, comparisons of predicted versus actual data were made on the early part of the breakthrough curve before the carbon was saturated, and/or systems with relatively short mass-transfer zones (MTZ) were studied. There is no model presently avaUable that can be used universally. Until such time as one is developed, it will be necessary to test each liquid in a dynamic system and use empirical methods to design the plant-scale units. Generally, the tests can be controlled better in the laboratory as opposed to in-plant testing. However, tests should be conducted in the plant if any of the following conditions exist the liquid to be treated would deteriorate or change in characteristics during  [c.306]

Solids concentration varies over the thickener s height, and at the lower levels where the solution is dense, settling becomes retarded. In this region the upward fluid velocity can exceed the particle settling velocity irrespective of whether this condition exists in the upper zone or not. Figure 17 illustrates this situation, where curve II denotes a higher feed rate. A proper design must therefore be based on an evaluation of the settling rates at different concentrations as compared to the vertical velocity of the fluid. If the feed rate exceeds the maximum of the design, particulates are unable to settle out of the normal clarification zone. Hence, there is an increase in the solids concentration, resulting in hindered settling. The result is a corresponding decrease in the sedimentation rate below that observed for the feed sluny. The feed rate corresponding to the condition of just failing to initiate hindered settling represents the limiting clarification capacity of the system. That is, it is the maximum feed rate at which the suspended solids can attain the compression zone. The proper cross-sectional area can be estimated from calculations for different concentrations and checked by batch sedimentation tests on slurries of increasing concentrations. You will find some problems in the section on Questions for Thinking and Discussing that illustrate the need to check the thickener s calculated area against concentrations at various points in the vessel (including both the clarification and thickening zones). Figure 18 shows the effect of varying the underflow rate on the thickening capacity. In this example, the depth of the thickening zone (compression zone) increases as the underflow rate decreases hence, the underflow solids concentration increases, based on a constant rate of feed.  [c.302]

Note The reagent can be employed on silica gel and cellulose layers. The coloration of the stained chromatogram zones is dependent on the temperature and duration of heating. For instance, cholesterol appears bluish-pink after heating to 75 — 80 °C for 3 —5 min [1], but yellow to brown-colored after heating for 20 — 30 min (cf. Procedure Tested ).  [c.386]

Allow the plant to run automatically for a period of some days either with no artificial load or with a small one of fixed value. If no means of recording are built into the plant then recorders should be introduced and placed in representative positions in the various zones for the duration of the tests. Periodically examine the traces or monitor printouts. These will give an indication as to whether the plant is controlling correctly on light load.  [c.453]

In the case of corrosion tests in the sea or in other large volumes of water, i.e. as opposed to tests in waters flowing within pipes, all the specimens to be compared should be suspended at the same depth or should pass through the same range of depths. Isolated specimens exposed at different depths will not be corroded in the same way as continuous specimens that extend through the total range of depth to be studied. This is especially the case with specimens exposed to sea-water from above high tide to below low tide. Where the behaviour of structures, such as piling, that pass through these zones is to be investigated, the test specimens must be continuous and large enough to extend through the total range in order to take into account differential aeration and other possible concentration cells that may have such a tremendous effect on the results secured . For example, in sea-water exposure, isolated specimens of steel exposed in the tidal zone have corroded 10 times as fast as portions of continuous specimens of the same steel in the same zone that extended also below low-tide level  [c.1075]

Superior. The Superior retort is different from all the other AGR processes in that it consists of a slowly rotating circular grate instead of the vertical shafts, rotating dmms, or screw conveyors used by other technologies (Fig. 8). The Superior technology is an adaptation of the circular grate system used to calcine limestone (see Lime AND LIMESTONE). Raw oil shale is loaded onto the rotating circular grate which transports the sotids through the same zones as shown in Figure 2 sotids preheat, retorting, char combustion, shale cooling, and air preheating. Because the gas composition varies within each of these zones, each zone is separated by a baffle screen as the sotids are transported around the circle. The Superior retort was tested in Colorado in the late 1970s.  [c.350]

The propagation mechanism can be described by considering the blade row to be a cascade of blades as shown in Figure 7-32. A flow perturbation causes blade 2 to reach a stalled condition before the other blades. This stalled blade does not produce a sufficient pressure rise to maintain the flow around it, and an effective flow blockage or a zone of reduced flow develops. This retarded flow diverts the flow around it so that the angle of attack increases on blade 3 and decreases on blade 1. The stall propagates downward relative to the blade row at a rate about half the block speed the diverted flow stalls the blades below the retarded-flow zone and unstalls the blades above it. The retarded flow or stall zone moves from the pressure side to the suction side of each blade in the opposite direction of rotor rotation. The stall zone may cover several blade passages. The relative speed of propagation has been observed from compressor tests to be less than the rotor speed. Observed from an absolute frame of reference, the stall zones appear to be moving in the direction of rotor rotation. The radial extent of the stall zone may vary from just the tip to the whole blade length. Table 7-1 shows the characteristics of rotating stall for single and multistage axial-flow compressors.  [c.309]

Application of the Coe and Clevenger equations tends to underestimate the required thickener area as reported by Scott (1968b). In an alternative approach to using batch settling tests for continuous thickener design, Kynch (1952) presented a graphical method based on the concentrations and fluxes in the settling zones which Talmage and Fitch (1955) demonstrated to overestimate the required thickener area. The various methods are compared and contrasted by Osborne (1990). In order to extend the range of parameter values from batch settling tests, Font and Laveda (1996) presented an extension of a method using a semi-batch test whereby periodically the supernatant clear liquor is withdrawn and a volume of suspension is added.  [c.87]

Tests on a wide range of alloys at temperatures varying from 704 to 927°C have been made by Bernsen et al." to determine the temperature limits beyond which engineering materials carburise when held in contact with graphite. Table 7.27 lists the maximum penetrations of the carburised zones while nickel in general showed no visible evidence of carburisation the associated hardness measurements indicated solution of carbon even at 704°C. At this temperature the chromium-containing alloys showed little tendency to carburisation, but at 816°C carburisation leading to the formation of chromium carbide was rapid.  [c.1074]

There are numerous quoted examples of intergranular stress-corrosion cracking in tempered martensitic stainless steels " and abundant work relating this to the generation of non-equilibrium solute content profiles at the grain boundaries due to intergranular precipitationThus, for a Super 12Cr-Mo-V stainless steel tested in a boiling 0.01 M NaOH plus 0.1 M NaCl solution, susceptibility was worst when a continuous chromium-depleted concentration profile was produced at the grain boundaries by tempering . Further heat treatment that caused coarsening of the M23Q precipitates generated overlapping diffusion fields that removed the continuous chromium-depletion zones and removed susceptibility to cracking.  [c.1199]

High-frequency experiments do not normally allow enough time for processes more akin to stress-corrosion cracking to appear in corrosion fatigue tests, as made clear in the previous sections on carbon and low-alloy steels. Some evidence that stress corrosion can occur during corrosion fatigue crack growth in stainless steels has been observed in tests at 3 Hz on austenitic stainless steel (type 304) in various halide solutions at ambient temperature where plateaux or periods of constant crack growth rate over specific ranges of were observed. The influence of pure water environments at temperatures up to 300°C is not large, however, in solution-annealed stainless steels . One particular technological problem worthy of special mention concerns environmentally-induced intergranular cracking in type 304 sensitised stainless steels in Boiling Water Reactor environments, typically at 260 to 290°C. Sensitisation of type 304 steel causes chromium depletion at the grain boundaries in the heat-affected zones of type 304 stainless steel pipe welds. A great deal of work has been done to characterise the mechanism of environmental attack. There is little doubt that intergranular cracking in this material is due to selective dissolution of the chromium-depleted zones at the relatively high corrosion potentials achieved in normal oxygenated (200 ppb) BWR coolants. Further, extensive slow strain-rate stress-corrosion tests have shown that the rate of cracking depends on the imposed strain rate. Similarly, in corrosion fatigue tests, intergranular cracking can also be detected provided both the frequency and the applied AA values are low enough. By contrast, no evidence of intergranular cracking is found when  [c.1307]

Stainless steels and Ni-base alloys containing Mo, such as type 3I6L (0-03% C max.) and Hastelloy C, are found to give very high corrosion rates in the HNO3 test even when they are immune to intergranular attack when subjected to other tests that reveal sensitisation due to chromium-depleted zones furthermore, such alloys even after being subjected to a sensitising heat-treatment do not give rise to intergranular attack in most conditions of service. This high corrosion rate is considered to be due to the formation of a submicroscopic a-phase, and although positive proof is not available its presence is substantiated by the fact that the phase becomes identifiable after longer periods at the sensitising temperatures, although in this form it has little effect on the corrosion rate. It would appear that the a-phase dissolves rapidly during the HNO, test, and since it has a high chromium content the solution becomes enriched in Cr(vi) with a consequent increase in the corrosion rate of the alloy. It follows that the test is unsuitable for evaluating the behaviour of stainless steels that may precipitate ff-phase, unless the alloy is to be used in service for nitric acid plant.  [c.1035]


See pages that mention the term Zones tests : [c.884]    [c.240]    [c.176]    [c.783]    [c.1035]   
Industrial power engineering and applications handbook (2001) -- [ c.0 ]