Spray stresses

Fluidized-bed reactor systems put other unique stresses on the VPO catalyst system. The mixing action inside the reactor creates an environment that is too harsh for the mechanical strength of a vanadium phosphoms oxide catalyst, and thus requires that the catalyst be attrition resistant (121,140,141). To achieve this goal, vanadium phosphoms oxide is usually spray dried with coUoidal siUca [7631-86-9] or polysiUcic acid [1343-98-2]. Vanadium phosphoms oxide catalysts made with coUoidal sUica are reported to have a loss of selectivity, while no loss in selectivity is reported for catalysts spray dried with polysUicic acid (140). 

Curl Control. Many grades of paper tend to cud, especially as humidity varies, because of the stresses produced duting the dryiag process. This is especially troublesome when only one side of the paper receives a surface treatment. Judicious appHcation of water to the opposite side of the dry sheet followed by redryiag may correct the curling. Water may be appHed by surface appHcation at the size press, water box, or calender stack or it may be sprayed on. Small amounts of water can be appHed to the paper surface as a foam with exceUent results. 

Quenching. After solution treatment, the product is generally cooled to room temperature at such a rate to retain essentially all of the solute in solution. The central portions of thicker products caimot be cooled at a sufficient rate to prevent extensive precipitation in some alloys. Moreover, some forgings and castings are dehberately cooled slowly to minimize distortion and residual stress produced by differential cooling in different portions of the products. Cold water, either by immersion or by sprays, is the most commonly used cooling medium. Hot water or a solution of a polymer in cold water is used when the highest rates are not desired. Dilute Al—Mg—Si and Al—Mg—Zn extmsions can be effectively solution heat treated by the extmsion process therefore, they may be quenched at the extmsion press by either air or water. 

In the tidal zone and the spray zone (known as the splash zone), cathodic protection is generally not very effective. Here thick coatings or sheathing with corrosion-resistance materials (e.g., based on NiCu) are necessary to prevent corrosion attack [4]. The coatings are severely mechanically stressed and must be so formed that repair is possible even under spray conditions. Their stability against cathodic polarization (see Section 17.2), marine growths, UV rays and seawater must be ensured [4,5]. 

APAOs has limited their utility in a number of applications. The broad MWD produces poor machining and spraying, and the low cohesive strength causes bond failures at temperatures well below the softening point when minimal stress is applied. To address these deficiencies, metallocene-polymerized materials have been developed [17,18]. These materials have much narrower MWDs than Ziegler-Natta polymerized materials and a more uniform comonomer distribution (see Table 3). Materials available commercially to date are better suited to compete with conventional EVA and EnBA polymers, against which their potential benefits have yet to be realized in practice. 

Material Density (g/cm 1 Coating weight (kg/m ) 0-025 mm thickness Brinell hardness Ratio of contraction stresses in sprayed deposits 0-51 mm thick Compressive strength (stress to collapse) (MN/m )... 

Carter, V. E. and Campbell, H. S., Protecting Strong Aluminium Alloys Against Stress Corror sion with Sprayed Metal , British Corrosion Journal, 4, No. 1, 15-20, Jan. (I%9) and 4 No. 4, 1%-198, July (1%9)... 

Fusion bonded epoxy AWWA/ANSI C213 BS 3900 Electrostatic spray in factory and for joints in field 0-3-0-65 Higher temperature iimitations and superior soii stress resistance compared with enamels. Requires careful handling in the field. Quality of pipe steel important. 

Fig. 2-54 Tensile test bars of two different plastics under the same stress were sprayed with acetone. The top one cracked quickly, but the other did not fail.

Patients prescribed intranasal steroids should be instructed to shake the product gently before each use and prime the pump before the first use or if not used for more than 1 week. Clear nasal passages before use, and avoid nose blowing for 10 to 15 minutes after use. Rare cases of septal perforation have been reported therefore, administration of the spray away from the septum should be stressed. Effects are not immediate, and regular use is... 

Forced air, water mist, or water spray cool the mold after it leaves the oven. Once the mold [. cools sufficiently for the polymer inside to solidify, it is opened. The cooling time must take. into account the resin, the wall thicknesses, and the metal from which the mold is fabricated, ff.. Very rapid cooling of the mold can introduce stresses that can weaken or distort the final part. 

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