Nozzles classification

Appendix 4 gives definitions and rules for stress analysis for shells, flat and formed heads, and tube sheets, layered vessels, and nozzles including discontinuity stresses. Of particular importance are Table 4-120.1, Classification of Stresses for Some Typical Cases, and Fig. 4-130.1, Stress Categories and Limits of Stress Intensity. These are veiy useful in that they clarify a number of paragraphs and simphfy stress analysis. 

Rheological Classification of Drilling Fluids 829. Flow Regimes 830. Principle of Additive Pressures 834. Friction Pressure Loss Calculations 836. Pressure Loss Through Bit Nozzles 839. 

Figure 4-163 shows a steel body PDC bit with standard-size cutters lightly set on a deep inner cone profile. This bit has changeable nozzles and is best described as having a ribbed flow pattern although there are open face characteristics near the center and bladed characteristics near the gage. The lADC classification code in this case is S 7 4 4. 

Centrifuges are used for the classification of particles in size ranges below 10 /im. Two types are used solid bowl centrifuges, usually with a cylindrical, conical bowl, rotated about a horizontal axis and nozzle bowl machines, fitted with discs. 

For steady injection of a liquid through a single nozzle with circular orifice into a quiescent gas (air), the mechanisms of jet breakup are typically classified into four primary regimes (Fig. 3 2)[4°][41][22°][227] according to the relative importance of inertial, surface tension, viscous, and aerodynamic forces. The most commonly quoted criteria for the classification are perhaps those proposed by Ohnesorge)40] Each regime is characterized by the magnitudes of the Reynolds number ReL and a dimensionless number Z ... 

Because of the particle-wall and particle-classifier impacts, one drawback of this type of mill is the potential for buildup of compressed product in the mill or on the classifier. This can affect milled particle size by changing the open volume in the mill or open area in the classifier, especially if classifier vanes or gas nozzles become plugged or blocked. Buildup at the exit of the mill or in the classifier typically results in a gradual increase in the average-milled particle size over time owing to reduced classification efficiency. Specifically,... 

Most such mills are variations on one of the fundamental configurations depicted in Fig. 21-71. The designs differ from each other by the arrangement of the nozzles and the classification section. In the following paragraphs the jet mill types are briefly discussed. 

Coldstream Process [11.7] (see the flow sheet Fig. 11.5). This process is a mechanical comminution and employs air blasts to accelerate particles against a target with sufficient energy to cause fracture (particle velocities near Mach 2). The air is cooled by expansion from the nozzles, protecting the scrap from oxidation. After screening or air classification, oversize material is recycled. 

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