Governing Thickness

When components are joined by welding, the thickness to be used in applying the heat treatment provisions should be that of the thieker component measured at the joint, except as follows. 

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Governing thickness nsed to determine impact testing requirements shall be the greater of the following ... 

Impact testing is not required for parts with a governing thickness of 25 mm (1 in) or less. 

The governing thickness for heads is based on that portion of the head which is in tension. For a 2 1 S.E. head this is the crown position where R = 0.90. 

The governing thickness of flat heads and blind flanges is 1/4 of actual thickness. 

Solution (Wet) Spinning. In the most widely used solution spinnerette system (60) the spinnerette consists of two concentric capillaries, the outer capillary having a diameter of approximately 400 ]Am and the central capillary having an outer diameter of approximately 200 ]lni and an inner diameter of 100 ]lni. Polymer solution is forced through the outer capillary while air or Hquid is forced through the inner one. The rate at which the core fluid is injected into the fibers relative to the flow of polymer solution governs the ultimate wall thickness of the fiber. Figure 19 shows a cross section of this type of spinnerette. 

Although microporous membranes are a topic of research interest, all current commercial gas separations are based on the fourth type of mechanism shown in Figure 36, namely diffusion through dense polymer films. Gas transport through dense polymer membranes is governed by equation 8 where is the flux of component /,andare the partial pressure of the component i on either side of the membrane, /is the membrane thickness, and is a constant called the membrane permeability, which is a measure of the membrane s ability to permeate gas. The ability of a membrane to separate two gases, i and is the ratio of their permeabilities,a, called the membrane selectivity (eq. 9). 

The most important design dimensions of a thickener are pool area and depth. The pool area is chosen to be the largest of the three layer requirements. In most cases, only the zone-settling and compression layer requirements need to be considered. However, if the clarity of the overflow is critical, the clarification zone may need the largest area. As to the pool depth, only the compression layer has a depth requirement because the concentration of the soHds in the underflow is largely deterrnined by the time detention and sometimes by the static pressure. Thickness of the other two layers is governed only by practical considerations. 

The frequency response or switching speed of the bipolar transistor is governed by the same processes which control the speed of thep—n junction, the capacitance associated with the movement of charge into and out of the depletion regions. To achieve high frequencies the dimensions of the active areas and parasitic circuit elements must be reduced. The two critical dimensions are the width of the emitter contact and the base thickness, W. The cutoff frequency,, is the frequency at which = 57 / - b /t > where is the emitter-to-coUector delay time and is the sum of the emitter... 

If expression is effective, it reduces the permeabiHty of the cake being compacted and, as a consequence, the resistance to flow of the Hquid increases considerably (27). The effectiveness of expression is governed by cake thickness, specific resistance, consoHdation properties, and shear forces. 

Example The equation governing chemical reaction in a porous catalyst in plane geometry of thickness L is... 

This subsec tion includes rules governing weided-joint designs and the degree of radiography, with efficiencies for welded joints specified as functions of the quahty of joint. These efficiencies are used in the formulas in Subsec. A for determining vessel thicknesses. 

For many particles, the diffuse-charge layer can be characterized adequately by the value of the zeta potential. For a spherical particle of radius / o which is large compared with the thickness of the diffuse-charge layer, an electric field uniform at a distance from the particle will produce a tangential electric field which varies with position on the particle. Laplace s equation [Eq. (22-22)] governs the distribution... 

It has been also shown that when a thin polymer film is directly coated onto a substrate with a low modulus ( < 10 MPa), if the contact radius to layer thickness ratio is large (afh> 20), the surface layer will make a negligible contribution to the stiffness of the system and the layered solid system acts as a homogeneous half-space of substrate material while the surface and interfacial properties are governed by those of the layer [32,33]. The extension of the JKR theory to such layered bodies has two important implications. Firstly, hard and opaque materials can be coated on soft and clear substrates which deform more readily by small surface forces. Secondly, viscoelastic materials can be coated on soft elastic substrates, thereby reducing their time-dependent effects. 

Volume 1, Chapter 9 explains the criteria for choosing a diameter and wall thickness of pipe. This procedure can be applied to choosing a coil diameter in an indirect fired heater. Erosional flow criteria will almost always govern in choosing the diameter. Sometimes it is necessary to check for pressure drop in the coil. Typically, pressure drop will not be important since the whole purpose of the line heater is to allow a large pressure drop that must be taken. The allowable erosional velocity is ffiven bv ... 

The various items of equipment in the production facility are connected hy valves, fittings, and piping to enable and control flow from one piece of equipment to another. Chapter 9 of Volume 1 discusses factors governing the choice of line size and wall thickness. This chapter describes the various types of valves and fittings commonly used in production facilities and presents some common piping details and specifications. 

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