Flow, valve type

Bubble caps were used almost exclusively as cross-flow-plate dispersers until about 1950, when they were largely displaced by simple or valve-type perforations. Many varieties of bubble-cap design were used (and therefore are extant in many operating columns), but in most cases bell caps of 75- to 150-mm (3- to 6-in) diameter were utilized. 

For the twin arrangements, a two-way, six-ported, continuous-flow valve will be required. If it is a tapered plug type, a means of lifting the plug will be required. The purpose of the tapered plug valve is to provide... 

Sizing, 451, 453, 455, 459, 462 Sonic flow, 461 Types, illustrations, 411-421 Rupture disk, liquids, 462, 466 Rupture disk/pressure-relief valves combination, 463 Safely relief valve, 400 See Relief valve Safety valve, 400, 434 Safety, vacuum, 343 Scale-up, mixing, 312, 314—316 Design procedure, 316-318 Schedules/summaries Equipment, 30, 31 Lines, 23, 24 Screen particle size, 225 Scrubber, spray, 269, 270 Impingement, 269, 272 Separator applications, liquid particles, 235 Liquid particles, 235 Separator selection, 224, 225 Comparison chart, 230 Efficiency, 231... 

Figure 8.26(A) is an example of a valve type interface [329]. Helium carrier gas is provided to the headspace saiq)ler and is split into two flow paths. One path is flow-controlled and provides a constant flow of carrier gas which passes from the headspace unit through the heated transfer line to the gas chromatograph. The second flow path is pressure-regulated and, in the standby mode, the seunple loop and seuapling needle are flushed continuously by the helium flow. At a time determined by the operator, the sampling needle pierces the septum and helium pressurizes the headspace vial to any desired pressure. The headspace gas is then allowed to vent through the sample loop. Once filled, the sample loop is placed in series with the normal carrier gas flow and its contents are driv Bbhrough the heated...

This equation defines the flow coefficient, Cv. Here, SG is the fluid specific gravity (relative to water), pw is the density of water, and hv is the head loss across the valve. The last form of Eq. (10-29) applies only for units of Q in gpm and hv in ft. Although Eq. (10-29) is similar to the flow equation for flow meters, the flow coefficient Cv is not dimensionless, as are the flow meter discharge coefficient and the loss coefficient (Af), but has dimensions of [L3][L/M]1/2. The value of Cv is thus different for each valve and also varies with the valve opening (or stem travel) for a given valve. Values for the valve Cv are determined by the manufacturer from measurements on each valve type. Because they are not dimensionless, the values will depend upon the specific units used for the quantities in Eq. (10-29). More specifically, the normal engineering (inconsistent) units of Cv are gpm/ (psi)1/2. [If the fluid density were included in Eq. (10-29) instead of SG, the dimensions of Cv would be L2, which follows from the inclusion of the effective valve flow area in the definition of Cv]. The reference fluid for the density is water for liquids and air for gases. 

Hydraulic actuators use fluid displacement to move a piston in a cylinder positioning the valve as needed for 0-100% fluid flow. This type actuator is incorporated when a large amount of force is necessary to operate the valve. 

Check Valve A valve which permits flow of fluid in only one direction. Often a check valve can be nothing more than a spring, ball, and seat separating two openings. Common valve types include in-line check valves and right-angle check valves. 

Two main types of volumetric filler exist. In the first type, a predetermined volume of liquid can be dosed using either a magnetic inductive volumetric flow meter or a mass flow meter. Alternatively, measuring cylinders can be used that incorporate a level probe. The product is fed to a set level in the metering cylinder, at which point the flow valve is closed off from the supply tank. A typical can filler operating at 1,500 cans of 330 ml capacity per minute will fill as per the supply contract within 2.5 ml. However, a standard deviation for a volumetric filler as low as 0.58 ml has been quoted. As with the probe filler, these fillers are fitted with electro-pneumatic valves, enabling accurate control of the... 

Valve Types Types of valves are categorized according to their design style. These styles can be grouped into type of stem motion— linear or rotary. The valve stem is the rod, shaft, or spindle that connects the actuator with the closure member (i.e., a movable part of the valve that is positioned in the flow path to modify the rate of flow). Movement of either type of stem is known as travel. The major categories are described briefly below. 

Fig. 4 a. Valve type A restriction perpendicular to fluid flow... 

For a complete treatment of the many aspects of control valve sizing, refer to the Instrument Engineers Handbook. For some basic equations to calculate the required valve coefficients (C ) for various liquid and gas flow applications using different valve types, refer to Tables 2.66 and 2.67. 

Valve Type Trim Type Flow Direction XT h Fd Fs Cd = Cv/d2 K... 

Valve trays. Figure 6.216 illustrates the dry pressure drop of a typical valve tray as a function of vapor velocity. At low vapor velocities, all valves are closed (i.e., seated on the tray deck). Vapor rises through the crevices between the valves and the tray deck, and friction losses through these crevices constitute the dry pressure drop. Once the closed balance point (CBP) is reached, there is sufficient force in the rising vapor to open some valves. A further increase in vapor velocity opens more valves. Since vapor flow area increases as valves open, pressure drop remains constant until all valves open. This occurs at the open balance point (OBP). Further increases of vapor velocity cause the dry pressure drop to escalate in a similar manner to a sieve tray. When two weights of valves are used in alternate rows on the tray, a similar behavior applies to each valve type. The result is the pressure drop-vapor velocity relationship in Fig. 619e. 

Valve type Typical flow rangeability Stem movement... 

Critical vapor flow A heavy-duty angle valve is suggested for a steam pressure-reducing application. Determine the capacity required and compare an alternate valve type. The fluid is saturated steam flow W is 78,000 lb/h (9.8 kg/s) inlet pressure is 1260 psia (8688 kPa) and outlet pressure 1 2 is 300 psia (2068.5 kPa). 

Choose the valve type and determine its critical-flow factor for the cavitation situation. If... 

Before selecting a valve, the function of each valve type must be considered first. Several valve types, listed in Table 8.1, are used for on-off service, prevention of back flow, and throttling. Figure 8.2 to 8.4 shows only a few examples of valve types. For a discussion of many other valve types see Reference 8.2. 

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