Orifice flanges

ORFM—6, Orifice flanges and plate for Recording Flotv Meter No. 6... 

OTrRFC—1, Orifice flanges and plate used w ith Transmitter for Recording Flow Controller No. 1... 

Decide and show those ancillary instruments needed for the monitoring of the plant operation by the operators and for trouble-shooting and plant development. It is well worthwhile including additional connections for instruments which may be needed for future trouble-shooting and development, even if the instruments are not installed permanently. This would include extra thermowells, pressure tappings, orifice flanges, and extra sample points. 

The standard method of measuring flows in a process plant is by use of the orifice plate and orifice flanges, shown in Fig. 6.7. Actually, we rarely measure flows directly. More commonly, we measure the pressure drop across an orifice plate. This pressure drop is due to the increase in kinetic energy of a fluid as it accelerates through the small hole in the orifice plate. The energy to provide the increased velocity comes from the pressure of the flowing fluid, in accordance with the following ... 

Look at the tab sticking out of the orifice flanges (see Fig. 6.7). If the orifice plate is installed in the correct direction, there will be a number stamped onto the tab, toward the flow. This is the orifice plate hole diameter for example, if you see 0.374 stamped on the tab, the orifice hole diameter should be 0.374 in. 

The reason the orifice flanges are kept close to the orifice plate is that when the liquid velocity decreases, downstream of the orifice plate, the pressure of the liquid goes partly back up. Figure 6.8 illustrates this point. It is called pressure recovery. Whenever the velocity of a flowing fluid (vapor or liquid) decreases, its pressure goes partly back up. An extreme example of this is water hammer. The reason the pressure at the end of the pipe in Fig. 6.8 is lower than at the inlet to the pipe is due to frictional losses. 

Orifice Flange Matl Drill If Stam awfiy—Rotnrv ... 

One should note that Fig. 6.1 displays how any pipe experiment can be set up to find this unknown / factor. The hL value is experimentally determined by taking readings of v and P The P value is directly read as shown, by reading the liquid column heights. The velocity, however, must be read by adding a venturi tube or orifice flange to Fig. 6.1 for the velocity reading. 

Pneumatic valve Manual valve Pressure regulator valve I I Orifice flange M Retention valve Z Filter... 

Figure 5.20 shows the orifice (discharge) coefficient as a function of the orifice Reynolds number ( Rerf) and p = d D. There are a variety of standard orifice plate and pressure tap designs (e.g., Miller, 1983). The ASME specifications for the most common concentric square-edged orifices are shown in Figure 5.21. The various pressure tap locations are illustrated in Figure 5.22. Radius taps, for which the location is scaled to the pipe diameter, are the most reliable. Comer taps and flange taps are the most convenient, as they can be installed in the orifice flange and so do not require...

A flashing liquid must have enough static head to offset the line friction loss and the total loss through an orifice. When the process includes flashing liquids, the vessel from which the liquid is being drawn and the orifice flange itself must be given a definite elevation or a relative elevation. 

The elevation of a line can also be influenced by valves and instruments in the line. Often a more convenient access platform can be provided for valves arranged in the top yard bank. The preferred location of lines Avith orifice runs is near the edge of the yard with orifice flanges near a yard column, for more convenient portable ladder access. 

FOR HEAVIER FLANGES (OVER 400 LAs), ORIFICE FLANGES, ANCHORS OR SPECIAL EOUlPliENT IN THE LINES SPACING SHOULD BE miVlOUAUy CALCUUTED. 

If an orifice flange is not available for this purpose, the regular pipe welding neck flange can be drilled, bored and taped as shown in Figure 7-90 providing the flange is at least 1-1/8-inch thick — preferably thicker. 

Figure 7-90. Orifice flange adapted for installing a T/C well and assembly.

Other standard types such as reducing flanges, socket-welding flanges, orifice flanges, and nonstandard flanges are also available for certain rating. ... 

Orifice flanges need not be accessible from grade or a platform but should be positioned at a location and elevation that can be reached by a portable ladder. Care must be taken at horizontal banks of lines to allow for adequate space for side-oriented taps and, when required, close-coupled transmitters. liqjend-ing on service, orifice flanges can be mounted in the vertical and horizontal seaions of piping, as shown in Exhibit 14-21, or with specific upstream and downstream dimensional requirements, as shown in Exhibit 14-22. For less common flow instruments (e.g., Pitot tubes and Annubars), advice from the instrument engineer is necessary for location and dimensional requirements. 

Medium Orifice Flanges Venturi Tubes Location EXHIBIT 14-22... 

The reason the orifice flanges are kept close to the orifice plate is that when the liquid velocity decreases downstream of the orifice plate, the pressure of the liquid goes partly back up. Figure 10.8... 

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