Narrow-faced flanges

Narrow-faced flanges, Figure 13.34b, c, d where the face contact area is located within the circle of bolts. 

The raised face, narrow-faced, flange shown in Figure 13.34 is probably the most commonly used type of flange for process equipment. 

The standard includes nominal values (flange diameters) of between 25 and 160 mm. A considerable differentiating feature of the various types is the width of the positioning face. Whereas types A, C, and E have a narrow positioning face, B, D, and F have wide ones. The most common type is A according to ISO 12164 type E was specially developed for high-speed cutting (Fig. 3). 

Hoods can have plain openings of a round or square pipe. Hoods may have flanges around their edges, have very narrow slots, and enclose a process. Some hoods form a canopy over a tank or process. For most, the air velocity at some distance in front of the hood is a function of the shape and air flow. Table 25-2 lists properties of various hood types. Slots (small aspect ratio openings) help to distribute uniformly the velocity of air in front of a larger hood face. The face velocity is the air velocity at the hood opening. 

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