Beside still with Flanges Types, Piping & Fabrication also will explain about contact surface finish and I hope all of this articles will be useful to all of us. And with Flange Types and Contact Surface Finish on Pipe System we will continue.
Optional-Type Flanges.
This type covers designs where the attachment of the flange to the nozzle neck or the vessel or pipe wall is such that the assembly is considered to act as a unit, which shall be calculated as an integral flange, except that for simplicity the designer may calculate the construction as a loose-type flange, provided that stipulated load values are not exceeded.
It is important in flange design to select materials and to proportion dimensions of bolts, flanges, and gaskets to ensure that the necessary compression will be maintained on the joint faces over the expected life of the equipment.
Several distinct phases of the problem are involved: (1) type of flange facing, (2) finish of contact surfaces, (3) gasket type and proportions, (4) bolt load required to secure and maintain a tight joint, and (5) proportions of flange needed to support the bolt load.
Types of Flange Facing.
It is important in flange design to select materials and to proportion dimensions of bolts, flanges, and gaskets to ensure that the necessary compression will be maintained on the joint faces over the expected life of the equipment.
Several distinct phases of the problem are involved: (1) type of flange facing, (2) finish of contact surfaces, (3) gasket type and proportions, (4) bolt load required to secure and maintain a tight joint, and (5) proportions of flange needed to support the bolt load.
Types of Flange Facing.
There are numerous types of contact facings for flanges, the simplest of which is the plain face provided with a ‘‘smooth tool finish.’’ Class 125 cast-iron flanged fittings are provided with this type of facing. For steel flanges and fittings, the typical facings (Fig. A2.19) are taken from the American Standard for Steel Pipe Flanges and Flanged Fittings, ASME B16.5 and ASME B16.47. The raised face, the lapped, and the large male-and-female facings have the same dimensions, which provide a relatively large contact area. Where metal gaskets are used with these facings, the gasket area should be reduced to increase the gasket compression.
The flange-facing types illustrated in Fig. A2.19 range in size and contact area in the following order: large tongue-and-groove, small tongue-and-groove, small male-and-female, and ring joint. Because of the small gasket contact area, a tight joint may be secured with the ring-type facing using low bolting loads, thereby resulting in lowered flange stresses (ASME B16.5).
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| FIGURE A2.18 Commonly used flanged joints. (a) Screwed flange to fitting joint, plain face; (b) screwed flange pipe joint, male-and-female face; (c) lapped pipe to fitting joint, square corner; (d) lapped pipe to pipe joint, round corner; (e) ring and groove joint, welding neck flange to fitting; ( f ) lapped pipe to fitting joint, Sarlun seal welded; and (g) lapped pipe to fitting joint, Sargol seal welded |
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| FIGURE A2.19 Typical flange facings (for dimensions, see ASME B16.5) |
The flange-facing types illustrated in Fig. A2.19 range in size and contact area in the following order: large tongue-and-groove, small tongue-and-groove, small male-and-female, and ring joint. Because of the small gasket contact area, a tight joint may be secured with the ring-type facing using low bolting loads, thereby resulting in lowered flange stresses (ASME B16.5).
