Orifice Flanges ( Class 300 Orifice Flanges )
Orifice flanges are widely used in conjunction with orifice meters for measuring the rate of flow of liquids and gases. They are basically the same as standard welding neck, slip-on and screwed flanges except for the provision of radial, tapped holes in the flange ring for meter connections and additional bolts to act as jack screws to facilitate separating the flanges for inspection or replacement of the orifice plate. Welding neck flanges: the welding neck flange is normally referred to as the "high hup" flange. It is designed to transfer stresses to the pipe, thereby reducing high stress concentrations at the base of the flange. The welding neck flange is the best designed butt-welded flange of those currently available because of its inherent structural value. It is expensive because of the design. Slip-on flanges: the slip-on flange has a low hub because the pipe slips into the flange prior to welding. It is welded both inside and out to provide sufficient strength and prevent leakage. Slip-on flanges are all bored slightly larger than the O.D. of the matching pipe. They are preferred over welding neck flanges by many users due to their lower initial cost, but final installation cost is probably not much less than that of the welding neck flange because of the additional welding involved. Threaded (screwed flanges): the threaded flange is similar to the slip-on flange, but the bore is threaded. Its chief merit is that it can be assembled without welding, explaining its use in low pressure services at ordinary atmospheric temperatures, and in highly explosive areas where welding create a hazard
- Jack screw provision:
- Each flange shall have a machine bolt mounted in a hole drilled on the flange centerline at 90deg. from the pressure taps, for use as jackscrew. Machine bolt shall be regular, with one heavy hex. Nut.
- A slot shall be provided in the flange 0.06in. (1.6mm) wider than the width across flats of the nut. The depth of the slot shall admit the nut so that there is no interference with the joining of the flanges when bolted together without orifice plate.
- Pressure taps:
- Each orifice flange is provided with two pressure tap holes extending radically from the outside diameter of the flange to the inside diameter of the flange.
- The 0.94in. (23.8mm) locating dimension for raised face and 0.75in. (19.1mm) for ring joint shall be measured at the bore.
- Each pressure tap hole shall be equipped with a pipe plug.
- Facing: the finish of facing shall be in accordance with MSS standard practice SP-6, finishes for contact face of connecting-end flanges of ferrous values and fittings.
- Flange threads:
- Threaded flanges shall have an American National Standard taper pipe thread conforming to ANSI B2.1.
- The thread shall be concentric with the axis of the flange and variations in alignment shall not exceed 0.06in. (1.6mm) per foot.
- The flanges are made with counter-bores at the back of the threads shall be chamfered to the diameter of the counter-bore at an angle of approximately 45 degrees with the axis of the thread to afford easy entrance in making a joint. The chamfer shall be concentric with the thread.
- In order to permit the pipe to be inserted to the face of the flange, the threads should have full root diameters through to the face of the flange, or shall have a counter-bore at the face of the flange.
- The gagging notch of the working gage shall come flush with the bottom of the chamfer in all threaded flanges and shall be considered as being the interaction of the chamfer cone and the pitch come of the thread. This depth of chamfer is approximately equal to 1/2 of the pitch of the thread.
- The maximum allowable thread variation is one turn large or small from the gagging notch.
- Tolerances: tolerances on all dimensions shall be as shown in ANSI B16.5 except for those shown below:
- Tolerance on location of center of pressure tap hole 2 from flange face shall be: Flanges smaller than nominal sizes 4 +/- 0.02in.(0.5mm); Flanges nominal size 4 and larger +/- 0.03in.(0.8mm).
- Bore diameter tolerance (welding neck flanges only) is +/-0.5% of nominal value.
| Nominal pipe size (mm) | Outside diam. of flange / D (mm) | Thickness of flange (t) / raised face (mm) | Diam. of hub at base / X (mm) | Diam. of raised face / G (mm) | Diam. of hub at bevel / A (mm) | Length thru hub (T) / welding neck / raised face (mm) | Length thru hub (T) / slip-on & threaded / raised face (mm) | Bore (B) / welding neck (mm) | Bore (B) / slip-on (mm) |
|---|---|---|---|---|---|---|---|---|---|
| 1 | 124 | 38.1 | 53.8 | 50.8 | 33.5 | 82.6 | 47.8 | 26.7 | 34.5 |
| 1-1/4 | 133 | 38.1 | 63.5 | 63.5 | 42.2 | 84.1 | 46.0 | 35.1 | 43.2 |
| 1-1/2 | 155 | 38.1 | 69.9 | 73.2 | 48.3 | 85.9 | 47.8 | 40.9 | 49.5 |
| 2 | 165 | 38.1 | 84.1 | 91.9 | 60.5 | 85.9 | 49.3 | 52.6 | 62.0 |
| 2-1/2 | 191 | 38.1 | 100.1 | 104.6 | 73.2 | 88.9 | 50.8 | 62.7 | 74.7 |
| 3 | 210 | 38.1 | 117.3 | 127.0 | 88.9 | 88.9 | 52.3 | 78.0 | 90.7 |
| 4 | 254 | 38.1 | 146.1 | 157.2 | 114.3 | 91.9 | 53.8 | 102.4 | 116.1 |
| 5 | 279 | 38.1 | 177.8 | 185.7 | 141.2 | 101.6 | 53.8 | 128.3 | 143.8 |
| 6 | 318 | 38.1 | 206.2 | 215.9 | 168.4 | 100.1 | 53.8 | 154.2 | 170.7 |
| 8 | 381 | 41.1 | 260.4 | 269.7 | 219.2 | 111.3 | 62.0 | 202.7 | 221.5 |
| 10 | 445 | 47.8 | 320.5 | 323.9 | 273.1 | 117.3 | 66.5 | 254.5 | 276.4 |
| 12 | 521 | 50.8 | 374.7 | 381.0 | 323.9 | 130.0 | 73.2 | 304.8 | 327.2 |
| 14 | 584 | 53.8 | 425.5 | 412.8 | 355.6 | 142.7 | 76.2 | 336.6 | 359.2 |
| 16 | 648 | 57.2 | 482.6 | 469.9 | 406.4 | 146.1 | 82.6 | 387.4 | 410.5 |
| 18 | 711 | 60.5 | 533.4 | 533.4 | 457.2 | 158.8 | 88.9 | 438.2 | 461.8 |
| 20 | 775 | 63.5 | 587.2 | 584.2 | 508.0 | 162.1 | 95.3 | 489.0 | 513.1 |
| 24 | 914 | 69.9 | 701.5 | 692.2 | 609.6 | 168.1 | 106.4 | 590.6 | 616.0 |
Main Product:
steel & stainless flange, coupling, nipple etc.