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Specials

Dimensions of Restriction Orifice Plates for ASME B16.5 Raised Face Flanges

Restriction Orifice Plate
NPS DIA
D3
L N P T
1/2 13 0.24 1.5 30 1.5
3/4 19 0.34 1.5 30 1.5
1 25 0.42 2 30 2
1.1/2 40 0.64 3 30 3
2 51 1 6 30 3
3 76 1.5 8 40 3
4 102 1.5 10 40 5
6 152 1.5 15 40 5
8 202 3.5 15 40 7
10 253 3.5 19 45 7
12 302 3.5 20 45 10
14 341 6 20 45 10
16 392 6 21 50 11
18 443 8 23 50 13
20 494 8 25 50 16
24 595 10 29 60 18
NPS ASME B16.5 Flange Class
150 300 600 900 1500 2500
S
1/2 110 110 110 115 115 120
3/4 110 110 110 115 115 120
1 110 115 115 120 120 125
1.1/2 110 120 120 125 125 130
2 110 115 115 125 125 130
3 115 120 120 125 135 140
4 115 125 125 130 140 150
6 115 120 130 135 145 170
8 120 125 135 145 155 170
10 120 130 145 145 165 190
12 125 135 140 145 165 195
14 130 140 145 150 175  
16 130 145 150 155 180  
18 130 145 155 160 195  
20 135 150 155 165 205  
24 135 160 165 190 2205  
NPS ASME B16.5 Flange Class
150 300 600 900 1500 2500
DIA
D4
1/2 48 54 54 64 64 70
3/4 57 67 67 70 70 77
1 67 73 73 80 80 86
1.1/2 86 96 96 99 99 118
2 105 111 111 143 143 146
3 137 149 149 168 175 197
4 175 181 194 206 209 235
6 222 250 266 289 282 317
8 279 307 320 358 352 387
10 339 361 399 434 434 475
12 409 422 456 497 520 549
14 450 485 491 519 577  
16 513 539 564 573 640  
18 548 596 611 637 703  
20 605 653 681 697 754  
24 716 773 789 836 899  

Tolerances

D1 & D2 = ± 1%
D3 = ± 1 mm
D4 = 0/-0.4 mm
L = ± 0.1 mm
N = see note 6
P = ± 0.1 mm
S = ± 0.1 mm
T = see note 2

Notes:

  1. Marking
    The Upstream side of the orifice tab shall be stamped at the indicated locations with:
    - the word UPSTREAM
    - the Tag Number
    - the ASME flange class, followed by RF
    - the nominal pipe size (NPS)
    - the measured orifice D1 (in mm)
    - the material of the orifice plate
    - the type of orifice plate (Square, Restriction etc.)
    Letter height approx. 4 mm
  2. Welding of tab
    Tab may be integral with orifice plate up to and including 7 mm plate thickness.
    In other cases full penetration joint to be applied.
  3. Finish of plate
    The upstream and downstream faces of the orifice plate to a diameter equal to D3 shall have a surface roughness Ra ≤ 0.8 µm ASME B46.1.
    The remaining annular part (between D4 & D3) of upstream and downstream faces shall have a surface roughness Ra between 3.2 and 3.6 µm ASME B46.1. This finish shall be obtained by machining with a round nosed cutting tool having a 0.8 mm radius at a feed rate between 0.35 and 0.45 mm per revolution.
  4. Concentricity
    The centre of the orifice shall not differ from the centre of the plate by more than 0.1 mm for ≤ NPS 8 and 0.2 mm for > NPS 8.
  5. Finish of throat
    The throat and outlet cone shall have a surface roughness Ra ≤ 0.4 µm ASME B46.1.
    All edges shall be sharp and free from burrs, so that when viewed with the naked eye no light is reflected by the corners.
  6. Plate thickness
    The difference between any two measurements of plate thickness, for annular part D1-D3, shall not differ by more than 0.001 DN in mm.
    The plate shall not depart from flatness along any diameter by more than 0.01 D3.
    Tolerance for N shall be:
    N ≤ 6 mm +0.1/-0.25 mm
    N > 6 mm +0/-1.5 mm
    Thickness for annular part D3-D4, may be slightly less, max 0.05 mm, due to surface finishing difference between D1-D3 & D3-D4. (see note 3)

General Notes:

  • Dimensions are in millimeters unless otherwise indicated.
  • Allowable pressure difference 20 bar for temperatures up to 400 °C and D1/D3 ≥ 0.1. The thickness of the plate needs to be verified for strength in case the pressure difference is higher than 20 bar and/or the temperature is beyond 400 °C. Based on the outcome of the calculation the thickness of the plate needs to be adjusted.
  • DIA D1 & DIA D2 - to be specified by purchaser.
  • Material to be specified by purchaser.

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