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

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:

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
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.
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.
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.
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.
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.