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What is Orifice Flange?

What is Orifice Flange?

An orifice flange is a specialized type of flange used in conjunction with an orifice plate to measure the flow rate of liquids, gases, or steam in a pipeline. These flanges are designed to accommodate pressure tapping points, allowing for accurate differential pressure measurement across the orifice plate. Orifice flanges are widely utilized in industries such as oil and gas, chemical processing, water treatment, and power generation.

Types of Orifice Flanges

There are different types of orifice flanges based on their design and application. These include:

  1. Weld Neck Orifice Flange – Provides high strength and is suitable for high-pressure applications.

  2. Slip-On Orifice Flange – Easier to install and is often used in low-pressure systems.

  3. Threaded Orifice Flange – Used in low-pressure applications where welding is not feasible.

  4. Socket Weld Orifice Flange – Suitable for small-diameter pipelines with moderate pressure.

  5. Blind Orifice Flange – Used for testing or temporarily shutting off flow in a pipeline.

ASME B16.36 Orifice Flange
Stainless Steel Orifice Flange
ASME B16.36 Carbon Steel Orifice Flange
Carbon Steel Orifice Flange

Orifice Flange Standards

ASME B16.36 Orifice Flange

ASME B16.36 Orifice Flange

ASME B16.36 Orifice Flange

ASME B16.5 Orifice Flange

ASME B16.36 Orifice Flange

ANSI/ASME B16.47 Orifice Flange

ASME B16.36 Orifice Flange

API 6A Orifice Flange

Orifice Flange Dimensions – Class 300 to Class 2500

orifice flange dimensions

Class 150 Orifice Flange Dimensions (Weld Neck Raised Face)

Nominal sizeOCRXAYTgNo. of holesDiam. of holesDiam. of boltsDiam. of bolt circle
1″4.881.522.121.323.2501/04/0740.695/8″3.5
12438.150.853.833.582.66.417.515.988.9
1 1/2″6.121.52.882.751.93.3801/04/0740.813/4″4.5
155.438.173.269.948.385.96.420.619.1114.3
2″6.51.53.623.312.383.3801/04/0780.695/8″5
165.138.191.984.160.585.96.417.515.9127
2 1/2″7.51.54.123.942.883.501/04/0780.813/4″5.88
190.538.1104.6100.173.288.96.420.619.1149.4
3″8.251.554.623.53.503/08/0780.813/4″6.62
209.638.1127117.388.988.99.520.619.1168.1
4″101.56.195.754.53.6201/02/0780.813/4″7.88
25438.1157.2146.1114.391.912.720.619.1200.2
6″12.51.58.58.126.633.9401/02/07120.883/4″10.62
317.538.1215.9206.2168.4100.112.722.419.1269.7
8″151.6210.6210.258.634.3801/02/071217/8″13
38141.1269.7260.4219.2111.312.725.422.2330.2
10″17.51.8812.7512.6210.754.6201/02/07161.121″15.25
444.547.8323.9320.5273.1117.312.728.425.4387.4
12″20.521514.7512.755.1201/02/07161.251 1/8″17.75
520.750.8381374.7323.913012.731.828.6450.9
14″232.1216.2516.75145.6201/02/07201.251 1/8″20.25
584.253.8412.8425.5355.6142.712.731.828.6514.4
16″25.52.2518.519165.7501/02/07201.381 1/4″22.5
647.757.2469.9482.6406.4146.112.735.131.8571.5
18″282.382121186.2501/02/07241.381 1/4″24.75
711.260.5533.4533.4457.2158.812.735.131.8628.7
20″30.52.52323.12206.3801/02/07241.381 1/4″27
774.763.5584.2587.2508162.112.735.131.8685.8
24″362.7527.2527.62246.6201/02/07241.621 1/2″32
914.469.9692.2701.5609.6168.112.741.138.1812.8

Class 300 Orifice Flange Dimensions (Weld Neck Raised Face)

Size in InchSize in mmOuter Dia.Flange Thick.Hub ODWeld Neck ODWelding Neck LengthRF Dia.RF HeightPCDOrifice Hole diaNo of BoltsBolt Size UNCRF Stud LengthHole SizeISO Stud SizeWeight in kg
ABCDEFGHI
12512536.65433.48150.8288.96.445/81253/4M164.5
1 1/24015536.67048.384732114.36.443/41357/8M206.5
25016536.68460.38492.121276.485/81253/4M167
2 1/26519036.61007387104.82149.26.483/41357/8M207.5
38021036.611788.9871272168.39.583/41357/8M209.4
410025536.6146114.390157.2220012.783/41357/8M2013.2
615032036.6206168.398215.92269.912.7123/41357/8M2014.6
820038039.7260219.1110269.92330.212.7127/81451M2430
1025044546.1321273116323.82387.312.71611651 1/8M2741
1230052049.3375323.81293812450.812.7161 1/81801 1/4M3062
1435058552.4425355.6141412.82514.412.7201 1/81851 1/4M3084
1640065055.6483406.4144469.92571.512.7201 1/41951 3/8M33111
1845071058.8533457157533.42628.612.7241 1/42051 3/8M33138
2050077562587508160584.22685.812.7241 1/42151 3/8M33171
2460091568.3702610167692.22812.812.7241 1/22401 5/8M39247

Class 600 Orifice Flange Dimensions (Weld Neck Raised Face)

Size in InchSize in mmOuter Dia.Flange Thick.Hub ODWeld Neck ODWelding Neck LengthRF Dia.RF HeightPCDOrifice Hole diaNo of BoltsBolt Size UNCRF Stud LengthHole SizeISO Stud SizeWeight in kg
ABCDEFGHI
12512536.65433.58150.8788.96.445/81253/4M165.5
1 1/24015536.67048.384737114.36.443/41357/8M207.8
25016536.68460.38492.171276.485/81253/4M168.3
2 1/26519036.61007387104.87149.26.483/41357/8M2010.8
38021036.611788.9871277168.39.583/41357/8M2012.6
410027538.1152114.3102157.27215.912.787/81501M2419
615035547.7222168.3117215.97292.112.71211801 1/8M2737
820042055.6273219.1133269.97349.212.7121 1/81951 1/4M3053
1025051063.5343273152323.87431.812.7161 1/42201 3/8M3386
1230056066.7400323.8156381748912.7201 1/42301 3/8M33102
1435060569.9432355.6165412.8752712.7201 3/82401 1/2M36150
1640068576.2495406.4178469.97603.212.7201 1/22601 5/8M39190
1845074582.6546457.2184533.4765412.7201 5/82801 3/4M42240
2050081588.9610508190584.27723.912.7241 5/83001 3/4M42295
24600940101.6718609.6203692.27838.212.7241 7/83352M48365

Class 900 Orifice Flange Dimensions (Weld Neck Raised Face)

Size in InchSize in mmOuter Dia.Flange Thick.Hub ODWeld Neck ODWelding Neck LengthRF Dia.RF HeightPCDOrifice Hole diaNo of BoltsBolt Size UNCRF Stud LengthHole SizeISO Stud SizeWeight in kg
ABCDEFGHI
12515038.15233.58350.87101.66.447/81501M245.4
1 1/24018038.17048.389737123.86.4411601 1/8M277.8
25021538.110560.310292.17165.16.487/81501M3011.5
2 1/26524541.312473105104.87190.56.4811651 1/8M2715.8
38024038.112788.91021277190.59.587/81501M2422
410029044.5159114.3114157.2723512.781 1/81801 1/4M3022
615038055.6235168.3140215.97317.512.7121 1/81951 1/4M3070
820047063.5298219.1162269.97393.712.7121 3/82301 1/2M36119
1025054569.9368273184323.87469.912.7161 3/82401 1/2M36204
1230061079.4419323.82003817533.412.7201 3/82601 1/2M36303
1435064085.8451355.6213412.87558.812.7201 1/22801 5/8M39400
1640070588.9508406.4216469.9761612.7201 5/82901 3/4M42510
18450785101.9565457.2229533.47685.812.7201 7/83302M48738
20500855108622508248584.27749.312.72023552 1/8M52932
246001040139.7749609.6292692.27901.712.7202 1/24452 5/8M641511

Class 1500 Orifice Flange Dimensions (Weld Neck Raised Face)

Size in InchSize in mmOuter Dia.Flange Thick.Hub ODWeld Neck ODWelding Neck LengthRF Dia.RF HeightPCDOrifice Hole diaNo of BoltsBolt Size UNCRF Stud LengthHole SizeISO Stud SizeWeight in kg
ABCDEFGHI
12515038.15233.58350.87101.66.447/81501M245.4
1 1/24018038.17048.389737123.86.4411601 1/8M277.8
25021538.110560.310292.17165.16.487/81501M2411.5
2 1/26524541.312473105104.87190.56.4811651 1/8M2715.8
38026547.713388.91171277203.29.581 1/81851 1/4M3022
410031054162114.3124157.27241.312.781 1/42051 3/8M3322
615039582.6229168.3171215.97317.512.7121 3/82651 1/2M3670
820048592.1292219.1213269.97393.712.7121 5/83001 3/4M42119
10250585108368273254323.87482.612.7121 7/83451M48204
12300675123.9451323.82833817571.512.71623802 1/8M52303
14350750133.4495355.6298412.8763512.7162 1/44152 3/8M56400
16400825146.1552406.4311469.97704.812.7162 1/24502 5/8M64510
18450915162597457.2327533.47774.712.7162 3/45002 7/8M72738
20500985177.8641508356584.27831.812.71635453 1/8M76932
246001170203.2762609.6406692.27990.612.7163 1/26203 5/8M901511

Class 2500 Orifice Flange Dimensions (Weld Neck Raised Face)

Size in InchSize in mmOuter Dia.Flange Thick.Hub ODWeld Neck ODWelding Neck LengthRF Dia.RF HeightPCDOrifice Hole diaNo of BoltsBolt Size UNCRF Stud LengthHole SizeISO Stud SizeWeight in kg
ABCDEFGHI
12516038.15733.59250.871086.447/81501M246.5
1 1/24020544.57948.31117371466.441 1/81801 1/4M3013
25023550.89560.312792.17171.46.4811851 1/8M2719
2 1/26526557.211473143104.87196.86.481 1/82051 1/4M3024
38030566.713388.91681277228.69.581 1/42301 3/8M3343
410035576.2165114.3190157.2727312.781 1/22601 5/8M3966
6150485108235168.3273215.97368.312.7823502 1/8M52172
8200550127305219.1318269.97438.212.71223852 1/8M52261
10250675165.1375273419323.87539.812.7122 1/24902 5/8M64485
12300760184.2441323.84643817619.112.7122 3/45402 7/8M72730

Material

  • Carbon Steel (ASTM A105, A350 LF2) – Ideal for moderate pressure and temperature conditions.
  • Stainless Steel (ASTM A182 F304, F316, F321) – Provides excellent corrosion resistance.
  • Alloy Steel (ASTM A182 F11, F22, F91) – Used in high-temperature and high-pressure environments.
  • Duplex & Super Duplex Stainless Steel – Offers superior corrosion resistance in aggressive environments.
  • Nickel Alloys (Inconel, Hastelloy, Monel) – Used in extreme conditions such as chemical processing.

Pressure Ratings of Orifice Flanges

  • Class 150 – Suitable for low-pressure applications.
  • Class 300 – Used in medium-pressure systems.
  • Class 600 – Common in higher pressure environments.
  • Class 900 – For high-pressure systems.
  • Class 1500 & 2500 – Used in extremely high-pressure applications.

Components of an Orifice Flange Assembly

  1. Orifice Flanges – The main flanges that hold the orifice plate in place.

  2. Orifice Plate – A plate with a precisely machined hole that creates a pressure differential.

  3. Gaskets – Ensures a leak-proof seal between the flanges and the orifice plate.

  4. Stud Bolts & Nuts – Secure the flanges together.

  5. Jack Screws – Help in easy removal of the orifice plate.

  6. Tapping Points – Allow for pressure measurement.

Advantages

  • Accurate Flow Measurement – Ensures reliable readings in industrial applications.
  • Cost-Effective – More economical compared to other flow measuring devices.
  • Durability – Manufactured from robust materials to withstand harsh conditions.
  • Ease of Installation – Simple to integrate into existing pipeline systems.
  • Standardization – Available in multiple standard sizes and pressure ratings.

Application

  • Oil & Gas – Flow monitoring in pipelines and refineries.
  • Chemical Processing – Accurate measurement of chemical flows.
  • Water Treatment Plants – Monitoring water distribution and treatment processes.
  • Power Plants – Measuring steam and fluid flow.
  • HVAC Systems – Ensuring proper flow of air and gases.

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