Weld Neck Flange Dimensions : Class 150 to Class 2500

Weld Neck Flange Dimensions: Class 150 to Class 2500

Weld neck flanges are widely used in high-pressure piping systems due to their strong and durable design. They are characterized by a long tapered hub that provides excellent stress distribution and resistance to bending. Weld neck flanges are available in various pressure classes, ranging from Class 150 to Class 2500, and their dimensions are standardized by ASME B16.5.

This article provides detailed dimension tables for weld neck flanges across different pressure classes, including diameter, thickness, bolt circle diameter, and number of bolts.

Weld Neck Flange Overview {#weld-neck-flange-overview}

Weld neck flanges are designed for high-pressure and high-temperature applications. They are welded directly to the pipe, ensuring a strong and leak-proof connection. The dimensions of weld neck flanges are standardized to ensure compatibility across different manufacturers and systems.

Key Features:

Tapered Hub: Provides stress distribution and resistance to bending.
Raised Face (RF): Common sealing surface for high-pressure applications.
Available Pressure Classes: Class 150, 300, 600, 900, 1500, and 2500.

Dimension Tables for Weld Neck Flanges {#dimension-tables-for-weld-neck-flanges}

Below are the dimension tables for weld neck flanges according to ASME B16.5. Dimensions are in millimeters (mm).

Class 150 Dimensions {#class-150-dimensions}

Nominal Pipe Size (NPS)	Outside Diameter (OD)	Bolt Circle Diameter (BCD)	Number of Bolts	Bolt Hole Diameter	Flange Thickness (T)	Hub Diameter (B)	Raised Face Height (RF)
1/2	89	60.3	4	15.9	11.2	21.3	1.6
1	108	79.4	4	15.9	12.7	27.7	1.6
2	152	120.7	4	19.1	15.7	53.5	1.6
4	229	190.5	8	19.1	19.1	102.3	1.6
6	279	241.3	8	22.2	22.2	154.1	1.6
8	343	298.5	8	22.2	24.3	202.7	1.6

Class 300 Dimensions {#class-300-dimensions}

Nominal Pipe Size (NPS)	Outside Diameter (OD)	Bolt Circle Diameter (BCD)	Number of Bolts	Bolt Hole Diameter	Flange Thickness (T)	Hub Diameter (B)	Raised Face Height (RF)
1/2	95	66.7	4	15.9	14.3	21.3	2.0
1	117	82.6	4	15.9	16.7	27.7	2.0
2	165	127	8	19.1	20.7	53.5	2.0
4	254	190.5	8	22.2	24.3	102.3	2.0
6	318	261.9	12	22.2	28.6	154.1	2.0
8	381	333.4	12	25.4	31.8	202.7	2.0

Class 600 Dimensions {#class-600-dimensions}

Nominal Pipe Size (NPS)	Outside Diameter (OD)	Bolt Circle Diameter (BCD)	Number of Bolts	Bolt Hole Diameter	Flange Thickness (T)	Hub Diameter (B)	Raised Face Height (RF)
1/2	95	66.7	4	15.9	15.7	21.3	2.0
1	124	88.9	4	19.1	19.1	27.7	2.0
2	184	139.7	8	19.1	25.4	53.5	2.0
4	292	215.9	8	22.2	31.8	102.3	2.0
6	394	292.1	12	25.4	38.1	154.1	2.0
8	483	362.0	12	28.6	44.5	202.7	2.0

Class 900 Dimensions {#class-900-dimensions}

Nominal Pipe Size (NPS)	Outside Diameter (OD)	Bolt Circle Diameter (BCD)	Number of Bolts	Bolt Hole Diameter	Flange Thickness (T)	Hub Diameter (B)	Raised Face Height (RF)
1/2	108	69.9	4	15.9	22.2	21.3	2.0
1	133	95.3	4	19.1	25.4	27.7	2.0
2	197	152.4	8	22.2	31.8	53.5	2.0
4	318	241.3	8	25.4	41.3	102.3	2.0
6	419	317.5	12	28.6	50.8	154.1	2.0
8	521	393.7	12	31.8	57.2	202.7	2.0

Class 1500 Dimensions {#class-1500-dimensions}

Nominal Pipe Size (NPS)	Outside Diameter (OD)	Bolt Circle Diameter (BCD)	Number of Bolts	Bolt Hole Diameter	Flange Thickness (T)	Hub Diameter (B)	Raised Face Height (RF)
1/2	121	76.2	4	15.9	25.4	21.3	2.0
1	152	101.6	4	19.1	28.6	27.7	2.0
2	216	165.1	8	22.2	38.1	53.5	2.0
4	343	266.7	8	28.6	50.8	102.3	2.0
6	470	393.7	12	31.8	63.5	154.1	2.0
8	610	482.6	12	35.0	76.2	202.7	2.0

Class 2500 Dimensions {#class-2500-dimensions}

Nominal Pipe Size (NPS)	Outside Diameter (OD)	Bolt Circle Diameter (BCD)	Number of Bolts	Bolt Hole Diameter	Flange Thickness (T)	Hub Diameter (B)	Raised Face Height (RF)
1/2	133	82.6	4	15.9	28.6	21.3	2.0
1	165	114.3	4	19.1	31.8	27.7	2.0
2	267	190.5	8	25.4	47.8	53.5	2.0
4	406	317.5	8	31.8	63.5	102.3	2.0
6	559	482.6	12	35.0	82.6	154.1	2.0
8	711	571.5	12	41.3	101.6	202.7	2.0

Key Notes on Dimensions {#key-notes-on-dimensions}

Raised Face (RF): The raised face height is typically 1.6 mm for Classes 150 and 300 and 2.0 mm for Classes 600 and above.
Bolt Holes: The number and size of bolt holes increase with the flange pressure class to ensure a secure connection.
Tapered Hub: The hub dimensions vary depending on the pipe size and pressure class to provide optimal stress distribution.

Frequently Asked Questions (FAQ) {#faq}

1. What is the purpose of a weld neck flange?

A weld neck flange is designed to provide a strong and leak-proof connection in high-pressure and high-temperature piping systems.

2. How are weld neck flange dimensions standardized?

Weld neck flange dimensions are standardized according to ASME B16.5, ensuring compatibility across different manufacturers.

3. What is the difference between Class 150 and Class 2500 flanges?

The main difference lies in their pressure-handling capacity. Class 150 flanges are suitable for low-pressure applications, while Class 2500 flanges are designed for extremely high-pressure systems.