In early 2025, we received an order from a Vietnamese client for ASME B16.5 & B16.47 Weld Neck Flanges. Upon receiving the order, we immediately arranged production based on our years of accumulated experience.Regarding delivery time, the customer urgently required these blind flanges. Therefore, production was immediately arranged upon receiving the order. The procurement department closely monitored the production progress throughout and provided timely updates to the customer to ensure on-time delivery. Regardless of order value or quantity, treating every order with meticulous care has always been Shanghai Zhengcheng’s steadfast business philosophy. Before each flange leaves the factory, the quality inspection department conducts comprehensive dimensional testing in accordance with ASME B16.5 & B16.47 standards (including outer diameter, thickness, sealing surface tolerances, etc.), ensuring the products fully meet the customer’s application requirements.
| NO | Description | Material | Unit | Quantity |
| 1 | BLIND FLANGE 32″ RF 150# ASME B16.47 SR.A | SA-350 LF2 CL.1 | PCS | 4 |
| 2 | FLANGE 1″ LWN RF L=157 300# ASME B16.5 | SA-350 LF2 CL.1 | PCS | 1 |
| 3 | FLANGE 1″ LWN RF L=159 300# ASME B16.5 | SA-350 LF2 CL.1 | PCS | 1 |
| 4 | FLANGE 2″ LWN RF L=154 300# ASME B16.5 | SA-350 LF2 CL.1 | PCS | 1 |
| 5 | FLANGE 2″ LWN RF L=176 300# ASME B16.5 | SA-350 LF2 CL.1 | PCS | 4 |
| 6 | FLANGE 1″ WN RF THK.4.55 300# ASME B16.5 | SA-350 LF2 CL.1 | PCS | 4 |
| 7 | FLANGE 10″ WN RF THK.12.7 150# ASME B16.5 | SA-350 LF2 CL.1 | PCS | 4 |
| 8 | FLANGE 16″ WN RF THK.12.7 150# ASME B16.5 | SA-350 LF2 CL.1 | PCS | 6 |
| 9 | FLANGE 16″ WN RF THK.9.53 150# ASME B16.5 | SA-350 LF2 CL.1 | PCS | 6 |
| 10 | FLANGE 2″ WN RF THK.5.54 300# ASME B16.5 | SA-350 LF2 CL.1 | PCS | 5 |
Weld Neck Flanges Introduction
Weld neck flanges are a common type of pipe connection component. Their most distinctive feature is the long-neck tapered structure, which allows for beveled welding with pipes, achieving a seamless connection between the pipe and flange. This design effectively distributes stress and reduces stress concentration at the joint, making it particularly suitable for high-temperature, high-pressure applications and conditions involving severe temperature and pressure fluctuations. Weld neck flanges are typically manufactured from materials such as carbon steel, stainless steel, and alloy steel. They are extensively utilized in piping systems across industries including petroleum, natural gas, chemical processing, power generation, and marine engineering.
ASME B16.5 Standard Overview
The ASME B16.5 standard covers pipe flanges and flanged fittings in sizes from ½ inch to 24 inches, with pressure ratings ranging from Class 150 to Class 2500. It provides detailed requirements for dimensions, tolerances, materials, and pressure–temperature ratings to ensure quality and safety. ASME B16.5 Weld Neck Flanges are highly regarded for their tapered hub design, which reduces stress at the weld joint and ensures reliable performance in demanding, high-pressure pipeline applications.
ASME B16.47 Standard Overview
The ASME B16.47 standard applies to larger flanges, covering 26 inches to 60 inches in nominal pipe size. It includes two series:
Series A
Thicker, heavier, and designed for higher mechanical strength, commonly used in oil & gas and critical infrastructure.
Series B
Thinner, lighter, and more cost-effective, widely used in waterworks and general engineering projects.
Together, ASME B16.5 & B16.47 Weld Neck Flanges provide complete solutions from small to extra-large pipelines.
Material: SA-350 LF2 CL.1
SA-350（ASTM A350）: This is an ASME material specification titled “Standard Specification for Carbon and Low-Alloy Steel Forgings, Requiring Notch Toughness Testing for Piping Components.” It mandates strict chemical and mechanical properties to ensure integrity.
LF2: This denotes the grade of steel within the SA-350 specification. LF2 is a carbon or low-alloy steel forging designed to provide enhanced impact toughness, particularly in low-temperature service.
CL.1: This specifies the class within the LF2 grade. Class 1 has a higher maximum carbon content compared to Class 3, making it a robust and widely used option for various low-temperature applications without the need for stricter welding controls.
ASME B16.5 Class 300 Weld Neck Flange Dimensions
Class 300 Weld Neck Flange Dimensions：
| Nominal Pipe Size | A | B | C | D | E | F | G | H | I | J | |
| inch | mm | mm | mm | mm | mm | mm | mm | mm | Holes | mm | mm |
| 1/2 | 21.30 | 95.20 | 15.70 | 14.20 | 52.30 | 21.30 | 38.10 | 35.00 | 4 | 15.70 | 66.55 |
| 3/4 | 26.70 | 117.3 | 20.80 | 15.70 | 57.15 | 26.70 | 47.70 | 42.90 | 4 | 19.00 | 82.50 |
| 1 | 33.40 | 123.9 | 26.70 | 17.50 | 62.00 | 33.50 | 53.80 | 50.80 | 4 | 19.00 | 88.90 |
| 1 1/4 | 42.20 | 133.3 | 35.10 | 19.00 | 65.00 | 42.20 | 63.50 | 63.50 | 4 | 19.00 | 98.50 |
| 1 1/2 | 48.30 | 155.4 | 40.90 | 20.60 | 68.30 | 48.30 | 69.85 | 73. 15 | 4 | 22.30 | 114.3 |
| 2 | 60.30 | 165. 1 | 52.60 | 22.30 | 69.85 | 60.45 | 84.00 | 91.90 | 8 | 19.00 | 127.0 |
| 2 1/2 | 73.00 | 190.5 | 62.70 | 25.40 | 76.20 | 73.15 | 100.0 | 104.6 | 8 | 22.30 | 149.3 |
| 3 | 88.90 | 209.5 | 78.00 | 28.40 | 79.25 | 88.90 | 117.3 | 127.0 | 8 | 22.30 | 168.1 |
| 3 1/2 | 101.6 | 228.6 | 90.20 | 30.20 | 81.00 | 101.6 | 133.3 | 139.7 | 8 | 22.30 | 184.1 |
| 4 | 114.3 | 254.0 | 102.4 | 31.70 | 85.80 | 114.3 | 146.0 | 157.2 | 8 | 22.30 | 200.1 |
| 5 | 141.3 | 279.4 | 128.3 | 35.00 | 98.50 | 141.2 | 177.8 | 185.7 | 8 | 22.30 | 234.9 |
| 6 | 168.3 | 317.5 | 154.2 | 36.50 | 98.50 | 168.4 | 206.2 | 215.9 | 12 | 22.30 | 269.7 |
| 8 | 219.1 | 381.0 | 202.7 | 41.10 | 111.2 | 219.2 | 260.3 | 269.7 | 12 | 25.40 | 330.2 |
| 10 | 273.0 | 444.5 | 254.5 | 47.70 | 117.3 | 273.0 | 320.5 | 323.8 | 16 | 28.40 | 387.3 |
| 12 | 323.8 | 520.7 | 304.8 | 50.80 | 130.0 | 323.8 | 374.6 | 381.0 | 16 | 31.70 | 450.8 |
| 14 | 355.6 | 584.2 | To be specified by the Purchaser |
53.80 | 142.7 | 355.6 | 425.4 | 412.7 | 20 | 31.70 | 514.3 |
| 16 | 406.4 | 647.7 | 57.15 | 146.0 | 406.4 | 482.6 | 469.9 | 20 | 35.00 | 571.5 | |
| 18 | 457.2 | 711.2 | 60.45 | 158.7 | 457.2 | 533.4 | 533.4 | 24 | 35.00 | 628.6 | |
| 20 | 508.0 | 774.7 | 63.50 | 162.0 | 508.0 | 587.2 | 584.2 | 24 | 35.00 | 685.8 | |
| 24 | 609.6 | 914.4 | 69.85 | 168.1 | 609.6 | 701.5 | 692.1 | 24 | 41.10 | 812.8 | |
ASME B16.47 Class 150 Weld Neck Flange Dimensions
Class 150 Weld Neck Flange Dimensions:
| Nominal Pipe Size |
O.D. of Flange,O |
Minimum Thickness of Flange, tf [Note (1)] |
Length Through Hub, Y |
Diam. of Hub, X [Note (2)] |
Hub Diam. Top, A [Note (3)] |
Raised Face Diam., R |
Drilling | Diam. of Bolt |
Minimum Fillet Radius, r1 |
||
| Diam. of Bolt Circle |
No. of Bolt Holes |
Diam. of Bolt Hole |
|||||||||
| 26 | 34.25 | 2.63 | 4.69 | 26.62 | 26.00 | 29.50 | 31.75 | 24 | 13⁄8 | 11⁄4 | 0.38 |
| 28 | 36.50 | 2.75 | 4.88 | 28.62 | 28.00 | 31.50 | 34.00 | 28 | 13⁄8 | 11⁄4 | 0.44 |
| 30 | 38.75 | 2.88 | 5.32 | 30.75 | 30.00 | 33.75 | 36.00 | 28 | 13⁄8 | 11⁄4 | 0.44 |
| 32 | 41.75 | 3.13 | 5.63 | 32.75 | 32.00 | 36.00 | 38.50 | 28 | 15⁄8 | 11⁄2 | 0.44 |
| 34 | 43.75 | 3.19 | 5.82 | 34.75 | 34.00 | 38.00 | 40.50 | 32 | 15⁄8 | 11⁄2 | 0.50 |
| 36 | 46.00 | 3.50 | 6.13 | 36.75 | 36.00 | 40.25 | 42.75 | 32 | 15⁄8 | 11⁄2 | 0.50 |
| 38 | 48.75 | 3.38 | 6.13 | 39.00 | 38.00 | 42.25 | 45.25 | 32 | 15⁄8 | 11⁄2 | 0.50 |
| 40 | 50.75 | 3.50 | 6.38 | 41.00 | 40.00 | 44.25 | 47.25 | 36 | 15⁄8 | 11⁄2 | 0.50 |
| 42 | 53.00 | 3.75 | 6.69 | 43.00 | 42.00 | 47.00 | 49.50 | 36 | 15⁄8 | 11⁄2 | 0.50 |
| 44 | 55.25 | 3.94 | 6.94 | 45.00 | 44.00 | 49.00 | 51.75 | 40 | 15⁄8 | 11⁄2 | 0.50 |
| 46 | 57.25 | 4.00 | 7.25 | 47.12 | 46.00 | 51.00 | 53.75 | 40 | 15⁄8 | 11⁄2 | 0.50 |
| 48 | 59.50 | 4.19 | 7.50 | 49.12 | 48.00 | 53.50 | 56.00 | 44 | 15⁄8 | 11⁄2 | 0.50 |
| 50 | 61.75 | 4.32 | 7.94 | 51.25 | 50.00 | 55.50 | 58.25 | 44 | 17⁄8 | 13⁄4 | 0.50 |
| 52 | 64.00 | 4.50 | 8.19 | 53.25 | 52.00 | 57.50 | 60.50 | 44 | 17⁄8 | 13⁄4 | 0.50 |
| 54 | 66.25 | 4.69 | 8.44 | 55.25 | 54.00 | 59.50 | 62.75 | 44 | 17⁄8 | 13⁄4 | 0.50 |
| 56 | 68.75 | 4.82 | 8.94 | 57.38 | 56.00 | 62.00 | 65.00 | 48 | 17⁄8 | 13⁄4 | 0.50 |
| 58 | 71.00 | 5.00 | 9.19 | 59.38 | 58.00 | 64.00 | 67.25 | 48 | 17⁄8 | 13⁄4 | 0.50 |
| 60 | 73.00 | 5.13 | 9.38 | 61.38 | 60.00 | 66.00 | 69.25 | 52 | 17⁄8 | 13⁄4 | 0.50 |
Flange RF Face Introduction
The Raised Face (RF) is the most common flange facing for ASME B16.5 & B16.47 Weld Neck Flanges.
Design: The RF features a small, raised annular ring around the bore. This raised section is typically machined with a serrated concentric or spiral groove pattern (serration). The purpose of this design is to increase the surface pressure on a flat gasket placed between two flanges, creating a superior seal that prevents fluid or gas leakage.
Versatility: The RF face is incredibly versatile. It is suitable for a wide range of services, from moderate to high pressures and temperatures, and is compatible with various gasket materials like soft iron, graphite, and PTFE. This universality makes it the default choice for countless applications.
Advantages of Low-Temperature Steel Weld Neck Flanges
✅High toughness at –46°C.
✅Strong resistance to brittle fracture.
✅Reliable sealing under thermal cycling.
✅Cost-effective alternative to stainless steel.
✅Proven performance in LNG service.
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