Various Types of Flange Connections, Their Usage & Dimensions (ASME B16.5 & B16.47)

Flange connections are one of the most critical elements in industrial piping systems used in oil & gas, petrochemical, power plants, and process industries. They provide a reliable method for joining pipes, valves, pumps, and equipment while allowing easy maintenance, inspection, and replacement.

This detailed engineering guide covers various types of flange connections, their applications, and dimensional standards as per ASME B16.5 and ASME B16.47.

1. What is a Flange Connection?

A flange is a mechanical component used to connect pipes, valves, or equipment using bolting and gasket sealing. The connection ensures leak-proof service under pressure and temperature conditions.

Main Components:

• Flange pair
• Gasket
• Bolting (studs & nuts)

2. Types of Flange Connections

2.1 Welding Neck Flange (WN)

Welding neck flanges are designed for high-pressure and high-temperature applications. They have a long tapered hub that provides excellent stress distribution.

• Used in critical services (refineries, high-pressure lines)
• Butt welded to pipe
• Excellent fatigue resistance

2.2 Slip-On Flange (SO)

Slip-on flanges are easy to install and cost-effective. The pipe is inserted into the flange and fillet welded.

• Used in low to moderate pressure systems
• Less expensive than WN flange
• Lower strength compared to WN

2.3 Blind Flange (BL)

Blind flanges are used to close the end of a piping system or pressure vessel.

• No bore (solid disk)
• Used for isolation and pressure testing
• Withstands high pressure

2.4 Socket Weld Flange (SW)

Socket weld flanges are designed for small-diameter high-pressure piping.

• Pipe inserted into socket
• Fillet weld applied
• Used in chemical plants and steam systems

2.5 Lap Joint Flange (LJ)

Lap joint flanges are used with stub ends and allow easy alignment.

• Ideal for frequent dismantling
• Used with lined piping
• Low cost and reusable

2.6 Threaded Flange (THD)

Threaded flanges are used where welding is not allowed.

• Screwed connection
• Used in hazardous areas
• Limited to low pressure

3. Embedded Flange Diagram

4. ASME B16.5 Standard Overview

ASME B16.5 covers pipe flanges and flanged fittings for sizes NPS ½ inch to 24 inch.

Pressure Classes:

• Class 150
• Class 300
• Class 600
• Class 900
• Class 1500
• Class 2500

Key Dimensions:

• Outside Diameter (OD)
• Bolt Circle Diameter (BCD)
• Number of Bolts
• Bolt Hole Diameter
• Flange Thickness

5. ASME B16.47 Standard Overview

ASME B16.47 covers large diameter flanges from NPS 26 to 60 inches.

Two Series:

• Series A (MSS SP-44) – heavier, fewer bolts
• Series B (API 605) – lighter, more bolts

6. Dimensional Comparison (Example)

Size	Class	OD (mm)	Thickness (mm)	Bolt Qty
4"	150	228.6	24	8
8"	300	343	38	12
16"	600	610	89	20

7. Selection Criteria

Choosing the correct flange depends on:

• Pressure & Temperature
• Fluid type (corrosive, toxic)
• Maintenance requirements
• Cost considerations

8. Advantages of Flanged Connections

• Easy assembly and disassembly
• Leak-proof sealing with proper gasket
• Suitable for high-pressure applications

9. Limitations

• Higher cost compared to welding
• Requires space for bolting
• Potential leak paths if not maintained

10. Engineering Best Practices

• Use proper torque tightening sequence
• Select correct gasket type
• Ensure alignment during installation
• Follow ASME code compliance

11. Conclusion

Flange connections are indispensable in industrial piping systems. Understanding types, applications, and standards such as ASME B16.5 and B16.47 ensures safe and efficient design. Engineers must carefully select flange types based on service conditions, cost, and maintenance requirements.

Flange Connections: Types, Usage & Dimensions (ASME B16.5 & B16.47)

This engineering-grade guide explains flange types, applications, dimensional standards, and includes practical calculators for real-world piping design.

Types of Flanges

• Welding Neck (WN): High pressure & temperature
• Slip-On (SO): Cost-effective, moderate service
• Blind (BL): Isolation and testing
• Socket Weld (SW): Small bore high pressure
• Lap Joint (LJ): Frequent dismantling
• Threaded (THD): No welding zones

ASME Standards

Engineering Best Practices

• Follow proper bolt tightening sequence
• Use calibrated torque wrench
• Select correct gasket (spiral wound, RTJ)
• Ensure alignment and cleanliness