A Complete Guide to Steel Flanges

Discover our comprehensive guide to steel flanges, which will help you gain a deep understanding of what a steel flange is and how to choose the right one for your specific application needs.

Steel flanges are typically connected to other pipe fittings using welding attachments and are sealed to other flanges using bolts and gaskets. These components play a crucial role in industrial processes, connecting various systems such as water pipelines, oil filtration machinery, food processing equipment, and pressure vessels.

Over the years, these industrial elements have been manufactured in a variety of specifications, each serving an essential function across different industries.

Ensuring safe connections between pipes is vital to prevent leaks in the piping system. Flanges keep the pipes securely connected, enabling them to operate safely over a longer period.

Steel Flanges Specification

Manufacturing standard of pipe flanges is ASME B16.5

This standard includes NPS ½ to NPS 24 metric inches, covering pressure-temperature ratings, dimensions, tolerances, materials, sizes, tolerances, marking, testing, and opening methods of flanges.

The flange class rating includes 150, 300, 400, 600, 900, and 1500, available in sizes from NPS ½ to NPS 24 metric inches. Class 2500 flanges are available in sizes NPS ½ to NPS 12, with bolt diameters and flange bolt holes specified in inch units.

ASME B16.5 flanges are made from forged or cast materials. Blind flanges and specific reducing flanges can be fabricated from forged, cast, or plate materials. This standard also covers requirements and recommendations for flange bolting, gaskets, and joints.

Different Types of Flanges

Weld Neck Flanges		This type of flange is welded to the pipe ends at the neck Typically butt welded to a pipe Used in high-pressure situations More durable than slip-on flanges under stress
Slip On Flanges		This pipe flange slips over the pipe Lower cost than weld neck flange Manufactured with an ID slightly larger than the pipe’s OD
Socket Weld Flanges		It has a female socket where the pipe is fitted Fillet welding is done from the OD on the pipe Similar to a slip-on flange, but with a bore and counter bore dimension Counter bore is larger than the O.D. of the matching pipe Suitable for pipes with a nominal diameter of 150 or less
Lap Joint Flanges		Used on piping fitted with lapped pipe (lap joint stub ends) Composed of two parts: a stub end and a loose backing flange Similar to a slip-on flange, but with a radius where the flange face and bore meet
Threaded Flange		Also known as a screwed flange Has threads within the flange bore that align with the pipe's male thread Used in utility services like air and water Similar to a slip-on flange, but with a threaded bore
Blind Flange		A blind flange is a round plate with no center hole and all necessary bolt holes Used to close off the ends of a piping system
Orifice Flange		Used with orifice meters Measures liquid or gas flow rate in the appropriate pipeline
Long Welding Neck Flange		Has a very long neck Features a tapered neck and a bevel end Has a straight short pipe as the neck of a long weld neck flange
Weldoflange and Nipoflange		A Welding Neck flange combined with a Weldolet or Nipolet
Expander and Reducing Flange		Used to increase or decrease the bore size of a pipeline A strong alternative to butt weld reducers

Steel Pipe Flange Material Grades

Reducing weld neck flange have pressure rating of class 150 to class 2500

ASME creates the flange class, taking into account there are several pressure and temperature ratings. There are seven classes i.e. 150, 300, 400, 600, 900, 1500 and 2500. And the reducing weld neck flange can be worked at this pressure rating of class. The pressure rating specifies the highest tolerable pressure at a stated temperature. For instance, a class 2500 flange can resist more pressure and it is heavier compared to 1500 flange. Here, the class 2500 flange signifies that the flange is workable at this rated temperature without getting cracked or damaged.

Galvanized Pipe Flange Working Pressure

Standard size range of socket weld and slip on flanges is 1/2″ to 24″

The standard size range of socket weld and slip on flanges is important for many industries as it provides fastening to the piping system. Socket weld and slip on flanges are typically manufactured in the standard size range from ½” to 24”.

Understanding the categorization and distinction between flanges across countries is essential for flawless combination and consistency in global projects.

Flange standardization ensures safety and similarity across a broad range of global industries. It facilitates global trade by offering a common base for fabricators, suppliers, and consumers.

Steel Flange Dimension Chart

WNRF Flange Weight Chart