Flanged Fittings, ASTM A105 Flange with A234 WPB Tee for Oil and Gas System Component

Why Combine a Flange with a Fitting?

Piping systems have two fundamental types of joints:

1. Permanent Joints: Welded joints for strength, integrity, and leak resistance.

2. Removable/Demountable Joints: Flanged or threaded joints for maintenance, inspection, and equipment connection.

A "Flange + Fitting" combination strategically places a removable joint at a specific, critical point in an otherwise permanent system. The fitting (e.g., elbow, tee, reducer) changes the flow direction or pipe size, while the flange provides the bolted, dismountable interface.

Specification of Forged Flanges

Specification of Buttweld Fittings

Common Standard Configurations

A. Flanged Fittings (Integral Flange)

The flange is cast or forged as one piece with the fitting body. This is a single, ready-to-install unit.

Examples:

Flanged Elbow: Changes direction (90° or 45°) with flanged ends.

Flanged Tee: Creates a branch with all three ends flanged.

Flanged Reducer: Changes pipe size with flanged ends.

Standard: ASME B16.5 (Pipe Flanges and Flanged Fittings: NPS ½" to 24"). This standard covers the dimensions, ratings, and tolerances for these specific fittings.

B. Fabricated Combinations (Flange + Welding Fitting)

This involves welding a standard flange to a standard welding fitting. It's the most common and flexible approach.

Components Used:

Flange: Per ASME B16.5 or B16.47.

Welding Fitting: Per ASME B16.9 (Butt-Weld) or B16.11 (Socket-Weld/Threaded).

Most Common Example: Flanged Outlet Tee
This is a Butt-Weld Tee (B16.9) with a Flange (B16.5) welded to its branch outlet.

Specification: Tee, BW x BW x RF (Butt Weld x Butt Weld x Raised Face Flange).

Other Examples:

Flanged Stub End: A Lap Joint Flange + a Stub End (B16.9) for easy-alignment systems.

Flanged Nozzle: A welding boss or coupling (B16.11) with a flange welded on for instrument connections.

Applications

Flanged tees are used across industries where piping needs to be modular or accessible:

• Water & Wastewater Treatment: For diverting flow to different processing tanks or filters.

• Chemical & Petrochemical Plants: In lines requiring frequent pigging, cleaning, or catalyst loading/unloading.

• Power Generation: In cooling water, feedwater, and auxiliary systems where equipment needs isolation.

• Shipbuilding & Offshore: For ballast, bilge, and seawater systems that require robust, bolt-together piping.

• HVAC & Industrial Plumbing: In large-scale chilled water or steam distribution headers.