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MS Pipes & Fittings

Mild Steel (MS) Pipe Flanges

MS FLANGE_edited.png

Mild Steel (MS) Pipe Flanges are critical components used to connect pipes, valves, pumps, and other equipment to form a piping system. They provide easy access for cleaning, inspection, or modification. Unlike welded joints, flanged connections are semi-permanent and can be dismantled easily.

1. Primary Technical Standards

MS flanges are manufactured according to various international and national standards depending on the pressure and application:

  • ASME/ANSI B16.5: The most common global standard for pipe flanges (1/2" to 24").

  • BS 10: British standard (Table D, E, F, H) widely used in older Indian plumbing systems.

  • IS 6392: The Indian standard for steel pipe flanges.

  • DIN Standards: German standards (e.g., DIN 2576, DIN 2527) common in European machinery.

2. Common Types of MS Flanges

Type
Technical Description
Best For
Slip-On (SORF)

Slides over the pipe and is welded both inside and out.

Low-pressure, easy alignment.

Blind (BLRF)

A solid disc used to seal the end of a pipeline.

Inspection ports or future expansions.

Weld Neck (WNRF)

Features a long tapered hub that is butt-welded to the pipe.

High-pressure and extreme temperatures.

Socket Weld (SWRF)

Pipe is inserted into a socket before welding.

Small diameter, high-pressure lines.

Lap Joint

Used with a stub end; the flange can rotate freely.

Systems requiring frequent dismantling.

Threaded

Screwed onto the pipe without welding.

Low pressure; areas where welding is hazardous.

3. Pressure Ratings (Class)

Under the ASME B16.5 standard, flanges are categorized by their ability to handle pressure at specific temperatures:

  • Class 150: Standard utility (Water/Air).

  • Class 300: Medium industrial.

  • Class 600, 900, 1500, 2500: High-pressure oil, gas, and steam applications.

4. Dimensional Data (Reference: ASME B16.5 Class 150)

Nominal Pipe Size (NB)
Outside Diameter (mm)
Thickness (mm)
No of Bolt Holes
Bolt Circle Dia (mm)
1/2" (15mm)

90

11.2

4

60.3

1" (25mm)

110

14.3

4

79.4

2" (50mm)

150

19.1

4

120.7

4" (100mm)

230

23.9

8

190.5

6" (150mm)

280

25.4

8

241.3

5. Flange Facing Types

The "Face" determines the gasket surface and the seal quality:

  • Flat Face (FF): Used when the mating flange is cast iron (prevents cracking).

  • Raised Face (RF): The most common; concentrates more pressure on a smaller gasket area.

  • Ring Type Joint (RTJ): A groove is cut for a metal ring gasket; used for very high pressures.

6. Material & Finish

  • Material Grade: Commonly ASTM A105 (Forged Carbon Steel) or IS 2062 Gr. B (Mild Steel Plate).

  • Surface Coating: * Black: Self-color/Anti-rust oil.

    • Galvanized: Hot-dip zinc coating to prevent corrosion.

    • Yellow/Blue Primer: For temporary protection during transit.

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