Custom CNC Machining Blind Flange Reliable Stainless Steel High Pressure Blind Flanges

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What is a Blind Flange?

A blind flange is a solid disk used to terminate or close the end of a piping system, pressure vessel, or equipment opening. It is essentially a flange without a center bore (hole). Unlike other flanges that connect pipes, valves, or other equipment, the primary purpose of a blind flange is to block off a section of pipe or a nozzle, providing a secure and leak-proof seal. This allows for easy future expansion of the pipeline, safe isolation of a section for maintenance, or pressure testing.

Materials

Blind flanges are manufactured from a wide variety of materials to suit different service conditions, including:

• Carbon Steel: ASTM A105, A350 LF2.

• Stainless Steel: ASTM A182 F304/304L, F316/316L, F321.

• Alloy Steel: ASTM A182 F11, F22, F91.

• Duplex & Super Duplex Stainless Steel: ASTM A182 F51, F53, F55.

• Non-Ferrous Metals: Copper, Brass, Aluminum, Titanium.

• Special Alloys: Inconel, Monel, Hastelloy.

• Plastics: PVC, CPVC, PP, PVDF.

Surface Treatments

Surface treatments are applied to enhance performance, improve corrosion resistance, and ensure a tight seal. Common treatments include:

• Galvanizing: A zinc coating for corrosion protection.

• Paint or Powder Coating: Provides a protective layer and color coding.

• Electroplating: Deposits a thin layer of metal like chrome or nickel.

• Passivation: For stainless steel, to remove free iron and enhance the natural chromium oxide layer.

• Rubber or Plastic Lining: For highly corrosive applications.

Specifications

Blind flanges conform to various international standards which define their dimensions, pressure ratings, and manufacturing tolerances. Key specifications include:

• Pressure Ratings: Class 150, 300, 600, 900, 1500, 2500 (ASME B16.5).

• Size Range: Typically from 1/2 inch (DN15) to over 60 inches (DN1500).

• Facing Types: Raised face (RF), Flat face (FF), Ring-type joint (RTJ).

• Standards: ASME B16.5, ASME B16.47, EN 1092-1, MSS SP-44, API 6A.

Application Fields

Blind flanges are critical components in numerous industries for isolation, safety, and testing purposes. Their main applications are in:

• Oil and Gas Industry: Pipeline systems, refineries, offshore platforms.

• Chemical and Petrochemical Plants: For handling corrosive fluids.

• Water and Wastewater Treatment: Isolating sections of water mains.

• Power Generation: In boiler systems and steam lines.

• Shipbuilding and Marine Engineering: Piping systems on vessels.

• Pharmaceutical and Food Processing: Where hygiene and isolation are crucial.

Excellent  Case: Pressure Testing a New Pipeline Section

A new section of a high-pressure natural gas pipeline was installed and needed testing before use. Engineers sealed the end with a Class 600, 24-inch carbon steel raised-face blind flange, then filled the pipeline with water and pressurized it above normal levels. The blind flange held the pressure perfectly, proving that all welds and fittings were leak-free and safe. After testing, the flange could be removed to connect the next section. This step was essential to ensure long-term safety and prevent failures.