A blind flange, also known as a blank flange or cap flange, is a solid flange without a central hole. It is mainly used to temporarily or permanently seal the end or branch of a pipeline system to prevent media flow or leakage. It plays an important role in isolating and sealing pipeline systems.

Structural Features

Centerless hole design: This is the most significant feature of a blind flange, allowing it to completely seal the pipe port and prevent media from passing through.

Sealing surface: Common sealing surface types include flat face (FF), raised face (RF), ring-type joint (RTJ), etc., to meet different sealing requirements.

Bolt holes: Bolt holes matching the paired flange are provided around the perimeter for fixing and sealing. Fastening to other flanges is achieved through bolted connections.

Thickness: It is usually thicker than a standard flange of the same specification to withstand system pressure and prevent deformation, ensuring sealing and stability under different pressure conditions.

Material Selection

Carbon steel: Such as ASTM A105, etc., has good strength and economy, suitable for pipeline systems in general industrial environments, and can withstand certain pressure and temperature.

Stainless steel: For example, 304, 316L, etc., has excellent corrosion resistance and oxidation resistance, and is often used in chemical, food, pharmaceutical and other industries with high corrosion resistance requirements.

Alloy steel: Can meet the requirements of high temperature, high pressure and other special working conditions, and is widely used in power, petrochemical and other fields.

Other materials: Non-ferrous metals such as copper and aluminum, and plastic materials such as PVC and PPR, can also be used to manufacture blind flanges according to special needs to adapt to different media and working environments.

Specifications and Dimensions

Size range: Generally 1/2″-60″ (DN15-DN1500), to meet the different needs of small-diameter to large-scale industrial pipelines.

Pressure rating: Common pressure ratings include Class 150, 300, 600, 900, 1500, 2500lb, and PN2.5, PN6, PN10, PN16, PN25, PN40, etc. Different pressure ratings correspond to different application scenarios and pipeline system requirements.

Type Classification

Standard blind flange: The most common type, with a solid disc design, suitable for most conventional applications, with different pressure ratings and flange face types.

Blind flange with handle: With a handle or lug for easy installation and removal, especially suitable for occasions requiring frequent operation, improving work efficiency and safety.

Gasket-type blind flange: Consists of two thin metal rings and a central gasket, suitable for systems that require regular inspection or cleaning, allowing for quick disassembly without affecting the entire flange connection.

Figure-eight blind flange: Shaped like the number "8", one side is a blind flange, and the other side is a flange with a hole. Rotation allows the pipeline to be opened or closed, making it ideal for process switching.

Manufacturing standards: Common manufacturing standards include ASME/ANSI B16.5, ASME B16.47 Series A/B, DIN, JIS, etc. Different standards may have differences in size, tolerance, and materials, ensuring the quality and interchangeability of blind flanges.

Application Areas

Wind power industry	Shipbuilding	Mechanical manufacturing
Nuclear power industry	Oilfield industry	Chemical industry