Introduction to ANSI/ASME Blind Flanges
1. Origin of the Standard
ANSI/ASME flanges are mainly defined by ASME B16.5 (Pipe Flanges and Flanged Fittings), which was developed by the American Society of Mechanical Engineers (ASME) and approved by the American National Standards Institute (ANSI).
In China, the chemical industry standard HG20622-97 was issued to align with international engineering needs. It adopts and references parts of ASME B16.5, making it widely applicable in both domestic and export projects.
2. Definition of Blind Flanges (BL)
A Blind Flange (BL) is a flange without a central bore. Its main purposes are:
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To close the ends of piping systems or vessel openings, providing a reliable seal.
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To facilitate maintenance or testing, since it can be easily removed when necessary.
Unlike welding neck flanges or threaded flanges, blind flanges are not used to connect pipes but to block off a section of a pipeline.
3. Applicable Pressure Ratings
The provided dimensions correspond to PN20 / Class150 pressure ratings:
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PN20: Nominal pressure 20 bar (approximately 2.0 MPa).
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Class150: ANSI pressure class 150 lbs.
This pressure rating is one of the most commonly used in low-pressure piping systems, such as in chemical plants, water supply projects, shipbuilding, and general industrial pipelines.
4. Product Applications
Blind flanges are widely applied in:
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Chemical and petrochemical industries
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Water treatment and environmental projects
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Oil & gas pipelines
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Power plants and shipbuilding
They are essential wherever a pipe end, valve, or pressure vessel needs to be sealed, isolated, or tested.
