A pipe blind flange is a solid, unbored flange used to close the end of a piping system, valve, or pressure-vessel nozzle. To select one, match its nominal pipe size, flange standard, pressure class, material, facing, and bolt pattern to the connected equipment and service conditions. A pressure-class label alone does not tell you the allowable working pressure: the applicable pressure–temperature rating depends on the governing standard and material group. I recommend confirming those details against the project specification before requesting a quotation or placing an order.
Please visit our website for more information on this topic.
This guide is for engineers, procurement teams, fabricators, and distributors comparing blind flange dimensions and ratings for a new project or replacement. It explains how the main specifications fit together, what to check when matching a flange to a line, and what information to provide a supplier. Longrun can review stainless steel flange requirements alongside pipe specifications to help buyers prepare a consistent inquiry.
Unlike a weld neck or slip-on flange, a blind flange has no opening for fluid flow. Bolted to a mating flange with a suitable gasket, it provides a removable closure for a pipe end or equipment connection. This makes it useful where a line needs a defined termination, access for inspection, or the possibility of future extension.
Blind flanges are used in process and utility piping, water systems, chemical facilities, and other installations where the selected material and rating suit the service. They may also be used to isolate a connection during maintenance, but a flange should not be treated as a substitute for an engineered isolation and safety procedure. Actual use must follow the system design and applicable site requirements.
Blind flange dimensions are not determined by nominal pipe size alone. The governing standard and pressure class also affect dimensions such as outside diameter, thickness, bolt-circle diameter, number and size of bolt holes, and facing details. The flange must match the mating component, not merely the pipe’s nominal size.
For many North American piping applications, ASME B16.5 covers flange sizes from NPS 1/2 through NPS 24, with dimensions and pressure–temperature ratings organized by class and material group. For larger steel flanges, ASME B16.47 covers NPS 26 through NPS 60 and includes Series A and Series B dimensions. These standards are not interchangeable by assumption; confirm the specified series, edition, and connection details before ordering.
As a nominal-size reference, NPS 6 is commonly associated with DN 150, while NPS 24 is commonly associated with DN 600. These designations identify nominal pipe size and do not give the flange’s outside diameter or thickness. Use the applicable standard table or an approved drawing for those physical dimensions, and check that the bolt pattern matches the mating flange.
Common flange facings include raised face (RF), flat face (FF), and ring-type joint (RTJ), where specified by the applicable standard and service. The blind flange facing must suit the mating flange and selected gasket; combining incompatible facing arrangements can prevent correct seating. For replacement orders, a drawing, flange marking, or measured interface details can help resolve uncertainty.
Pressure class is a standardized designation, not a universal pressure value in pounds per square inch. For example, Class 150 does not mean the flange is suitable for every service at 150 psi. The allowable pressure depends on the relevant pressure–temperature table, material group, flange standard, and design conditions.
ASME B16.5 includes class designations such as 150, 300, 400, 600, 900, 1500, and 2500, but availability and allowable ratings vary by size and material. As temperature changes, the permitted pressure can change too. The system designer should verify the required rating at the actual design temperature and pressure rather than selecting by class number alone.
Link to Longrun
For a reliable selection, compare the flange’s material specification and standard rating with the line’s design pressure and temperature, including any project-specific requirements. Consider the connected equipment and bolting as part of the same joint. If the operating conditions, fluid, or governing code are unclear, request engineering clarification before buying.
Material selection should account for the fluid, temperature, corrosion conditions, and project specification. Stainless steel blind flanges are often considered where corrosion resistance is important, but “stainless steel” by itself is not a complete material specification. Commonly specified forged stainless grades include ASTM A182 F304/304L and F316/316L; the appropriate grade must be confirmed for the particular service.
Buyers should also check whether the order calls for a forged product form, a particular material standard, heat or traceability documentation, or other inspection requirements. Do not assume that a grade, manufacturing route, or document package is included unless it is stated in the quotation and order. Where a blind flange connects to stainless steel pipe, verify that the flange and pipe specifications are compatible with the project’s material and joining requirements.
A clear request for quotation helps a supplier check the exact product rather than estimate from a partial description. Include the standard and edition if specified, nominal size, pressure class, facing, material grade, quantity, and delivery destination. Attach a drawing or mating-flange details when the connection is non-standard or when replacing an unidentified part.
Blind flange pricing can vary with size, class, material, manufacturing requirements, quantity, documentation, and delivery terms. Larger dimensions or higher classes may require different material and production planning than common stock items, but availability is supplier- and order-specific. Request a written quotation that separates product specification, quantity, documentation, packaging, and freight assumptions where possible.
Minimum order quantities and lead times should be confirmed for the exact grade and configuration. If a project has a fixed delivery date, share it with the RFQ and ask the supplier to confirm availability and schedule in writing. Avoid treating a general estimate as a commitment until the final specification and order details have been reviewed.
At Longrun, we support B2B buyers sourcing stainless steel piping products by reviewing the requested flange and pipe specifications together. Share your connection details, operating conditions, material requirements, quantity, and delivery location so our team can assess the inquiry and clarify any missing selection information. Final suitability should always be verified against the project design and governing requirements.
Select a pipe blind flange by matching the dimensional standard, nominal size, class, facing, material, and service conditions to the mating connection and system design. Do not interpret a class number as a standalone pressure value, and do not use nominal pipe size as a substitute for checking the flange’s full dimensions and bolt pattern. For larger flanges, confirm whether the specified standard and series apply.
Before ordering, compile the design pressure and temperature, size, standard, class, material grade, facing, quantity, and documentation needs. Then request a written quotation and review its technical details against the project specification. Send those requirements to Longrun to discuss a suitable stainless steel blind flange sourcing option and obtain a project-specific quotation.
The company is the world’s best Pipe Blind Flange supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.