What identifies a flange?
Read nominal size, pressure class, flange type and facing together. Weld-neck, slip-on and threaded connections form different assemblies. Bolt circle, hole count and facing must match the mating component. Outside diameter is a starting measurement for replacement, but does not identify the product without its connection standard.
Record the existing markings, nominal size and facing. Use the latest drawing revision where available. Nearly matching hole layouts do not establish interchangeability between standards. Any need to enlarge holes or adapt a part requires separate assessment within the design scope.
Is PN or Class the operating pressure?
Pressure class is defined within a standard and read with material and temperature. One number should not be used as an allowable pressure for every alloy and temperature. A dimensional standard alone also does not define material chemistry and mechanical acceptance. Prepare the enquiry using project design conditions and product specifications.
Facing, gasket and bolting
Flat or raised facing is chosen with the mating flange and gasket arrangement. Surface condition, gasket geometry and assembly method influence sealing. The material name alone is incomplete. Verifying the gasket and assembled joint is a separate technical scope from supplying raw metal or a single flange.
Bolts, studs and nuts require matching threads and mechanical requirements. A stainless label or across-flats dimension does not establish a finished nut’s property class. In hot or corrosive service, assess bolting material and condition against the assembly operating conditions.
What else matters for a blind flange?
A blind flange closes an opening; a plate with similar bolt holes is not automatically a substitute. Specify connection standard, class, facing and material together. For a special closure drawing, thickness and inspection requirements must come from the design rather than catalogue assumptions.
Listing type, size, class, facing, material and quantity separately makes omissions visible. Add required documents and tests. Quotations can then be compared against the same assembly and acceptance requirements rather than a flange name alone.