This question appears when a metric piping package, valve or imported skid must connect to an ASME line. The labels can look reassuring: both sides may show a raised face and a similar nominal pressure. Those similarities do not establish interchangeability. A bolted joint works only when the bolt pattern, contact geometry, gasket and design conditions agree.

What Type B1 and Type B2 Mean

EN 1092-1 identifies flat face as Type A and raised face as Type B. The standard then distinguishes B1 and B2 for different applications. The designation belongs to the EN system. The project must identify the exact standard edition, DN, PN and facing variant rather than writing only “raised face.”

An ASME B16.5 RF designation also describes a raised face, but it belongs to an NPS and Class system. Similar names describe function, not a guarantee that the two faces share the same diameter, height, finish or bolt pattern.

Five Compatibility Checks Before Mating

Why “Both Are Raised Face” Is Not Enough

The gasket load path begins at the bolts and passes through both flanges into the gasket. If the drilling does not align, the joint cannot be assembled as designed. If the raised-face diameters or gasket contact areas differ, compression can become uneven. A face-finish mismatch can also change gasket friction and sealing behavior. A fabricated adapter or transition spool may solve an interface problem, but the project engineer must design and approve it.

Do not enlarge bolt holes, force bolts at an angle or select a gasket merely because it fits inside both bores. Those field changes can invalidate the intended joint geometry and documentation.

Product Selection and RFQ Boundary

For an ASME-side connection, the ASTM A182 F316L weld neck flange and ASTM A182 F316L slip-on raised face flange illustrate two product routes. The correct type still depends on piping design, welding details, material specification and the mating component. These links do not imply that an ASME product is automatically compatible with an EN Type B1 or B2 flange.

An RFQ for a mixed-standard interface should include the EN and ASME component drawings, standard editions, size, pressure designation, material, facing, gasket, bolting and design conditions. Mark any proposed adapter as a project-specific item.

Frequently Asked Questions

Is EN 1092-1 B1 the same as ASME raised face?

No automatic equivalence exists. The two labels come from different standards. Compare controlled dimensions, drilling, finish, gasket and ratings.

Can B1 and B2 be treated as the same facing?

No. EN 1092-1 identifies them for different applications. State the required variant and edition on the RFQ.

Can a custom gasket make two mismatched flanges compatible?

A gasket cannot correct incompatible drilling or uncontrolled face geometry. Any engineered transition needs design review and an approved drawing.

What should the supplier confirm?

Ask for the governing standards, dimensional drawings, facing finish, material specification, marking and documentation for each component.

References and Image Source Index

1. BSI Knowledge: BS EN 1092-1:2018 overview.
2. ASME: B16.5 official scope page.
3. Company internal presentation “ASME B16.5 Flange Important Matters”: company product photographs and direct technical excerpts identified as EN 1092-1:2018 and ASME B16.5-2025. The licensed standards govern.