The sealing systems are not interchangeable
A raised-face flange has a machined annular contact area above the surrounding flange face. A selected flat or spiral-wound gasket is compressed between the mating raised faces by the bolting system. Gasket type, dimensions, filler, winding and inner or outer rings follow the piping specification.
An RTJ flange has a precision-machined groove. A matching metallic ring gasket is loaded between the grooves. Ring profile, ring number, material, hardness and flange-groove geometry work as one system. A flat gasket does not convert an RTJ facing into RF service.
| Item | Raised face (RF) | Ring type joint (RTJ) |
|---|---|---|
| Sealing element | Selected sheet or spiral-wound gasket system | Matching metallic ring gasket |
| Machined interface | Raised annular face and surface finish | Groove profile, dimensions and finish |
| Matching requirement | Flange standard, class, NPS and facing | Flange standard, class, NPS, facing and ring designation |
| Installation control | Gasket centring, clean faces and bolting procedure | Correct unused ring, undamaged grooves and controlled bolting |
| Field conversion | Requires engineered compatibility review | Requires engineered compatibility review |
ASME B16.5 fixes the flange interface, not the valve duty
ASME B16.5 covers pressure-temperature ratings, materials, dimensions, tolerances, marking and testing for pipe flanges and flanged fittings across its published NPS and Class ranges. A valve requisition should name ASME B16.5, the edition, Class, NPS and facing.
The valve design remains subject to its product standard and ASME B16.34 or another stated design basis. The applicable rating is based on material group and temperature. “Class 1500 RTJ” is an interface description, not a complete allowable-pressure statement.
RTJ requires exact ring and groove data
The ring designation is determined by the governing flange table for the selected Class and NPS. The ring material must be suitable for the process and compatible with the flange hardness requirements. The supplier should not select a ring from nominal pipe size alone.
Record whether rings are included with the valve package. Store and handle them as sealing components. A ring that has been loaded or damaged should not be assumed reusable; follow the project gasket procedure and ring manufacturer’s instructions.
- Flange standard and edition
- NPS and pressure Class
- RTJ facing and ring designation
- Ring profile and material required by the piping specification
- Responsibility for supplying rings and bolting
Face-to-face must be checked on replacements
Changing from RF to RTJ can change the valve end-to-end dimension. For an applicable straightway valve, check the ASME B16.10 X adjustment for the exact Class and NPS, then confirm the approved drawing and site fit.
Request an approved general-arrangement drawing showing end-to-end, flange outside diameter, bolt circle, hole pattern, facing, ring groove and bore. For brownfield work, compare those values against measured site dimensions before releasing the order.
Choose the facing from the piping class
RTJ is used where the piping specification calls for a metal ring-joint interface. RF remains common across a broad range of services. Neither facing is inherently the right answer without the flange class, material, temperature, leakage requirements and site maintenance practice.
A change of facing is a piping-system deviation. It affects mating flanges, gaskets, spare parts, dimensions and installation procedure and requires documented project approval.
Specification checks
- State ASME B16.5 edition, NPS, Class and RF or RTJ facing.
- For RTJ, state or request confirmation of ring number, profile and material.
- Confirm whether gaskets, rings, studs and nuts are included.
- Approve the valve end-to-end and detailed flange drawing before fabrication or replacement.
- Treat any RF/RTJ change as a documented piping deviation.
Catalogue and RFQ
Standards publisher references
Published by Nordic Valves Ab Oy, the operator of FerraForge. These links describe the publishers’ official scope. Purchase documents must state the edition required by the project and include any amendments or owner specifications.
- ASME B16.5 - Pipe Flanges and Flanged FittingsASME · Official scope for Class-designated pipe flanges, dimensions, facings, materials and ratings.
- ASME B16.20 - Metallic Gaskets for Pipe FlangesASME · Official scope for ring-joint, spiral-wound and metal-jacketed gasket materials, dimensions and markings.
- ASME B16.10 - Face-to-Face and End-to-End Dimensions of ValvesASME · Official scope for valve installation dimensions by material, type, size, rating class and end connection.
- ASME B16.34 - Valves - Flanged, Threaded, and Welding EndASME · Official scope covering valve pressure-temperature ratings, materials, dimensions, testing and marking.