VENTURI / Technical insight
Valve Connections: RF, RTJ and Face-to-Face Fit
Quick answer
Matching DN/NPS and pressure class is not enough for a replacement valve. Verify the flange standard, RF or RTJ facing, bolt pattern, gasket, face-to-face length and installation clearances together.
What is the difference between RF and RTJ?
RF uses a raised gasket face; RTJ uses a groove for a matching metal ring gasket. They are different sealing arrangements. For RTJ, match ring type, number, material and groove dimensions. For RF, check gasket type, dimensions and facing condition. An arbitrary gasket change cannot make incompatible faces match.
Why can flanges with the same DN fail to match?
Nominal size does not define bolt count, hole diameter or bolt-circle diameter. EN and ASME systems, and different classes within one system, can differ. If the old nameplate is unreadable, use an approved drawing or complete connection measurements rather than outside diameter alone.
How should face-to-face and end-to-end lengths be compared?
Dimensional standards such as ASME B16.10 address defined valve types, materials, sizes, classes and connections; lengths are not universal. Confirm the series and measurement reference faces on the drawing. Welded ends also need pipe wall thickness and weld preparation. Resolve mismatch through an engineered arrangement, not by forcing the pipe.
Which measurements belong in a replacement order?
Start with the nameplate, overall photograph, length and connection standard. Add clearances for body, rising stem and actuator maintenance. A butterfly disc moves into the pipe, so check bore and adjacent components. Send these details to Venturi for a quotation matched to the existing layout.
| Check | Information for the decision |
|---|---|
| RF | Raised face, matching gasket and bolting |
| RTJ | Matching groove, ring type/number and material |
| Weld end | Wall thickness, end preparation and end-to-end length |
Frequently asked questions
Can RF and RTJ be directly joined?+
They are not interchangeable. The project must specify compatible facings and gaskets.
Does the same DN mean the same face-to-face length?+
No. Valve type, length series, rating and connection can change the dimension.
Contact Venturi for selection and technical verification against your application requirements.
