RF vs RTJ Flanged Valves: Which Face to Specify for High Pressure
Technical guide · Supreme Valves India · Updated 2026-10-24
Valve enquiries for Class 600 and above usually specify the flange facing as either raised face (RF) or ring type joint (RTJ). The choice is set by the piping class, but it changes the gasket, the valve's end-to-end length and the inspection requirements, so it is worth understanding both.
Raised face (RF)
The sealing surface is a raised ring around the bore. Under ASME B16.5 the raised face height is 1.6 mm (1/16 inch) for Class 150 and 300, and 6.4 mm (1/4 inch) for Class 400 and above. A flat gasket sits on the raised face and is compressed by the bolts.
- Gaskets: spiral wound gaskets to ASME B16.20 with inner and outer rings are standard in process piping; compressed fibre, PTFE and graphite sheet gaskets are used at lower duties.
- Surface finish: a serrated or phonographic finish, typically 3.2 to 6.3 µm Ra (125 to 250 µin), lets the gasket grip and seal.
- Use: by far the most common facing for Class 150 to 600, and widely used at higher classes too.
Ring type joint (RTJ)
Each flange face has a machined groove. A solid metal ring sits in the grooves of both flanges, and bolt load deforms the ring slightly so it seals metal to metal along the groove walls.
- Gaskets: oval or octagonal R rings to ASME B16.20 for ASME flanges; RX and BX pressure-energised rings for API 6A wellhead equipment.
- Materials: soft iron, low carbon steel, 4 to 6 percent chrome, 304, 316 and alloys, chosen to be softer than the groove.
- Use: high pressure and high temperature service, often Class 900 and above; also specified at Class 600 by some operators for hydrocarbon, hydrogen, offshore and wellhead systems, and where fire resistance of the joint matters.
Side-by-side
| RF | RTJ | |
|---|---|---|
| Seal | Compressed flat or spiral wound gasket | Metal ring deformed into grooves |
| Typical classes | 150 to 600, also higher | 600 to 2500, API 6A |
| Tolerance of misalignment | Moderate | Low; flanges must be well aligned |
| Reuse of gasket | No | No; ring is replaced at each make-up |
| Inspection | Face finish and flatness | Groove dimensions, finish and hardness |
| Valve length | RF dimension per ASME B16.10 | Separate RTJ dimension, often longer |
Practical points for valve buyers
- Match the piping class. The facing comes from the piping material specification. Don't substitute one for the other.
- Check end-to-end length. RTJ valves often have a longer B16.10 dimension than RF valves of the same type and class, which matters on replacements.
- State the ring number. For RTJ, give the ring type and number (for example R-37) or let the supplier select it per ASME B16.5 for the size and class.
- Groove protection. RTJ grooves are easily damaged in handling. Specify end protectors and check the grooves at receipt.
- Groove inlay. For corrosive or sour service, carbon steel valves can have stainless steel or alloy 625 weld overlay in the ring grooves.
- Testing. Shell tests are done with the ends blanked; for RTJ valves the test fixtures seal in the groove. Ask for groove dimensional and hardness checks to be recorded if your specification requires it.
RFQ checklist
- Valve type, size and class.
- Facing: RF (with finish if non-standard) or RTJ (with ring number or "per B16.5").
- Flange standard: ASME B16.5 up to NPS 24, ASME B16.47 Series A or B above.
- Body material, groove inlay if required, and service (sour, hydrogen, offshore).
- Whether gaskets or rings are to be supplied with the valve.
Send the line list with facing and class per tag and we will confirm end-to-end dimensions and ring numbers in the quotation.
Frequently asked questions
Can an RF valve be bolted to an RTJ flange?
No. The faces are incompatible: a raised face cannot seat a ring gasket, and an RTJ groove does not give a spiral wound gasket a flat sealing surface. Both mating flanges and the valve ends must have the same facing.
Is an RTJ valve longer than an RF valve?
Often yes. ASME B16.10 lists separate face-to-face or end-to-end dimensions for ring joint ends, which for many valve types and classes are longer than the RF dimension. Check the dimension when replacing a valve in existing piping.
Why must the ring gasket be softer than the groove?
The ring seals by deforming slightly into the groove under bolt load. If the ring is harder than the groove, it damages the groove instead of deforming. Ring material is chosen to be softer than the flange material, and grooves in carbon steel valves are sometimes inlaid with stainless steel or alloy for corrosion and hardness.
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