RF vs RTJ Valve Flange: Choosing the Right Face Type for Your Joint

The Short Answer

RF (raised face) and RTJ (ring-type joint) are two flange face designs used to seal the bolted connections of valves and piping. RF flanges seal by compressing a gasket between two flat raised faces; RTJ flanges seal by squeezing a metal ring into a machined groove. RTJ is typically chosen for higher pressure and higher temperature services where a compressible gasket cannot hold, while RF is the economical standard for most lower and moderate pressure duties.

How Each Face Seals

An RF flange has a raised circular surface that carries the gasket. When the flange bolts are torqued, the gasket is compressed between the two raised faces and fills the surface irregularities, forming the seal. The raised face also protects the gasket and helps center it during assembly. RF is simple, cheap, and works well with the standard gasket materials used across most industrial services.

An RTJ flange uses a machined groove on the face that receives a metal ring (often octagonal or oval in cross-section). Tightening the bolts forces the ring into the groove, deforming it plastically to form a metal-to-metal seal. There is no soft gasket to age, degrade, or blow out, which is why RTJ appears in severe services where a gasket failure would be dangerous or where the temperature rules out elastomer and soft gasket materials.

RF vs RTJ: Side by Side

Aspect	RF (Raised Face)	RTJ (Ring-Type Joint)
Sealing mechanism	Compressed soft gasket	Deformed metal ring in groove
Typical pressure range	Lower and moderate classes	Higher classes
Temperature range	Limited by gasket material	Broad, metal ring withstands high temperature
Assembly skill	Simple, standard gasket	Requires careful ring seating and torque
Gasket replacement	Routine maintenance item	Ring can be reused if undamaged, but often replaced
Relative cost	Lower	Higher machining and material cost
Typical service	Water, oil, gas, general process	High-pressure gas, severe process services

The table is a general guide; the applicable flange standard defines which face types are available for each pressure class, and that standard should govern the selection. The choice between the two is therefore not a preference but a consequence of the service conditions and the standard.

Choosing the Right Face Type

The first constraint is the flange standard itself: for a given pressure class, the standard may specify whether RF or RTJ (or both) is available. Within the allowed options, the service conditions decide. If the temperature and pressure are moderate and the fluid is not hazardous, RF with a suitable gasket is typically the economical choice, and the gasket is selected for the fluid and temperature. If the service is high-pressure gas, flammable or toxic media, or high temperature where gasket life is a concern, RTJ is generally preferred because the metal ring does not degrade like a soft gasket.

Assembly is a practical differentiator. RTJ joints need the ring seated cleanly and the bolts torqued to the procedure; a mis-seated ring leaks immediately and is awkward to correct. RF joints are more forgiving for field crews. For maintenance organizations without specialized training, RF is easier to keep reliable — another reason it dominates ordinary service.

The applicable flange standard is the final arbiter. The standard defines the face dimensions, the pressure-temperature ratings, and the gasket and ring details for each face type, and it is not optional to follow it. When a valve or mating pipe flange is ordered, the face type and the pressure class must match across the connection, and the standard governs which combinations are valid. Ordering a valve by nominal size alone, without stating the face type and class, is a common source of field mismatches that cost time and money at installation.

Gaskets, Bolting, and Assembly Details

The gasket and bolting details reinforce the difference. An RF joint uses a soft gasket — commonly a sheet, spiral-wound, or other compressible type matched to the fluid and temperature — and the gasket is expected to be replaced each time the joint is opened. An RTJ joint uses a metal ring that, if undamaged, can be reused, though most maintenance procedures replace it anyway because the ring is inexpensive relative to the cost of a leak. Bolting torque is more critical on RTJ joints: the ring must be seated and compressed uniformly, and uneven torque is the most common cause of a failed metal seal. On RF joints, the gasket material and the surface finish of the raised face determine the seal, and a damaged face should be refinished before reassembly.

Spare part strategy differs too. A utility or plant carrying RF gaskets in standard materials and sizes can cover most of its network; RTJ rings are more service-specific and usually stocked per flange size and class. If the maintenance team is not trained on metal-ring joints, the practical reliability of RF is often better in ordinary service, while RTJ earns its place where the service severity leaves no alternative.

Application Scenario: A High-Pressure Gas Header vs a Water Line

Consider two connections on the same plant. On a water service line at moderate pressure, an RF flange with a standard gasket is the obvious choice: cheap, easy to assemble, and the gasket is a routine replacement item. On a high-pressure natural gas header, the same utility would typically specify RTJ flanges, because the metal ring holds the joint tight under high pressure and temperature where a soft gasket would risk extrusion or blowout. Mixing the two face types in one connection — an RF flange against an RTJ flange — is not a valid joint and should be avoided; the two designs are not interchangeable. For the pressure class logic behind these choices, see PN vs Class pressure rating and the overview of valve pressure classes.

This article provides general educational knowledge only and is not professional engineering advice.

Tags: Valve Standards