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Aramid Fiber RTJ Gasket: Material Limits and Correct Gasket Selection

Quick Answer: A standard RTJ gasket is a solid metal ring. An aramid fiber RTJ gasket is not a standard ASME B16.20 or API 6A ring joint gasket. If the application requires aramid fiber, the correct product is usually an aramid fiber sheet gasket, a spiral wound gasket with aramid filler, or a custom cut non-metallic gasket. Send CORASEALS the flange standard, ring number, pressure class, fluid, operating temperature and pressure, and required quantity for a specific recommendation.

What a Standard RTJ Gasket Does

An RTJ gasket seats in a machined groove on a flange. The flange may follow ASME B16.5, ASME B16.20, API 6A, or API 17D. When the flange bolts are tightened, the metal gasket deforms into the groove. This creates a high-integrity seal for high pressure oil, gas, refinery, and wellhead connections.

RTJ gasket type codes include R, RX, and BX. R series ring numbers are listed in ASME B16.20. RX and BX ring numbers are used in API 6A and API 17D service. Each ring number matches a specific groove geometry and pressure class. A wrong ring number will not seal correctly, even if the outside diameter looks close.

Why an Aramid Fiber RTJ Gasket Is Not Standard

Standard RTJ sealing depends on controlled deformation of a metallic ring. RTJ materials include soft iron, low-carbon steel, Type 304 stainless steel, Type 316 stainless steel, and corrosion-resistant nickel alloys such as alloy 625. Aramid fiber composites do not have the same yield behavior under RTJ groove load. A non-metallic ring in a standard RTJ groove can extrude, split, or fail at high pressure.

Aramid fiber is strong and abrasion resistant. Those properties support sheet gaskets, spiral wound filler, and some cut gaskets. The fiber alone cannot reproduce the sealing action of a solid metal RTJ ring. When a customer requests an aramid fiber RTJ gasket, CORASEALS checks whether the flange has a standard RTJ groove or a non-standard gasket seat.

When Aramid Fiber Is the Right Gasket Material

Aramid fiber is commonly used in compressed non-asbestos sheet gaskets. The sheet also contains an elastomer binder. The binder controls chemical resistance and temperature limit. Typical service includes water, steam, oil, and many industrial fluids. Do not use an aramid fiber sheet gasket in a standard RTJ groove unless the flange design is non-standard and the pressure and temperature are within the sheet gasket rating.

Aramid fiber also works as spiral wound gasket filler. The filler sits between metal winding strips. This design handles thermal cycling, raised face flanges, and many piping, heat exchanger, and pump connections. The filler choice is not a substitute for an RTJ ring.

• Aramid fiber sheet gasket: cut from compressed sheet, used on raised face and flat face flanges.
• Spiral wound gasket with aramid filler: used with a metal winding and centering ring.
• Custom cut aramid gasket: produced from a drawing for non-standard sealing seats.

How to Specify the Correct Gasket

For a standard RTJ gasket, provide the following data:

• Flange standard: ASME B16.5, ASME B16.20, API 6A, API 17D, or other.
• Nominal pipe size and bore size.
• Ring number: R20, R24, RX20, BX150, or the code from the existing part.
• Pressure class: 150, 300, 600, 900, 1500, 2500, or the API class.
• Medium: oil, gas, water, steam, chemical, or hydrocarbon.
• Temperature and pressure: actual operating range.
• Material preference: soft iron, low-carbon steel, stainless steel, or corrosion-resistant alloy.

For an aramid fiber sheet gasket or spiral wound gasket, provide:

• Flange standard and pressure class.
• Gasket ID, OD, and thickness.
• Fluid and temperature.
• Sheet ma