Super Duplex Steel RTJ Gasket

Super duplex grades (S32750 and S32760) contain significantly higher chromium (25%), molybdenum (3–5%), and nitrogen than standard austenitic steels like 316L. This raises the PREN above 40, giving exceptional resistance to pitting and crevice corrosion in chloride environments. Their yield strength (≥ 550 MPa) is roughly double that of 316L (≥ 210 MPa), allowing a smaller, lighter gasket to achieve the same sealing performance at higher pressure classes.

Specify super duplex when your service involves: (a) chloride concentrations above 200 ppm at temperatures over 60°C, (b) sour gas (H2S) service covered by NACE MR0175, (c) reducing acids such as H2SO4 or HCl (S32760 preferred), (d) pressure classes 2500 and above in offshore or subsea environments, or (e) any application where stress corrosion cracking of standard austenitic steels is a documented risk.

Both are super duplex grades with PREN above 40. S32750 is the more widely stocked and specified grade and is fully covered by NACE MR0175. S32760 adds tungsten (0.5–1.0%) and copper (0.5–1.0%), which improve corrosion resistance in reducing acid environments. For most offshore and chloride service applications S32750 is the standard choice; S32760 is specified when reducing acids or mixed acid streams are present.

Our R and RX type gaskets are manufactured for pressure classes 150 through 20,000 psi per ASME B16.5 and ASME B16.47. BX type gaskets are manufactured to API 6A for wellhead pressure ratings of 2,000, 3,000, 5,000, 10,000, 15,000, and 20,000 psi working pressure. The maximum allowable working pressure depends on the ring number, material grade, and operating temperature — contact our technical team with your P-T conditions for a specific recommendation.

Yes. Every order is supplied with a 3.1 Mill Test Report (MTR) as standard, providing full traceability from the original mill heat to the finished gasket. The MTR includes: heat / batch number, chemical analysis, mechanical test results, heat treatment record, and dimensional check confirmation. 3.2 MTRs (countersigned by a TPI inspector) are available on request. PMI (Positive Material Identification) testing by XRF is performed on every batch and results are included in the documentation package.

All sealing contact surfaces (the oval/octagonal profiles of R-type and the pressure-bearing faces of BX and RX types) are finish-machined to a surface roughness of Ra 0.8 – 3.2 μm (125 – 250 μin RMS) in compliance with ASME B16.20. Sealing faces are free from tool marks, scratches, pits, or any surface discontinuities that could impair the metal-to-metal seal. Non-sealing surfaces are finished to Ra ≤ 6.3 μm.

We maintain ready stock of the most common ring numbers in S32750 for sizes 1/2″ to 6″ across Classes 150 to 2500. Standard orders from stock are dispatched within 3–5 working days with full documentation. For non-stock ring numbers, special sizes, or large-quantity orders, our manufacturing lead time is typically 2–4 weeks. Urgent project requirements can often be accommodated — contact our team with your ring numbers and quantities.

ASME B16.20 requires that the hardness of the RTJ gasket must be lower than the hardness of the mating flange grooves. For super duplex gaskets (HRC ≤ 32), the matching flange material should have a hardness of HRC 35 or above — this is typically achieved with carbon steel or alloy steel flanges. When flanging in super duplex to super duplex, matching hardness must be carefully reviewed with the flange and gasket manufacturer to ensure preferential deformation of the gasket.