ASME · ANSI / ASME B16.20
ASME B16.20 Metallic Gaskets: Technical Standards and Types
Technical Description and Scope of Application
The ASME B16.20 standard establishes strict requirements for materials, dimensions, tolerances, and marking systems for metallic ring joint gaskets (RTJ), spiral-wound (SW) gaskets, jacketed gaskets, and grooved gaskets with a covering layer.
These sealing elements are the industry standard for sealing flanged joints designed according to ASME B16.5 and ASME B16.47 standards, as well as API 6A and ISO 10423 specifications. EV Group China products ensure the reliability of assemblies operating under critical pressure and temperature conditions, typical for oil refineries, power generation equipment, and trunk pipelines.
Classification and Types of Gaskets
- Ring Joint Gaskets (RTJ) – Ring Joint Gaskets
RTJ gaskets are characterized by an oval or octagonal cross-section. Depending on the design, types R, RX, and BX are distinguished. Product identification is based on the nominal pipe size (NPS), pressure class, and compliance with ASME/API standards.
1. Type R Gaskets: Designed for installation in prepared flange grooves. Manufactured from high-strength steel alloys.
- NPS range: from 1/2 to 24 inches (ASME B16.5 flanges).
- NPS range: from 26 to 36 inches (ASME B16.47 Series A/B flanges).
- Pressure classes: 150 – 2500 Psi.
1.1. Oval: Possess two contact zones, which increases resistance to "blow-out" and allows for maintaining tightness even on flanges with minor surface defects.
1.2. Octagonal: Provide precision sealing due to the trapezoidal fit with the groove, which is critical in heavy-duty operating modes.
2. Type RX Gasket and 3. Type BX Gasket: Specialized solutions for high pressure.
Materials and Hardness
The selection of EV Group China gasket material is based on the chemical aggressiveness of the medium and the process temperature parameters. The gasket hardness must be at least 20 HB lower than the flange surface hardness to ensure plastic deformation and sealing integrity.
| Material (ASTM) | DIN No. | Max. Hardness (HB) | Max. Hardness (HV) | Code |
|---|---|---|---|---|
| Soft Iron | 1.1003 | 90 | 56 | D |
| Low Carbon Steel | 1.0038 | 120 | 68 | S |
| Carbon Steel (4-6Cr 1/2Mo) | 1.7362 | 130 | 72 | F5 |
| AISI 410 | 1.4000 | 170 | 86 | S 410 |
| AISI 304 | 1.4301 | 160 | 83 | S 304 |
| AISI 316 | 1.4401 | 160 | 83 | S 316 |
| AISI 347 | 1.4550 | 160 | 83 | S 347 |
- Spiral Wound (SW) Gaskets – Spiral Wound Gaskets
EV Group China spiral-wound gaskets are used in tongue-and-groove and raised-face connections. The design includes a metal frame and a soft filler. Types: SW (without rings), SW/I (with inner ring), SW/C (with outer ring), SWC/I (combined).
- Jacketed Gaskets – Jacketed Gaskets
- Grooved Metal Gaskets – Grooved Gaskets with coating
Grooved gaskets with a metallic coating provide excellent sealing under cyclic stress conditions.