Overview
ASME B16.20 is a dimensional and product standard for defined metallic gasket constructions used with pipe flanges. Its scope includes ring-joint gaskets, spiral-wound metal gaskets, metal-jacketed gaskets, and grooved metal gaskets with covering layers. The standard addresses items such as materials, dimensions, tolerances, and markings within its stated scope.
Referencing ASME B16.20 does not complete the purchase description. The buyer still needs gasket type, flange standard, nominal size, pressure class, material combination, thickness or style, inner and outer ring requirements, service conditions, quantity, and project-specific testing or documentation.
Why It Matters for Pipe Components
A gasket can be manufactured to a recognized dimensional standard and still be unsuitable for the fluid or joint. The winding metal, filler, ring material, jacket, facing layer, and hardness need to match pressure, temperature, corrosion, oxidation, and contamination requirements.
The associated flange standard also matters. ASME B16.20 gaskets are dimensionally related to specific flange systems within the standard’s scope. A gasket selected by nominal size alone may not match the facing or groove.
Marking and traceability are important when multiple materials or pressure classes are stored together. Incorrect ring color, unreadable marking, or mixed batches can cause installation errors even when the gasket dimensions are correct.
Methods, Parameters, or Process
Build the order by identifying the flange joint first and the gasket construction second.
| Order field | Why it matters | Example control |
|---|---|---|
| Gasket construction | Selects the applicable dimensional and material requirements | Spiral wound, ring joint, jacketed, or grooved metal |
| Flange system | Confirms dimensional compatibility | Applicable ASME flange standard and class |
| Nominal size and class | Selects the correct gasket dimensions | NPS and pressure class |
| Metallic materials | Controls corrosion, strength, and temperature capability | Winding, ring, jacket, or solid ring material |
| Filler or facing | Controls sealing and chemical compatibility | Graphite, PTFE, or project-approved material |
| Style and rings | Defines centering and inner-ring arrangement | Project-approved style and ring configuration |
| Documents | Provides batch and material evidence | Certificate, material declaration, dimensional report |
Supplier and Inspection Checklist
- Confirm the required ASME B16.20 edition in the contract.
- Identify the mating flange standard, size, class, and facing.
- Specify exact gasket construction and material combination.
- Confirm inner and outer ring requirements for spiral-wound gaskets.
- Verify ring-joint profile, material, hardness, and mating groove.
- Inspect windings, centering rings, jacket seams, grooves, and facing layers for damage.
- Check markings against the purchase order and packaging labels.
- Control storage to prevent moisture, distortion, contamination, and edge damage.
- Define any low-emission, fire, oxygen, sour-service, or chemical restrictions separately.
- Confirm the flange assembly procedure provides suitable bolt load for the selected gasket.
Application to Pipe Fittings, Valves, and Flanges
Spiral-wound gaskets are widely used with raised-face flanges and may also be specified for certain flat-face arrangements. Ring-joint gaskets fit machined RTJ grooves and require strict compatibility between ring profile, dimensions, material, hardness, and flange groove.
Metal-jacketed and grooved-metal gaskets are used in selected piping and equipment joints where the joint design can provide the required compression. Valves and equipment nozzles may have special gasket requirements even when their end drilling matches an ASME flange standard.
FAQ
Does ASME B16.20 provide flange dimensions?
No. It covers defined gasket constructions. Flange dimensions and ratings come from the applicable flange standard.
Does B16.20 specify one gasket material for every service?
No. The purchaser must select a suitable material combination for the fluid, temperature, pressure, and project requirements.
Can a ring-joint gasket be used on a raised-face flange?
No. Ring-joint gaskets require compatible RTJ grooves and the correct flange design.
Is a spiral-wound gasket reusable?
A removed gasket is generally replaced. Reuse should occur only under an approved qualified procedure.
Should the gasket supplier provide certificates?
The required documentation depends on the purchase order. Material and batch declarations are commonly requested for critical service.
Next Steps
State the flange standard, size, class, facing, gasket construction, all materials, quantity, and documentation. Verify the current project-required edition before release for manufacture.
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