What Is ASTM F104?
ASTM F104 is the Standard Classification System for Nonmetallic Gasket Materials. It provides a standardized line callout notation for specifying flat sheet gasket materials used in pressure-containing joints in piping, flanges, valves, and industrial equipment. The standard covers compressed non-asbestos fiber (CNAF) sheet, rubber sheet, cork-rubber composites, PTFE-based materials, and other non-asbestos nonmetallic gasket stocks.
An F104 designation encodes a material’s base type, class, grade, and up to seven test properties including tensile strength, compressibility, recovery, creep relaxation, sealability, fluid resistance, and temperature resistance. It is widely used by gasket fabricators, fluid system engineers, and industrial distributors to specify gasket sheet without reference to a proprietary product name.
How to Read an ASTM F104 Line Callout
An F104 callout consists of a base material designation followed by alphanumeric callout numbers for each of seven possible test property requirements. For example, a callout of F712300 indicates a compressed fiber sheet (F7) with specific compressibility, recovery, and fluid resistance requirements encoded in the digits that follow.
| Position | Meaning | Common Values |
|---|---|---|
| 1st character (Letter) | Base material / sheet type | F = Compressed fiber; R = Rubber sheet; C = Cork-rubber; T = PTFE |
| 2nd character (Digit) | Material class / subtype | Defines fiber type, rubber compound, or PTFE form |
| 3rd–9th positions | Test property callout numbers | Each position corresponds to a specific ASTM test for compressibility, sealability, fluid resistance, etc. |
| “0” in any position | No requirement for that property | Property is not tested or not specified |
Each digit position corresponds to a numbered test in the F104 standard, and the digit value indicates the specific requirement level. A zero in any position means that property is not required. Use the decoder above to look up every position in an F104 callout and understand what material and test levels are specified.
Common ASTM F104 Gasket Sheet Types
- F7 — Compressed Non-Asbestos Fiber (CNAF): The most common industrial gasket sheet. Made from aramid, glass, or carbon fiber with rubber binders. Used in steam, hot water, oils, and general chemical service.
- R — Rubber Sheet: Solid rubber gasket sheet in nitrile, EPDM, neoprene, SBR, or natural rubber. Selected based on fluid and temperature compatibility.
- C — Cork-Rubber Composite: Good compressibility and vibration damping. Used in oil pan gaskets, valve covers, and low-pressure applications.
- T — PTFE-Based Sheet: Excellent chemical resistance, low friction. Used in aggressive chemical service, food processing, and pharmaceutical applications.