ASTM C547

Covers — preformed mineral fiber pipe insulation (mineral wool or glass fiber) for elevated-temperature piping and equipment, defining composition, dimensions, thermal conductivity, and physical/fire properties.

Does NOT cover (exclusions) — the following are governed elsewhere:

• Cold/cryogenic insulation (cellular glass, PIR) → ASTM C552 / C591.
• Chloride limits for use on austenitic stainless → ASTM C795.
• Heat-loss/thickness calculation → ISO 12241.
• Insulation dimensions / inner-diameter sizing to fit the pipe → ASTM C585.
• Weatherproof jacketing over the insulation → ASTM C1136.

Where the insulated pipe is austenitic stainless, C547 must be combined with the C795 chloride requirements.

C547 sets minimum requirements for the insulation product:

• Composition & Form — mineral fiber preformed to pipe-size hollow cylinders, by temperature grade.
• Service temperature — classified into Types/Grades by maximum use temperature, spanning hot service up to roughly 650 °C (1200 °F) for the highest grades; always select by the pipe's design temperature.
• Thermal Conductivity — maximum k-value versus mean temperature.
• Physical Properties — density, compressive/flexural behavior, and moisture/fire performance.
• Marking — product type/grade and temperature limit.

Verified by these test methods:

• ASTM C335 — steady-state thermal conductivity of pipe insulation (k-value).
• ASTM C411 — hot-surface performance / maximum use temperature.
• ASTM C356 — linear shrinkage after soaking heat.
• ASTM C1104 — water-vapor sorption.
• ASTM E84 — surface burning characteristics (flame spread / smoke developed).
• ASTM C795 — leachable chloride acceptance when installed on austenitic stainless.

ASTM C547 is the standard for preformed mineral fiber pipe insulation used on hot piping and equipment. Non-combustible and available in temperature grades, its preformed cylinders install quickly and deliver reliable thermal performance for energy conservation and personnel protection.

Two service cautions define its correct use: on austenitic stainless steel it must also satisfy the ASTM C795 leachable-chloride limits to prevent external stress-corrosion cracking, and it must be kept dry — wet mineral fiber loses insulating value and drives corrosion under insulation (CUI). Thickness and heat loss are calculated per ISO 12241.

Engineering Note: Always pair C547 with weatherproof jacketing and, on stainless lines, with C795 compliance — a soaked or high-chloride insulation system quietly damages the pipe it was meant to protect.