How do we determine the filler material by the color of the color band in spiral wound gasket

Reading the color band on the outer edge of a spiral wound gasket takes two seconds and tells you the filler inside — the most important selection parameter for a flanged joint. The same rule applies across flange gaskets: a wrong filler turns a routine gasket change into a leak, a production shutdown or a safety incident.

How the Color Band Codes the Filler

A 4 mm band is applied to the outer edge of the winding, so it stays visible after the gasket is fitted. Four fillers cover most services in ASME B16.20 spiral wound gaskets.

• Gray — flexible graphite (F.G.), for high-temperature steam and hot oil.
• White — polytetrafluoroethylene (PTFE), for strong acids and strong alkalis.
• Pink — mica-graphite (MICA-GRA), for flue gas and other high-temperature gases.
• Light green — ceramic fiber (CER), for extreme heat such as incinerators.

The colors follow the natural shade of the filler, so an engineer who knows the materials can read the band without a data sheet.

Temperature Limits and Media

The filler sets the working window of the seal. A spiral wound gasket is compressed between two pipe flanges: the metal winding carries the load, while the filler decides the maximum and minimum service temperature.

Filler temperature limits per ASME B16.20 (continuous operating temperature). Medium, pressure and thermal cycling reduce practical limits.

Application notes often list 450 °C for flexible graphite, while the ASME B16.20 table above allows 510 °C. Take the lower figure as the design limit until the gasket data sheet confirms otherwise.

Reading the Stripe in the Field

Labels burn, corrode or peel; the band is part of the gasket and survives where paper does not. Three checks take less than a minute.

• Match the band to the service: gray for steam and hot oil, white for aggressive chemistry, pink or light green for hot gas.
• Check the medium temperature against the filler limit before installation: 260 °C is the ceiling for PTFE, and 600 °C calls for ceramic fiber.
• Make sure the band is intact and the outer ring is not deformed; a damaged ring changes the seating stress.

If the band is unreadable, do not guess the filler — replace the gasket.

Frequently Asked Questions

What does a gray stripe mean on a spiral wound gasket?

Gray marks flexible graphite. It suits high-temperature steam and hot oil and, per ASME B16.20, covers roughly -212 °C to 510 °C.

Which filler should I choose for strong acids and alkalis?

White marks PTFE. It resists strong acids and strong alkalis, but its continuous service limit is about 260 °C, so hot chemical streams need a different filler.

Can a flexible graphite gasket be used at 600 °C?

No. The ASME B16.20 limit for flexible graphite is 510 °C. At 600 °C choose light green ceramic fiber; pink mica-graphite tops out at about 590 °C.

What is the difference between the pink and light green bands?

Pink is mica-graphite for flue gas and hot gases up to about 590 °C. Light green is ceramic fiber for extreme heat up to about 1090 °C, for example in incinerators.