The correct filler for turbine flanges, generator casings, supercritical steam headers and high-temperature furnace connections where standard graphite fails through oxidation and electrical conductivity. Phlogopite mica filler, stable to 1,000°C. ASME B16.20 compliant. UK-supply.
Standard flexible graphite filler has two critical limitations that make it the wrong choice for turbine, generator and high-temperature furnace flanges in Indian power and steel plants.
Flexible graphite begins oxidising in air above 450°C, progressively losing mass and sealing integrity. Phlogopite mica is thermally stable to 1,000°C in oxidising atmospheres — no mass loss, no degradation. For supercritical boilers operating above 550°C and gas turbine casing flanges at 700°C+, mica is the technically correct specification.
Graphite is electrically conductive. On turbine and generator flanges where dissimilar metals are present, graphite filler creates a galvanic cell — causing accelerated corrosion of flange faces and stud bolts. Mica is a full electrical insulator, eliminating galvanic corrosion risk entirely. This is the primary reason turbine OEMs specify mica on generator and turbine casing joints.
Mica filler produces very low fugitive emissions — below the TA-Luft threshold — making it suitable for steam, hydrogen and VOC service where emissions compliance is required.
Every order is supplied with mill test certificates for all metallic components, mica filler material certification, ASME B16.20 compliance statement, and dimensional inspection report.
Main steam and reheat steam flanges at NTPC's supercritical units operate above 565°C at 247 bar. Graphite oxidises at these conditions. Mica filler in 316L SS winding — ASME B16.20 — is the correct specification.
Gas turbine casing flanges and steam turbine body joints operate at 600–800°C. Mica's electrical insulation prevents galvanic corrosion between the carbon steel casing and stainless-steel studs — a failure mode commonly seen with graphite-filled gaskets in turbine applications.
Blast furnace hot blast mains, reheat furnace door seals and hot gas duct connections operate between 600–900°C. Mica filler with Inconel 625 or Alloy 800 winding provides long-term sealing stability that graphite cannot achieve at these temperatures in an oxidising atmosphere.
High-temperature process flanges in NPCIL pressurised heavy water reactors require full traceability, nuclear-grade certification, and low chloride content. Mica filler — chloride content <5 ppm — meets these requirements. Nuclear-grade documentation package available on request.
Glass tank crown connections and industrial kiln flanges operate at 800–950°C. Mica filler is the correct specification up to 1,000°C; ceramic fibre filler is recommended above this.
Chemical reformer and cracker outlet flanges, hydrogen heater connections and high-temperature heat exchanger nozzles where the operating temperature exceeds 450°C — the safe limit for graphite in air.
| Filler material | Phlogopite mica (preferred) or muscovite mica. Phlogopite rated to 1,000°C; muscovite to 700°C. Phlogopite is specified as standard for high-temperature service. |
| Maximum temperature | 1,000°C (phlogopite) · 700°C (muscovite). Stable in oxidising (air) atmosphere. No mass loss. |
| Electrical insulation | Full insulator — no electrical conductivity. Eliminates galvanic corrosion on turbine and generator flanges with dissimilar metals. |
| Chloride content | <5 ppm — very low. Safe for austenitic SS, Incoloy, and Hastelloy flanges. No stress corrosion cracking risk. |
| Maximum diameter | Up to 52" (1,320 NB). Custom sizes on request. Large-diameter mica-filled SWG is not available from Indian suppliers. |
| Pressure classes | Class 150, 300, 600, 900, 1500, 2500 LBS. Full ASME B16.47 range available. |
| Winding material options | 316L SS · Incoloy 800/825 · Hastelloy C-276 · Alloy 20 · Inconel 625 · Duplex 2205 |
| Inner ring | 316L SS standard · exotic alloys on request |
| Outer ring (centring) | Carbon steel · 304/316 SS option |
| Applicable standards | ASME B16.20 · ASME B16.47 Ser A & B · DIN EN 1514-2 |
| Fugitive emissions | TA-Luft suitable. Suitable for steam, hydrogen and VOC service. |
| Delivery terms | CFR Mumbai standard. Emergency orders available by airfreight. Lead time: 4–6 weeks standard. |
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