For equipment and piping which is to be operated intermittently or continuously at temperatures up to 500°C, the insulation may be mineral wool with temperature rating of 500°C. All mineral wool shall be water repellent and tested for water absorption and retention. Mineral wool blankets for piping and vessels greater than 36″ shall conform to ASTM C592. They shall have density of at least 128 kg/m3 and shall be faced with wire mesh inside and either wire mesh, expanded metal, or glass mat outside.

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