Selection guide
Materials and wear
Metal selection on a fan has one job: survive the gas. Wear selection has another: survive the solids. They are separate decisions and we treat them separately, because a fan that solves one and ignores the other still fails.
Gas
Materials chosen against the gas
- Mild steel
- Default for clean, dry air and non-corrosive gas up to the standard temperature tiers; structural grades include IS 2062 E250 and E350
- Pressure vessel plate
- SA516 Gr.70 where casing or drum sections need a specified carbon steel plate grade
- SS 304 / 304L
- General purpose austenitic stainless, roughly 18 percent chromium and 8 percent nickel; the L grade is the low-carbon option for welded corrosion service
- SS 316 / 316L
- Adds about 2 to 3 percent molybdenum for pitting resistance in chloride and acidic environments; the workhorse on scrubber and coastal duty
- SS 321
- Titanium-stabilised austenitic grade used for elevated temperature service and weld stability
- SS 310
- High chromium and nickel austenitic grade chosen for hot oxidation resistance in the upper temperature tiers
- SS 410
- Martensitic grade where hardness and wear matter alongside modest corrosion resistance
- Duplex 2205
- High strength and good chloride resistance where austenitic grades are not enough
- FRP
- Lining or full construction for aggressive wet chemistry at low temperature
- Titanium
- The answer when the chemistry has defeated everything else, chosen on analysis and costed honestly
Solids
Wear protection chosen against the dust
Abrasion is a mechanical conversation: hardness, particle size, shape, velocity and impact angle. A backward curved wheel in a clean airstream may never need more than a paint touch-up in twenty years; the same wheel on cement dust will lose its blade profile in months and then quietly stop making its pressure.
Hard-facing
Weld-overlay hard material on blade leading edges, inlet ring and cutwater. Where abrasion is severe, replaceable wear plate is better engineering than a thick weld build-up.
Wear plate
Through-hardened abrasion plate is specified by hardness, commonly quoted as a Brinell figure – a 450 HBW grade is the familiar one for heavy impact and sliding wear.
Designed to be replaced
Bolted liners and a wear ring as a part number. Scraping a casing back to metal on a shutdown is a repair nobody books twice.
- Where dust hits first
- Blade leading edge, then the inlet ring, then the casing cutwater and the housing just past it
- What accelerates it
- Velocity, particle hardness and the volume of solids; all three are yours to control
- How we judge it
- Material name, particle size range, load per hour, and whether the fan sits before or after the arrester
- What it costs
- A few percent of the machine to specify, and a multiple of that to discover
Heat
Temperature changes the metal conversation
Our published temperature tiers for the high temperature family run to 150, 250, 350, 500 and 650 C. The practical consequences at each tier are the material grade, the design cold clearance for thermal growth, the bearing isolation method and the lubricant. Mild steel remains usable on the wheel up to roughly 300 to 350 C in our build practice; beyond that the austenitic and high-temperature grades take over, and the drawing has to show which is used where.