Impellers and shafts are the fan parts most often needed, and they are made to order, so quote the fan’s serial number and plan on weeks or months. Across a set of landfill ammonia stripping plant enquiries, impeller and shaft spares were quoted at anywhere from about three weeks to about ten weeks delivered, plus sea freight where air was not used.
The challenge: a fan that is not an off-the-shelf item
The stripping plants use large centrifugal fans for ambient air, economiser and exhaust gas duty. Each is built to a duty and identified by a serial number. If an impeller cracks or a shaft wears, the plant may have to stop, and the part cannot be bought off a shelf.
The approach: order by serial number
- Impeller and shaft pairs: a quotation for two lines listed an impeller and a shaft for each fan, identified by serial number, delivered in 9 to 10 weeks by air freight.
- Drive shaft and bearing assembly: for a large fan, the complete shaft and bearing assembly was quoted as one item, delivery 8 to 9 weeks by air.
- Stainless steel impeller: for a feed fan, a stainless steel impeller was quoted, 4 to 5 weeks from the UK plus 5 to 6 weeks of shipping.
- Complete blower, excluding skid and motor: an ambient air blower was quoted together with its flexible connectors.
- Alternative maker: one shaft and impeller quotation came from a different fan manufacturer, which is worth knowing when the original maker’s lead time is long.
Take care with fan identity
Each quotation named the fan by serial number and, in most cases, the line it served. Check the serial number against the right line before ordering, particularly where several lines have similar fans.
Why it works
The manufacturer can reproduce the exact impeller and shaft from the serial number. Ordering both together, when the impeller is replaced, avoids a second outage for a worn shaft. Delivery by air shortens the sea-freight time but costs more.
What to consider for your own project
- Record serial numbers for every fan.
- Replace impeller and shaft together when practical.
- Weigh air against sea freight.
- Ask about an alternative maker if lead time is critical.
- Hold the long-lead parts.
For hot exhaust fans in particular, see our post on replacing a hot exhaust gas fan.
FAQ
Why do I need a serial number?
The impeller and shaft are made for a specific fan.
How long do fan spares take?
From a few weeks to a few months.
Should I replace the shaft with the impeller?
Often yes, to avoid a second outage.