Flexible connectors, or bellows, on a hot gas fan absorb vibration and thermal movement between the fan and its ducting, and they wear out first. For three economiser fan connections at a landfill stripping plant, multi-layer high-temperature connectors 350 mm long were quoted, with the existing clamp bars re-used.
The challenge: movement and heat at the fan
A large fan vibrates. The hot ducting expands and contracts. A rigid connection between them would crack, so a flexible joint is installed at the fan’s inlet and outlet. The joint is made of layered material, and it ages in heat. A failed joint leaks hot gas into the plant room.
The approach: three connectors, three shapes
| Position | Internal size | Length |
|---|---|---|
| Line 2 fan inlet | 1,070 mm diameter | 350 mm |
| Line 2 fan outlet | 1,172 x 1,100 mm | 350 mm |
| Line 3 fan outlet | 1,120 x 868 mm | 350 mm |
Note that one is round and two are rectangular: connectors are made to the shape of the fan flange. The quoted lead time was four to five weeks ex-works in the UK, with seven to ten days to the site.
The clamp bars stay
The existing stainless steel clamp bars hold the connector to the flange, and they were re-used. That reduces the order to the part that wears, but it means the bars and flanges must be in good condition.
Part of a larger spares picture
Another fan spares quotation included flexible connectors at the inlet and outlet of the exhaust gas blower and the outlet of the ambient air blower, ordered together with the blower itself.
Why it works
Multiple layers allow the material to flex while keeping gas in. Specifying inside dimensions and length lets the maker build to the actual flange. The connectors are cheap compared with the cost of an unplanned outage.
What to consider for your own project
- Measure the flanges, not the old connector, which may have stretched.
- State temperature and gas composition.
- Inspect the clamp bars before deciding to reuse them.
- Keep spares for each size.
- Replace in pairs at a fan, inlet and outlet.
For the fan parts themselves, see our post on fan impellers and shafts.
FAQ
What is a fan bellows?
A flexible joint that absorbs vibration and thermal movement between a fan and its ducting.
Can the clamp bars be reused?
Yes, if they are undamaged, as in this quotation.
How long is lead time?
Four to five weeks plus delivery.