The short answer
CFBC erection follows a fixed dependency chain: structure, drum lift, water wall panels, cyclones and loop seal, ducting, refractory, hydro test, then light-up. Refractory curing and cyclone alignment are the two activities that most often govern the critical path.
A circulating fluidised bed boiler is not erected in the order the drawings are numbered. It is erected in the order the dependencies allow, and getting that order wrong is how schedules are lost.
The dependency chain
| Stage | Governs | Typical risk |
|---|---|---|
| Structural steel | Everything above it | Foundation and anchor bolt deviation |
| Drum lift | Water wall hanging | Crane availability, weather window |
| Water wall panels | Enclosure and pressure test | Panel damage in transit, fit-up |
| Cyclones & loop seal | Gas path completion | Alignment, heavy lift access |
| Ducting & air system | Fan commissioning | Site fabrication volume |
| Refractory | Light-up | Curing time — cannot be compressed |
| Hydro test | Box-up and insulation | Repair joints found late |
| Light-up | Handover | Interlock and E&I readiness |
The drum lift is the moment everyone remembers
It is also the one with the most preparation behind it. The lift plan, ground bearing capacity, crane configuration, rigging arrangement and weather window all have to line up on the same day. Water wall panels hang from the drum and top headers, so nothing above the furnace progresses until it is set and levelled.
Practical points
- Verify anchor bolt positions and elevations before the steel goes up, not after
- Confirm the crane's ground bearing pressure against the actual made-up pad
- Set and check drum level before releasing the crane, not the next morning
- Protect nozzle and manhole faces before any hot work starts nearby
Cyclones: heavy, high, and unforgiving on alignment
The cyclones and loop seal are what make a CFBC a CFBC — solids circulate through them continuously. They are heavy, they sit high, and their alignment with the furnace outlet and return leg has to be right. Misalignment here does not simply look wrong; it affects circulation behaviour once the unit is in service.
Refractory is the activity you cannot compress
Refractory installation and curing follows a defined heat-up curve. That curve is a material property, not a negotiating position. Planners who try to claw back schedule by shortening curing damage the lining and pay for it during the first operating campaign.
Hydro test: find repairs early or pay for them late
The hydro test is a verification, not a discovery exercise. If your NDT coverage and hold-point discipline have been sound, the test confirms what you already know. If they have not, you find out at the worst possible time — after box-up has started, with insulation crews mobilised and waiting.
Light-up and load raising
First firing depends on far more than the boiler: fans, fuel feeding, ash handling, instrumentation, interlocks and the control system all have to be ready together. Mechanical completion is not the same as being ready to light up. Build the punch list closure and E&I interface into the schedule explicitly, or it becomes the invisible tail that adds two weeks.
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