Packaged vs Field-Erected Boilers: How a Boiler Reaches Site
A packaged boiler is built and tested in the factory and shipped as one or a few units ready to connect. A field-erected boiler is shipped in pieces and assembled where it will run. The choice is mostly set by size, and it shapes schedule, cost and how inspection is done.
You'll learn
- Define packaged and field-erected boilers
- Know what limits the size of a packaged boiler
- Compare schedule, cost and risk
- Understand how inspection differs between the two
Before this: Fire tube, water tube and smoke-cum-water tube
Built in the factory, or built on site
A packaged boiler leaves the factory as a complete unit: pressure parts, burner or furnace, fans, pumps, controls and often the mountings, all on a skid. On site it needs a foundation, connections for fuel, water, steam, power and the chimney, and commissioning.
A field-erected boiler is too large to transport whole. Drums, tube panels, headers, structure, ducting and refractory arrive separately and are assembled, welded and tested at the plant. Large water tube boilers, travelling grate and fluidized bed boilers, and power plant boilers are built this way.
How they compare
| Packaged | Field-erected | |
|---|---|---|
| Size limit | What a truck and the roads can carry | Practically none |
| Site work | Days to weeks | Months |
| Quality control | Factory welding, jigs and testing | Site welding; depends on site conditions and supervision |
| Cost at small sizes | Lower | Higher |
| Cost at large sizes | Not available | The only option |
| Fuel flexibility | Usually oil, gas or a fixed solid fuel | Designed around the fuel, including mixed and difficult fuels |
For most process plants below the largest sizes, a packaged or modular boiler is quicker to commission and carries less construction risk. Field erection becomes necessary when capacity, pressure or the fuel system outgrows what can be shipped, and it allows the boiler to be designed around one plant’s fuel and layout.
Schedule, inspection and the middle ground
For a regulated boiler, inspection follows the construction. A packaged boiler’s pressure parts are inspected and hydraulically tested at the manufacturer under the Indian Boiler Regulations, with the inspecting authority’s stamping, before shipment; the site then registers and commissions it. A field-erected boiler’s pressure parts are inspected during manufacture in the shop and again during erection, with site welds examined and a hydraulic test of the assembled boiler before registration.
Most of the schedule risk in a field-erected boiler is on site: weather, crane availability, welder qualification, and the interfaces with civil works and other contractors. A delay in the boiler’s foundation delays everything above it.
Between the two sits modular construction: pressure parts shipped as a few large, factory-built modules — a furnace module, a convection module, an economizer — that bolt or weld together on site. It keeps most welding in the factory while exceeding what a single packaged unit can carry, and it is how many medium-sized solid-fuel boilers are now supplied.
Key takeaways
- Packaged boilers arrive complete and tested; field-erected boilers are built on site.
- Transport limits packaged size; above that, field erection is the only route.
- Packaged means shorter site work and factory quality control; field-erected means fuel and layout flexibility.
- Modular construction sits between the two.