Vertical cross-tube boilerW
Vertical cross-tube boiler
Vertical fire-tube boilerW
Vertical fire-tube boiler
Vertical boiler with horizontal fire-tubesW
Vertical boiler with horizontal fire-tubes
Vertical fire-tube boilerW
Vertical fire-tube boiler
Sentinel boilerW
Sentinel boiler
Spiral watertube boilerW
Spiral watertube boiler
Vertical boilerW
Vertical boiler