The smoke tubes are going through the boiler and the exhaust gas flows inside of the tubes. This construction makes the boiler suitable for connection to more than one engine with separate exhaust gas sections in one boiler.
The boiler can either work with forced circulation with evaporation in a separate steam drum or as a natural circulating boiler with a built-in steam drum at the top.
The boiler can be controlled by a surpuls valve and a condenser, or by a three-way exhaust gas damper. The boiler are pre-assembled and delivered as a complete unit.