Water tube package boilers are designed by minimizing header-type water tube steam boilers in order to meet smaller-capacity system requirements. They consist of vertical-flow water tubes; therefore, water tube package boilers are safer than fire-tube (flame–smoke tube) boilers.

They are designed according to operational needs and can be coupled with stoker or rotary grate systems, placing user requirements at the forefront in terms of technological flexibility. Although the flame pass rate is higher compared to fire-tube boilers, the outer surface is not covered with tube–flat bar systems; instead, it is lined with firebrick and insulated with rock wool to retain heat within the boiler and maximize energy utilization, thereby achieving the highest efficiency.

Depending on the steam capacity, the boiler is equipped with one or two steam drums. Steam transfer to the plant is carried out through these drums. Package boilers can be designed according to the physical conditions of the facility, are easy to operate and maintain, and offer long service life with safe operation.