In our last blog, we reviewed the three common types of watertube boilers: D-Type, O-Type, and A-Type. There is, however, another package watertube boiler on the market today; the Ds-type, providing a fourth option to consider when you are planning for a new boiler. In fact, the Ds-type design is patented and manufactured by Superior Boiler and is one of their most popular watertube boiler models.
The configuration for this type of boiler is similar to the D-Type, with one upper steam drum, one lower drum, and one convection bank. One of the main differences lies in the convection bank flow area (the bank of tubes that provide convection heat transfer), which is much larger and utilizes upside-down L shaped tubes. This larger area means a reduced boiler pressure drop on the flue gas side. A smaller fan is required, reducing both cost and energy usage.
With Ds-type boilers, the furnace is more centralized and the cross section is more square compared to the rectangular furnace cross section of a D-type boiler. The square shape improves the heat flux from the burner due to walls being more equidistant from the heat source, and with a more uniform heat flux we get improved heat transfer with lower emissions.
Compared to D-type boilers, the Ds-type offers additional features and advantages: 
- Improved shipping and rigging due to a more centralized center of gravity.
- More compact footprint; roughly 1-2ft shorter than typical package boiler.
- No need for a burner platform since the burner is lower to the ground.
- The option to be designed with a top exhaust outlet, providing space savings with the ability to mount the economizer in a vertical configuration above the boiler. D-type boilers are limited to a side outlet and horizontal, ground-mounted configuration.
- An overall lower capital cost caused by fewer transitions and breeching, smaller fan requirement, better heat transfer, and better performance.
The Ds-type boiler is also known as Superior’s “Shawnee” model. With design pressures of up to 1,200 psi, these boilers can be built to supply as little as 10,000 lbs/hr to as much as 250,000 lbs/hr of saturated or superheated steam. The patented design provides an unmatched, compact footprint and is a great option when looking to replace an existing unit or add capacity to your facility.
Contact us today to learn more about how Superior’s Ds-type boiler could be a good match for your next project. 800-227-1966