	Steam boilers

Sunrod steam boilers

Water and steam flow diagram

Blue: the downcomers lead the water from the steam drum to the circular water drum.
Red and blue: the waterwalls lead the water and steam emulsion back to the steam drum.
Note the heavy steaming in the Sunrod tubes. Red: Steam to the consumers.

A waterwall made of panel tubes makes a gas-tight furnace from which the flue gases pass through the Sunrod pin tube elements to the smoke-box on the top of the boiler.
You may consider the Sunrod boiler as a hybrid between fire tube boilers and water tube boilers. The waterwall consists of water tubes, but the Sunrod element is a flue tube with a water-tube inside.
Svenska Maskinverken originally designed the Sunrod boiler but nowadays several boilermakers manufacture them.

Sunrod Marine Steam Boilers flow diagram

If you have a circulation pump for an exhaust gas economizer connected to the lower drum then avoid starting or stopping the pump while the burner is firing, since the water flow in the waterwall might be disturbed.
For the very same reason the drain valves on the waterwall headers mustn't be opened when the burner is firing. This goes for all boilers with water cooled furnace walls.

Sunrod Boiler type CPDB
A small size Sunrod Boiler
0.5 to 6 tons of steam per hour.

Sunrod boilers
Two Sundrod boilers just lifted onboard into a hardly half-finished ship at a shipyard.

Sunrod steam boilers

Steam boilers

Sunrod steam boilers

Water and steam flow diagram