Smoke Tube Fired Boiler DDFC (Pvt.) Ltd. Smoke Tube Fired Boiler; DDFC (Pvt.) Ltd. DDFC manufactures smoke tube boilers in the following capacities and pressure ratings. feed water. This in turnreduces fuel consumption of theboiler. These units are offered as astandard with all natural gas firedboilers with capacity of 2 TPH orlarger.