From Lexicanum

Siege Dreadnoughts are equipped for breaking through fortified enemy positions. They are armed with an assault drill with a built-in heavy flamer on one arm and an Inferno Cannon on the other. The assault drill is designed to grind through defensive walls and bunkers. Once the wall is penetrated, the incorporated heavy flamer unleashes a torrent of flame that can engulf an entire bunker and incinerate anything within. The Inferno cannon uses huge amounts of fuel and is uncontrollable in its consumption so the likelihood of running out of fuel mid-battle is greater than on normal flame weapons.^1-p11

Images

Forge World:

Siege Dreadnought

Sources

• ¹:Imperial Armour Update 2006, p11