The brand WNS type gas steam boiler is horizontal three return shell type wet back boiler boiler, mainly by the host shell, and tube plate, corrugated furnace, combustion chamber, two flue tubes and three flue tubes, head hole, manhole, hand hole, pipe, and smoke box, explosion-proof door, base etc.. The boiler is equipped with a combustion engine, automatic control system, water pump, economizer and other auxiliary valve instrument