The oven is preheated by burning Gaoliang sorghum straw () at the base. Rock salt is preheated in a wok. The resulting liquid-gas mixture is preheated by flowing through a heat exchanger. The parts are not preheated as they are for the conventional fluidized bed dip process. The entire board may be preheated to a temperature that all components can withstand indefinitely. Tool steels should also be preheated to prevent cracking in the heat-affected zone. The dried mold is then assembled, preheated, and the metal poured. The fill material may be a preheated solid or a liquid. Washer fluid may sometimes be preheated before being delivered onto the windshield. The chips normally first enter the "presteaming" where they are wetted and preheated with steam. The boilers were fitted with economizers that preheated their feed water. Their patented system takes a small gas turbine and mixes it with preheated air. When starting, the glow plug is electrically preheated by electric current. The fuel was used to cool rear roller bearing, which also preheated the fuel. Continuous stills are charged with preheated feed liquor at some point in the column.