Question Relating to Feedwater Heating

Q: One very common traditional means of delivering feed water to a boiler was through a clack-valve on the back plate and along a pipe past the firebox to the front end of the boiler. Does this arrangement act as a basic form of preheating as the feed water passes the firebox end of the boiler?

Dave Wardale’s response: Not in the thermodynamic sense that preheating is understood, i.e. as reclamation of otherwise waste heat, as the heating effect in this case comes from the surrounding boiler water/steam before this has done any work in the cylinders. It is therefore merely a part of the boiler evaporative heat transfer. The reason for such an arrangement was probably to precipitate scale on the feed-pipe walls, the pipe presumably being fairly easy to remove and descale (or descale in-situ by removing the clack-valve).

Note: this type of feed delivery would probably not be ideal with Porta-type feed-water treatment.