Boilers, coal, and propulsion infrastructure

Steam efficiency has two halves: the boiler must convert fuel into steam efficiently, and the engine must extract as much work as possible from that steam. Higher-pressure and more complicated boilers could produce greater performance, but accessibility, repairs, and the risk of replacing an entire boiler remained operational concerns. Different navies followed different technical and maintenance paths, balancing maximum power against the reliability needed for worldwide service. Marine steam also depended on earlier uses of engines in mines and freight transport, followed by the infrastructure that moved goods along canals and out to sea. A coal-fired ship was only useful if ports could supply fuel in a usable form and load it aboard. Discarded engines and old patents still merit attention because a design rejected under earlier metallurgy or infrastructure may answer a later problem.