Hello Colin, that sounds like a very interesting project of building a traction engine. Keep in mind that many of these engines had manual feedwater pumps installed as well as the steam injectors, the later had a tendency if not properly maintained to not function properly and always at the wrong time. By having the manual pump as a backup the operator did not have to worry about not getting water into the pressure vessel due to a malfunction. Some even had a Wilikinson style of steam driven pump so as to enjoy not having to 'muscle' the water into service. I'd still incorporate a back up system into your design/project. Best of luck
BC1
Jim