I can answer that question, steam engines & boilers require constant service & attention. Onboard vessels the "mud drum" had to be shoveled out.
Water was drawn first to the mud drum & held while solids were allowed to settle out. Deposits clogging valves & encrusting the fire tubes could reduce pressure or even cause a catastrophic failure. Grates had to be kept clean & clinkers removed while underway.
The his article is a good basic overview of the evolution of steam propulsion. It was not uncommon for over 100 people to be hideously scalded & suffer traumatic amputations from boiler failures.
In an age where tolerances were a trifle rough, bushings, actuator arms, leather bearings, lignum vitae ( an exceedingly hard wood ) crankshaft bushings, etc. were replaced at regular intervals between overhauls.
During overhauls, the engine, running gear & boilers are essentially manufactured. That process could take months or over a year to complete.
Read more here.
Link:
Steam power emerged in the 18th century as a driving force of the Industrial Revolution.
nbwinc.com
Tennessee Valley not only does maintenance & inspections of their own steam engines, they completely restore steam engines.
Read more here.
Delve into the meticulous art of railway restoration at TVRM. Experience history revived through passionately rehabilitated locomotives and coaches.
www.tvrail.com