Complex sentence: In January 1802 Richard Trevithick came to Coalbrookdale, where boiler plates for steam engines had been made for half a century; he built and tested a stationary engine which he had patented; it operated with an unprecedentedly high boiler pressure of 145 psi.
Split into simpler sentences: In January 1802 Richard Trevithick came to Coalbrookdale, where boiler plates for steam engines had been made for half a century. He built and tested a stationary engine which he had patented; it operated with an unprecedentedly high boiler pressure of 145 psi.