High-pressure steam locomotive

A high-pressure steam locomotive is a steam locomotive with a boiler that operates at pressures well above what would be considered normal for other locomotives. Most locomotives operate with a steam pressure of 200 to 300 psi (1.38 to 2.07 MPa). In the later years of steam, boiler pressures were typically 200 to 250 psi (1.38 to 1.72 MPa). High-pressure locomotives can be considered to start at 350 psi (2.41 MPa), when special construction techniques become necessary, but some had boilers that operated at over 1,500 psi (10.34 MPa).