I've seen various types of boilers in industries e.g. 7 bar, 10 bar, 30 bar etc. What exactly in the operations / design of these boilers sets the steam pressure that will be produced? For simplicity let us restrict ourselves to fire tube coal fired boilers that produce saturated steam. Something like in the sketch below. https://commons.wikimedia.org/wiki/...media/File:Steam_Boiler_2_English_version.png Is the pressure set by just the balance between the heat input rate & the steam removal rate? i.e. If you stoke a boiler fast enough you raise the Pressure so long as you have enough area & the shell can take the Pressure? Conversely if you consume steam fast enough every boiler becomes a low pressure boiler? Is my understanding correct? Or is there another mechanism?