Minimum pegging steam pressure is normally 1.5 bar. As the boiler load increases it is desired to have higher temperature FW so with a change in system load (until extraction pressure is available) the pegging steam pressure (when CRH is established i.e. CRH pressure is sufficient) is also varied for energy efficiency.
Dec 30 2019 · Thats optimal at normal temperatures. Pressure changes of a few psi one way or the other can be brought about by atmospheric conditions. Most boilers are safe up to around 30 psi at which point seals can begin to fail. Modern boilers arent nearly as dangerous as early steam engines but you can still damage them and require costly repairs.
Now the steam coming out of the kitchen kettle (and out of the imaginary spout on our boiler) is exposed to atmosphere and is therefore at Atmospheric Pressure of 101.3 kPa. The temperature of steam at this atmospheric pressure is the same as the temperature of boiling water at atmosperic pressure
In a typical wet steam turbines the exhausted steam condenses in the condenser and it is at a pressure well below atmospheric (absolute pressure of 0.008 MPa which corresponds to 41.5°C). This steam is in a partially condensed state (point F) typically of a quality near 90%.
To go from 212F water to low pressure steam requires another 970 BTUs per pound. Increasing the pressure increases the temperature of the phase change and increases the amount of energy the water/steam can carry. At pressures higher than