Flash Steam
Flash Steam is a consistent occurrence in a steam system. Whenever condensate is being released from a higher pressure steam line to a lower pressure it occurs. For example, a steam line operating at 100 psig will have a saturation temperature of 338oF. When the condensate that is formed in this steam line is discharged to the atmosphere, the condensate temperature at atmospheric conditions can not be more than 212oF. This change in energy must be converted and that is accomplished by flashing some of the condensate into steam. Keep in mind that when the condensate is flashed back into steam, the steam takes up a much larger volume and this volume needs to be accounted for when sizing condensate return lines. The amount of flash steam that is going to be produced can be calculated and should be done when designing a condensate return line, however utilizing a Flash Steam Chart can also provide a quick reference tool to help calculate the amount of flash steam that will occur. When designing condensate return lines for condensate/flash steam flow the line velocity should not exceed 4500 feet per minute. Velocities above this rate can cause water hammer issues in your return line.
For additional information of Flash Steam and Condensate Return lines refer to the following Best Practices from Swagelok Energy (www.swagelokenergy.com):
Swagelok Energy Best Practices No.7 – Flash Steam
Swagelok Energy Best Practices No 14 – Condensate Return
