The Importance of Steam Quality for Steam-System Process Operation

Often, operational problems in steam systems are misattributed because the system’s steam quality is not closely monitored. A clear understanding of steam quality can help to better address these issues Steam quality describes the proportion of saturated steam (vapor) in a saturated condensate (liquid)/steam (vapor) mixture. A steam quality of 0 indicates 100% liquid (condensate), while a steam quality of 100 indicates 100% steam. One pound of steam with 95% steam and 5% liquid entrainment has a steam quality of 0.95, for example. The parameters needed to obtain a steam-quality measurement are temperature, pressure and entrained liquid content. A high percentage (88% or more) of industrial steam systems use saturated steam for process applications. Saturated steam (meaning steam that is saturated with energy) is completely gaseous and contains no liquid. The boiler operation uses chemical energy from a fuel source to deliver energy to the boiler water. Inside the boiler, liquid gains energy from the combustion process and changes state into saturated steam. As illustrated in Figure 1, water enters the boiler at point A, and the water gains sensible energy (h f) up to point B. The change of state is referenced as point B in Figure…