When we talk about vapour quality in industrial steam boilers, this means the mass fraction of steam in the mixture of liquid water and steam that is circulating through the boiler.
The value of this fraction ranges from 0 to 1. A value of 0 means liquid water (with no steam), and 1 means saturated steam (all steam).
The vapour quality has a low value when there is enough liquid water to be deposited at the bottom of the pipes, and it has high values when the water is only in the form of droplets suspended in the steam.
The vapour quality is extremely important in industrial steam boilers, as the more water the steam contains (the lower the vapour quality), the less heat from it can be used, or in other words, the lower the output from the installation.
ATTSU boilers with a high steam chamber guarantee a vapour quality of 99%, which ensures the highest quality steam.