Opened-Loop Boiler

http://en.wikipedia.org/wiki/PID_controller

An open-loop boiler expends the steam without condensing it and returning it as feedwater.

in other words, the make up water is the only source of generating steam. Having said that, the boiler which needs high quality of water have to use this system? am i right?

I don't think so; I believe a closed-loop boiler may need some water treatment, but not as much an open-loop boiler would. I'm not sure, however.

in my factory, my plant is using twin bed deionised systen and softeners system which is a high pressure boiler up to operational 85bar.