I've never seen it actually written down anywhere, but standard practice in any boiler plant I ever worked in was to blow down the glass and column at the start of your shift, and record it in the logbook.
I guess I should have said a shore based non-propulsion boiler in the private sector. Thanks all for the info it helped. Also just FYI we blow our BGG down at approx. 200PSI during light-off.
Thanks again