Regulation 6
The manager of every mine in which shells are used shall make and ensure the efficient carrying out of arrangements to secure that—
every shell in use and the fittings thereof are examined by a competent person appointed for that purpose by him at intervals, in the case of a shell which has been filled below ground since the last examination thereof, not exceeding thirty days, and, in any other case, not exceeding ninety days to ascertain whether there has been any significant change in the outer diameter of the shell and the condition of the screw threads with which the firing head engages the shell;
no shell is subjected to heat treatment or machining by any person other than the manufacturer thereof or in pursuance of arrangements approved by an inspector by notice served on the manager.
Any person who has made such an examination shall enter a report thereof in a book provided for the purpose by the owner of the mine.