(c)“boiler” means a pressure vessel in which steam is generated for use external to itself by application of heat which is wholly or partly under pressure when steam is shut off but does not include a pressure vessel,—(i)with capacity less than twenty-five litres, such capacity being measured from the feed check valve to the main steam stop valve; or(ii)with less than one kilogram per centimetre square design gauge pressure and working gauge pressure; or(iii)in which water is heated below one hundred degrees centigrade;
