Pondering some LOLER issues I came across this in CRR429/2002 and thought I'd share. This obviously supports the views perviously expressed here by others and has me converted! "The requirement to thoroughly examine equipment dates back to the introduction of steam power into factories. There were a large number of explosions of steam boilers and it was found that a legal requirement to have the boilers regularly examined by a competent person did dramatically reduce the number of these accidents. The examination of the boilers meant that the factory had to be closed down whilst this work was carried out and this normally only occurred during the Easter holidays. Because Easter was a moveable feast the maximum time set for the intervals between thorough examinations was chosen as 14 months to accommodate the holiday period." (Easter itself being linked to Lent and the phases of the Moon)

I was told during one of my diploma classes that the 14 months 'allowed for seasonal variations'. I certainly like your reasoning a lot better!!

I've just done an internet search for information about boiler examination frequency - partly out of curiosity and partly out of scepticism about the allowable 14 month frequency being due to Easter's calenderial meanderings. I found nothing to either support or challenge the notion, though admittedly this may stem from poor searching ability on my part. On a slightly related theme I've got an old OS&H magazine article somewhere (i.e. not sure where) which includes an old cartoon from "Punch" the former satirical magazine in Victorian times. The cartoon shows a steam engine on a railway with a large well-dressed man tied to its front. The cartoon caption reads something like "Using a railway company director to prevent accidents". As locomotive boiler explosions and train collisions were fairly common at the time the cartoon was very topical in suggesting that if such men were forced to travel in a highly vulnerable place on the front of a locomotive, they would be very keen to ensure that all effective measures were taken to prevent such events!