Hi Pd's,
Gerald.....sorry my friend but it does not mean what you are thinking....
To find the Bar/litre capacity you must multiply the total capacity (total internal volume ) in litres by the actual working pressure in Bars.
Note well, this is not the same as the amount of water used to fill the boiler for normal running, but means the volume of water required to entirely fill the boiler to overflowing with all air expelled.
E.G... 1 ltr total capacity x 3 bar (approx 45psi) = 3 bar/ltrs = exempt
or E.G... 500 ml total capacity x 6 bar (approx 90 psi) = 3 bar/ltrs = exempt.
whereas: 1 ltr total capacity at 4 Bar (approx 60psi) = 4 bar/ltrs = NON EXEMPT.
For those who choose to test, even though their boiler may be within the exempt range (I personally think this is a good idea, since even a small boiler can become a dangerous thing if it fails under steam pressure)...then the only acceptable procedure is to follow the rules as laid out in the document, just as would be done for any non-exempt boiler.
This would be applicable to both pressure and steam test procedures.
I should point out...stress...that these rules are at the moment, specifically for the UK...it remains to be seen if they are adopted in other countries....although I am sure some, at least, will do so eventually...especially those who have previously embraced the general UK testing codes.
I hope this clarifies things a bit more for you.
Best Regards.
Sandy.
PS...there is a rumour going round that a place named Woolongong...has adopted the opposite rule...in that they are exempting boilers larger than 1ltr water capacity, regardless of working pressure....and that the small ones are to be subjected to 10 times the UK guide line test pressures.....He He....that should stop them invading the Scottish waters!! in their chain driven steam boats. LOL.

:music