A much better reference is Nigel Brown's. He was a Proof Master after all! On page 266 of his London Gumakers book, he explains that Bar was not introduced until 1989. Also the imperial proof marks that could be requested from 1984 to 1989 used the Tons SERVICE pressure while the metric version used the Kg PROOF pressure.
Thanks much for the explanation, Toby. It looks as if, during that transitional period, our British cousins were doing their best to confuse those of us on the other side of the Pond. We'd had time to grow accustomed to a service pressure proofmark, only to see a transition to a proof pressure mark. Although I expect the latter might have something to do with all the other CIP countries using proof pressure marks.
Back 20 years ago, when I was working on an article for Shooting Sportsman magazine, we sent the article in draft to Roger Hancox for his comments. His reply clarified another area of confusion re the interpretation of the bars marks:
"The article mentions that at the time of SAAMI's creation, pressures were measured with crushers. And when later they began using transducers they discovered that readings were different and designated crusher readings as LUP (lead units of pressure). The same applies to the CIP but unlike SAAMI they still call the crusher values bar!"
He then went on to explain that the standard CIP pressure values of 650 bar service pressure and 850 bar proof pressure have equivalent transducer values of 740 bar service and 960 bar proof. Prior to that explanation, I was attempting to convert from bar values to psi values by multiplying by 14.5, which obviously produced the wrong results. We're still stuck using psi values on this side of the Pond . . . once again demonstrating that the Americans and the British are, indeed, two peoples divided by a common language.
Last edited by L. Brown; 10/17/21 06:56 AM.
