Per the 1954 Rules of Proof, here are the equivalent service pressure values:
3 tons--8,938 psi
3 1/4 tons--9,682 psi
3 1/2 tons--10,427 psi
4 tons--11,917 psi

BUT the 1954 numbers were also measured by lead crusher units (LUP) rather than transduced psi, which would be about 10% psi higher.

However, the CIP standard proof pressure of 850 BAR (kg per sq. cm.) = 10,730 psi service pressure.

This implies that the CIP conversion for the 1954 TONS measurement is different from the 1989 BAR measurement.

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