On Tue, 19 Nov 2019 19:15:47 -0000, NY wrote:

Ah, I always wondered what the 47 kg related to. I wasn't sure whether
it was a gross weight, cylinder weight and gas weight. But it's 47 kg of
gas, plus a variable weight of cylinder, making up to around 80-90 kg
gross. I presume each cylinder is weighed "empty", then filled until the
gross weight is empty weight plus 47 kg.

Cylinder weights vary and how "empty" a cylinder is varies as well.
So simple weighing and adding 47 kg of gas don't work. One of the
sets of numbers on the embossed ali collar is the true empty weight
of that cylinder. That is entered into the filling machine that then
adds gas so the gross weight is cylinder label weight plus 47 kg.

--
Cheers
Dave.