hi
in our LPG Bobtails (LPG truck) , usually we get all the valves (internal valves, excess flow valve....etc) from REGO a USA company, I am sure if u r working with LPG bobtails u know this comapny very well.
please check this link for full information about excess flow valve (types, flow, Size....etc)
http://www.regoproducts.com/PDFs/L-500_Section-F.pdf