about 105 tons per million standard cubic feet of pipeline gas processed per hour by the invention and at exchanger 55 about 100 tons hence a large tonnage of valuable refrigeration is generated from energy that would be wasted if the pressure of pipeline gas were reduced by isenthalpic expansion as practiced at many letdown control stations fig3 shows a modification of the flow diagram of fig2 which enables the process of the invention to deliver refrigeration at two levels reference numerals appearing in fig2 are applied to corresponding elements of fig3 two new elements in fig3 are high level refrigeration exchangers with reference numerals 80 and 81 comparing fig3 with the portion of fig2 which it replaces it is evident that elements 37 39 40 and 41 of fig2 have been eliminated the expanded gas in line 51 after passing through low level refrigeration exchanger 52 flows through high level refrigeration exchanger 80 rather than exchanger 46 before entering expander 53 the further expanded gas in line 54 after passing through low level refrigeration exchanger 55 flows through high level refrigeration exchanger 81 before passing through exchanger 46 the gas leaving exchanger 51 at 123 psia and 10 u00b0 f issues from exchanger 80 at 120 psia and 33 u00b0 f similarly the gas leaving exchanger 55 at 37 psia and 10 u00b0 f issues from exchanger 81 at 34 psia and 33 u00b0 f it is noteworthy that the aforesaid 105 tons.