A cryogenic gas processing system of a liquid natural gas plant, the system comprising: a chiller; a low temperature separator including an inlet fluidically connected to the chiller, a first outlet and a second outlet; a flash drum including an inlet fluidically connected to the LTS and a plurality of conduits; and a heat exchanger fluidically connected to the second outlet of the LTS and the plurality of conduits of the flash drum, characterised in that the heat exchanger comprises: a first side bar formed from a nickel-iron alloy; a second side bar formed from a nickel-iron alloy, the second side bar being spaced from the first side bar; a fin element formed from a nickel-iron alloy extending between the first side bar and the second side bar forming a first layer of the heat exchanger, the fin element including an inner passage and being formed from a nickel-iron alloy; a first nickel-iron alloy bond joining the fin element and the first side bar; and a second nickel-iron alloy bond joining the fin element and the second side bar; a parting sheet extending between, and connected to, the first side bar and the second side bar, the parting sheet being formed from a nickel-iron alloy, wherein the parting sheet is joined to each of the first and second side bars through a corresponding nickel-iron alloy bond. a chiller; a low temperature separator including an inlet fluidically connected to the chiller, a first outlet and a second outlet; a flash drum including an inlet fluidically connected to the LTS and a plurality of conduits; and a heat exchanger fluidically connected to the second outlet of the LTS and the plurality of conduits of the flash drum, characterised in that the heat exchanger comprises: a first side bar formed from a nickel-iron alloy; a second side bar formed from a nickel-iron alloy, the second side bar being spaced from the first side bar; a fin element formed from a nickel-iron alloy extending between the first side bar and the second side bar forming a first layer of the heat exchanger, the fin element including an inner passage and being formed from a nickel-iron alloy; a first nickel-iron alloy bond joining the fin element and the first side bar; and a second nickel-iron alloy bond joining the fin element and the second side bar; a parting sheet extending between, and connected to, the first side bar and the second side bar, the parting sheet being formed from a nickel-iron alloy, wherein the parting sheet is joined to each of the first and second side bars through a corresponding nickel-iron alloy bond. a first side bar formed from a nickel-iron alloy; a second side bar formed from a nickel-iron alloy, the second side bar being spaced from the first side bar; a fin element formed from a nickel-iron alloy extending between the first side bar and the second side bar forming a first layer of the heat exchanger, the fin element including an inner passage and being formed from a nickel-iron alloy; a first nickel-iron alloy bond joining the fin element and the first side bar; and a second nickel-iron alloy bond joining the fin element and the second side bar; a parting sheet extending between, and connected to, the first side bar and the second side bar, the parting sheet being formed from a nickel-iron alloy, wherein the parting sheet is joined to each of the first and second side bars through a corresponding nickel-iron alloy bond.