A method for re-condensing a boil-off gas stream (100, 500) comprising natural gas from a storage tank (101, 501), the method comprising: (a) at least partially condensing the boil-off gas stream (100, 500) in a first heat exchanger (104, 504) against a two phase refrigerant stream to form an at least partially condensed boil-off gas stream (102, 502) and a gaseous refrigerant stream (106, 506), the two phase refrigerant stream comprising no more than 5 mol% hydrocarbons and at least 90 mol% of at least one selected from the group of nitrogen and argon, the two-phase refrigerant stream having a gas phase portion and a liquid phase portion in the first heat exchanger; (b) returning the at least partially condensed boil-off gas stream (102, 502) to the storage tank (101, 501); (c) heating the gaseous refrigerant stream (106, 506) in a second heat exchanger (110, 510) against a high pressure refrigerant stream to form a warmed refrigerant stream (112, 512); (d) compressing the warmed refrigerant stream (112, 512) in a compression system (114, 514) to form a compressed refrigerant stream; (e) cooling the compressed refrigerant stream in a third heat exchanger to form the high pressure refrigerant stream; (f) cooling the high pressure refrigerant stream against the gaseous refrigerant stream (106, 506) in the second heat exchanger (110, 510) to form a high pressure cooled refrigerant stream (121, 521); (g) separating the high pressure cooled refrigerant stream (121, 521) into a first portion (124, 524) and a second portion; (h) expanding the second portion of the high pressure cooled refrigerant stream to form an expanded refrigerant stream (108, 508); characterised in that the method comprises: (p) controlling a position of a first valve as a function of a pressure of the gaseous refrigerant stream and a first set point, the first valve being positioned downstream from the first heat exchanger and upstream from the second heat exchanger and in fluid flow communication with the gaseous refrigerant stream; and (q) setting the first set point as a function of a pressure of the storage tank.. (a) at least partially condensing the boil-off gas stream (100, 500) in a first heat exchanger (104, 504) against a two phase refrigerant stream to form an at least partially condensed boil-off gas stream (102, 502) and a gaseous refrigerant stream (106, 506), the two phase refrigerant stream comprising no more than 5 mol% hydrocarbons and at least 90 mol% of at least one selected from the group of nitrogen and argon, the two-phase refrigerant stream having a gas phase portion and a liquid phase portion in the first heat exchanger; (b) returning the at least partially condensed boil-off gas stream (102, 502) to the storage tank (101, 501); (c) heating the gaseous refrigerant stream (106, 506) in a second heat exchanger (110, 510) against a high pressure refrigerant stream to form a warmed refrigerant stream (112, 512); (d) compressing the warmed refrigerant stream (112, 512) in a compression system (114, 514) to form a compressed refrigerant stream; (e) cooling the compressed refrigerant stream in a third heat exchanger to form the high pressure refrigerant stream; (f) cooling the high pressure refrigerant stream against the gaseous refrigerant stream (106, 506) in the second heat exchanger (110, 510) to form a high pressure cooled refrigerant stream (121, 521); (g) separating the high pressure cooled refrigerant stream (121, 521) into a first portion (124, 524) and a second portion; (h) expanding the second portion of the high pressure cooled refrigerant stream to form an expanded refrigerant stream (108, 508); characterised in that the method comprises: (p) controlling a position of a first valve as a function of a pressure of the gaseous refrigerant stream and a first set point, the first valve being positioned downstream from the first heat exchanger and upstream from the second heat exchanger and in fluid flow communication with the gaseous refrigerant stream; and (q) setting the first set point as a function of a pressure of the storage tank.. (p) controlling a position of a first valve as a function of a pressure of the gaseous refrigerant stream and a first set point, the first valve being positioned downstream from the first heat exchanger and upstream from the second heat exchanger and in fluid flow communication with the gaseous refrigerant stream; and (q) setting the first set point as a function of a pressure of the storage tank..