PURPOSE: To reduce the cost down of a cooling water piping structure, and to simplify the branched pipings of the cooling water even in a case of increasing the number of the gas centrifugal separators compared with the conventional system.

CONSTITUTION: A desired cooling water supplying device is constituted by means of connecting many gas centrifugal separators in parallel via branched pipings 4 of cooling water and confluent pipings 5 of the cooling water. In this case, when the number of the gas centrifugal separators to be set may become enlarged, the terminal flow becomes little, and the optimum flow distribution becomes to be kept, thereby the flow distribution is kept by the change of the lengths of the above mentioned connecting pipings 4, 5. By such means, the flow resistance can be changed optionally by means of changing the lengths of the pipings 4, 5, thereby the flow quantity distribution to the cooling water to the gas separators can be set according as an object, and the structure can be simplified with plenty.