Rotary machine system and negative pressure unit

A rotary machine system comprising:

• a rotary machine including a rotor having a rotor shaft rotatable about an axis, a casing covering the rotor from an outer side in a radial direction centered on the axis, and a shaft bearing device rotatably supporting the rotor shaft with respect to the casing;
• a drain line that recovers lubricating oil supplied to the shaft bearing device;
• an oil tank that stores the lubricating oil recovered through the drain line;
• and
• a negative pressure unit that is disposed partway along the drain line and reduces pressure inside the shaft bearing device, wherein
• the negative pressure unit includes
• an oil inlet connected to the drain line and communicating with the shaft bearing device,
• an oil outlet connected to the drain line and communicating with the oil tank,
• an oil flow pipe that connects the oil inlet and the oil outlet and forms a flow path for the lubricating oil, and
• an ejector that includes a suction port connected to the oil flow pipe and extracts gas in the oil flow pipe through the suction port to reduce pressure in the oil flow pipe,
• the oil flow pipe includes an oil retention pipe that is located on a downstream side of the suction port in a flow direction of the lubricating oil and is capable of storing the lubricating oil below the oil inlet and the oil outlet in a vertical direction,
• the rotary machine system further comprises a gas discharge pipe connected to a discharge port from which a drive gas supplied in the ejector is discharged, and the oil flow pipe, and
• the gas discharge pipe is connected to the oil flow pipe between a position where the lubricating oil is stored in the oil retention pipe and the oil outlet.