Abstract: The present invention relates to a technique of preventing idling rotation of a submersible pump used for delivering liquefied gas, such as liquefied ammonia, liquid hydrogen, liquid nitrogen, liquefied natural gas, liquefied ethylene gas, or liquefied petroleum gas. A fluid-path switching apparatus (5) includes: a flow-passage structure (45) having a first flow passage (41), a second flow passage (42), and a third flow passage (43); and a valve element (47) for allowing the third flow passage (43) to selectively communicate with the first flow passage (41) or the second flow passage (42). The first flow passage (41) communicates with a discharge outlet (1b) of the submersible pump (1), the second flow passage (42) communicates with an interior of the suction vessel (2), and the third flow passage (43) communicates with a discharge port (8) of the suction vessel (2).

Abstract: The present invention relates to a sealing system for a pump configured to pressurize a volatile liquid, such as liquid ammonia. The sealing system (2) includes a stuffing box (35) forming a barrier chamber (30) and a pump-side seal chamber (43), a mechanical seal (20) arranged in the barrier chamber (30), and a barrier-gas supply system (32) for supplying a barrier gas into the barrier chamber (30). The barrier gas has a pressure higher than a pressure of the volatile liquid in the pump-side seal chamber (43). The pump-side seal chamber (43) is located between an impeller (7) of the pump (1) and the mechanical seal (20). The barrier-gas supply system (32) includes a pressure control valve (50) configured to maintain a constant difference between pressure in the barrier chamber (30) and pressure in the pump-side seal chamber (43).

Abstract: The present invention relates to a sealing system for a pump configured to pressurize a volatile liquid, such as liquid ammonia. The sealing system (2) includes a stuffing box (35) forming a barrier chamber (30) and a pump-side seal chamber (43), a mechanical seal (20) arranged in the barrier chamber (30), and a barrier-gas supply system (32) for supplying a barrier gas into the barrier chamber (30). The barrier gas has a pressure higher than a pressure of the volatile liquid in the pump-side seal chamber (43). The pump-side seal chamber (43) is located between an impeller (7) of the pump (1) and the mechanical seal (20). The barrier-gas supply system (32) includes a pressure control valve (50) configured to maintain a constant difference between pressure in the barrier chamber (30) and pressure in the pump-side seal chamber (43).