Pumps – Motor driven – With means to prevent heat transfer between pump and motor
Reexamination Certificate
1999-08-19
2001-06-26
Freay, Charles G. (Department: 3746)
Pumps
Motor driven
With means to prevent heat transfer between pump and motor
C062S646000, C062S050600
Reexamination Certificate
active
06250896
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a pump for a cryogenic liquid, in particular a liquid obtained during an air distillation process, for example liquid oxygen.
DESCRIPTION OF THE RELATED ART
Pumps intended to pump cryogenic liquids, such as for example liquid oxygen, are known which have an electric motor and generally comprise two separate components, one of which is at ambient temperature and comprises an electric motor, and the other of which is at the temperature of the cryogenic liquid and comprises a pumping component driven by the electric motor.
U.S. Pat. No. 5,545,015 describes a cryogenic-liquid pump driven by a hydraulic motor.
In order to prevent the cryogenic liquid from warming up, expensive thermal insulation is arranged between the motor component and the pumping component in order to reduce the heat exchange between these two components.
Furthermore, the cryogenic liquids pumped in air-distillation plants often contain a large proportion of oxygen, which can pose serious problems in the event of short-circuit in the electrical equipment of the motor, causing dangerous metal fires.
SUMMARY OF THE INVENTION
The object of the invention is to overcome the various drawbacks by providing a pump which is more reliable and which can be manufactured at a relatively low cost price.
To that end, the invention relates to a pump for a cryogenic liquid, in particular liquid oxygen, comprising a hydraulic motor which is supplied with a motor liquid under pressure and drives a wheel for pumping the said cryogenic liquid, characterized in that it comprises relative sealing means preventing contamination of the cryogenic liquid by transfer of the motor liquid from the motor to the pumping wheel.
The pump according to the invention may also have one or more of the following characteristics:
it is immersed in the cryogenic liquid to be pumped,
the motor liquid under pressure is supercooled,
the motor liquid has a density in excess of 400 kg/m
3
,
the hydraulic motor comprises a driving wheel which is driven by the said motor liquid and is mounted on a shaft common with the pumping wheel,
the said common shaft is supported by bearings lubricated by means of the motor liquid,
the said relative sealing means comprise a labyrinth seal arranged around the common shaft, between the driving wheel and the pumping wheel.
the relative sealing means allow transfer of cryogenic liquid from the pumping wheel to the motor.
The cryogenic liquids to be pumped and the motor liquid may be selected so that the arrival of the cryogenic liquid in the motor does not cause vaporization either of the cryogenic liquid or of the motor liquid.
The invention furthermore relates to a unit for pumping a cryogenic liquid, characterized in that it comprises, arranged in a compartment which is thermally insulated and is filled with the cryogenic liquid to be pumped, two pumps as defined above which are immersed in the cryogenic liquid to be pumped and are arranged in parallel in a duct carrying the motor liquid under pressure.
The pumping unit according to the invention may furthermore have the characteristic according to which the pumping unit furthermore comprises, arranged in the duct carrying the motor liquid, means for switching between supply of the motor liquid to one or the other of the two pumps,
the motor liquid is a cryogenic liquid. A cryogenic liquid is a liquid such as oxygen, nitrogen or argon.
the motor liquid is miscible with the cryogenic liquid which is pumped.
The invention furthermore relates to a plant for distillation of a gas, in particular air, comprising at least a first and a second column, the pressure prevailing in the first column being higher than that prevailing in the second column, characterized in that it comprises a pump as defined above for pumping a cryogenic liquid delivered by one of the said columns, the said pump being driven by a motor liquid delivered by the plant.
The distillation plant according to the invention may furthermore have one or more of the following characteristics:
the distillation plant comprises a double column, including in particular a medium-pressure column and a low-pressure column,
the said cryogenic liquid which is pumped is an oxygen-rich liquid,
the said cryogenic liquid which is pumped is a liquid which comes from an argon column,
the said cryogenic liquid which is pumped is a liquid which comes from a low-pressure column and is intended to be sent to a vaporizer,
the said columns are arranged side by side,
the said motor liquid is liquid air delivered by a heat-exchange line,
the said motor liquid is an oxygen-rich liquid,
the said motor liquid is a low-oxygen liquid.
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Evora Robert Z.
Freay Charles G.
L'Air Liquide Societe Anonyme pour l'Etude et l'E
Young & Thompson
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