JPS637271B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention forcibly transfers the low-temperature liquefied gas from a tank storing the low-temperature gas such as liquid nitrogen or liquid natural gas to another location such as a tank truck. More specifically, the transfer device includes a transfer path equipped with a valve connected to the lower part of a tank storing low-temperature liquefied gas, a pump installed at a position downstream of the valve in the transfer path, and a pump driven by the pump. The present invention relates to a low-temperature liquefied gas transfer device for forcibly transferring low-temperature liquefied gas from a tank.

This type of transfer device generally operates the pump intermittently by opening the valve only during transfer. Therefore, during non-transfer operations, the pump downstream of the valve and the forced The temperature of the transfer path has risen to around room temperature due to the influence of the ambient temperature (generally atmospheric temperature), so if the pump is started in this state, the low-temperature liquefied gas extracted from the tank will vaporizes in the transfer path from the valve to the pump and at the pump, creating a bubble region in the pump chamber, and when the bubbles disappear, the water (liquid) impact causes acoustic vibrations. This is disadvantageous in that it causes a so-called cavitation phenomenon, which reduces the efficiency of the pump and, in turn, causes damage to the impeller and pump casing.

In view of the above circumstances, an object of the present invention is to make it possible to reliably avoid the cavitation phenomenon during intermittent transfer operations.

In the low-temperature liquefied gas transfer device according to the present invention, in the configuration described above, a reflux path to the upper part of the tank, which has an upward flow path portion, is connected to a position downstream of the pump in the transfer path, and A sensor for detecting passage of the low-temperature liquefied gas in a liquid state is provided in the flow path, and an on-off valve is provided for supplying and stopping the low-temperature liquefied gas and for communicating and cutting off the transfer path and the tank via the reflux path. and by opening the valve, the low-temperature liquefied gas is returned to the tank via the reflux path, and a switch for starting the pump is turned on based on the detection result of the passage of the low-temperature liquefied gas in liquefied form by the sensor. The low-temperature liquefied gas is forcibly transferred from the tank via the transfer path by operating the on-off valve.

That is, according to the device of the present invention, when it is necessary to transfer from a tank to a tank truck or the like, the pump is prevented from starting when it is near room temperature, and the low-temperature liquefied gas is circulated through the reflux path, and the pump and The transfer path leading up to this point is cooled, and when these are sufficiently cooled and the conditions are such that the low-temperature liquefied gas does not vaporize in the transfer path or pump, in other words, it is installed in the reflux path downstream of the pump. Only when the sensor detects that the low-temperature liquefied gas from the transfer path is flowing in the reflux path in liquid form will the pump start switch be turned on and activated to start the pump. It is possible to prevent the phenomenon from occurring. Therefore, even when the pump, etc. is exposed to the atmosphere and the temperature of the pump, etc. has risen to around room temperature when starting transfer work, the pump can be started reliably without causing cavitation. This not only allows for efficient transfer work at all times, but also improves the durability of the pump.

Next, an embodiment of the present invention will be described in detail based on illustrative drawings. A forced transfer path 3 equipped with an on-off valve 6 is installed at the bottom of a tank 1 which is insulated to store low-temperature liquefied gas such as liquid nitrogen. A pump 2 is connected to the transfer path 3 near the tank 1 via a valve 10.
(generally, a centrifugal type or reciprocating type is used) is interlocked and connected to the electric motor 7, and the on-off valve is located downstream of the pump 2 in the forced transfer path 3. 6, a return flow path 4 for the tank 1, comprising an upward flow path portion 4a and a flow path portion 4b with an on-off valve 8 that is horizontally or almost horizontally connected to the upper space in the tank 1; are connected at the lower end of the upward flow path portion 4a, and a vertical bypass flow path 9 is connected to the upward flow path portion 4a of the return flow path 4 via horizontal or nearly horizontal communication path portions 9a, 9b. However, nitrogen gas N ₂ is compressed and sealed inside this bypass passage 9, and when low-temperature liquefied gas enters in a liquid phase, the sealed compressed gas condenses and liquefies, causing the internal pressure to rapidly increase. There is a sensor 5 that descends to
A pressure switch PS is inserted in the motor starting circuit to automatically start the pump 2, that is, the motor 7, when the internal pressure of are electrically connected so that they can be opened and closed automatically and reciprocally by turning on the pressure switch PS.

Therefore, even if the motor power circuit is turned on and the valve 10 is opened when it is necessary to transfer low-temperature liquefied gas, the pressure switch will not be activated.
Since the PS remains off, the pump 2 is not started, the valve 6 is closed, and the valve 8 is open, so the low temperature liquefied gas in the tank 1 is transferred to the transfer path 3.
Natural circulation occurs within the valve 10, pump 2, and reflux path 4 to cool them. At this time, a part of the low-temperature liquefied gas is inside the pump 2 and the transfer path 3 where the temperature is rising.
Even if some parts are vaporized, the cavitation phenomenon does not occur because the pump 2 is inactive. Then, when the pump 2 and the reflux path 4 are sufficiently cooled and the low-temperature liquefied gas does not vaporize, a part of the liquefied gas flowing in the flow path portion 4a is diverted into the bypass flow path 9 and the sensor 5 , the compressed gas sealed in this sensor 5 is instantly condensed and liquefied, and its internal pressure drops rapidly, which causes the pressure switch to
The PS operates to automatically start the motor 7 and the pump 2, open the valve 6, and close the valve 8, after which the low-temperature liquefied gas is forcibly transferred via the pump 2 as specified.

In particular, when the sensor 5 is interposed in the bypass 9 parallel to the upward flow path portion 4a as in the above embodiment, while the pump 2, transfer path 3, and return flow path 4 are not sufficiently cooled, Since the gas mixed with vaporized gas goes straight through the upward flow path section 4a and does not enter the bypass 9, there is no possibility that this gas-liquid mixture will cause the sensor 5 to malfunction, and the intended purpose can be achieved more reliably. There are advantages.

As is clear from the above explanation, by using the device of the present invention, the pump can be reliably and automatically started without causing cavitation, and the temperature This method simplifies the labor-intensive task of turning on the pump when the temperature has dropped to a predetermined temperature while measuring the temperature, and has the advantage of greatly contributing to labor savings.

Note that although reference numerals are written in the claims section for convenient comparison with the drawings, the present invention is not limited to the structure shown in the accompanying drawings.

[Brief explanation of the drawing]

The drawing is a conceptual diagram showing an embodiment of a low-temperature liquefied gas transfer device according to the present invention. 1... Tank, 2... Pump, 3... Transfer path,
4... Return flow path, 4a... Channel portion, 5... Sensor, 6, 8... Open/close valve, 9... Bypass flow path, 1
0...Valve, PS...Start switch.

Claims (1)

[Claims] 1. A transfer path 3 equipped with a valve 10 is connected to the lower part of a tank 1 storing low-temperature liquefied gas, and a pump 2 is installed at a position downstream of the valve 10 in the transfer path 3, A low-temperature liquefied gas transfer device that forcibly transfers low-temperature liquefied gas from a tank 1 by driving the pump 2, and includes an upward flow path portion 4a at a downstream position of the transfer path 3 from the pump 2. A reflux path 4 is connected to the upper part of the tank 1, and a sensor 5 for detecting passage of the low temperature liquefied gas in liquid form is provided in the flow path portion 4a, and a sensor 5 for detecting the passage of the low temperature liquefied gas in liquid form is connected to the flow path 4, and a sensor 5 for detecting the passage of the low temperature liquefied gas in a liquid state is connected to the flow path 4. On-off valves 6 and 8 are provided to communicate and shut off communication between the tank 1 and the tank 1 via the reflux path 4, and by opening the valve 10, the low-temperature liquefied gas is transferred to the tank 1 via the reflux path 4.
The starting switch PS of the pump 2 is turned on and activated based on the detection result of the passage of low-temperature liquefied gas in liquid form by the sensor 5, and the on-off valves 6 and 8 are operated to allow the low-temperature liquefied gas to pass through the transfer path 3. A low-temperature liquefied gas transfer device characterized in that the low-temperature liquefied gas is forcibly transferred from the tank 1 by using the low-temperature liquefied gas. 2. The low-temperature liquefied gas transfer device according to claim 1, wherein the sensor 5 is provided in a bypass flow path 9 connected in parallel to the flow path portion 4a of the reflux path 4.