JP2011196417A - Alarm device for lng tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alarm device for an LNG tank for preventing the frequent occurrence of an alarm.SOLUTION: This alarm device 1 for the LNG tank includes level gauges 10 and 12 for measuring a liquid level of liquefied natural gas in the LNG tank 5 for string the liquified natural gas, an alarm contact point part 20 for outputting an alarm when a measuring result of the level gauges 10 and 12 exceeds a preset reference level and an alarm unit 30 for generating the alarm based on alarm output of the alarm contact point part 20. A timer relay part 22 is arranged between the alarm contact point part 20 and the alarm unit 30, for supplying the alarm output to the alarm unit 30 when a state of performing the alarm output by the alarm contact point part 20 continues for a specific time.

Description

  The present invention relates to an alarm device for an LNG tank that generates an alarm when the liquid level of liquefied natural gas (LNG) stored in the LNG tank is an abnormal level.

  Conventionally, as a level meter for detecting the level of liquefied natural gas in an LNG tank, a capacitance type (so-called C type) level meter or a float type (so-called D type) level meter has been used. Yes. When the measurement result of the level meter exceeds a preset reference level, an alarm by sound or lamp display is generated. Specifically, as the reference level, the lower limit liquid level in the normal range, the lower liquid level than the lower limit, and the upper liquid level in the normal range are set. ing. And when the measurement result of the level meter is lower than the lower limit liquid level in the normal range liquid level (LNG tank level low), if it is lower than this lower limit liquid level (LNG tank level abnormally low), normal An alarm is generated when the liquid level is higher than the upper limit liquid level in the range (the LNG tank level is high).

  Further, as this type of conventional technique, there is a technique described in Patent Document 1. According to Patent Document 1, when an abnormality occurs during LNG acceptance work, an alarm device installed in each place is activated, and an abnormality is alarmed by the monitoring CRT in the measurement control system of the instrument room. It is disclosed that an audio warning is given by a speaker.

JP 7-239289 A

  By the way, when LNG transported by a large LNG ship is received in an LNG tank (for example, a tank having a height of 30,000 mm), the LNG in the LNG tank is reduced to a low LNG tank level (for example, 2,500 mm) and an LNG tank. The level must be paid out to an abnormally low level (for example, 2,000 mm) or lower, that is, to a reference level or lower. For this reason, alarms of LNG tank level low and LNG tank level abnormally low always occur. In addition, after receiving LNG, the LNG tank level may be higher than the reference level (27,000 mm). For this reason, an alarm of LNG tank level high may occur. When an alarm occurs, an operation such as resetting the alarm is performed.

  However, when an alarm of LNG tank level low, LNG tank level abnormally low, or LNG tank level high occurs, the level meter measurement results go up and down near the reference level, and the alarm contact is repeatedly turned on and off to alert Has the problem of frequent occurrence. As a result, the alarm may need to be reset many times. Further, in the case of an alarm by voice, there is a possibility that other alarms may be difficult to hear due to frequent alarms.

  An object of the present invention is to provide an alarm device for an LNG tank that solves such problems and prevents frequent alarms.

  In order to achieve the above object, the present invention has the following configuration.

  (1) Level measurement means for measuring the level of liquefied natural gas in a tank that stores liquefied natural gas, and an alarm output when the measurement result of the level measurement means exceeds a preset reference level. An alarm device for an LNG tank comprising an alarm output means for performing and an alarm means for generating an alarm based on the alarm output of the alarm output means. The alarm output means is provided between the alarm output means and the alarm means. An alarm device for an LNG tank, comprising a timer relay for supplying an alarm output to the alarm means when the alarm output state continues for a specific time.

  According to (1), the measurement result by the level measuring means may fluctuate in the vicinity of a preset reference level, and the alarm output of the alarm output means may be intermittently turned on and off. In this case, the timer relay generates an alarm output with a delay of a specific time and supplies it to the alarm means when the ON state is maintained for a specific time after the alarm output means is turned on. Thereby, it is possible to prevent frequent alarms from occurring in the alarm means.

  (2) In (1), the reference level is a minimum level in a range of liquid level set in advance as a normal range, a maximum level in a range of liquid level set in advance as a normal range, and the minimum level An alarm device for an LNG tank, characterized by having an abnormal level set to a low level.

  According to (2), when the liquid level of the LNG tank is the lowest level (LNG tank level low), the abnormal level (LNG tank level abnormally low), and the highest level (LNG tank level high), an alarm is generated. Is possible.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the alarm apparatus for LNG tanks which prevented the alarm from occurring frequently.

It is a figure which shows the outline | summary of the alarm device for LNG tanks in one Embodiment of this invention. It is a block diagram which shows the structure of the alarm contact part and timer relay part which concern on one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an explanatory diagram showing an outline of an alarm device for an LNG tank according to an embodiment of the present invention. The LNG tank alarm device 1 includes a capacitance type (C type) level meter 10, a float type (D type) level meter 12, an alarm contact unit 20, a timer relay unit 22, and an alarm device 30.

  The capacitance type level meter 10 and the float type level meter 12 are provided in the LNG tank 5 and measure the liquid level of LNG stored in the LNG tank 5. The capacitance level meter 10 can perform measurement with higher accuracy than the float level meter 12. On the other hand, the float type level meter 12 has an advantage that it is not electrically influenced by the object to be measured (here, LNG).

  The alarm contact unit 20 includes a plurality of alarm contacts 20a to 20e (see FIG. 2) that are turned on and off depending on whether the measurement results of the capacitance level meter 10 and the float type level meter 12 exceed the reference level. I have. In the present embodiment, the reference level is set to be the lowest level of the LNG tank level, the highest level of the LNG tank level, and the lowest level in the range of the liquid level set in advance as the normal range. Three types of abnormal LNG tank level abnormally low are set. More specifically, the height of the LNG tank 5 is 30,000 mm, the normal range of the liquid level is 2,500 mm to 27,000 mm, the LNG tank level low is 2,500 mm, and the LNG tank level high is 27 2,000 mm, LNG tank level abnormally low is set to 2,000 mm. When any of the alarm contacts 20a to 20e (see FIG. 2) is turned on, an alarm output is supplied to the timer relay unit 22. The timer relay unit 22 outputs an alarm when the alarm contact is turned on for a specific time (10 seconds in this embodiment). That is, the timer relay unit 22 outputs the alarm output from the alarm contact unit 20 with a delay for a specific time.

  The alarm device 30 generates an alarm when an alarm output is supplied from the timer relay unit 22. For example, a warning report notification by voice using a speaker or a visual warning report notification using a display lamp is performed. The alarm device 30 is installed in the control room 40. In the control room 40, an alarm device 30 of the LNG tank alarm device 1 provided in another LNG tank 5, an alarm device of another facility, and the like are installed. It is possible to know the occurrence of an abnormality or a state before the occurrence of the abnormality by the alarm device.

  FIG. 2 is a block diagram illustrating the configuration of the alarm contact unit 20 and the timer relay unit 22 according to an embodiment of the present invention. The alarm contact unit 20 includes three alarm contacts 20 a, 20 b, 20 c connected to the capacitance type level meter 10 and two alarm contacts 20 d, 20 e connected to the float type level meter 12. The alarm contact 20a and the alarm contact 20d are turned on when the LNG tank level is low, that is, when the liquid level is lower than 2500 mm. The alarm contact 20b is turned on when the LNG tank level is abnormally low, that is, when the liquid level is lower than 2,000 mm. The alarm contact 20c and the alarm contact 20e are turned on when the LNG tank level is high, that is, when the liquid level is higher than 27,000 mm.

  The timer relay unit 22 includes five timer relays 22a to 22e. Here, the five timer relays 22a to 22e are all the same. A timer relay 22a is connected to the alarm contact 20a. Similarly, a timer relay 22b is connected to the alarm contact 20b, a timer relay 22c is connected to the alarm contact 20c, a timer relay 22d is connected to the alarm contact 20d, and a timer relay 22e is connected to the alarm contact 20e.

  Next, the operation will be described. For example, when the capacitance level meter 10 measures 2,499 mm, for example, the alarm contact 20a is turned on, and an alarm output is supplied to the timer relay 22a. The timer relay 22a supplies an alarm output when the alarm output is continuously supplied for 10 seconds. That is, an alarm output is supplied from the timer relay 22a to the alarm device 30 with a delay of 10 seconds from the time when the alarm contact 20a is turned on. Thereby, the alarm device 30 of the control room 40 is activated, and the worker can know that the liquid level level of the LNG stored in the LNG tank 5 has become low.

  Further, when the electrostatic capacity type level meter 10 measures, for example, 2,501 mm before 10 seconds from the time when the alarm contact 20a is turned on, the alarm contact 20a is turned off, and the timer relay 22a is reset. Therefore, the reset timer relay 22a supplies an alarm output when it is continuously supplied for 10 seconds after the alarm contact 20a is turned on next time. The same applies to the other timer relays 22b to 22e. When the alarm contacts 20b to 20e are turned on, that is, when the alarm output is being supplied for 10 seconds, the alarms are output from the timer relays 22b to 22e. An alarm output is supplied to the device 30. If the alarm contacts 20b to 20e are turned off before 10 seconds have passed since the alarm contacts 20b to 20e are turned on, the timer relays 22b to 22e are reset.

  Here, when the fluctuation tendency of the liquid level in the LNG tank 5 was examined, it was found that the liquid level did not change rapidly. Therefore, since it can be estimated that the period during which the measurement results of the capacitance level meter 10 and the float type level meter 12 are in the state of moving up and down around the reference level is short, there is a problem even if the timer relays 22a to 22e are used. I found that there was no. In the setting of the timer relay 22 in the present embodiment, the maximum time from on to off in the alarm performance is 5 seconds, so 10 seconds including a margin of 5 seconds is set as the specific time. This setting is an example, and the present invention is not limited to this. That is, the specific time (delay time) can be set as appropriate according to the fluctuation tendency of the liquid level in the LNG tank. In the present embodiment, the timer relays 22a to 22e are all the same, but may be set differently depending on the type of the reference level. Further, the circuits of the timer relays 22a to 22e may be configured so that the specific time set for the timer relays 22a to 22e can be changed by an operator operation by the control room 40.

  As described above, according to the present embodiment, the measurement results of the capacitance type level meter 10 and the float type level meter 12 fluctuate in the vicinity of the preset reference level, and the alarm contact unit 20 The alarm output may turn on and off intermittently. In this case, the timer relay unit 22 delays the alarm output by the specified time when the alarm contact unit 20 is turned on and the alarm output is supplied for a specified time (for example, 10 seconds). Generated and supplied to the alarm 30. Thereby, even if the alarm output of the alarm contact unit 20 is intermittently turned on and off, it is possible to prevent the alarm device 30 from generating frequent alarms.

  In addition, when alarms occur frequently, there is a risk of getting used to the operation of resetting alarms, and the worker's awareness of attention may be reduced. On the other hand, according to this embodiment, since alarms can be prevented from occurring frequently in the alarm device 30, it is possible to prevent a worker's attention consciousness from being lowered.

  In addition, when alarms occur frequently, they may occur at the same time as other alarms, which may make it difficult to check other alarms. On the other hand, according to the present embodiment, it is possible to prevent alarms from occurring frequently in the alarm device 30, and therefore, it is possible to prevent omission of confirmation of other alarms.

DESCRIPTION OF SYMBOLS 1 Tank alarm device 5 LNG tank 10 Capacitance type level meter 12 Float type level meter 20 Alarm contact part 20a, 20b, 20c, 20d, 20e Alarm contact 22 Timer relay part 22a, 22b, 22c, 22d, 22e Timer relay 30 Alarm 40 Control room

Claims (2)

Level measuring means for measuring the liquid level of the liquefied natural gas in the tank storing the liquefied natural gas;
Alarm output means for outputting an alarm when the measurement result of the level measuring means exceeds a preset reference level; and
In an alarm device for an LNG tank comprising alarm means for generating an alarm based on the alarm output of the alarm output means,
The LNG tank is provided with a timer relay between the alarm output means and the alarm means for supplying the alarm output to the alarm means when the alarm output means is outputting the alarm for a specified time. Alarm device.   The reference level includes a minimum level in a range of liquid level set in advance as a normal range, a maximum level in a range of liquid level set in advance as a normal range, and an abnormal level set lower than the minimum level. The alarm device for an LNG tank according to claim 1, comprising:

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