JPH0240170B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for inspecting a differential pressure type liquid level gauge used to detect the liquid level height of a storage tank in which liquefied carbon dioxide gas is stored. Conventionally, when inspecting a differential pressure type level gauge, a pressure generating means that generates a known pressure is connected to the differential pressure type level gauge to check whether the indications of the differential pressure type level gauge are correct. It was being inspected. In such a test,
It cannot be confirmed whether the actual liquid level height of the storage tank where liquefied carbon dioxide gas is stored is displayed correctly. Therefore, in some prior art techniques, an inspection method as shown in FIG. 1 is used. The storage tank 1 in which liquefied carbon dioxide gas is stored includes a differential pressure type liquid level gauge 8, which will be described later, and a connecting pipe 2 that connects the top and bottom of the storage tank 1. In the connecting pipe 2, pots 3a and 3b are interposed close to the top of the storage tank 1, and pots 4a and 4b are interposed close to the bottom of the storage tank 1. A vertical conduit 2a extending vertically is formed in the connecting pipe 2, and a plurality of pots 5 are disposed in the vertical direction corresponding to the height of the storage tank 1 in this vertical conduit 2a. When the liquid level height is determined by the differential pressure type liquid level gauge, open the cocks 3a, 3b; 4a, 4b,
After matching the liquid level height of the vertical pipe 2a with the liquid level height of the storage tank 1, the pots 3a, 3b; 4a, 4b are closed to correspond to the liquid level height determined by the differential pressure type liquid level gauge. Open the container 5a. Kokotoku 5a
When liquefied carbon dioxide gas flows out from the tank 5a and liquefied carbon dioxide gas does not flow out from the tank 5 provided directly above the tank 5a, it is confirmed that the differential pressure type liquid level gauge is correct. In such a method, the liquefied carbon dioxide boils at the liquid level of the vertical pipe portion 2a, making it difficult to accurately measure the liquid level height of the storage tank 1. In order to prevent boiling, it was necessary to keep the vertical pipe portion 2a cold. Therefore, the vertical pipe portion 2a has a large diameter,
A great deal of money was spent. In another prior art, a liquid level gauge 2b as shown in FIG. 2 is used in place of the vertical pipe portion 2a of the prior art described above. The liquid level gauge 2b is provided with a glass window in an elongated hole 5b extending vertically. The liquid level height of the storage tank 1 can be directly read from this glass window. This liquid level gauge 2
Similarly to the above-mentioned vertical pipe portion 2a, it was also necessary to keep the pipe portion b cool, and a large amount of money was spent to prevent the liquid level from boiling. An object of the present invention is to solve the technical problems of the prior art and to provide a method for testing a differential pressure type liquid level gauge that allows the accuracy of the differential pressure type liquid level gauge to be easily and accurately tested. Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a simplified configuration diagram for explaining an inspection method of a differential pressure type liquid level gauge according to an embodiment of the present invention. The storage tank 7 in which the liquefied carbon dioxide gas 6 is stored includes:
A differential pressure type liquid level gauge 8 is connected. The storage tank 7 is
It is loaded on a ship or the like, and liquefied carbon dioxide gas 6 is injected into the storage tank 7 from a tank truck 9 or the like. To explain the operating state of the differential pressure type liquid level gauge 8, the liquid pipe line 12 drawn out from the bottom 7a of the storage tank 7
The liquid level H of the liquefied carbon dioxide calculated from the pressure difference ΔP between the pressure PL on the side and the pressure PG on the side of the gas pipe 13 drawn out from the upper part of the storage tank 7 is determined by the indicator 14. It is read directly. Below, this pressure difference ΔP
shows the relationship between pressure PL and PG. ΔP=PL−PG …(1) ∴ΔP=(h・γG+H・γL−H0・γG) −{h・γG+(H−H0)・γG} …(2) ∴ΔP=H・(γL−γG) ...(3) Here, ΔP is pressure difference, PL is liquid side pressure, PG is gas side pressure, H is liquid level height, h is gas phase height, H0
is the height from the bottom 7a of the storage tank 7 to the indicator 14, γL is the liquefied carbon dioxide specific gravity, and γG is the carbon dioxide specific gravity. Therefore, the pressure difference ΔP in the first equation is transformed as shown in the second equation, and as shown in the third equation, the liquid level height H of the liquefied carbon dioxide gas and the specific gravity γL of the liquefied carbon dioxide gas
It is derived as the product of the difference between γG and carbon dioxide specific gravity γG.
When the temperature and pressure are constant, the liquefied carbon dioxide specific gravity γL and the carbon dioxide specific gravity γG are known quantities. The indicator 14 of the differential pressure type liquid level gauge 8 is provided with a bellows (not shown) that deforms due to the pressure difference between the liquid pipe line 12 and the gas pipe line 13. A scale plate 16, which will be described later, is provided so that a pointer 15 of 14 indicates the liquid level height H. Note that this bellows is temperature compensated. Table 1 shows the liquid level H of liquefied carbon dioxide calculated from the third formula, the weight of liquefied carbon dioxide, the weight of carbon dioxide, and the total weight of carbon dioxide, i.e. (liquefied carbon dioxide +
The relationship between the weight of carbon dioxide gas and the liquid level height in terms of water column is shown.

【table】

[Table] In this calculation, the pressure inside the storage tank 7 is 21.5
Kg/cm ² G, and the specific gravity of liquefied carbon dioxide γL is
1.012ton/ ^m3 , and carbon dioxide specific gravity γG is 0.058ton/m3.
Let it be ^m3 . Note that this storage tank 7 has an inner diameter of 2000 mm, for example, and is designed as a 27 ton tank. Figure 4 shows the scale plate 16 of the indicator 14 shown in Figure 3.
FIG. The scale plate 16 is formed into a disk shape. On this scale plate 16, the total carbon dioxide specific gravity shown in Table 1 is graduated outward in the circumferential direction in units of tons.
The liquid level height converted into a water column shown in Table 1 is graduated in mmH ₂ O inward in the circumferential direction.
A drive shaft 17 connected to the bellows is provided at the center of the scale plate 16, and a pointer 15 (see FIG. 3) is rotatably fixed to the drive shaft 17. Referring again to FIG. 3, a liquid side main valve 18 is provided in the liquid pipe line 12 near the storage tank 7. A gas side main valve 19 is provided on the gas pipe line 13 closer to the storage tank 7 . The liquid pipe line 12 and the gas pipe line 13 are connected to the indicator 1 at a height H0 from the bottom 7a of the storage tank 7.
Connected to 4. A bypass line 20 is provided between the gas line 13 near the storage tank 7 and the liquid line 12 connected to the indicator 14. Bypass line 2
0, a bypass valve 21 is interposed. A three-way cock 22 is interposed between the gas side main valve 19 of the gas line 13 and the bypass line 20 to make the pressure of the gas line 13 equal to atmospheric pressure. A three-way socket 23 is interposed between the liquid side main valve 18 of the liquid pipe line 12 and the bypass pipe line 20.
A flexible pressure tube 24 is connected to this three-way pot 23. This pressure-resistant pipe 24 is connected to a micro-pressure generating pump 25 as pressure generating means.
The low pressure generating pump 25 is, for example, a pneumatic manual plunger type. The low pressure generating pump 25 is connected to one end of a pressure gauge 27, for example, a U-shaped water column pressure gauge, through a pressure tube 26. Water is stored in this U-shaped tube, and the other end of the pressure gauge 27 is opened to the atmosphere. Therefore, the pressure generated by the low pressure generating pump 25 is directly read by the pressure gauge 27 as the height of the water column. Inspection of the differential pressure type liquid level gauge 8 according to the present invention is performed by the following steps 1 to 3. In step 1, it is confirmed whether or not the display on the differential pressure type liquid level gauge 8 when the storage tank 7 is filled with the liquefied carbon dioxide gas 6 is correct. However, here, the term "set filling" refers to a state in which liquefied carbon dioxide gas is stored from the bottom 7a of the storage tank 7 to a height corresponding to, for example, 90% of the internal volume of the storage tank 7. An overflow port 10 is opened at a position corresponding to 90% of the internal volume of the storage tank 7 from the bottom 7a of the storage tank 7. The overflow port 10 is communicated with an overflow port valve 11 provided below the storage tank 7 through a pipe 28 . The liquefied carbon dioxide gas 6 is injected from the tank truck 9 in an amount slightly larger than the set filling amount. At this time, if the overflow port valve 11 is left slightly open, the excess liquefied carbon dioxide gas 6
becomes dry ice from the overflow port valve 11 and is discharged to the outside. When this dry ice stops being white and changes to colorless carbon dioxide gas, the overflow port valve 1
1 is opened, the liquid side main valve 18 of the liquid pipe line 12 and the gas side main valve 19 of the gas pipe line 13 are opened, and the scale plate indicated by the pointer 15 of the indicator 14 of the differential pressure type liquid level gauge 8 is opened. 16
Read directly. The pointer 15 may accurately indicate 100% shown on the scale plate 16, or it may indicate within the error range of the volume caused by manufacturing precision of the storage tank 7. Note that the liquid level immediately after injection of the liquefied carbon dioxide gas 6 is unstable due to boiling, so please follow the guideline 1.
5 becomes stable, then read the scale displayed on the scale plate 16. In step 2, when the pressure difference between the liquid pipe line 12 side and the gas pipe line 13 side is zero, that is, the storage tank 7
Check the display on the differential pressure type liquid level gauge 8 when there is no liquefied carbon dioxide gas 6. When the bypass valve 21 is opened, the pressure difference becomes zero, and the pointer 15 of the indicator 14 may indicate the zero pressure difference converted into water column. However, even when the pressure difference is zero, the total carbon dioxide specific gravity is shown assuming that carbon dioxide remains in the storage tank 7. Note that when opening the bypass valve 21, first the liquid side main valve 18 is opened, and then the bypass valve 21 is opened. In step 3, the display on the differential pressure type liquid level gauge 8 is checked when the liquid level height of the liquefied carbon dioxide gas 6 in the storage tank 7 decreases below 100% storage. Liquid pipe line 1
2, the gas side main valve 19 of the gas pipe 13, and the bypass valve 21 are closed, and the gas pipe 1
The pot 22 interposed in the pipe 3 is opened under atmospheric pressure, and the pot 23 is switched so that the pressure tube 24 and the pipe line 12 communicate with each other. Calculated pressure differences when a certain amount of liquefied carbon dioxide 6 is stored in the storage tank 7 at a fixed amount, for example, 90% and 70% of the set filling amount, are generated by the micropressure generation pump 25, and the differential pressure liquid is generated. The pointer 15 of the indicator 14 of the face meter 8 may indicate each value on the scale plate 16. When the difference between the pressure indicated by the pressure gauge 27 and the scale indicated by this indicator 14 is, for example, in the range of ±38 mmH ₂ O, this differential pressure type liquid level gauge 8 detects the liquefied carbon dioxide in the storage tank 7. It is possible to accurately measure the liquid level height of 6. Note that, prior to performing the inspection in step 3, the liquefied carbon dioxide gas 6 in the storage tank 7 must reach 100%
A calculated pressure difference in a state where % is stored is generated by the micro-pressure generating pump 25, and it is confirmed whether the indicator 14 is operating correctly. As described above, according to the present invention, by connecting the pressure generating means to the differential pressure type liquid level gauge, the differential pressure type liquid level gauge can be inspected accurately and easily.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram for explaining a certain prior art, Fig. 2 is a perspective view for explaining another prior art, and Fig. 3 is an inspection of a differential pressure type liquid level gauge according to an embodiment of the present invention. FIG. 4, a simplified configuration diagram for explaining the method, is a front view of the scale plate 16 of the indicator 14 shown in FIG. 3. 6... Liquefied carbon dioxide gas, 7... Storage tank, 7a... Storage tank bottom, 8... Differential pressure type liquid level gauge, 10... Overflow port, 12...
Liquid pipe line, 13... Gas pipe line, 14... Indicator, 15...
Pointer, 16... Scale plate, 20... Bypass conduit, 21
...Bypass valve, 22, 23...Three-way valve, 25...
Low pressure generation pump, 27...pressure gauge.

Claims (1)

[Claims] 1. In order to detect the liquid level height of a storage tank in which liquefied carbon dioxide gas is stored, a liquid pipe line led out from the lower part of the storage tank and a liquid pipe line led out from the upper part of the storage tank are provided. An indicator is installed on the way where the gas pipe is connected,
In the inspection method for a differential pressure type liquid level gauge that displays a liquid level height according to the difference between the liquid pipe side pressure and the gas pipe side pressure, the storage tank is filled with a set amount of liquefied carbon dioxide gas. An overflow port is provided at a corresponding height, a cock is interposed in the gas pipe line to match the pressure of the gas pipe line with atmospheric pressure, and an overflow port is provided in the liquid pipe line between the storage tank and the indicator. A pressure generating means is interposed in the tank, and liquefied carbon dioxide is injected into the storage tank at a level slightly higher than the height of the overflow port, and the state of the liquefied carbon dioxide flowing out from the overflow port is determined, and a predetermined amount of liquefied carbon dioxide is injected into the storage tank. When liquefied carbon dioxide gas is stored to match the set filling amount of gas, check whether the display on the differential pressure type liquid level gauge is 100%, and check the liquid pipe side pressure and gas pipe side pressure. Check whether the display on the differential pressure liquid level gauge is zero when the difference between When the bottle is opened, the pressure on the gas pipe side is set to atmospheric pressure, and the pressure generating means is applied from the liquid pipe side to a pressure calculated assuming that liquefied carbon dioxide gas exists in the storage tank. . A method for inspecting a differential pressure type liquid level gauge, comprising checking whether the display of the differential pressure type liquid level gauge matches the pressure.