JPH0132454B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method and apparatus for testing volatile liquid storage tanks for leaks.

(Prior art) In general tank leakage inspection, the tank is pressurized or depressurized after all the liquid stored in the tank is drained to make it an empty tank, and the change in the pressure in the tank is checked over time in the pressurized or depressurized state. The tank is being inspected for leaks. However, the process of emptying the tank takes a lot of time and is expensive, can be very dangerous depending on the liquid stored, and requires more time for pre-preparation and post-processing than the actual inspection time, so there is no time loss. It's huge.

Japanese Patent Publication No. 57-46495 discloses a method that eliminates these drawbacks and allows safe and reliable inspection of liquid in a storage tank.
However, with this method, if the stored liquid is evaporative, the pressure may increase as if a leak has occurred even though there is no leak, and it takes time to determine this. , and also had the disadvantage of causing errors.

OBJECTS OF THE INVENTION An object of the present invention is to provide a leak testing method and apparatus for a volatile liquid storage tank that eliminates the above-mentioned drawbacks.

(Structure of the Invention) The leakage testing method for a volatile liquid storage tank of the present invention includes a step of hermetically closing a volatile liquid storage tank;
A step of bringing the inside of the tank to a constant reduced pressure state, a step of measuring the atmospheric pressure inside the tank after a predetermined period of time from this step and bringing the tank to atmospheric pressure, and a step of bringing the inside of the tank to the atmospheric pressure to a certain level. It is characterized by comprising a step of bringing the tank into a pressurized state and a step of measuring the atmospheric pressure inside the tank a predetermined time after this step.

The volatile liquid storage tank leakage inspection device of the present invention includes a step of airtightly closing the volatile liquid storage tank;
A step of bringing the inside of the tank to a constant reduced pressure state, a step of measuring the atmospheric pressure inside the tank after a predetermined period of time from this step and bringing the tank to atmospheric pressure, and a step of bringing the inside of the tank to the atmospheric pressure to a certain level. It is characterized by comprising a step of bringing the tank into a pressurized state and a step of measuring the atmospheric pressure inside the tank a predetermined time after this step.

(Example of the invention) Embodiments of the present invention will be described below with reference to the drawings.

In Figure 1, 1 is the storage tank to be inspected, 2
3 is a ventilation pipe connected to the upper part of the tank 1;
4 is a metering pipe connected to the upper part of the tank 1;
5 is a suction pipe connected to the lower part of the tank 1;
6 indicates a liquid supply pipe communicating with the upper part of the tank 1, and 6 indicates a volatile liquid such as gasoline or light oil stored in the tank 1.

In the method and apparatus of the present invention, a small airtight container 7
A pressure regulating pump 8 is connected to the upper part of the metering tube, and the metering tube is inserted into the metering tube 3 through the valve 9, hose 10, valve 11 and elbow 12 at the lower opening of the small airtight container 7. The upper end of the conduit 13 having a diameter smaller than 3 is connected. Furthermore, as shown in detail in FIG.
a and a vertical pipe part 14b whose lower part is hermetically engaged with the upper part of the measuring tube 3.
A connecting fitting 17 that is brought into contact with the outer periphery of the conduit 13 via a ring 16 is airtightly fixed,
A manometer 1 is attached to the horizontal pipe portion 14a of the T-joint 14.
5 is connected, and the other end of the manometer 15 is open to atmospheric pressure. A cap 19 is screwed onto the upper part of the connecting fitting 17 through a packing 18 to make the space between the connecting fitting 17 and the outer periphery of the conduit 13 airtight. Also, the tip of the conduit 13 is positioned inside the tank 1. Note that if the tip of the conduit 13 is located near the liquid level of the volatile liquid 6, this liquid will be agitated during the pressurization operation step described later, promoting evaporation of the volatile liquid 6 in the tank 1. At that time, the vapor pressure fluctuation becomes extremely large, making it impossible to obtain good results, so the tip should be sufficiently immersed in the storage liquid 6.

Next, the ventilation pipe 2, the suction pipe 4, and the liquid supply pipe 5 are covered with blind lids to make the inside of the tank 1 airtight, and the pressure reduction pump 8 is driven on the pressure reducing side to bring the small airtight container 7 into a reduced pressure state. , the valves 9 and 11 are opened to apply negative pressure to the conduit 13, and a portion of the volatile liquid 6 in the tank 1 is drawn up and stored in the small airtight container 7. In this pressure reduction operation step, if a pump or other liquid extraction device is connected to the tank 1, the liquid may be pumped up by the pump or the like.

By pumping up a portion of the volatile liquid 6 in the tank 1 in this manner, the valves 9 and 11 are closed while the pressure in the space within the tank 1 is reduced (for example, to 200 mmH ₂ O). At this time, a pressure difference between the manometer 15 and the atmospheric pressure is generated depending on the reduced pressure state in the tank 1.

However, when there is a leak in the tank 1, etc., air enters from the outside because the pressure inside the tank 1 is reduced, and as a result, the pressure inside the tank 1 increases over time, causing a pressure difference (water column difference) on the manometer 15. ) is decreasing.

Generally, it is possible to determine whether or not there is a leak in the tank 1, etc., only by the amount of decrease in the water column difference measured by the manometer 15, but depending on the type of stored liquid, there may be no leakage due to the influence of the vapor pressure of the liquid. However, there are cases where the pressure increases as if a leak is occurring. At this time, a self-recorder (not shown) is connected to a branch pipe (not shown) of the horizontal pipe portion 14a of the T-joint 14.
If connected, the vapor pressure inside tank 1 can be automatically recorded. This variation due to vapor pressure is
This will be briefly explained using the graph in the figure.

In Figure 3, curve A is the relationship between elapsed time and pressure for liquids with relatively low vapor pressure, such as water or kerosene, and shows that if there is no leakage, there will be no change in pressure even if time elapses. There is. If there is a leak, the pressure will return to atmospheric pressure within a short period of time, as shown by curve C, and the pressure will not rise above atmospheric pressure.

Liquids with high vapor pressure such as volatile oil have a pressure increase due to vapor pressure even though there is no leakage, so as shown in curve B, the pressure increases over time, creating the illusion that there is a leak. I am forced to do it.
However, it is difficult to suppress the evaporation of liquid;
The higher the vapor pressure of a liquid, the more difficult it is to determine whether there is a leak. Therefore, in a leakage test for a liquid storage tank with high vapor pressure, the effect of vapor pressure can be offset by continuously performing a pressurization operation step, which will be described later, together with a depressurization operation step.

That is, after the above-described pressure reduction operation step is completed, for example, a valve 20 provided on the manometer 15 is opened to open the inside of the tank 1 to the atmosphere to return it to atmospheric pressure, and then the valve 20 is closed to make the tank 1 airtight again. Next, the pressure regulator pump 8 is set to the pressurizing side and driven, the small airtight container 7 is pressurized, the valves 9 and 11 are opened, and the volatile liquid 6 in the container 7 that has been pumped in the previous step is transferred through the conduit 13. The liquid is returned to the tank 1 through the medium. In this liquid storage return step, the volatile liquid 6 may be returned to the tank 1 only by gravity without pressurizing the small airtight container 7. The space inside the tank 1 becomes pressurized depending on the amount of liquid returned, for example, by ( _10336-200 ) _mmH2O higher than atmospheric pressure (10336mmH2O),
The manometer 15 indicates the pressure difference between the tank 1 and the atmospheric pressure depending on the pressure state inside the tank 1 . At this time, if there is a leak in tank 1, etc., since the inside of tank 1 is under pressure, air, etc. will leak to the outside and the pressure inside tank 1 will decrease over time.The inside of tank 1 is shown in Figure 4. Conversely, the pressure increases.

That is, in FIG. 4, the period A to U is the record in the depressurizing operation step, and the period E to E is the record in the pressurizing operation step. A~i, E~o is the initial instability period, and is not used as judgment data for leakage inspection.The time of the linearly changing part of the pressure change after the depressurization operation process is T, and the amount of change is is P, the time of the linearly changing portion of the pressure change after the pressurizing operation step is T', and the amount of change is P'. In the case of a stored liquid with low vapor pressure without leakage in a tank or the like, both P and P' take values close to zero, and P/T≈P'/T'. Even if the vapor pressure of the stored liquid is high, if there is no leakage into the tank etc., P/T≒P'/T'.

If there is a leak in the tank, etc. P (pressure change after depressurization operation process) = Pressure increase due to leakage + steam pressure Next door P′ (pressure change after pressurizing operation process) = Steam pressure – pressure loss due to leakage Therefore, whether the liquid has a low vapor pressure or a liquid with a high vapor pressure, P/T≫P'/T'.

As a result, the presence or absence of leakage can be determined extremely easily.

Liquids have more or less unique vapor pressures, and the method of the present invention is very effective when inspecting liquids in storage tanks.

As described above, according to the present invention, even if a liquid with high vapor pressure is stored, it is extremely safe in its remaining state.
It is possible to reliably inspect the tank for leakage, and when the leakage inspection device for volatile liquid storage tanks of the present invention is used for inspection, the liquid will not come into direct contact with the outside air outside of the tank at all. There are great benefits such as not causing any pollution problems.

In the volatile liquid storage tank leakage inspection device of the present invention, a small airtight container 7 is provided, and the volatile liquid in the tank 1 is pumped up into this container to reduce the pressure in the tank 1 to a predetermined value. The inside of the tank 1 is pressurized to a predetermined value by returning the pumped volatile liquid to the inside of the tank 1.
Of course, the same inspection can be performed by applying means for supplying compressed air into the tank or evacuating the tank using a vacuum pump, as shown in Japanese Patent No. 25836.

However, according to this method, it is difficult to treat the gas exhausted by a vacuum pump to reduce the pressure in the tank, and if it is released into the atmosphere, problems such as fire and pollution may occur.

On the other hand, the apparatus of the present invention has the advantage that such problems do not occur at all.

In the present invention, the vertical pipe portion 14 of the T-joint 14
If the diameters of the measuring tube 3 and the measuring tube 3 are different, a bushing (not shown) can be inserted between the two to connect them, and the liquid supply tube 5 can stand vertically from the tank 1 without bending. In some cases, this liquid supply pipe 5 may be used instead of the measuring pipe 3.

In addition, in the volatile liquid storage tank leakage inspection device of the present invention, an inner pipe 13 communicates between the small airtight container 7 and the liquid phase portion of the tank 1, and an outer pipe communicates between the gas phase portion of the tank 1 and the manometer 15. 3 was constructed using heavy pipes, so for example, the
Compared to the case shown in Japanese Patent No. 46495, there are advantages in that fewer holes need to be made in the tank and that the handling thereof is simple and convenient.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the leakage inspection device for a liquid storage tank according to the present invention, Fig. 2 is an explanatory diagram of its main parts, Fig. 3,
FIG. 4 shows an example of the inspection curve. 1...Storage tank, 2...Vent pipe, 3...Measuring pipe, 4...Suction pipe, 5...Liquid supply pipe, 6...Stored liquid, 7...Small airtight container, 8...Pressure/depressurization pump,
9...Valve, 10...Hose, 11...Valve, 12...
...Elbow, 13...Conduit, 14...T-joint, 14
a...Horizontal pipe part, 14b...Vertical pipe part, 15...
Manometer, 16... O-ring, 17... Connection fitting, 18... Packing, 19... Cap, 2
0... Valve.

Claims (1)

[Scope of Claims] 1 A step of airtightly closing a volatile liquid storage tank, a step of bringing the inside of the tank into a constant reduced pressure state, and a step of measuring the air pressure inside the tank after a predetermined period of time after this step, and then closing the tank. The method is characterized by comprising a step of bringing the pressure to atmospheric pressure, a step of bringing the inside of the tank, which has been brought to atmospheric pressure, into a constant pressurized state, and a step of measuring the air pressure inside the tank after a predetermined period of time from this step. Leak testing method for volatile liquid storage tanks. 2. A mechanism for making the inside of the volatile liquid storage tank airtight and open, a small container, an outer pipe communicating with the inside of the volatile liquid storage tank, and one end of which is inserted into the outer pipe and has one end connected to the volatile liquid storage tank. an inner pipe for suction and injection of the stored liquid in the tank, the other end of which is communicated with the lower part of the tank and the other end of which is communicated with the small container; a liquid suction and injection mechanism connected to the inner pipe; and the volatile liquid storage tank. A leakage testing device for a volatile liquid storage tank, comprising: a manometer connected to the outer pipe for measuring the pressure in the gas phase; and a pressurization/depressurization mechanism connected to the small container.