JPS6046650B2 - Pressure test method for liquid storage tank - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure test method for a storage tank containing a liquid having a specific gravity lower than water, such as liquefied gas. Regarding the method.

Generally, a storage tank that substantially contains a low-temperature liquid requires a pressure test before storing the liquid, but the pressure test has conventionally been performed after the storage tank has been manufactured.

In other words, as shown in Fig. 1, in the conventional storage tank, after installing and fixing the tank bottom plate 1 on the square foundation, this tank bottom plate 1 is installed and fixed.
It is manufactured by placing the storage tank side plate 2, which has an integral cylindrical structure with a height dimension larger than the actual upper limit L of low-temperature liquid and L, on top and welding the two together.After manufacturing, the test water is placed in the tank. The pressure resistance test of the storage tank is carried out by injecting water into the tank.

However, since the specific gravity of the test water is 1, which is greater than the specific gravity of the actual liquid (liquefied gas), which is 0.5 to 0.6, the pressure resistance test is performed based on the pressure distribution P of the test water, and the actual density during storage of the actual liquid. At present, the actual liquid pressure distribution P2 acting on the storage tank side plate 2 is set to be P, ≧P2 at the lower maximum pressure portion.

However, in such a test method, the test water level W becomes lower than the actual liquid levels L and L due to the difference in specific gravity between the test water and the actual liquid as described above. There was a problem in that there was a part 2a where no test water pressure was applied even though the actual liquid pressure was applied to the test water.

Therefore, if the test water levels W and L at which test water pressure should be applied to almost the entire surface of the storage tank side plate 2 are the same as the actual liquid levels L and L, a considerable test water pressure that greatly exceeds the actual liquid pressure will be applied to the lower part of the storage tank side plate 2. Since a large stress is generated in each of the storage tank side plate 2 and the storage tank bottom plate 1 during this process, various problems occur, including the necessity to considerably increase the thickness of these plates, which is extremely uneconomical.

This invention was made to solve the above problems.
The purpose of this is to separate and form the storage tank side plate on the storage tank bottom plate in the order of the upper layer forming part and the lower layer forming part, so that each of the upper and lower layer forming parts can be individually pressure tested in sequence during the storage tank manufacturing process. As a result, a test water pressure higher than the actual liquid pressure was applied to the entire surface of the side plate of the storage tank at a test water level lower than the upper limit of the actual liquid in the storage tank, thereby improving the reliability of the storage tank pressure test. This paper proposes a pressure test method for liquid storage tanks. A second embodiment of this invention will be described below.
This will be explained based on the diagram and FIG.

First, a storage tank bottom plate 10 having an annular frame wall 11 on the upper part of the peripheral edge and integrally formed of a steel plate having high low temperature toughness is installed and fixed on a cold insulating floor board or a foundation, and the outer circumference of the frame wall 11 is fixed. A storage tank outer shell 14 made of concrete or metal is constructed in the tank. Next, the upper layer forming portion 12a of the storage tank side plate is assembled on the frame wall 11 of the storage tank bottom plate 10 in a liquid-tight manner as shown by the solid line in FIG.

The upper layer forming portion 12a is the completed storage tank side plate 1 shown in FIG.
2, and is made of the same steel plate as the storage tank bottom plate 10, and is placed on the frame wall 11 and welded, or if appropriate sealing means is used to seal it. The space between the frame wall 11 and the frame wall 11 is sealed in a liquid-tight state.

After the upper layer forming portion 12a of the storage tank side plate 12 is assembled on the storage tank bottom plate 10 in this manner, its upper end opening is covered with the roof 13 in a sealed state.

The roof 13 may be welded in advance to the upper opening edge of the upper layer forming portion 12a. Through the above steps, a semi-finished storage tank t which is made into an airtight container by the storage tank bottom plate 10, the upper layer forming part 12a of the storage tank side plate 12, and the roof 13 is configured inside the storage tank outer shell 14. The upper layer forming section 12 is formed by injecting and filling the test water into the upper layer forming section 12.
.

Perform the pressure test in a. In this case, the test water level W in the semi-finished storage tank t. Ll is the upper limit of actual liquid L in the completed storage tank T (see Figure 3), which will be described later. L is approximately 112, and the test water pressure distribution P1'' at this time becomes larger than the actual liquid pressure distribution P2 due to the difference in specific gravity between the test water and the actual liquid.

If the safety of the upper layer forming portion 12a of the storage tank side plate 12 is confirmed by carrying out the pressure test (water test),
Drain the test water from the semi-finished storage tank t.

After the test water is removed, the upper layer forming part 12a is separated from the frame wall 11 of the storage tank bottom plate 10, raised to a predetermined height, and held at the raised position by appropriate means.

In this case, as the means for raising the upper layer forming part 12a, since the upper layer forming part 12a has a covered cylinder shape with the roof 13, it may be floated by injecting air pressure into the inside thereof, or by other methods such as A crane or the like may be used. Next, as shown in FIG. 3, the lower layer forming portion 12b of the storage tank side plate 12 is assembled between the frame wall 11 of the storage tank bottom plate 10 and the upper layer forming portion 12a in the raised position.

Then, this lower layer forming portion 12b is welded to each of the frame wall 11 and the upper layer forming portion 12a.

Once the completed storage tank T has been constructed through the above steps, test water is again injected into the completed storage tank T to perform a final pressure test.

In this case, the test water level W in the completed storage tank T. L2 is set approximately at the middle of the upper layer forming portion 12a that has already been tested.

Therefore, the test water level W. The upper limit L of the actual liquid in the completed storage tank T
．． lower than L, and the lower layer forming part 1 of the storage tank side plate 12
The test water pressure distribution P1 acting on 2b is the actual fluid pressure distribution P2
Become bigger.

As a result of the above, a test water pressure higher than the actual liquid pressure was applied to the entire surface of the completed storage tank side plate 12, and the completed storage tank side plate 12
The pressure resistance and safety of the entire surface can be accurately confirmed.

After the safety is confirmed, the test water in the completed storage tank T is extracted, and the completed storage tank T is used as a storage tank for low-temperature liquids such as LPG, LNG, etc., that is, actual liquids with a smaller specific gravity than water.

As described above, in the method of the present invention, the storage tank side plate is divided into an upper layer forming part and a lower layer forming part, and the tank side plate is formed on the tank bottom plate from the upper layer forming part, and each of the upper layer forming part and the lower layer forming part is formed in this order. Since the water pressure tests were conducted separately, the following effects can be obtained.

(1) In the manufacturing process of a storage tank that accommodates an actual liquid with a specific gravity lower than water, such as liquefied gas, the storage tank side plate can be divided into an upper layer forming part and a lower layer forming part and a hydraulic pressure test can be performed individually, so the formation of each layer during the test The test water level inside the tank will be much lower than the upper limit of the actual liquid in the completed storage tank, and therefore, unlike when carrying out a tank pressure test using the upper limit of the actual liquid water level as the test water level, it is necessary to increase the thickness of the tank bottom plate and storage tank side plate. There is no.

(2) Since the pressure test is carried out from the upper layer formation part where the actual liquid pressure distribution is smaller than that of the lower layer formation part of the storage tank side plate, the test water level during the pressure resistance test of the lower layer formation part is set to a range lower than the upper limit of the actual liquid. It can be higher than the test water level of the forming part,
Therefore, a test water pressure greater than the actual liquid pressure can be applied to the upper and lower layer forming portions of the storage tank side plate at a test water level lower than the upper limit of the actual liquid.

(3) Therefore, according to the method of the present invention, it is possible to easily conduct an accurate pressure test on the entire surface of the storage tank side plate without creating any parts on the storage tank side plate where the pressure test cannot be performed or where the pressure test is incomplete. The reliability of storage tank pressure tests can be greatly improved.

[Brief Description of the Drawings] Fig. 1 is a partial cross-sectional view of a storage tank shown to explain the conventional method, Fig. 2 is an explanatory diagram of the implementation of the method of the present invention, and Fig. 3 is a partial cross-sectional view of a storage tank shown by the method of the present invention. FIG. 2 is an enlarged cross-sectional view of a state in which a physical pressure test is being carried out.

Claims (1)

[Claims] 1. In a pressure test method for a storage tank containing an actual liquid with a specific gravity lower than that of water, after conducting a water pressure test on the upper layer forming part of the storage tank side plate formed on the storage tank bottom plate and sealed between the storage tank bottom plate and the storage tank The side plate upper layer forming portion is separated from the storage tank bottom plate and lifted up, and the storage tank side plate lower layer forming portion integrally formed between them is subjected to a water pressure test at a test water level higher than the water level at the time of the water pressure test and lower than the upper limit of the actual liquid in the storage tank. Characteristic pressure test method for liquid storage tanks.