JPH0313700Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention is a low-liquid system that can accurately and reliably detect liquid levels in tanks installed on ships or offshore structures, especially low liquid levels. This relates to a position detection device.

[Prior Art] Conventional liquid level gauges used on ships and the like include a float type, an electromagnetic float type, a radio wave type, an air purge type, and a pressure receiving type.

In the float type, as shown in Figures 3 and 4, lashing fittings d and e are attached to the sounding stand b installed on the tank top a and the tank bottom c, respectively.
Two guide wires f, f are strung in the vertical direction via these lashing fittings d, e, and a float g is attached so as to be movable up and down along these guide wires f, f. One end of the unwound measuring tape i is connected, and the liquid level depth r in the tank j is measured by replacing the vertical movement of the float g with the unwinding length of the measuring tape i.

The electromagnetic float type is a float with a built-in permanent magnet q along a guide pipe p with a large number of built-in reed switches n, as shown in Figures 5 and 6.
g ₁ is attached so that it can be raised and lowered, and when float g ₁ goes up and down, the reed switch n that is close to the permanent magnet q
emits an electric signal m to remotely display the liquid level r.

The radio wave type transmits a radio wave t from a dedicated transmitter s installed at the top of the tank to the liquid level k, as shown in Figure 7.
The liquid surface depth r is measured by firing the liquid toward the liquid surface k and measuring the reflection time from the liquid surface k.

In the air purge type, as shown in Fig. 8, an air purge unit U is arranged at the top a of the tank, and a hub W is inserted from the lower end of the air purge pipe V into the inside of the tank storage liquid.
Measure the lowest pressure at which it can be released.

In the pressure receiving type, pressure gauges x ₁ , x ₃ , and x ₂ are placed at high, low, and intermediate positions in tank j, respectively, as shown in Figure 9, and the liquid level depth r is determined by the following formula. .

r = Index of pressure gauge x ₃ x Installation height of pressure gauge x ₂ / Index of pressure gauge x ₃ - Index of pressure gauge x ₂ [Problem to be solved by the invention] As mentioned above, there are many types. Level gauges are now in use, but in order to prevent marine pollution, crude oil tankers are now required to clean their crude oil tanks during loading and unloading based on IMO regulations, so the ability to accurately detect low liquid levels is important. It's starting to be seen. However, each of the liquid level gauges described above has the following problems, and it has been desired to develop a new detection device. In other words, in the float type, when the float g moves downward, it comes into contact with the lashing fitting e at the bottom, so it is impossible to measure a liquid level lower than the liquid level at this time. Tape i is easy to break, and when cleaning a crude oil tank, the float g will be damaged if it is hit by water from the cleaning machine, so the float g must be rolled up.

With the electromagnetic float type, the height y of float _g1 is large, so the lowest measurable liquid level cannot be reduced.
There is a limit to the installation interval of reed switches n, and it is not possible to improve the accuracy of indication.

Radio wave systems generally have unstable accuracy, and erroneous indications often occur, especially near the bottom of the tank.
In order to prevent diffused reflection, it is necessary to secure a radio wave reflecting surface (not shown) at the bottom of the crude oil tank, which imposes restrictions on the installation location.

The air purge type generally has poor accuracy, especially low liquid level detection accuracy.

The pressure-receiving type is fundamentally unsuitable for detecting low liquid levels.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems. A box body with a liquid-tight structure in which a magnetic coil is arranged so that its axis is almost vertical, and a float with a rod-shaped iron core erected on the top, and the iron core moves vertically inside the magnetic coil. The iron core sliding portion of the box is configured to be liquid-tight while being supported by the box so as to be able to do so.

[Function] Since the float is supported via an iron core provided at the top, it can descend until it touches the bottom of the tank, making it possible to detect low liquid levels to the lowest possible level. Additionally, since liquid changes are detected as impedance changes in the magnetic coil and extracted in the form of electrical signals, low liquid levels can be displayed remotely.

[Example] Hereinafter, an example of the present invention will be described based on the drawings. FIG. 1 shows a first embodiment of the present invention, and the main parts of the device are a storage box 3 with a liquid-tight structure fixed to the tank bottom 1 via a support member 2, and the inside of this storage box 3. The float 7 includes a magnetic coil 4 disposed at the top thereof, and a float 7 having a rod-shaped iron core 6 erected at the center of the upper surface with a member 5 interposed therebetween.

The magnetic coil 4 is supported almost vertically by a support (not shown) in the center of the storage box 3, and the coil terminal is guided outside the storage box via a conductor 8 and connected to a monitoring board (not shown) inside the ship. ) etc.

A hole passing through the storage box 3 and the support member 2 is provided at a position where the axis 15 of the magnetic coil 4 intersects with the storage box 3 and the support member 2, and the iron core 6 of the float 7 passes through this hole to the magnetic coil. It extends within 4. A seal 9 with low frictional force is placed in the hole to prevent tank liquid from entering the storage box 3 through the gap between the iron core 6 and the hole, and compressed air is introduced into the storage box 3 as necessary. You may.

Next, the operation of this device will be explained. If the liquid level k in the tank is high enough, float 7
The float rises until the upper surface 10 of the float comes into contact with the lower surface of the support member 2, as shown by the imaginary line, and the top of the iron core 6 is located near the top of the magnetic coil 4. Now, when the liquid level k falls as shown by the solid line, the float lower surface 12 descends until it comes into contact with the tank bottom 1 (arrow x), and the iron core 6 also descends to the position shown by the solid line.
This movement of the iron core 6 causes the impedance of the magnetic coil 4 to change, and this change is transmitted as an electric signal m to a monitoring board (not shown) in the ship through the conductor 8.

A second embodiment of the invention is shown in FIG. In this example, a cylindrical body 13 made of a non-magnetic material that protrudes into the storage box 3a is attached to the bottom of the storage box 3a in a liquid-tight manner.
A magnetic coil 4a is disposed outside the cylinder 13, an iron core 6 is inserted into the cylinder 13, and the periphery of the lower part of the storage box 3a is firmly supported on the tank bottom 1 by a support member 2a. There is no difference from the first embodiment other than this.

It should be noted that the present invention is not limited to the above-described embodiments, and it goes without saying that various changes can be made without departing from the gist of the present invention.

[Effects of the invention] As described above, the present invention exhibits the following excellent effects.

(i) The float is supported via an iron core erected on the top surface. Therefore, the lowering movement is not hindered by the lashing metal fittings as in the past, and low liquid levels can be detected down to the lowest possible level (approximately 20 mm).

(ii) Since a change in the tank liquid level is detected as a change in impedance of the magnetic coil, remote display is possible by extracting the change in impedance to the outside as an electric signal, resulting in labor savings.

(iii) The structure is strong and does not have parts that are susceptible to vibration, such as the measurement tape and guide wire found in conventional devices.

[Brief explanation of the drawing]

Figures 1 and 2 are the first and second figures of the present invention.
Figures 3 to 9 are explanatory diagrams of conventional liquid level gauges, Figure 3 is a side view of the float type, and Figure 4 shows the parts in Figure 3. An enlarged view, FIG. 5 is a partially cutaway side view of the electromagnetic float type, and FIG. 6 is an enlarged cutaway view of the part shown in FIG.
Figure 7 is a cutaway side view of the radio wave type, Figures 8 and 9.
The figures are side views of an air purge type and a pressure receiving type, respectively. In the figure, 1 is the tank bottom, 2 and 2a are support members,
3 and 3a are storage boxes, 4 and 4a are magnetic coils, 6 is an iron core, and 7 is a float.

Claims (1)

[Scope of utility model registration request] A box body with a liquid-tight structure, which is attached to the bottom of a liquid tank via a support member at a required distance from the bottom of the liquid tank, has a magnetic coil arranged so that its axis is substantially vertical, and a rod-shaped iron core at the top. The iron core is supported by the box body so as to be able to move vertically inside the magnetic coil, and the iron core sliding part of the box body is configured to be liquid-tight. Characteristic low liquid level detection device.