JPS613012A - Measurement of liquid level in liquefied gas container using ultrasonic wave - Google Patents

Abstract

PURPOSE:To facilitate measurement of a liquid level in a liquefied gas container, by connecting an ultrasonic transmitter-receiver to the outer wall of a liquefied gas container to transmit a pulsed ultrasonic wave, and measuring a liquid level of a liquefied gas from changes of the reflected ultrasonic wave. CONSTITUTION:An ultrasonic transmitter-receiver 1 is brought into contact with the outer wall of a container (b) at a position below the liquid level of a liquefied gas (a) in the container (b). When a pulsed ultrasonic wave is transmitted from the transmitter-receiver 1, the wave propagates through the liquefied gas (a) having a relatively large density and is reflected by the outer wall of the container (b), that is, reciprocated. Thus, a pulsed signal is obtained from the transmitter-receiver 1 as its output signal at a time duration corresponding to the time required for the wave to reciprocate. However, when a pulsed ultrasonic wave is transmitted from a position on the outer wall of the container (b) above the liquid level of the liquefied gas (a), since it is difficult for the ultrasonic wave to propagate through the gas of the liquefied gas, the ultrasonic wave propagates through the inside of the wall of the container (b) while being reflected thereby, so that a densely pulsed signal is obtained as an output signal of the transmitter-receiver 1. Accordingly, the transmitter-receiver 1 is moved along the outer wall of the container (b) while being in contact with the outer wall to obtain changes in the output signal of the transmitter-receiver 1, thereby measuring the liquid level of the liquefied gas (a).

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention utilizes ultrasonic waves to process liquefied gases such as LPG (
This invention relates to a method for measuring the liquid level position in a liquefied petroleum gas (liquefied petroleum gas) container.

(Prior art) For example, it is important for LPG sales businesses to measure the liquid level in ItPG containers, but it is also important for LPG sales businesses to measure the liquid level in ItPG containers. Many LPG consumers use LPG by connecting an AT LPG container to a single gas meter.
The reality is that LPG containers are not equipped with level gauges, even though the amount of LPG remaining in each container varies considerably.

Conventionally, the following two methods have been used to measure the amount of LPG.

The first method is to measure the weight of the empty container and the weight of the container filled with LPG using a platform scale, and calculate the amount of LPG from the difference in weight.

The second method is to use a gas meter to continuously measure the amount of gas released after LPG filling is completed at a filling workshop.

(Problem to be Solved by the Invention) The first method can be carried out by a person with designated national qualifications at a specific filling work site that is fully equipped with statutory safety equipment such as gas alarms and fire extinguishers. However, since a platform scale that can measure the weight of an LPG container is usually not installed at the consumer site, the liquid level cannot be measured at the location where the container is installed.

In the second method, since each container is not equipped with a gas meter, the liquid level position in the container cannot be measured, and therefore, when replacing the container, the container is removed without knowing the amount of remaining liquid in the container, which is inconvenient. was there.

The present invention provides a method for measuring the liquid level position in a liquefied gas container that can be measured at a location where the liquefied gas container is installed, which is simpler and cheaper than conventional measuring methods. Its purpose is to provide.

(Means for Solving the Problems) The present invention moves an ultrasonic transducer in contact with the outer wall of a liquefied gas container, and at each position, pulses are sent from the transducer toward approximately the central axis of the container. The present invention is characterized in that a shaped ultrasonic wave is emitted and its reflected wave is received by the transducer, and the liquid level position of the liquefied gas liquid in the container is measured from the position where the output signal changes.

(Function) As shown in Fig. 1 (4), the ultrasonic transducer (1) is brought into contact with the outer wall of the container below the liquid level of the liquefied gas liquid a, and the When a pulsed ultrasonic wave is emitted from the transducer (1), the ultrasonic wave easily propagates into a liquefied gas liquid a with a high density (for example, LL PG has a density pn = 0.5 g/cA), so the first As shown by the arrow in Figure (B), it is reflected from the wall of the container and reciprocates in the liquid a, and a pulsed signal is output as an output signal from the transducer (1) at time intervals corresponding to the reciprocating time. However, when pulsed ultrasonic waves are emitted from the outer wall of the container above the surface of the liquid a, the ultrasonic waves are emitted from a liquefied gas with a low density (for example, LPG has a density ρg = 2X).
10 g/-), so it is difficult to propagate to
) as shown by the arrow, it mainly circulates within the vessel wall with a part of it being reflected by the wall surface, and a dense pulse-like signal is output from the transducer (1) as an output signal.

Therefore, when the ultrasonic transducer (1) is moved while being in contact with the outer wall of the container, when the ultrasonic transducer (1) passes through the liquid surface that is the boundary between the liquefied gas liquid a and the liquefied gas gas C, the ultrasonic transducer (1)
The output signal output from changes. Therefore, the liquid level position of the liquefied gas liquid a in the liquefied gas container is measured from this changing position.

(Embodiment) FIG. 2 shows a block diagram of an apparatus used to implement an embodiment of the present invention.

In the figure, (1) is an ultrasonic transducer, and the transducer (1) is supplied with an amplitude of about -80V from a pulse generator (2).
A pulse wave with a duration of approximately α5μ seconds is detected by the timer (3) at approximately α
It is configured to be automatically applied every 2 seconds. The resonant frequency of the transducer (1) is, for example, the filling @5 ay which is currently the most widely distributed. and an automatic gain control circuit (6) for negative feedback, and this circuit detects differences in the waveforms of the output signals of the transducer (1).

(The power is a differentiator circuit, and the differentiator circuit (7) is a detection circuit (5)
(8) is a differentiation circuit (operated by a force output pulse, which operates continuously to activate an alarm such as a buzzer (9)). An alarm operating circuit that outputs a signal, OQ is a power supply check circuit that checks whether the power supply voltage has a predetermined value, 0υ is a power supply, and O2 is a power supply aυ and an amplifier circuit (4
), and is controlled by the output of the timer (3) and corresponds to the time from when the ultrasonic wave is emitted until the first reflected wave arrives (for example, only 11 seconds). This is a power supply control circuit that applies a power supply voltage to the amplifier circuit (4), and this circuit can reduce consumption of the power supply 0υ.

Next, a measurement method according to an embodiment of the present invention using the above device will be explained.

Now, as shown in FIG. 1(A), the ultrasonic transducer (1) coated with a thin coat of couplant is moved up and down along the wall surface while being lightly pressed against the outer wall of the liquefied gas container. When the transducer (1) is in contact with the outer wall of the container below the liquid level, the output signal output from the transducer (1) is a pulse-like signal at the time interval of reciprocating the liquefied gas liquid a. Therefore, a pulsed signal is output from the detector (5) via the amplifier circuit (4).

This signal is transferred to the alarm activation circuit (8) via the differential circuit (force).
The alarm (9) is triggered by a continuous activation signal.
For example, a buzzer sounds. When the transducer (1) is brought into contact with the outer wall of the container above the liquid level, the output signal from the transducer (1) is a densely packed pulse-like signal, so this signal is processed by the automatic gain control circuit ( 6), the signal is almost eliminated by passing through the amplifier circuit (4) whose amplification factor is controlled by the wave detector (5), and no output is generated from the wave detector (5). Even if the output is small, it will disappear by passing through the differential circuit (force),
Since the alarm operating circuit (8) is not driven, the buzzer, for example, does not sound.

Therefore, the level position of the liquefied gas liquid a can be determined from the position where the buzzer stops sounding by moving the transducer (1) from the bottom to the top.

FIG. 6 is an electrical circuit diagram embodying the block diagram shown in FIG. 2.

In the figure, the same symbols as in FIG. 2 indicate the same things.

Figure 4 (A) and Figure 4 (B) both show a transducer (1).
4 (Al is located above the liquid level).
When the automatic gain control circuit (6) is omitted in the illustrated circuit, FIG. 4(B) shows the output signal waveform at point X when the automatic gain control circuit (6) is provided, and FIG. 4(0)
is the output signal waveform at point X of the circuit shown in FIG. 3 when the transducer (1) is positioned below the liquid level.

Comparing these waveforms, we can see that the amplifier circuit (4) connected to the automatic gain control circuit (6) determines whether the liquid level is up or down and activates the alarm (9).
) can be understood to be a discrimination circuit that determines whether to operate or not.

An embodiment of the present invention using the apparatus shown in FIGS. 2 and 3 has been described above.
The liquid level position may be measured by observing the waveform on the tube, or changes in the output signal may be measured using a known technique (not shown or described).

Although LPG is illustrated as an example of the liquefied gas, liquefied natural gas (I, NG), liquid nitrogen, etc. may also be used.

(Effects of the Invention) The present invention moves an ultrasonic transducer in contact with the outer wall of a liquefied gas container, and emits pulsed ultrasonic waves from the transducer at each position toward approximately the central axis of the container. At the same time, the reflected wave is received by the transducer, and the liquid level position of the liquefied gas liquid in the container is measured from the position where the output signal changes. It is possible to measure the liquid level position immediately, which has the advantage of eliminating wasteful work in replacing containers and delivering them to filling stations.

[Brief explanation of drawings]

FIG. 1(A) is a cutaway side view of a main part of a liquefied gas container for explaining the measurement method of the present invention, and FIG. 1(B) is a cutaway cross-sectional view taken along the line E-B in FIG. 1(A). , Figure 1 (0) is the first
FIG. 2 is a block diagram of an apparatus used in an embodiment of the measuring method of the present invention, and FIG.
The figure shows a specific electric circuit diagram of the circuit shown in Fig. 2, and Fig. 4 (A) shows the output signal at point X when the automatic gain control circuit (6) is omitted in the circuit shown in Fig. 5. Waveform diagrams, Figures 4 (CB) and (0) show waveform diagrams of the output signal at point X of the circuit shown in Figure 6 when the transducer is positioned above and below the liquid level, respectively. a...Liquefied gas liquid b...Liquefied gas container C...
・Liquefied gas gas

Claims (1)

[Claims] An ultrasonic transducer is brought into contact with the outer wall of the liquefied gas container and moved, and at each position a pulsed ultrasonic wave is emitted from the transducer toward approximately the center axis of the container, and the reflected wave is transmitted to the transducer. A method for measuring the liquid level position in a liquefied gas container using ultrasonic waves, characterized in that the liquid level position of the liquefied gas liquid in the container is measured from the position where the output signal changes.