JPH0321457Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a mass flow rate measuring device, more specifically,
When transferring a predetermined mass of liquid with a constant density, it is often measured using a two-phase flow that includes a gas phase such as air at the beginning of the transfer, which causes measurement errors. This invention relates to a mass flow rate measuring device that solves these problems.

Prior art While supporting both ends of the pipe and allowing fluid to flow,
It is known that when the central part of this tube is driven at a predetermined frequency in a direction perpendicular to the tube, a Coriolis force is generated that is proportional to the magnitude of vibration at the support point and the mass flow rate. Mass flow meters are known. In Japanese Patent Publication No. 60-34683, the tube body is a curved tube that penetrates the support member, and
A reciprocating member having a frequency substantially equal to that of the curved tube is fixed to the support member so as to vibrate naturally in a substantially tuning fork shape with the curved tube. Since the natural frequency changes according to an inverse function of the density of the fluid to be measured, a change in density causes a change in the natural frequency.

Problems with the Prior Art Mass flow rate measurement is used to measure fluid flow rate with high precision as a means to replace volumetric flow rate measurement. When loading several dozen types of products using the same flow meter, such as when shipping chemical products by lorry, or when loading other types of chemical products after using nitrogen gas or air in advance to avoid product contamination, When controlling the thickness of the paint film using a robot, or when changing the paint color, the gas phase is mixed in from the liquid transfer, such as when cleaning with thinner and then blowing off the residual amount with air before moving on to other processes. There may be some process involved. In principle, in a mass flowmeter that uses Coriolis force, when the flow tube is vibrated, the measured fluid is also vibrated with the same frequency and amplitude, and Coriolis force is generated throughout the measured fluid, resulting in correct mass measurement. The flow rate is measured, but since the gas phase is a compressible fluid, there is a problem in that it is not possible to determine the correct mass flow rate for multiphase flow mixtures that include the gas phase.

Means to Solve the Problems Regarding the above-mentioned problems in mass flow measurement, it is possible to detect that the fluid to be measured is a two-phase flow with gas in it, and to adjust the flow of the fluid to be measured based on this detection result. or stop the operation. In the known Coriolis flowmeter, a U-shaped conduit is vibrated by fixing a reciprocating member having a natural frequency substantially equal to the U-shaped conduit to a supporting member in a tuning fork shape. Since the density of the fluid is constant, the natural frequency becomes large in a two-phase flow that includes a gas phase. Since this magnitude is a function of the amount of mixed gas, the upper limit frequency is determined by determining the permissible amount of mixed gas. Taking advantage of this, during the two-phase flow period when the liquid begins to flow, the main valve is closed to stop the fluid transfer and return it to the original liquid storage tank from the bypass path.
When the frequency corresponding to the permissible amount of gas is reached, the valve that closes the bypass passage is opened.

Embodiment FIG. 1 is a configuration diagram for explaining an embodiment of the mass flow measuring device according to the present invention. In the figure, 1 is a tank, 2 is a pump, 3 is a Coriolis force flow meter, and 4 is a main solenoid valve. , 5 is a vent valve, 6 is a mass calculation circuit, 7
is a mass flow rate integrator, 8 is a density meter (comparison circuit), 9
is an on/off control circuit. When shipping the liquid in tank 1 to a lorry, etc., at the initial stage of shipment, tank 1
The air entering the flow path from the main solenoid valve 4 to the main solenoid valve 4 mixes into the liquid sent out from the tank 1, and a two-phase fluid containing liquid and gas is measured, but as described above, In a multiphase flow in which gas, which is a compressible fluid, is mixed, the movement of the liquid in the flow tube in the Coriolis force mass flowmeter 3 is absorbed by the gas and is not sufficiently transmitted to the liquid. Unable to accurately measure mass flow rate.
Therefore, in the present invention, at the beginning of shipping, the main solenoid valve 4 is closed and the vent valve 5 is opened, and in this state, the pump 2 is driven to circulate the liquid in the tank 1 in the direction of the arrow for a while. As mentioned above, the frequency of the Coriolis force mass flowmeter 3 is higher in the case of a two-phase flow containing a gas phase than in the case of a two-phase flow that does not contain a gas phase, but as described above, during circulation operation, Since the mixed gas is separated into gas and liquid when returned to the tank 1, the frequency of the Coriolis force flowmeter gradually decreases. Here, the density of the liquid in the tank 1 is known, and the natural frequency of the Coriolis force mass flowmeter at this time is also known, so the density of the liquid at this time is assumed to be ρ _A , and the density meter (comparison circuit) 8 If you set it in advance,
When this set value ρ _A and the density conversion value ρ from the Coriolis force mass flowmeter 3 become equal, it means that no gas is mixed into the circulating liquid. Therefore, ρ=ρ _A
If the on/off control circuit 9 is activated to open the main solenoid valve 4 and the vent valve 5 is closed when the temperature reaches Flow rate can be measured accurately.

Effects As is clear from the above description, according to the present invention, it is possible to provide a mass flow rate measuring device that can ship a liquid that does not contain a gas phase component and is accurately proportional to the mass flow rate.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram for explaining one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...tank, 2...pump, 3...Coriolis force type flowmeter, 4...main solenoid valve, 5...vent valve, 6...mass calculation circuit, 7...mass flow totalizer, 8...density meter (comparison circuit), 9 ...On/off control circuit.

Claims (1)

[Scope of utility model registration request] A tank for storing a liquid with a determined density, a mass flowmeter that calculates the mass from the Coriolis force acting on a vibrating tube that drives the liquid transferred from the tank at a natural frequency, and a comparison circuit that compares the natural frequency of the vibrating tube determined by the vibration tube with the natural frequency of the liquid to be transferred, and when the natural frequency of the liquid to be transferred is higher than a predetermined value; The main valve of the transfer pipe is closed and the vent valve is opened to return the transferred liquid to the storage tank, and when the natural frequency of the transferred liquid falls within a predetermined range, the main valve is opened and the A mass flow rate measuring device characterized by opening a vent valve.