KR100299437B1 - Differential pressure-type flow detecting device and method - Google Patents

Abstract

PURPOSE: A differential pressure-type flow detecting device and method is provided to cut down the cost for a flushing work for repairing the clogging of a conduit and equipment for keeping the conduit warm on a winter season. CONSTITUTION: A differential pressure-type flow detecting device and method using as a small precise upper pressure detection transmitter instead of a pressure transmitter for correcting a temperature pressure without a box for keeping a pressure detecting conduit and a transmitter is composed of a main pipe(21) flowed with fluid, an orifice(22) inserted into the main pipe, an upper pressure detecting band valve(25) installed to the upside of fluid with centering on the orifice, an upper pressure detecting transmitter(23) detecting the pressure of the upside, a lower pressure detecting band valve(26) installed to the lower side of fluid with centering on the orifice, a lower pressure detecting transmitter(24) detecting the pressure of the lower side, a temperature detector(27) measuring the temperature of measurement fluid, a differential pressure computer(28) outputting measurement signals by using pressure deviation, and a temperature pressure correction computer(29) computing an approximate flow by the pressure of measurement fluid being the output signal of the measurement signals and the upper pressure detecting transmitter and the temperature of measurement fluid.

Description

Differential pressure flow detection device and method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow rate detection apparatus and method which is widely used in industrial fields, and more particularly to a differential pressure flow meter among flow meters used for process control and flow rate integration.

In general, a variety of methods are used to measure the flow of many liquids and gases used in the industrial field, the most widely used of these methods is the flow rate measurement method by Orifice (Orifice). This method detects the flow rate by using a pressure deviation generated upstream and downstream of an orifice installed and inserted into the pipe according to the flow of the fluid. In order to convert this pressure deviation into an electrical signal, a differential pressure type flow transmitter is used, and the converted electrical signal is converted into a proportional value to the maximum differential pressure of the design flow rate and output as a DC 4-20 mA signal as a measurement signal. It is widely used in control system, DCS (Data Collection System), etc.

The configuration of the differential pressure type flow rate detection apparatus according to the related art according to the related art is shown in FIG. 1, and referring to FIG. An orifice (102) is inserted into 101, and an upstream pressure detecting end valve (103) and a downstream pressure detecting end valve (104) are installed at both ends of the orifice (102). The differential pressure type flow transmitter 110 is installed at an appropriate position of the upper and lower sides according to the installation position, and the large transmitter box 114 and the upstream and downstream pressure detection stage valve 103 for managing the differential pressure type flow transmitter 110 are provided. Upstream pressure detection pressure gauge 105 and downstream pressure detection pressure gauge 106 for drawing the detected pressure from 104 to the differential pressure flow rate transmitter 110 are required, and the differential pressure flow rate transmitter 110 is required. ) Check, adjust, and repair The three-way valve 109 is provided. Further, drain valves 107 and 108 for flushing operations of the upstream and downstream pressure detecting pressure guiding pipes 105 and 106 are provided at the rear end of the pressure detecting pressure guiding pipes 105 and 106. In addition, the pressure transmitter 111 for temperature pressure correction for use in temperature and pressure correction is installed and operated separately.

As such, in the prior art, many accessories are required due to the installation of pressure detecting pressure pipes 105 and 106, the pressure transmitter 111 for temperature pressure correction, and the transmitter management box 114. There is a hassle that a flushing operation to repair the clogging phenomenon of the pressure detecting pressure gauge 105 and 106 due to the foreign matter must be performed periodically. In addition, there is a need for a heater and heating cable for insulating the winter pressure pipe, and there is a problem that leakage may occur at the connection part of the pressure pipe.

The present invention has been made to solve the above problems and to achieve an improvement. Accordingly, the object of the present invention is to use a flow rate detection method without the pressure detecting pressure pipes 105 and 106 and the transmitter management box 114, and instead of the conventional temperature pressure correction pressure transmitter 111, a small and precise upstream The present invention provides a differential pressure type flow rate detection device and method which can reduce the human and material consumption in the facility management that occurs periodically by using as the side pressure detection transmitter 23.

The technical problem to be solved by the present invention is to solve the conventional problems and to achieve an improvement. As a technical means for achieving the technical problem, the differential pressure flow rate detection device according to the present invention is a main pipe through which a fluid flows. ), An orifice inserted into the main pipe to measure the flow rate of the fluid flowing in a constant pipe, and an upstream pressure, which is installed upstream of the fluid around the orifice, to detect the upstream pressure of the fluid. An upstream pressure detection stage valve, an upstream pressure detection transmitter for detecting upstream pressure through the upstream pressure detection stage valve, and a downstream side of the fluid around the orifice, Downstream pressure detection stage valve for detecting downstream pressure generated in accordance with the A downstream pressure detection transmitter for detecting, a differential pressure calculator for outputting a measurement signal using a deviation between the upstream pressure transmitter signal and the downstream pressure transmitter signal, a measurement signal output from the differential pressure calculator and the upstream pressure detection And a temperature pressure correction calculator for calculating an approximate flow rate based on the measured fluid pressure output from the transmitter and the measured fluid temperature measured from the temperature detector.

1 is a configuration diagram of a conventional differential pressure flow rate detection device.

2 is a configuration diagram of the differential pressure type flow detection device according to the present invention.

3 is a block diagram of a differential pressure calculator according to the present invention.

Explanation of symbols on the main parts of the drawings

21 ...... Main PiPe 22 ...... Orifice

23 ....... Upstream pressure detection transmitter 24 ....... Downstream pressure detection transmitter

25 ....... Upstream pressure detection stage valve 26 ....... Downstream pressure detection stage valve

27 ...... Temperature detector 28 ....... Pressure calculator

29 ....... Temperature Pressure Compensation Calculator

Hereinafter, a configuration of an apparatus for performing flow rate detection according to the present invention will be described with reference to the accompanying drawings. 2 is a configuration diagram showing the configuration of the differential pressure type flow rate detection device according to the present invention. The differential pressure flow rate detection apparatus according to the present invention has an orifice inserted and installed in the main pipe 21 to measure the flow rate of the fluid flowing in the main pipe 21 and the constant pipe. 22), an upstream pressure detection stage valve 25 installed upstream of the fluid about the orifice 22 and for detecting the upstream pressure of the fluid, and the upstream pressure detection stage valve 25 An upstream pressure detection transmitter 23 for detecting an upstream pressure through the outlet, and installed at a downstream side of the fluid around the orifice 22 and for detecting a downstream pressure generated by a change in the use of the fluid. A downstream pressure detection transmitter 24 for detecting downstream pressure through a downstream pressure detection stage valve 26, a downstream pressure detection stage valve 26, and an upstream pressure detection transmitter 23 signal; Of the downstream pressure detection transmitter 24 signal From the differential pressure calculator 28 for outputting the measurement signal using the difference, the measurement signal output from the differential pressure calculator 28, and the measured fluid pressure and temperature detector 27 output from the upstream pressure detection transmitter 23; And a temperature pressure correction calculator 29 for calculating an approximate flow rate based on the measured fluid temperature.

The operation of the present invention configured as described above will be described in detail below with reference to the accompanying drawings. Referring to FIG. 2, the fluid flowing through the main pipe 21 has a difference in flow velocity between the upstream side and the downstream side by the orifice 22, resulting in a pressure deviation by Bernoulli's equation. The upstream pressure is detected by the upstream pressure detection transmitter 23 through the upstream pressure detection stage valve 25, and the downstream pressure is detected by the downstream pressure detection transmitter 24 through the downstream pressure detection stage valve 26. ) Is detected.

In the present invention, a differential pressure calculation function and a temperature pressure correction calculation function will be described below with reference to FIG. 3. 3 is a block diagram showing the configuration of the differential pressure calculator according to the present invention. The output signal of the upstream pressure detection transmitter 23 is applied to the input signal V1, and the output signal of the downstream pressure detection transmitter 24 is applied to the input signal V2. The deviation of both input signals is generated by the comparison deviation Vd. The reference voltage Vs proportional to the cross deviation Vd and the design maximum differential pressure generated by the variable resistor 34 generates a percentage Vsd relative to the reference voltage by the comparison operator 32. The percentage Vsd with respect to the reference voltage output by the comparator 32 is converted into a constant current (4 to 20 mA) usable for the measurement signal by the constant current circuit 33 and output.

As described above, the differential pressure measurement signal detected by the differential pressure calculator 28 is input to the temperature pressure correction calculator 29 and calculated as follows. The approximate flow formula for obtaining the fluid flow rate is

to be. Where K is the design constant, ΔP is the pressure deviation across the orifice 22, and the formula for calculating the pressure deviation on the upstream and downstream sides is

to be. Where Ph is the upstream detection pressure and P1 is the downstream detection pressure. In Equation (1), Pc is the measured fluid pressure, Pn is the design fluid pressure, Tc is the measured fluid temperature, and Tn is the design fluid temperature. Therefore, the measurement signal DELTA P output from the differential pressure calculator 28 is input to the temperature pressure correction calculator 29 and substituted into equation (1) to calculate the flow rate. In the same manner, the measured fluid pressure Pc, which is the value detected by the upstream pressure detection transmitter 23, and the measured fluid temperature Tc, which is the value measured by the temperature detector 27, are input to the temperature pressure correction calculator 29, It is substituted in 1) and an approximate flow volume is calculated.

As described above, according to the present invention, there is no need for a large transmitter box for managing transmitters, a pressure transmitter for temperature pressure correction, and an upstream and downstream pressure detection pressure pipe used in a conventional differential pressure flow detection apparatus and method. Therefore, there is no need for a heater and a heating cable to protect the pressure guiding pipe during the winter, and periodic flushing operation for repairing the plugging of the pressure guiding pipe due to foreign matters due to long-term use is unnecessary. In conclusion, according to the present invention, by reducing the conventional flow rate detection facility, it is possible to reduce all human and material expenses that may be caused by the transmitter box, the pressure transmitter for temperature pressure correction, and the pressure plate.

The above description is only a description of one embodiment of the present invention, the present invention is capable of various changes and modifications within the scope of the configuration.

Claims (2)

In the differential pressure type flow rate detection device for detecting the flow rate of the fluid flowing in the pipe 21, An orifice 22 inserted into a predetermined position in the pipe 21; An upstream pressure detection stage valve 25 provided upstream of the fluid on the basis of the orifice; An upstream pressure detection transmitter 23 for detecting an upstream pressure on the basis of an orifice through the upstream pressure detection end valve 25; A downstream pressure detection stage valve 25 provided downstream of the fluid about the orifice; A downstream pressure detection transmitter 24 for detecting a downstream pressure on the basis of an orifice through the downstream pressure detected valve 26; A temperature detector 27 for measuring the temperature of the fluid passing through the pipe; A differential pressure calculator 28 for calculating a differential pressure by using a deviation between the upstream pressure transmitter signal and the downstream pressure transmitter signal; The differential pressure ΔP across the orifice measured by the differential pressure calculator, the fluid pressure Pc measured from the upstream pressure detector, and the fluid temperature Tc measured from the temperature detector And a temperature pressure correction calculator (29) which calculates an approximate fluctuation by substituting (where K is a design constant, Pn is a design fluid pressure, and Tn is a design fluid temperature). In the differential pressure type flow rate detection method for detecting the flow rate of the fluid passing through the pipe, Insert an orifice into the main pipe, The upstream pressure detection transmitter 23 detects the pressure applied to the upstream side of the orifice through the upstream pressure detection end valve, and the pressure applied to the downstream side of the orifice. Detected by the downstream pressure detection transmitter 24 via the downstream pressure detection valve, Comparing the deviation of the output signal of the upstream pressure detection transmitter 23 with the output signal of the downstream pressure detection transmitter 24 to generate a pressure deviation Vd, The comparison operator 32 generates a percentage of the comparison deviation Vd with respect to the reference voltage Vs, and outputs the percentage Vsd of the comparison deviation with respect to the reference voltage as a measurement signal by the constant current circuit 33. Let's The temperature pressure correction operator 29 approximates the measured fluid pressure Pc, which is the pull signal of the differential pressure signal and the upstream pressure detection transmitter 23, and the measured fluid temperature Tc measured from the temperature detector 27. Wherein K is the design constant. Pn is the actual fluid pressure, Tn is the design fluid temperature, and the flow rate is calculated.