JPH01140023A - Preventing device of backflow of integrating flowmeter - Google Patents

Abstract

PURPOSE:To enable the accurate integration and indication of the amount of used gas without suffering the fluctuation of pressure on the upstream side and thereby to enable the improvement of the reliability of an integrating flowmeter, by providing a check valve in a bypass pipe of the main body of a governor. CONSTITUTION:When an upstream-side pressure P1 in a gas piping 1 is higher than a downstream-side pressure P2, a gas flows through a bypass pipe 16, and therefore a pressure in a control chamber 13 is reduced through a control pipe 18 by a venturi operation when the gas flows through a venturi 17. Accordingly, a sleeve 15 opens a gas communication path 16 under the pressure P1 to let the gas flow onto the downstream side. Moreover, a check value 19 is provided in the pipe 16. This valve 19 allows the gas to flow only from the upstream side to the downstream side through the pipe 16, not allowing it to flow onto the upstream side. Accordingly, the flow of the gas from the downstream side onto the upstream side is interrupted by the check valve 19. As the result, the gas does not flow through the venturi 17 either, and consequently the control chamber 13 of the main body 11 of a governor is put under the pressure P2. Thus, the gas communication path 14 is interrupted by pressing the sleeve 15 thereon, the thereby the backflow of the gas is prevented.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides an integrated flow rate system that is installed in the middle of a gas pipe connecting a gas supply side and a gas demand side and instructs to integrate the gas flow rate. This article relates to a backflow prevention device for meters.

(Conventional technology) Roots meters are often used as integrating flowmeters that are installed at large gas consumers such as factories and give instructions for integrating gas flow rates, as they have high measurement accuracy and a wide usable flow range. .

Figure 4 shows the state in which the roots meter is installed at a large consumer such as a factory, and 1 is a gas pipe connecting the gas supply side 2 and the gas demand side 3 as a large consumer; 2 is connected to 4, such as a general household. Gas demand side 3
That is, a factory or the like is provided with a roots meter 5 for measuring the gas used in the gas pipe 1, and the roots meter 5 is instructed to integrate the gas flow rate consumed within the factory. That is, in the factory, branch piping is installed to supply the gas supplied from the gas pipe 1 to each part, and the roots meter 5 indicates the amount of gas consumed in each part of the factory. ing.

By the way, the roots meter 5 is configured such that two rotors are rotatably provided inside the casing, and the rotors are rotated depending on the flow rate of gas to measure the gas flow rate.

Therefore, the pressure on the gas supply side 2 is high and the pressure on the gas demand side 3 is high.
When the pressure is low, the roots meter 5 integrates the used flow rate, but when the pressure is reversed, it subtracts it.

Usually, as gas is consumed on the gas demand side 3, the pressure decreases. Therefore, the gas passes through the roots meter 5 from the gas supply side 2, is supplied to the gas demand side 3, and the gas passing amount is integrated. However, when the factory is closed at night or on holidays, and gas is not consumed on the gas demand side 3, pressure fluctuations on the gas supply side 2 cause gas to flow between the gas supply side 2 and the gas demand side 3. It comes and goes through meter 5. Therefore, although the roots meter 5 repeats integration and subtraction, the amount of pressure fluctuation on the gas supply side 2 is not constant, and therefore the flow rate when passing through the roots meter 5 is not constant. At this time, since the instrumental error of the Roots meter 5 is not constant depending on the flow rate in the small flow rate range, the integrated value and the subtracted value are not the same even if the amount of gas flowing back and forth through the Roots meter 5 is the same, and the gas supply side The counter of the roots meter 5 is integrated or subtracted due to the pressure fluctuation.

(Problem to be Solved by the Invention) When gas is supplied from the gas supply side 2 to the gas demand side 3 through the roots meter as described above, even if no gas is consumed on the gas demand side 3, the gas supply side 2 There is a problem in that the Roots meter repeats integration and subtraction due to pressure fluctuations, and the Roots meter counter ends up increasing or subtracting large amounts.

This invention was made with attention to the above-mentioned circumstances, and its purpose is to be able to accurately integrate and indicate the amount of gas used without being affected by pressure fluctuations on the upstream side, and to provide an integrated flow rate. An object of the present invention is to provide a backflow prevention device for an integrated flow meter that can improve the reliability of the meter.

[Structure of the invention]

(Means and effects for solving the problem) This invention has the following features:
In the case where an integrating flow meter is installed midway in the gas piping connecting the gas supply side and the gas demand side to instruct the integration of the gas flow rate, the governor body and the gas piping on the upstream or downstream side of the integrating flow meter are installed. , a bypass pipe that bypasses the governor main body, a venturi that communicates with the control chamber of the governor main body and opens and closes the governor main body, and a check valve that prevents backflow provided on the upstream side of the venturi, and a check valve that prevents backflow is provided on the upstream side. When the downstream gas pressure becomes higher than the gas pressure in the venturi, the check valve shuts off the gas flow through the venturi, and the control pressure at that time shuts off the governor body to prevent backflow.

(Example) Hereinafter, one embodiment of the present invention will be described based on the drawings.

In FIG. 1, a backflow prevention device is provided on the upstream side of a Roots meter 5 as an integrated flow meter, and 11 is a governor body provided in the middle of the gas pipe 1. This governor main body 11 is a known AFV regulator, and a sleeve 15 is provided inside a governor case 12 of the governor main body 11 to open and close a gas flow passage 14 by the pressure of a control chamber 13.

Further, the gas pipe 1 is provided with a bypass pipe 16 that bypasses the governor main body 11, and this bypass pipe 16 is provided with a venturi 17, which is connected to the control chamber of the governor main body 11 via a control pipe 18. It communicates with 13. The venturi 17 controls the governor body 11 to open and close the gas flow passage 14. In other words, the upstream pressure Pl is the downstream pressure P2
When the pressure is higher, the gas flows through the bypass pipe 16, so when it flows through the venturi 17, it reduces the pressure in the control chamber 13 through the control pipe 18 due to venturi action, and the sleeve 15 reduces the pressure in the gas communication passage 14 by the upstream pressure P1. It is opened to allow gas to flow downstream.

Further, a check valve 19 is provided in the bypass pipe 16 located upstream of the venturi 17.

This check valve 19 allows gas to flow only from the upstream side to the downstream side through the bypass pipe 16, and blocks gas from flowing from the downstream side to the upstream side. Therefore, even if gas attempts to flow from the downstream side to the upstream side, it is blocked by the check valve 19, and as a result, gas also does not flow to the venturi 17, so that the control chamber 13 of the governor main body 11 flows downstream via the control pipe 18. The pressure P2 on the side presses the sleeve 15 to block the gas flow passage 14 and prevent backflow of gas.

Therefore, for example, when the factory is closed such as at night or on holidays, and the gas demand side 3 is not consuming gas,
On the other hand, when the gas consumption amount in a general household 4 on the gas supply side 2 is high, the pressure on the gas supply side 2, that is, the upstream side of the roots meter 5 is low, and the pressure downstream is high. Therefore, the gas on the downstream side tries to flow back through the roots meter 5, but the backflow prevention structure of the check valve 19 prevents the gas from flowing through the venturi 17 as well. The pressure P2 on the downstream side presses the sleeve 15 and blocks the gas flow path 14. Therefore, the gas on the downstream side does not flow backward through the roots meter 5.

Here, the results of experiments conducted by the present inventor will be explained. FIG. 2 shows the changes in the downstream pressure P2 when the upstream pressure P1 of a Roots meter without a backflow prevention device is intentionally varied. According to this, when the pressure P1 on the upstream side rises, the pressure P2 on the downstream side also rises, gas flows through the Roots meter 5 and is instructed to be integrated on the counter, and even if the pressure P1 on the upstream side falls, the counter is not subtracted, and when the upstream pressure P1 rises again, the counter is instructed to integrate. In this way, as the pressure P1 on the upstream side changes, the pressure P2 on the downstream side similarly changes, and the counter of the roots meter is integrated only when the pressure P1 on the upstream side increases again. However, as shown in Fig. 3, with a backflow prevention device provided upstream of the Roots meter, even if the upstream pressure P1 is intentionally varied as described above, the upstream pressure P1 is initially When the pressure rises, the pressure P2 on the downstream side rises accordingly, but even if the pressure P1 on the upstream side falls, the check valve 19 prevents the backflow to the upstream side. There is no backflow, and the indicated value on the counter remains constant.

In the above embodiment, the backflow prevention device was provided on the upstream side of the roots meter, but backflow can be similarly prevented even if it is provided on the downstream side of the roots meter. It can also be applied to flow meters.

〔Effect of the invention〕

As explained above, according to the present invention, since a check valve is provided in the bypass pipe of the governor body, the amount of gas used can be accurately integrated and indicated without being affected by pressure fluctuations on the upstream side of the integrating flowmeter. This has the effect of improving the reliability of the integrated flow meter.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a schematic configuration diagram showing one embodiment of the present invention;
3 and 3 are explanatory diagrams showing experimental results, and FIG. 4 is a schematic diagram of the conventional configuration. 1... Gas piping, 2... Gas supply side, 3... Gas demand side, 5... Roots meter (integrated flow meter), 11.
...Governor body, 14...Bypass pipe, 17...Venturi, 19...Check valve.

Claims (1)

[Claims] A gas pipe that connects the gas supply side and the gas demand side, an integrating flow meter installed in the middle of this gas pipe that instructs to integrate the gas flow rate, and the gas pipe on the upstream or downstream side of this integrating flow meter. a governor body provided therein, and a venturi provided in a bypass pipe that bypasses the governor body and communicates with a control chamber of the governor body to open and close the governor body;
A backflow prevention device for an integrating flowmeter, comprising a check valve provided upstream of the venturi to prevent backflow from the downstream side to the upstream side.