JP7528044B2 - Gas Supply System - Google Patents

Description

The present invention relates to a gas supply system that sends gas sent from the upstream side of a gas supply path to the downstream side.

The general supply system for city gas (hereafter simply referred to as "gas") is such that gas is sent out from the manufacturing plant at high pressure into a supply pipeline (supply route), which is then reduced to medium pressure by a medium pressure governor (pressure regulator) along the way before being sent to large factories and facilities, and the medium pressure gas is then further reduced to low pressure by a low pressure governor (pressure regulator) before being sent to ordinary homes and small commercial facilities.

However, in the city gas supply system described above, if the gas pressure in the low-pressure pipe connected downstream of the low-pressure governor becomes abnormally high due to a breakdown in the low-pressure governor or a rise in temperature, there is a risk of gas leaks from the low-pressure pipe or damage to the gas meter. For this reason, a safety device consisting of a pressure sensor that detects the gas pressure in the low-pressure pipe and an exhaust valve is usually installed midway along the low-pressure pipe, and when the pressure detected by the pressure sensor exceeds a predetermined set pressure, the exhaust valve is opened to release the gas in the low-pressure pipe into the atmosphere. However, releasing city gas into the atmosphere in this way is undesirable from the standpoint of environmental impact and safety.

In response to this, it has been proposed to provide a bypass pipe in parallel with the low-pressure governor between the low-pressure pipe and the medium-pressure pipe connected upstream of the low-pressure governor, and when the gas pressure in the low-pressure pipe exceeds a set pressure, the gas in the low-pressure pipe is forcibly returned to the medium-pressure pipe via the bypass pipe, thereby reducing the gas pressure in the low-pressure pipe (see, for example, Patent Document 1).

JP 2005-293126 A

However, the method proposed in the above-mentioned Patent Document 1 uses a pressure device (compressor) that pressurizes the gas in the low-pressure pipe (secondary piping) of the city gas supply pipeline to a pressure that exceeds the gas pressure in the medium-pressure pipe and discharges it into the medium-pressure pipe, as a means for forcibly returning the gas in the low-pressure pipe (secondary piping) to the medium-pressure pipe (primary piping), so new electrical equipment is required. Furthermore, this electrical equipment needs to be explosion-proof as a safety measure, which has the drawbacks of being expensive and requiring a lot of maintenance work.

The present invention aims to provide a gas supply system equipped with a reflux means capable of refluxing gas from a low pressure section to a high pressure section with a simple configuration for a gas supply path in which a relative difference in internal pressure occurs in the gas flow direction. Note that the terms "high pressure section" and "low pressure section" used here are names that correspond to the relative pressure levels in the gas supply path, and do not refer to legal pressure classifications.

In order to solve the above problems, the gas supply system of the present invention comprises a gas supply path, a bypass pipe provided in parallel with the supply path between a high-pressure section where the internal pressure of the supply path is relatively high and a low-pressure section where the internal pressure is relatively low, a check valve provided in the middle of the bypass pipe to prevent the flow of gas from the high-pressure section to the low-pressure section of the supply path, an ejector provided on the high-pressure section side of the bypass pipe relative to the check valve in the middle of the bypass pipe and having an intake port connected to the check valve side of the bypass pipe and an outlet port connected to the high-pressure section side, and an ejector for supplying a gas having a pressure higher than the pressure of the gas in the high-pressure section to the ejector. The device is equipped with a drive source that supplies the drive gas, a control valve that is provided between the ejector and the drive source, and a pressure sensor that detects the pressure of the gas in the low pressure section. When the pressure detected by the pressure sensor is equal to or lower than a predetermined set pressure, the control valve is closed to put the ejector in a non-driven state, and when the pressure detected by the pressure sensor exceeds the set pressure, the control valve is opened, and the ejector driven by the drive gas supplied from the drive source sucks in the gas in the low pressure section through the check valve, mixes it with the drive gas, and returns it to the high pressure section.

According to the above configuration, when the pressure of the gas in the low pressure section of the gas supply path exceeds the set pressure, the gas in the low pressure section is returned to the high pressure section without being released into the atmosphere, thereby preventing problems caused by an increase in gas pressure in the low pressure section. In addition, since an ejector with a simple structure and no rotating parts is used as the gas return means, costs can be kept lower than when a pressure device such as a compressor is used, and maintenance can be easily performed.

A specific example of a gas supply path to which the present invention can be applied is one in which a pressure regulator is provided midway along the supply path to reduce the pressure of the gas on the upstream side and send it downstream, with the primary piping connected to the upstream side of the pressure regulator forming the high-pressure part of the supply path, and the secondary piping connected to the downstream side of the pressure regulator forming the low-pressure part of the supply path.

It is also desirable that the control valve be configured to open and close automatically based on the detection results of the gas pressure in the low pressure section by the pressure sensor.

The driving source may be a gas cylinder filled with the same type of gas as the gas flowing through the supply path.

The gas supply system of the present invention can be particularly effectively applied when the gas is city gas and the supply path is a city gas supply pipe.

As described above, the gas supply system of the present invention uses an ejector to return the gas in the low pressure section to the high pressure section when the gas pressure in the low pressure section of the gas supply path exceeds a set pressure. This prevents problems caused by an increase in gas pressure in the low pressure section, keeps the cost of the gas return means low, and makes maintenance easy.

FIG. 1 is an explanatory diagram of a schematic configuration of a gas supply system according to an embodiment; FIG. 2 is an explanatory diagram of the general structure and operation of the ejector of FIG.

The following describes an embodiment of the present invention with reference to the drawings. This gas supply system is applied to a part of a city gas supply pipe (supply path), and as shown in FIG. 1, includes a low pressure governor (pressure regulator) 3 provided between a medium pressure pipe (primary side pipe) 1 and a low pressure pipe (secondary side pipe) 2 that constitute the supply path, a bypass pipe 4 provided in parallel with the low pressure governor 3 between the medium pressure pipe 1 and the low pressure pipe 2, a check valve 5 provided in the bypass pipe 4, an ejector 6 provided upstream of the check valve 5 in the bypass pipe 4, a gas cylinder 7 as a drive source for the ejector 6, a drive gas supply pipe 8 connecting the ejector 6 and the gas cylinder 7, a control valve 9 provided in the drive gas supply pipe 8, and a pressure sensor 10 that detects the pressure of the gas in the low pressure pipe 2.

The gas sent from the upstream side is sent from the medium pressure pipe 1 through the low pressure governor 3 to the low pressure pipe 2, from which it is supplied to ordinary households, small commercial facilities, etc.

The low-pressure governor 3 reduces the pressure of the medium-pressure (0.1 to 0.3 MPa) gas sent through the medium-pressure conduit 1 to approximately 2.3 KPa and sends it to the low-pressure conduit 2, with the medium-pressure conduit 1 being a high-pressure section with a relatively high internal pressure compared to the low-pressure conduit 2, and the low-pressure conduit 2 being a low-pressure section with a relatively low internal pressure. The check valve 5 opens and closes to prevent the flow of gas from the medium-pressure conduit 1 to the low-pressure conduit 2 and to allow only the flow of gas from the low-pressure conduit 2 to the medium-pressure conduit 1.

As shown in FIG. 2, the ejector 6 is composed of a body 11 having a supply port 11a and a suction port 11b, a nozzle 12 that is provided inside the body 11 and sprays the driving fluid supplied from the supply port 11a, and a tubular diffuser 13 that is attached to the body 11 so as to extend in the spray direction of the nozzle 12 and has a discharge port 13a at its tip. When high-pressure driving fluid is supplied to the supply port 11a of the body 11, the driving fluid is decompressed and accelerated by the nozzle 12 and sprayed at high speed, and the Venturi effect occurs, causing the space inside the body 11 to become low pressure, sucking the external fluid into the body 11 from the suction port 11b, and the external fluid and the driving fluid are mixed in the diffuser 13, decelerating and increasing the pressure, and then discharged from the discharge port 13a.

In this embodiment, the supply port 11a of the ejector 6 is connected to the drive gas supply pipe 8, the intake port 11b is connected to the check valve 5 side of the bypass pipe 4, and the discharge port 13a is connected to the medium pressure pipe 1 side of the bypass pipe 4.

The gas cylinder 7 connected to the ejector 6 by the driving gas supply pipe 8 is filled with a driving gas (driving fluid) that is the same type of gas as that flowing through the supply pipes (medium pressure pipe 1 and low pressure pipe 2) and compressed to a higher pressure (e.g., 19 MPa) than the pressure of the gas in the medium pressure pipe 1.

In addition, as described below, the control valve 9 is designed to automatically open and close based on the detection results of the gas pressure in the low-pressure conduit 2 detected by the pressure sensor 10.

This gas supply system has the above configuration, and its operation will be explained next.

First, when gas is being supplied normally, the pressure of the gas in the low pressure conduit 2 detected by the pressure sensor 10 is below a predetermined set pressure, and the control valve 9, which receives the pressure detection result from the pressure sensor 10, is kept closed. As a result, high pressure gas, which is the driving gas, is not supplied from the gas cylinder 7 to the ejector 6, so the ejector 6 is in a non-driving state. In addition, the action of the check valve 5 provided in the bypass piping 4 prevents the gas in the medium pressure conduit 1 from flowing at high pressure through the bypass piping 4 into the low pressure conduit 2, so a normal gas supply state is maintained.

On the other hand, if the gas pressure in the low-pressure conduit 2 rises due to a failure of the low-pressure governor 3 or an increase in temperature, etc., and the pressure detected by the pressure sensor 10 exceeds the set pressure, the control valve 9 that receives the detection result automatically opens, and high-pressure gas is supplied from the gas cylinder 7 to the ejector 6, driving the ejector 6. At this time, first, due to the action of the ejector 6 described above, the internal pressure of the bypass piping 4 between the ejector 6 and the check valve 5 becomes lower than the gas pressure in the low-pressure conduit 2, and the check valve 5 opens. As a result, the ejector 6 sucks in the gas in the low-pressure conduit 2 through the check valve 5, mixes it with the gas supplied from the gas cylinder 7, and returns it to the medium-pressure conduit 1. As a result, the gas pressure in the low-pressure conduit 2 drops, and the normal gas supply state can be restored.

As described above, in this gas supply system, when the pressure of the gas in the low-pressure conduit 2 exceeds the set pressure, the gas in the low-pressure conduit 2 is returned to the medium-pressure conduit 1 without being released into the atmosphere, thereby preventing problems caused by an increase in gas pressure in the low-pressure conduit 2. Furthermore, as the gas return means, an ejector 6 with a simple structure and no rotating parts is used, so compared to using a conventional compression device such as a compressor, there is no electrically driven part and no need for electrical equipment, which keeps costs low and simplifies maintenance.

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims, not by the meaning described above, and is intended to include all modifications within the meaning and scope of the claims.

For example, in the embodiment, the control valve 9 is automatically opened and closed based on the detection result of the gas pressure in the low-pressure conduit 2 by the pressure sensor 10, but the control valve can also be opened and closed remotely by an operator based on the detection result of the pressure sensor.

The driving source that supplies the driving gas to the ejector is not limited to a gas cylinder as in the embodiment, but may supply the driving gas to the ejector from a high-pressure gas line or the like that has a higher internal pressure than the high-pressure portion of the supply path.

The gas supply system of the present invention can be particularly effectively applied to a gas supply route that has a pressure regulator installed along the way, such as the city gas supply pipe of the embodiment, but it can also be applied to a gas supply route in which a high-pressure section with a relatively high internal pressure and a low-pressure section with a relatively low internal pressure are generated due to the difference in elevation of the piping position, etc.

1. Medium pressure pipe (primary piping)
2. Low pressure pipe (secondary piping)
3. Low pressure governor (pressure regulator)
4 Bypass piping 5 Check valve 6 Ejector 7 Gas cylinder (drive source)
8 Drive gas supply pipe 9 Control valve 10 Pressure sensor 11 Body 11a Supply port 11b Intake port 12 Nozzle 13 Diffuser 13a Discharge port

Claims (5)

a gas supply path, a bypass pipe provided in parallel with the supply path between a high pressure section where the internal pressure of the supply path is relatively high and a low pressure section where the internal pressure of the supply path is relatively low, a check valve provided in the bypass pipe and blocking a flow of gas from the high pressure section to the low pressure section of the supply path, an ejector provided on the high pressure section side of the check valve in the bypass pipe and having an intake port connected to the check valve side of the bypass pipe and an outlet port connected to the high pressure section side, a drive source that supplies a drive gas to the ejector having a pressure higher than the pressure of the gas in the high pressure section, a control valve provided between the ejector and the drive source, and a pressure sensor that detects the pressure of the gas in the low pressure section,
the supply path is a supply pipe for city gas, and the driving source is filled with a driving gas that is the same type as the gas flowing through the supply path and compressed to a higher pressure than the pressure of the gas in the high-pressure section,
When the pressure detected by the pressure sensor is equal to or lower than a predetermined set pressure, the control valve is closed to put the ejector in a non-operating state;
When the pressure detected by the pressure sensor exceeds the set pressure, the control valve is opened, and an ejector driven by the driving gas supplied from the driving source sucks in gas in the low pressure section through the check valve, mixes it with the driving gas, and returns it to the high pressure section. The gas supply system according to claim 1, characterized in that a pressure regulator is provided in the middle of the supply path to reduce the pressure of the gas on the upstream side and send it downstream, the primary side piping connected to the upstream side of the pressure regulator is the high pressure part of the supply path, and the secondary side piping connected to the downstream side of the pressure regulator is the low pressure part of the supply path. The gas supply system according to claim 1 or 2, characterized in that the control valve is automatically opened and closed based on the detection result of the gas pressure in the low pressure section by the pressure sensor. 4. The gas supply system according to claim 1, wherein the driving source is a gas cylinder. A gas supply system according to any one of claims 1 to 4, characterized in that the gas is city gas and the supply path is a city gas supply pipe.

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