JPH11125346A - Low pressure cutoff valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically cutoff fluid feed piping when disaster and a trouble occur and also to ensure safety during restoration. SOLUTION: A low pressure cutoff valve comprises a valve body 100 provided with a gas introduction port 109 opening to an outer peripheral part and a gas lead-out port 110; a valve rod 104 movable between valve opening and closing positions in the valve body 100 and energized in a valve closing direction through the force of a compression spring 108; and a diaphragm 124 to introduce fluid in the introduction port 109 and lock a stopper 121 to the step part 105c of the valve rod 104 moved to a valve opening position through compression of a pressure set spring 128 when a fluid pressure exceeds a set pressure, and hold a valve opening state. Further, a stopper unit 101 is provided to pull off a stopper 121 from the step difference part 105c of the valve rod 104 by pressing the diaphragm 124 by a pressure set spring 128 when a fluid pressure in the introduction port 109 is reduced to a value lower than a set pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low pressure gas installed in a gas supply pipe in a gas supply system (gas supply system) for supplying, for example, liquefied natural gas to each user (various facilities, homes, etc.). It relates to a shutoff valve.

[0002]

2. Description of the Related Art FIG. 1 is a system diagram showing a liquefied natural gas supply system.

[0003] Liquefied natural gas (LNG) is supplied to the LNG tank 1
And flows through the liquid supply pipe 2, is temporarily stored in the intermediate tank 3, and further flows as it is in the liquid supply pipe 2 and enters the reduced-pressure vaporizer 4 where it is vaporized and passes through the gas supply pipe 2 a For example, it is supplied to a combustion device 5 such as a gas stove installed at home.

[0006] A pressure reducing valve 6 is provided in the liquid supply pipe 2 between the LNG tank 1 and the intermediate tank 3, and the pressure of the LNG is reduced to, for example, about 5 kg / cm ² by the pressure reducing valve 6. 3 to be stored.

[0005] A cutoff valve 7 is provided in the liquid supply pipe 2 between the intermediate tank 3 and the decompression vaporizer 4, and LNG in the intermediate tank 3 is cut out by the cutoff valve 7 according to a required amount, and the pressure is reduced. It is supplied to the vaporizer 4 where it is decompressed and vaporized.

The natural gas vaporized by the decompression vaporizer 4 is:
The gas is supplied to each of the combustion devices 5 through the gas supply pipe 2a. The gas supply pipe 2a near the downstream side (in the gas flow direction) of the decompression / evaporation apparatus 4 is provided with a shutoff valve 8, The gas supply pipe 2a can be shut off in the event of a gas leak disaster due to an earthquake or the like, or when the gas pressure drops for some reason.

The combustion equipment 5 is provided with a combustion equipment side shut-off valve 9 and a gas amount adjustment valve 10, respectively.

[0008]

In the LNG supply system shown in FIG. 1, as described above, when gas leaks due to an earthquake or the like, the gas supply is immediately shut off to avoid danger. Further, if the gas is continuously supplied in a state in which the gas pressure is lowered, the combustion equipment 5 may not burn normally and may be misfired in some cases. It is necessary to close and stop the gas supply.

Here, conventionally, the closing operation of the shut-off valve 8 has been performed by a human (an operator in a facility where the decompression vaporizer 4 and the shut-off valve 8 are installed). Therefore, there is a problem that it takes time from the necessity of closing the shut-off valve 8 to the closing of the shut-off valve 8 by the operator, and since it is manually operated by the operator, the reliability of accident prevention is high. There was a problem with sex.

For this reason, it is conceivable to make the opening and closing of the shutoff valve 8 fully automatic. However, in order to fully automate the opening and closing of the shutoff valve 8, it is necessary to detect the gas pressure with a pressure detector. On the other hand, the pressure detector generally uses electric means. However, it is difficult to apply such electric means to a facility which handles extremely combustible gas such as LNG.

Further, even if the opening and closing of the shut-off valve 8 can be automated by some means, there is a risk that a problem may occur if the shut-off valve 8 automatically returns to the valve open position due to an increase in gas pressure.

That is, if the shut-off valve 8 is closed while the combustion equipment 5 is in use, the combustion equipment 5 is naturally extinguished, and if the illusion that the gas adjustment valve 10 is closed, the gas adjustment valve 10 is closed. There is a problem that when the device 10 automatically returns, the gas blows out from the combustion device 5 that is left open.

The present invention has been made based on such a background, and in the event of a disaster or trouble, the supply of fluid can be automatically cut off due to a decrease in pressure, and safety is confirmed at the time of restoration. It is an object of the present invention to provide a low-pressure shut-off valve capable of supplying a fluid after the pressure has been reduced.

[0014]

In order to achieve the above object, the present invention is provided in the middle of a fluid supply pipe, and when the fluid pressure flowing in the fluid supply pipe drops to a predetermined closing fluid pressure, the fluid is supplied to the fluid supply pipe. A low pressure shutoff valve for shutting off a supply pipe,
A valve body having a fluid inlet and a fluid outlet opening to the outer peripheral portion, provided in the valve body, movable between a valve open position and a valve closed position, and urged in a valve closing direction by a compression spring. The valve stem and one of the fluid inlet and the fluid outlet are introduced, and when the fluid pressure is equal to or higher than the set pressure, the pressure setting spring is compressed to move the valve to the valve open position. A diaphragm is provided so that the valve can be kept open by locking the valve, and when the fluid pressure at the fluid introduction port becomes equal to or less than the set pressure, the diaphragm is pushed by a pressure setting spring to push the stopper from the step portion of the valve rod. A low-pressure shutoff valve, comprising: a stopper unit configured to be pulled out.
It is related to.

According to the present invention, when the fluid pressure guided to the diaphragm from the gas inlet is normal, the stopper is urged via the diaphragm in the locking position direction against the urging force of the pressure setting spring. Is done. At this time, if the valve stem has been moved to the valve open position by the operator, the stopper enters the locking position and locks the step, thereby maintaining the valve open state.

On the other hand, when the gas pressure falls below the set pressure, which is the closing gas pressure, the urging force of the pressure setting spring for urging the diaphragm prevails, whereby the diaphragm is pushed and returns to the unlocked position, The stopper is pulled out of the step portion of the valve stem, and the valve stem moves to the valve closed position by the action of the compression spring to close the valve.

After that, even if the gas pressure returns to normal, the stopper cannot enter the step unless the valve stem is pulled up by the operator.

[0018]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

According to the present invention, for example, in the liquefied natural gas supply system shown in FIG. 1, the following semi-automatic operation, that is, the valve closing operation is automatically performed instead of the manual shut-off valve 8, and the valve opening operation is performed by an operator. And a low-pressure shut-off valve that is performed under the condition that the above operation is an essential condition.

The low-pressure shut-off valve of the present invention can of course be applied to various facilities having similar requirements other than the liquefied natural gas supply system.

FIG. 2 is a front sectional view of the low-pressure shut-off valve in the valve open state according to the embodiment of the present invention, FIG. 3 is a front sectional view of the low-pressure shut-off valve in the valve closed state, and FIG. FIG. 5 is a sectional view taken along line BB in FIG. 2.

As shown in FIG. 2, the low-pressure shut-off valve of the present embodiment comprises a valve body 100 and a stopper unit 101 having an axial direction perpendicular to the axial direction of the valve body 100.

The valve body 100 has a cylindrical main body 102 and a main body 102 whose center is hollow in the axial direction (up and down in FIG. 2, the same applies hereinafter).
A valve seat nipple 103 screwed into the main body case 102 from below, a valve stem 104 fitted to the center of the main body case 102 movably in the vertical direction (the valve opening direction and the valve closing direction), A connecting rod 105 inserted from above the main body case 102 and screwed with the upper part of the valve rod 104;
The main body case 102 is provided with a cap nut 106 that is screwed to the main body case 102 so as to close an upper opening of the main body case 102, and a handle 107 that is attached to an upper portion of the cap nut 106.

A coil-shaped compression spring 108 is elastically connected between the upper step portion 105d of the connecting rod 105 and the cap nut 106. In addition, as shown in FIG.
A gas inlet 109 is formed on one side of the outer circumference of 02.
A gas outlet 110 is formed on the other side on a different level so that the gas inlet 109 and the gas outlet 110 are connected or blocked by the valve rod 104 up and down.

As shown in FIG. 2, the valve stem 104 is provided with an O-ring 111 for closing and an O-ring 112 for preventing gas leakage, so that the main body case 102 and the valve seat nipple 103 come into contact with each other. The parts are also provided with O-rings 113 and 114 for preventing gas leakage.

On the other hand, in the stopper unit 101,
A structure in which the stopper 121, the connector 122, the transmission rod 123, the diaphragm 124, and the hexagon nut 125 are integrated in the diaphragm case 120 is moved in the left-right direction in FIG. 2, that is, the movement of the valve rod 104 (and the connection rod 105). It is fitted so that it can move in the direction perpendicular to the direction.

The rod-shaped stopper 121 has its tip (left end) projecting from the central opening of the connector 122 and further projecting from the tip of the diaphragm case 120. The connector 122 is screwed to the transmission rod 123, and the transmission rod 1
Reference numeral 23 is connected to the diaphragm 124 by a hexagon nut 125. Reference numeral 126 denotes an O-ring.

Between the stopper 121 and the transmission rod 123,
The spring 127 is interposed, and as described above,
The stopper 121, the connector 122, the transmission rod 123, and the diaphragm 124 are integrally formed with the diaphragm case 12.
It is configured to be movable in the left-right direction, which is the 0 axis direction.

Between the fixed step 120a on the diaphragm case 120 side and the diaphragm 124, a pressure setting spring 128 for urging the diaphragm 124 and the stopper 121 integral therewith to the right is interposed.

In the opening at the right end of the diaphragm case 120, a diaphragm cover 130 is provided with a bolt 129.
A gas is introduced from a gas inlet 131 formed in the diaphragm cover 130 into the internal space of the diaphragm case 120 between the diaphragm cover 130 and the diaphragm 124. Diaphragm cover 130 and diaphragm case 1
An O-ring 132 for gas sealing is provided at the contact portion 20.

As described above, the gas inlet 109 and the gas outlet 110 are formed in the main body case 102 of the valve main body 100 (see FIGS. 1 and 5).
As shown in FIGS. 4 and 5, a gas supply pipe 140 (the gas inlet 109 side is denoted by reference numeral 140a, and the gas outlet 110 side is denoted by reference numeral 140b) is connected to the gas outlet 110, respectively. The gas introduced from the gas supply pipe 140a to the gas inlet 109 flows through the passage inside the main body case 102 from the gas outlet 110 to the gas supply pipe 140b in a valve-open state.

In the example of FIG. 4, the gas supply pipe 140
a and a gas inlet 131 of the diaphragm cover 130.
Is connected by a gas branch pipe 141 so that the gas at the gas inlet 109 is connected to the gas inlet 1 of the stopper unit 101.
31. Therefore, the gas flowing in the gas supply pipe 140a is taken into the diaphragm case 120 from the gas inlet 131 via the gas branch pipe 141, and pushes the diaphragm 124 to the left by the gas pressure.

In the above, for example, the gas inlet 109
Induced gas pressure is 1.5kg / cm ^TwoIf it is
And the gas pressure is 0.4kg / cm^Two When it drops below
To automatically close the valve, the diaphragm 1
0.4kg / cm pressing 24^TwoGas pressure and pressure setting
If it is set so that the resilience of the spring 128 is exactly balanced
Good.

The operation of the low-pressure shut-off valve shown in FIGS. 2 to 5 will be described below.

FIG. 3 shows the valve closed state as described above.
To open this valve, the operator holds the handle 107 and pulls it upward. Then, the compression spring 10
8 while compressing (against the urging force of the compression spring 108)
The connecting rod 105 and the valve rod 104 integrated therewith are pulled up.

At this time, for example, the gas pressure flowing through the gas supply pipe 140 becomes a normal pressure (for example, 1.5 kg / cm).
² ), the pressure of the pressure setting spring 128 for urging the diaphragm 124 is overcome, and the diaphragm 124
Is pushed to the left in FIG.

The connecting rod 105 has a large diameter portion 105a, a small diameter portion 105b below the large diameter portion 105a, and a step portion 1 between the two.
05c, and the small-diameter portion 105
“b” faces the distal end surface of the stopper 121 via a stopper insertion hole formed in the main body case 102.

Accordingly, the stopper 121 moves (enters) leftward when the diaphragm 124 is pushed by the normal gas pressure taken into the diaphragm case 120, and is stopped by abutting against the small diameter portion 105b. Then, the upper side of the stopper 121 enters under the step portion 105c.

At this time, even if the operator releases his / her hand from the handle 107, the connecting rod 105 is locked at that position by the stopper 121, so that the valve is kept open. In this state, the gas flows normally in the gas supply pipe 140.

Next, a case where the pressure of the gas flowing through the gas supply pipe 140 is reduced will be described. The gas pressure at the gas inlet 109 is changed from a normal pressure of 1.5 kg / cm ² to the pressure setting spring 1.
When the pressure drops to 0.4 kg / cm ² or less, which is set at 28, the pressure setting spring 1 that pushes the diaphragm 124 rightward from the gas pressure that pushes the diaphragm 124 leftward.
28 wins, the diaphragm 124 moves rightward, and the stopper 121 also moves rightward.
As shown in (5), the stopper 121 is disengaged from the step portion 105c, and the engagement with the connecting rod 105 is released. Then, the connecting rod 105 and the valve rod 104 are moved to the lower valve closing position by the urging force of the compression spring 108 that urges the connecting rod 105 in the valve closing direction. At this time, the distal end surface of the stopper 121 faces the large diameter portion 105a.

In the valve closed position, the O-ring 111 provided in the tapered portion of the valve stem 104 presses against the upper end opening of the valve seat nipple 103 to shut off the gas passage. Downstream gas supply pipe 140b
The supply of gas to the is cut off.

As described above, the stopper 121 is movable between the locking position for locking the valve rod 104 at the valve open position and the unlocking position for releasing the locking of the valve rod 104. When the gas pressure drops to the closing pressure, the valve is automatically closed by retracting to the unlocked position by the action of the pressure setting spring 128.

On the other hand, when the gas pressure returns to the normal pressure, the gas pressure overcomes the urging force of the pressure setting spring 128 for urging the diaphragm 124.
The stopper 121 is urged in the locking position direction (left direction) via.

However, the tip of the stopper 121 is the connecting rod 1
05, facing the large diameter portion 105a,
The movement of the stopper 121 is prevented, and the valve remains in the closed state. In other words, in order to return to the valve open state again, the operation by the operator, that is, the grip
In addition, an operation of lifting the valve stem 104 upward is required.

Therefore, when the gas pressure returns to the normal state, the operator can notify each user first of that fact and alert the user to close the gas shutoff valve prior to the manual valve opening operation. .

The connecting rod 10 connected to the valve rod 104
5, a large diameter portion 105a, a small diameter portion 105b, and a step portion 105.
Although c is formed, when the valve stem 104 is integrated with the connecting rod 105 and the whole is regarded as a valve stem, a large diameter portion, a small diameter portion, and a step portion are formed on the valve stem 104.

It should be noted that the present invention is not limited to the above-described embodiment, but can be applied to the case where various fluids other than gas are handled. 101 gas inlet 13
1, the gas at the gas outlet 110 is supplied to the gas inlet 1 of the stopper unit 101.
It is needless to say that the present invention can be implemented in the same manner even if it is led to 31, and that various changes can be made without departing from the gist of the present invention.

[0048]

As described above, according to the present invention,
When the fluid pressure drops, the valve closes automatically.On the other hand, when the fluid pressure returns to the normal state, a low-pressure shut-off valve is configured so that the valve can be opened manually to ensure safety in the event of a disaster or accident. Security and safety at the time of restoration.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a liquefied natural gas supply system.

FIG. 2 is a front sectional view of the low-pressure shut-off valve in an open state according to the embodiment of the present invention.

FIG. 3 is a front sectional view of the low-pressure shut-off valve in a valve closed state according to the embodiment of the present invention.

FIG. 4 is a view in the direction of arrow A in FIG. 2;

FIG. 5 is a sectional view taken along line BB in FIG. 2;

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 Valve body 101 Stopper unit 104 Valve rod 105 c Step 108 Compression spring 109 Gas inlet 110 Gas outlet 121 Stopper 124 Diaphragm 128 Pressure setting spring 140 a, 140 b Gas supply pipe

Claims (1)

[Claims] 1. A low-pressure shut-off valve that is provided in the middle of a fluid supply pipe and shuts off the fluid supply pipe when a fluid pressure flowing through the fluid supply pipe drops to a predetermined closing fluid pressure. A valve body provided in the valve body, movable between a valve open position and a valve closed position, and urged in a valve closing direction by a compression spring. A fluid is introduced into one of the fluid inlet and the fluid outlet, and when the fluid pressure is equal to or higher than the set pressure, the pressure setting spring is compressed to lock the stopper at the step portion of the valve rod moved to the valve open position. By providing a diaphragm capable of holding the valve open state by this, when the fluid pressure of the fluid introduction port becomes equal to or less than the set pressure, the diaphragm is pushed by the pressure setting spring and the stopper is pulled out from the step portion of the valve rod. Stopper unit Low-pressure shut-off valve, characterized in that it includes.