JPH0854078A - Pilot type safety valve - Google Patents

Abstract

PURPOSE:To provide a pilot type safety valve which is constituted to form a device in a compact manner at a low cost, perform high-precise and simple operation to switch a set pressure, and facilitate confirmation of the switching position thereof. CONSTITUTION:To switch in a multistage a down operation force exerted on the spindle 29 of a pilot valve 3, three compression springs 40, 41, and 42 are arranged in a juxtaposing state. Through vertical movement of a rod 30, the positions of spring supports 34, 35, and 36 to which the end parts of the respective springs are attached are regulated to change the number of combinations of the compression springs 40, 41, and 42. The rod 30 is vertically moved through rotational operation of the cam 51 of a set pressure switching body 49 and the rotation position of the cam 51 is displayed on a display panel 52.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a safety valve used, for example, in a cargo tank of an LPG tanker, and more particularly to a pilot type safety valve whose set pressure can be changed according to the kind of gas to be loaded.

[0002]

2. Description of the Related Art Since an LPG tanker carries a plurality of types of gas, it is desirable that the safety valve used in the cargo tank of this tanker be capable of switching the set pressure according to the type of gas to be loaded. In addition, even if the type of gas is the same, since the safety factor of the material differs depending on the applicable law, there are cases where it is necessary to switch the set pressure according to the applicable law.

Conventionally, as shown in FIG. 11, a tank 1 is used as a switching device for switching the set pressure.
There is known a structure in which a spring direct acting low pressure safety valve 102 and a high pressure safety valve 103 are arranged in parallel with respect to 01, and a main valve 104 is arranged in series on the low pressure safety valve 102 side. . In the example of the drawing, two switching devices are attached for fail-safe. In this switching device, when the set pressure of the safety valve is set to the low pressure side, the main valve 104 is opened, and when it is set to the high pressure side, the main valve 104 is closed to use the high pressure safety valve 103. Has been done.

[0004]

However, in the structure of the conventional switching device as described above, it is necessary to increase the number of safety valves each time the switching level of the set pressure increases, and the number of safety valves must be increased accordingly. As a result, the piping becomes complicated and the entire apparatus becomes large, and the cost increase is inevitable. In addition, this conventional device has a problem that the switching operation of the set pressure is complicated and the switching status of each safety valve cannot be easily confirmed.

The present invention has been made in view of the above problems, and has a compact and inexpensive device configuration, can easily perform a setting pressure switching operation, and can easily confirm the switching position. The purpose is to provide a pilot type safety valve that can be used.

[0006]

In order to achieve the above-mentioned object, a pilot type safety valve according to the present invention comprises a main valve having a valve body for shutting off or connecting an inlet and an outlet,
A pilot valve provided in a pilot line that connects the inlet and the back pressure chamber of the valve body, and a spring incorporated in the spring chamber of the pilot valve when the pressure in the inlet exceeds a set pressure. In a pilot type safety valve that opens the operating pressure line portion of the pilot line against the force to open the valve element, a plurality of springs are arranged in parallel in the spring chamber, and the plurality of springs are arranged in parallel. It is characterized in that a biasing force switching means for switching the biasing force to a plurality of stages by changing the number of combinations of the above is provided.

The urging force switching means comprises a spring bearing for supporting the lower end portion of each spring, a rod having a stepped portion engaging with the spring bearing, and an operating shaft having a cam for vertically moving the rod. Is preferred. Further, it is preferable to include a display panel that displays the rotational position of the operation shaft. Also,
The pilot valve is preferably mounted laterally of the main valve so that a test gag may be mounted during a tightness test of the valve seat of the main valve.

[0008]

[Operation] When a fluid is introduced into the inlet of the main valve, this fluid is introduced into the back pressure chamber of the valve body of the main valve through the pilot line. The downward force of the back pressure chamber is larger than the upward force of the inlet, and the main valve is in the closed state. Further, at this time, the exhaust opening of the operation pressure line portion of the pilot line is closed by the urging force of the spring incorporated in the spring chamber of the pilot valve. In this state, when the fluid pressure at the inlet rises and exceeds the set pressure (the biasing force of the spring), the operating pressure line of the pilot line is opened and the working pressure introduced into the back pressure chamber drops. As a result, the valve body of the main valve is opened by the upward force from the inlet side, and the fluid on the inlet side is discharged to the outlet side. Further, when the fluid pressure drops due to the opening operation of the main valve, the exhaust opening of the operating pressure line of the pilot line is closed by the action opposite to the above, and the pilot that connects the inlet of the main valve and the back pressure chamber The line is opened, and in response to this, the working pressure of the back pressure chamber of the main valve rises and the valve body is also closed.

According to the present invention, a plurality of springs arranged in parallel in the spring chamber are arranged to switch the biasing forces of the springs in a plurality of stages, so that the overall height of the apparatus is suppressed and the apparatus is compact. It can have a different structure.

In this case, the urging force switching means includes a spring bearing for supporting the lower end of each spring, a rod having a step portion engaging with the spring bearing, and an operating shaft having a cam for moving the rod up and down. With the above, the set pressure (biasing force of the spring) can be easily switched only by vertically moving the rod by rotating the operation shaft. Further, if a display panel for displaying the rotational position of the cam shaft is provided, the switching position of the set pressure can be easily confirmed by this display panel.

When the pilot valve is attached to the side of the main valve, for example, a test gag can be attached to the top cover of the main valve to perform an airtight test of the valve seat of the main valve, and the safety valve as a whole has a high height. Can be kept low.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, specific embodiments of the pilot type safety valve according to the present invention will be described with reference to the drawings.

A longitudinal sectional view and a plan view of a pilot type safety valve according to an embodiment of the present invention are shown in FIGS. 1 and 2, respectively. As shown in these drawings, the pilot type safety valve of the present embodiment is composed of a main valve 1 and a pilot valve 3 mounted on a side of the main valve 1 via a bracket 2.

The main valve 1 has an inflow port 4 communicating with the primary side pipe.
And an outlet 5 communicating with the secondary pipe, and the inlet 4 is provided with an inlet nozzle 7 having a valve seat 6 at the tip. A valve disc guide 9 is fixed to a lower portion of a disc-shaped upper cover 8 provided on the upper face of the valve body by a flange portion at an upper end, and an inner peripheral surface of the valve disc guide 9 faces the valve seat 6. Then, the valve body 10 is slidably inserted in the vertical direction. This valve body 10 is normally biased in the closing direction by a valve spring (compression coil spring) 11 inserted between the valve body 10 and the lower surface of the upper surface cover 8 (this valve spring 1
1 may be omitted. ). Further, on the back side of the valve body 10, the upper surface cover 8, the valve body guide 9 and the valve body 1 are provided.
The back pressure chamber 12 is defined by 0.

Next, the detailed structure of the pilot valve 3 will be described with reference to FIG. As shown in the figure, in the valve body 13 of the pilot valve 3, an inflow passage 15 into which the pilot pressure of the inflow port 4 of the main valve 1 is introduced via a pilot conduit 14, and an outflow conduit 16 to the main valve An outflow passage 17 that communicates with the back pressure chamber 12 of No. 1 and a discharge passage 19 that communicates with the outflow port 5 (or the atmosphere) of the main valve 1 via a discharge conduit 18. Further, in the valve body 13, a vertical through hole 20 is provided.
a and a valve seat 20 having a communication hole 20b that connects the through hole 20a and the outflow passage 17 to each other is provided in a substantially central portion, and the guide rod 2 is provided in the through hole 20a of the valve seat 20.
1 is vertically movable. A first valve element 23 is provided above the valve seat 20 so as to come into contact with the upper end surface of the guide rod 21 and move up and down along the upper guide 22. Below the valve seat 20, the first valve body 23 of the guide rod 21 is provided. A second valve body 25 is provided which abuts on the lower end surface and is vertically moved along the lower guide 24. Here, the second valve body 25 is constantly urged in the upward direction by the compression spring 26 inserted between the valve body 25 and the lower guide 24. Further, the inflow passage 15 and the through hole 20a can be communicated with each other through the communication hole 24a formed in the lower guide 24, and the discharge passage 19 and the through hole 20a are connected with the communication hole 2 formed in the upper guide 22.
It is possible to communicate via 2a.

A cover 27 is attached to the upper surface of the valve body 13. A through hole is formed in the cover 27 at a substantially central portion, and the sleeve 2 is formed on the outer peripheral surface along the through hole.
A spindle 29 having 8 is provided so as to be vertically slidable. Then, the spindle 29 is pressed downward by the urging force of the compression springs 40, 41, 42 described later, so that a predetermined downward set pressure is applied to the first valve body 23.

The downward set pressure applied to the first valve body 23 is introduced through the inflow passage 15, flows in through the gap between the valve seat 20 and the second valve body 25, and rises upward in the first valve body. Opposed to the pilot pressure acting in the direction. Therefore, when the fluid pressure at the inlet 4, in other words, the pilot pressure is smaller than the set pressure, the second valve body 25 is pushed downward against the biasing force of the compression spring 26 via the guide rod 21. A gap is formed between the seat 20 and the second valve body 25, and the inflow passage 15 and the outflow passage 17 are communicated with each other. At this time, the valve seat 20 and the first valve body 23 are closed, and the communication between the outflow passage 17 and the discharge passage 19 is cut off. As a result,
The fluid in the inflow port 4 is a pilot pipe line 14, an inflow line 15,
Communication hole 24a, through hole 20a, communication hole 20b, outflow passage 1
7 and the outflow pipe 16 are introduced into the back pressure chamber 12 of the main valve 1 through the pilot line, and the downward force of the back pressure chamber 12 is increased by the difference in the pressure receiving areas of the front and back surfaces of the valve body 10. The main valve 1 is in a closed state by a force larger than the upward force of the inflow port 4.

In this state, when the fluid pressure at the inlet 4 rises and the upward force of the first valve body 23 exceeds the set pressure, a gap is formed between the valve seat 20 and the first valve body 23. Then, the valve seat 20 and the second valve body 25 are closed by the force of the upward pressure applied to the second valve body 25. This makes the inflow path 1
5 and the outflow passage 17 are disconnected, and the outflow passage 17
And the discharge path 19 communicate with each other. Thus, the back pressure chamber 12 is communicated with the outflow port 5 (or the atmosphere),
The working pressure introduced into the valve is reduced, and as a result, the valve body 10 of the main valve 1 is opened by the pressure from the inlet 4 side, and the fluid on the inlet 4 side is discharged to the outlet 5 side. Further, when the fluid pressure decreases due to the opening operation of the main valve 1 as described above, the force due to the upward pressure applied to the second valve body 25 falls below the set pressure, and the action opposite to the above causes the inflow passage 15 and the outflow passage 17 to flow.
And the communication between the outflow passage 17 and the discharge passage 19 are cut off, and accordingly, the valve body 10 of the main valve 1 is also closed.

The downward pressure set on the first valve body 23 is switched by the switching mechanism. Next, this switching mechanism will be described in detail. A bottom end of a vertically arranged long rod 30 is vertically slidably fitted in a bottomed hole 29a provided at an upper portion of the spindle 29. The bottom end of the rod 30 has a bottom end side. From the small diameter portion 30a,
A flange portion 30b and a large diameter portion 30c are formed, and a sleeve 31 is attached to the outer peripheral surface of the small diameter portion 30a.
Further, a release nut 32 is provided on the upper end of the rod 30.
And a release lock nut 33 for fixing the release nut 32 are screwed together.

At a position surrounding the lower end of the rod 30, a first spring receiver 34, a second spring receiver 35 and a third spring receiver 36 are slid up and down with respect to the rod 30 from the lower end side. It is movably installed. In the first spring receiver 34, the lower surface of the inner peripheral portion is in contact with the upper surface of the spindle 29, and the upper surface of the inner peripheral portion is the rod 30.
The lower surface of the flange portion 30b of the
The lower end surface of the spring receiver 35 is capable of abutting on the upper surface of the first spring receiver 34, and the lower surface of the inner peripheral portion is the rod 3
The upper surface of the large diameter portion 30c of the rod 30 is in contact with the lower surface of the inner peripheral portion of the third spring receiver 36. In addition, a first tubular body 37, a second tubular body 38, and a third tubular body that surround the rod 30 so as to face the first spring bearing 34, the second spring bearing 35, and the third spring bearing 36. Each body 39 is provided, and a spring chamber is formed in a space below each of the cylindrical bodies 37, 38, 39. Then, in the spring chamber, a spring receiving portion provided on the lower surface of each of the cylindrical bodies 37, 38, 39, the first spring bearing 34, and the second spring bearing 3 are provided.
5 and the third spring bearing 36 between the first compression spring 4
0, the second compression spring 41, and the third compression spring 42 are respectively inserted in parallel.

The first cylindrical body 37 is screwed onto the inner peripheral surface of a bonnet 44 which is bolted to the upper surface of the cover 27 via a cover spacer 43, and the bonnet 44 is attached.
The vertical position with respect to is adjustable, and the vertical position is fixed by the first lock nut 45. Similarly, the second tubular body 38 is screwed onto the inner peripheral surface of the first tubular body 37 so that the vertical position with respect to the first tubular body 37 can be adjusted, and the vertical position is the second lock. Nut 4
It is fixed by 6. Further, the third tubular body 39 is screwed onto the inner peripheral surface of the second tubular body 38 so that the vertical position with respect to the second tubular body 38 can be adjusted, and the vertical position is the third lock nut. It is fixed by 47. In addition, these cylindrical bodies 37, 38, 3
9 and the lock nuts 45, 46, 47 and the like are covered with a cover 48 screwed onto the outer peripheral surface of the bonnet 44. In addition, after the bonnet 44 is fixed, the first tubular body 37 and the second tubular body 3 are attached to the respective tubular bodies 37, 38, 39.
8, the compression springs 40, 41, 42 in the order of the third tubular body 39
It is assembled while adjusting the spring force of.

In order to perform a switching operation of the set pressure of the pilot valve 3, a set pressure switching body 49 is provided above the cover 48.
(See FIG. 4) is rotatably mounted. The set pressure switching body 49 extends in a direction orthogonal to the rod 30 and has an operation shaft 50 having one end (the right end in FIG. 4A) as an operation part, and the other end of the operation shaft 50. And a cam 51 attached to the section. Where the cam 51
As shown in FIG. 4B, the cam surfaces 51a, 51b, 51c (for example, a = 5 m) in which the distances a, b, c from the center of the operation shaft 50 sequentially change stepwise are shown.
m, b = 7 mm, c = 9 mm), and the cam nuts 51a, 51b, 51c are attached to the upper end of the rod 30 when the operation shaft 50 rotates.
The rod 30 is vertically moved by slidingly contacting the lower surface of the rod 2. Further, the switching position of the cam 51 is set to the two display panels 52 provided on the end side of the operation shaft 50.
It can be confirmed by the position of the spring pin 53 (see FIGS. 3 and 5). In this display board 52, H (H
ig), M (Middle) and L (Low) respectively indicate the switching level of the set pressure, and the cam surfaces 51a, 51b and 51c of the H, M and L are respectively release nuts 3.
It corresponds to the position of sliding contact with the lower surface of 2. The setting pressure is switched by removing the cover 54, aligning the rotation-preventing spring pin 53 with the groove portion of the display board 52, and then changing the cover 54.
It is done by fixing.

In such a configuration, the set pressure switching level is in the High (high pressure) state, in other words, in the state where the cam surface 51a of the cam 51 and the lower surface of the release nut 32 have a gap, as shown in FIG. As described above, the lower surface of the first spring bearing 34 is in contact with the upper surface of the spindle 29, and the lower surface of the flange portion 30b of the rod 30 and the lower surface of the second spring bearing 35 are the upper surfaces of the first spring bearing 34. And the lower surface of the third spring receiver 36 is in contact with the upper surface of the large diameter portion 30c of the rod 30. Therefore, the spindle 29 is pressed downward by the total spring force of the three spring forces of the first compression spring 40, the second compression spring 41, and the third compression spring 42.

The switching level of the set pressure is Middle.
In the (medium pressure) state, in other words, in the state where the cam surface 51b of the cam 51 is in sliding contact with the lower surface of the release nut 32, as shown in FIG. It is pushed up by the upper surface of the diameter portion 30c, the flange portion 30b of the rod 30 does not abut on either the first spring bearing 34 or the second spring bearing 35, and the lower surface of the second spring bearing 35. Remains in contact with the upper surface of the first spring receiver 34. Therefore, the spring force of the third compression spring 42 on the spindle 29 is released, and the spindle 29 is released by the first compression spring 4
The spring force is the sum of the two spring forces of 0 and the second compression spring 41, and the spring force is pressed downward.

Further, when the switching level of the set pressure is Low (low pressure), in other words, when the cam surface 51c of the cam 51 is in sliding contact with the lower surface of the release nut 32,
As shown in FIG. 8, the flange portion 3 of the rod 30
0b pushes up the second spring receiver 35, and the contact between the lower end of the second spring receiver 35 and the upper surface of the first spring receiver 34 is released. Therefore, the spindle 29
Second compression spring 41 and third compression spring 42 for
The respective spring forces are released, and the spindle 29 is pressed downward by the spring force of only the first compression spring 40.

As described above, according to the pilot type safety valve of the present embodiment, a plurality of (in this embodiment, 3) operation is performed by rotating the operation shaft 50 having the cam 51 at the tip thereof.
It is possible to easily switch the set pressure of the pilot valve 3 by selecting and combining the individual compression springs 40, 41, 42. Further, since the compression springs 40, 41, 42 are arranged in parallel, the height of the pilot valve 3 itself can be suppressed to a low level, and the pilot valve 3 can be installed in the main valve 1 like the present embodiment. By mounting it on the side, the safety valve can be made compact and simple as a whole. In addition, the protection device on installation is small, and it is not necessary to additionally combine a single set pressure pilot valve every time a large number of set pressures are required. Is excellent. Further, there is an advantage that the switching position of the set pressure can be confirmed at a glance on the display board 52.

In the present embodiment, the case where the set pressure is switched to three stages has been described, but in the structure of this embodiment, the set pressure is switched to two stages or to four stages or more. Is also possible.

Although not described in detail in the above description, an inverted conical recess 10a is formed at the center of the inner surface of the valve body 10 of the main valve 1 as shown in FIG. A test gag seat plug 55 is attached to a central portion of the upper surface cover 8 facing the place 10a in a normal use state. This plug 55 is removed during the airtightness test of the valve seat of the main valve 1, and instead of this plug 55, a test gag 56 as shown in FIG. 9 abuts the tip of the test gag 56 on the recess 54. To be installed.
Incidentally, such a structure is possible by disposing the pilot valve 3 on the side of the main valve 1.

Further, in this embodiment, the pilot valve 3 serves as the second valve body 25 and the compression spring 2 below the valve seat 20.
Although the so-called non-bleed type in which 6 and 6 are provided has been described, a bleed type in which the second valve body 25 and the compression spring 26 are removed can be adopted as shown in FIG. .

[0030]

As described above, according to the present invention, a plurality of springs arranged in parallel in the spring chamber can switch the biasing forces of the springs in a plurality of steps. A pilot type safety valve that can be applied to multiple types of fluids (gas) with different set pressures, because the set pressure can be easily switched even if the type of fluid used changes with a compact and inexpensive device configuration. Can be obtained. In this case, the urging force switching means includes a spring bearing that supports the lower end of each spring, a rod that has a step portion that engages with the spring bearing, and an operating shaft that has a cam that moves the rod up and down. Then, just by moving the rod up and down by rotating the operating shaft, the set pressure (spring biasing force)
Can be switched with high accuracy and easily, and by providing a display panel for displaying the rotational position of the camshaft, the switching position of the set pressure can be easily confirmed by this display panel.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a pilot type safety valve according to an embodiment of the present invention.

FIG. 2 is a plan view of a pilot type safety valve according to an embodiment of the present invention.

FIG. 3 is a vertical cross-sectional view of a pilot valve.

FIG. 4 is a front view (a) and its arrow A view (b) of a set pressure switching body that performs a setting pressure switching operation of a pilot valve.

FIG. 5 is a front view of a display panel that displays a cam switching position.

FIG. 6 is an explanatory diagram of a set pressure switching operation.

FIG. 7 is an explanatory diagram of a set pressure switching operation.

FIG. 8 is an explanatory diagram of a set pressure switching operation.

FIG. 9 is a front view of a test gag.

FIG. 10 is a cross-sectional view of essential parts of a pilot valve according to another embodiment.

FIG. 11 is a configuration diagram of a conventional set pressure switching device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main valve 3 Pilot valve 4 Inlet 5 Outlet 6 Valve seat 10 Valve body 10a Recess 11 Valve spring (compression coil spring) 12 Back pressure chamber 14 Pilot line 15 Inflow line 16 Outflow line 17 Outflow line 18 Discharge pipe Path 19 Discharge path 20 Valve seat 21 Guide rod 23 First valve body 25 Second valve body 26 Compression spring 29 Spindle 30 Rod 30a Small diameter portion 30b Flange portion 30c Large diameter portion 32 Release nut 34 First spring bearing 35 Second Spring receiver 36 third spring receiver 37 first cylinder 38 second cylinder 39 third cylinder 40 first compression spring 41 second compression spring 42 third compression spring 49 set pressure switching body 50 Operation Axis 51 Cam 52 Display Panel 53 Pin 54 Cover 55 Test Gag Seat Plug 56 Test Gag

Claims (4)

[Claims] 1. A main valve having a valve body that blocks or connects the inlet and the outlet, and a pilot valve provided in a pilot line that connects the inlet and the back pressure chamber of the valve, A pilot type in which when the pressure in the inlet exceeds a set pressure, the operating pressure line portion of the pilot line is opened against the urging force of a spring incorporated in the spring chamber of the pilot valve to open the valve body. In the safety valve, a plurality of springs are arranged in parallel in the spring chamber, and urging force switching means for switching the urging force to a plurality of stages by changing the number of combinations of the plurality of springs is provided. Pilot type safety valve. 2. The biasing force switching means includes a spring bearing for supporting the lower end portion of each spring, a rod having a step portion engaging with the spring bearing, and an operating shaft having a cam for vertically moving the rod. The pilot-type safety valve according to claim 1, further comprising: 3. The pilot type safety valve according to claim 2, further comprising a display panel that displays a rotational position of the operation shaft. 4. The pilot valve according to claim 1, wherein the pilot valve is attached to a side of the main valve so that a test gag is attached during an airtight test of a valve seat of the main valve. Pilot type safety valve described in.