CN214096462U

CN214096462U - Pressure measuring device

Info

Publication number: CN214096462U
Application number: CN202022930757.4U
Authority: CN
Inventors: 李婧
Original assignee: Petrochina Co Ltd
Current assignee: Petrochina Co Ltd
Priority date: 2020-12-07
Filing date: 2020-12-07
Publication date: 2021-08-31
Anticipated expiration: 2030-12-07

Abstract

The application discloses pressure measurement device belongs to the oil and gas equipment field. The device comprises a piston cavity, a metering tank, a pressure sensing assembly, a connecting pipe, a valve assembly and a piston structure, wherein the piston cavity is communicated with the metering tank; a first piston of the piston structure is positioned in the piston cavity, one end of the piston rod is connected with the first piston, and the other end of the piston rod is connected with the pressure sensing assembly; the pressure sensing assembly comprises a telescopic mechanism, a pressure sensor and a cushion block; the other end of the piston rod is connected with the first surface of the cushion block; the pressure sensor is connected with the second surface of the cushion block; the telescopic mechanism has a rod movable in a longitudinal direction. Can survey first pressure through piston chamber and pressure sensor subassembly, can survey the second pressure through the metering tank, first pressure and the mutual evidences of second pressure can improve pressure data's accuracy. The problem of lower accuracy that produces of measuring oil pressure power among the correlation technique is solved, the effect of efficiency and the accuracy of oil pressure power measurement has been reached.

Description

Pressure measuring device

Technical Field

The application relates to the field of oil and gas equipment, in particular to a pressure measuring device.

Background

In the oil exploitation operation, the natural gas dissolved in the oil in the well can cause the volume expansion of the oil, so that the oil spontaneously gushes out of the well, and the exploitation of the oil is facilitated. The volume of natural gas brought by each ton of oil produced is called the oil-gas ratio, and the oil-gas ratio of oil is currently determined by measuring the hydraulic pressure of oil. The oil-gas ratio not only influences whether the oil can be spontaneously gushed, but also has important guiding significance for subsequent processes in the mining operation. Therefore, the hydraulic pressure of the oil needs to be accurately measured.

At present, a pressure measuring device comprises a measuring cylinder and a piston positioned in the measuring cylinder, and the hydraulic pressure of oil is determined through the displacement generated by the movement of the piston after the oil enters the measuring cylinder.

However, the piston in the measuring cylinder is prone to wear, which may cause large errors in the measured data after multiple measurements.

SUMMERY OF THE UTILITY MODEL

The embodiment of the application provides a pressure measurement device. The technical scheme is as follows:

according to a first aspect of the present application, there is provided a pressure measurement device comprising: the device comprises a piston cavity, a metering tank, a pressure sensing assembly, a connecting pipe, a valve assembly and a piston structure;

the piston cavity comprises a first opening and a second opening, the metering tank comprises a third opening, the second opening is communicated with the third opening through the connecting pipe, and the metering tank is provided with a pressure scale;

the piston structure comprises a piston rod and a first piston, the first piston is positioned in the piston cavity, one end of the piston rod extends into the piston cavity and is connected with the first piston, and the other end of the piston rod is connected with the pressure sensing assembly;

the valve assembly comprises a first valve positioned at the first opening and a second valve positioned on the connecting pipe; the pressure sensing assembly comprises a telescopic mechanism, a pressure sensor and a cushion block, and the cushion block is provided with two opposite surfaces;

the other end of the piston rod is connected with a first surface of the two surfaces of the cushion block;

the pressure sensor is connected with a second surface of the two surfaces of the cushion block;

the telescopic mechanism is provided with a rod capable of moving along the length direction, and the pressure sensor is positioned in the extending direction of the rod.

Optionally, the first valve is a first one-way valve, and a liquid outlet of the first one-way valve is communicated with the first opening;

the second valve is a second one-way valve, and a liquid inlet of the second one-way valve is communicated with the second opening.

Optionally, the telescopic mechanism further comprises a hydraulic cylinder, the rod being mounted in the hydraulic cylinder.

Optionally, the pressure measuring device further comprises a tank body, and the piston cavity, the metering tank, the pressure sensing assembly, the connecting pipe, the valve assembly and the piston structure are located in the tank body.

Optionally, the piston cavity is mounted at the bottom of the box body, and the hydraulic cylinder is connected with the top of the box body.

Optionally, the metering tank is provided with a strip-shaped transparent window arranged along the height direction of the metering tank, and the scales are located at the strip-shaped transparent window.

Optionally, the metering tank further comprises a fourth opening, and the valve assembly further comprises a third valve mounted to the fourth opening.

Optionally, the fourth opening is located at the bottom of the metering tank.

Optionally, the metering tank has a second piston and a spring therein, one end of the spring is connected to the second piston, and the other end of the spring is connected to the top of the inner wall of the metering tank.

Optionally, a height of the third opening in a vertical direction is greater than a height of the second opening in the vertical direction.

The beneficial effects brought by the technical scheme provided by the embodiment of the application at least comprise: the device comprises a piston cavity, a metering tank, a pressure sensing assembly, a connecting pipe, a valve assembly and a piston structure, wherein a first valve and a second valve in the valve assembly are opened, test oil enters the piston cavity and drives a first piston positioned in the piston cavity and a piston rod connected with the first piston to move upwards, then the first valve and the second valve are closed, and first pressure of the test oil is obtained through the pressure sensing assembly connected with the other end of the piston rod; and opening a second valve, driving the first piston to move downwards through a telescopic mechanism in the pressure sensing assembly, and enabling the oil liquid to enter the metering tank through the connecting pipe so as to obtain a second pressure of the tested oil liquid based on the pressure scale on the metering tank. The first pressure and the second pressure are mutually verified, so that the accuracy of the obtained pressure data can be improved, and the pressure measurement can be completed. The problem of the lower accuracy that produces through piston pressure gauge measurement oil pressure force among the correlation technique is solved, the effect of efficiency and the accuracy of improvement oil pressure force measurement has been reached.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a structural view of a pressure measurement device according to an embodiment of the present application;

FIG. 2 is a block diagram of a metering tank in the apparatus of FIG. 1.

With the above figures, there are shown specific embodiments of the present application, which will be described in more detail below. These drawings and written description are not intended to limit the scope of the inventive concepts in any manner, but rather to illustrate the inventive concepts to those skilled in the art by reference to specific embodiments.

Detailed Description

Fig. 1 is a structural diagram of a pressure measurement device according to an embodiment of the present application, where the pressure measurement device 1 includes: piston chamber 11, metering tank 12, pressure sensing assembly 13, connecting tube 14, valve assembly 15, and piston structure 16.

The piston chamber 11 includes a first opening 111 and a second opening 112, the metering tank 12 includes a third opening 121, the second opening 112 and the third opening 121 are communicated through a connecting pipe 14, and the metering tank 12 has a pressure scale 122. Illustratively, as shown in fig. 1, the first opening 111 and the second opening 112 on the piston cavity 11 are disposed on the cavity wall of the piston cavity 11, and the first opening 111 and the second opening 112 are disposed opposite to each other. The third opening 121 is located on the wall of the metering tank 12, and the third opening 121 is connected to the second opening 112 through the connecting pipe 14. With such a structure, after the pressure data in the piston cavity is obtained, the oil can enter the metering tank 12 through the second opening 112, the connecting pipe 14 and the third opening 121.

Piston structure 16 includes piston rod 161 and first piston 162, and first piston 162 is located piston chamber 11, and one end of piston rod 161 stretches into piston chamber 11 and is connected with first piston 162, and the other end of piston rod 161 is connected with pressure sensing assembly 13. As shown in fig. 1, one end of the piston rod 161 located in the piston cavity 11 is connected to the first piston 162, and the other end of the piston rod 161 is connected to the pressure sensing assembly 13 and located outside the piston cavity 11. The oil introduced into the piston chamber 11 through the first opening 111 is mixed with gas, and the volume of the oil expands, so that the oil drives the first piston 162 and the piston rod 161 connected to the first piston 162 to move upward. The first piston 162 is tightly attached to the inner wall of the piston cavity 11, so that in the process of moving the first piston 162 upwards, oil is difficult to move upwards along a gap between the first piston 162 and the piston cavity 11, the accuracy of the subsequently measured oil pressure can be increased, and the data error is reduced.

The other end of the piston rod 161 is connected to the pressure sensing assembly 13, as shown in fig. 1, oil enters the piston cavity 11 through the liquid inlet pipe S and the first opening 111, the entered oil will press against the first piston 162 and apply a vertical upward pressure to the first piston 162, so that the first piston 162 and the piston rod 161 connected thereto move upward in the vertical direction under the pressure, and at the same time, the pressure value can be measured by the pressure sensing assembly 13 connected to the other end of the piston rod 161. The first pressure value of the oil supplied from the oil pipe S can be obtained by the pressure value, the piston rod 161, the first piston 162 and the fixed friction force.

The valve assembly 15 comprises a first valve 151 located at the first opening 111 and a second valve 152 located on the connecting pipe 14. As shown in fig. 1, a first valve 151 is disposed at the first opening 111 and connected to the liquid inlet pipe S, and the first valve 151 is used for controlling the oil to flow into the piston chamber 11. The second valve 152 is disposed on the connection pipe 14 to control the oil in the piston chamber 11 to flow into the metering tank 12. The first valve 151 and the second valve 152 are placed in a closed state, the oil flows into the piston cavity 11 through the liquid inlet pipeline S, so as to drive the first piston 162 and the piston rod 161 connected with the first piston to move upwards along the vertical direction, and the oil can flow into the metering tank 12 through the second valve 152, so that the rising height of the oil in the metering tank 12 can be conveniently observed subsequently.

The pressure sensing assembly 13 includes a telescoping mechanism 131, a pressure sensor 132, and a pad 133, the pad 133 has two opposite faces a, the other end of the piston rod 161 is connected to a first face a1 of the two faces a of the pad 133, and the pressure sensor 132 is connected to a second face a2 of the two faces a of the pad 133. As shown in fig. 1, an end of the piston rod 161 away from the first piston 162 is connected to the first surface a1 of the pad 133, the second surface a2 of the pad 133 is connected to the pressure sensor 132, and the telescoping mechanism 131, the pressure sensor 132, and the pad 133 are located on the same vertical line. With such a structure, when the oil enters the piston cavity 11 through the liquid inlet pipeline S and drives the first piston 162 and the piston rod 161 to move upwards, the pressure sensor 132 on the a2 surface of the pad 133 may contact the telescopic mechanism 131, and the pressure sensor 132 may generate a reading. The pressure sensor 132 is a device that can sense a pressure signal, convert the pressure signal into an electrical signal, and output and display the electrical signal. When the pressure sensor 132 contacts the telescoping mechanism 131, the telescoping mechanism 131 applies a vertically downward force to the pressure sensor 132, and the pressure sensor 132 converts the pressure signal into an electrical signal and outputs the electrical signal through an external display screen electrically connected with the electrical signal.

The telescopic mechanism 131 has a rod 1311 movable in the longitudinal direction, and the pressure sensor 132 is located in the extending direction of the rod 1311. Pressure sensor 132 is positioned directly below rod 1311 so that when the two are in contact, the reading of pressure sensor 132 is accurate. The rod 1311 in the telescopic mechanism 131 can move up and down in the vertical direction, after the oil enters the piston cavity 11 through the liquid inlet pipe S, the first piston 162 and the piston rod 161 move up under the pressure, when the pressure sensor 132 contacts the telescopic mechanism 131 and generates a reading, the first valve 151 and the second valve 152 are closed, the reading of the pressure sensor 132 continuously rises, when the reading is stable, the second valve 152 is opened, the rod 1311 moves down, the rod 1311 can drive the piston rod 161 and the first piston 162 to move down, and the oil can enter the metering tank 12 through the second opening 112, the connecting pipe 14 and the third opening 121.

In the application of the pressure measurement device 1 that the embodiment of the application provides, place first valve 151 and second valve 152 in the closed condition, fluid flows into piston chamber 11 through inlet pipe S, fluid drives first piston 162 and makes first piston 162 and piston rod 161 go upward along vertical direction, close first valve 151 and second valve 152, treat that pressure sensor 132 reading in the pressure sensing subassembly 13 is stable and later read this pressure value, and obtain the first pressure value of fluid that inlet pipe S provided through this pressure value, the dead weight of piston rod 161 and first piston 162. The second valve 152 is opened, a vertically downward pressure is applied to the piston rod 161 through the pressure sensing assembly 13, so that the piston rod 161 drives the first piston 162 to move downward, the oil in the piston cavity 11 can be squeezed into the metering tank 12 through the second opening 112, the connecting pipe 14 and the third opening 121 through the first piston 162, and then a second pressure value of the oil provided by the liquid inlet pipeline S is obtained through the rising height of the oil in the metering tank 12. First pressure numerical value and the mutual evidencing of second pressure numerical value through comparing the two, can improve the accuracy of the pressure data of the fluid of pressure measurement device survey among the inlet liquid pipeline S that this application embodiment provided.

Optionally, the first valve 151 is a first one-way valve, and a liquid outlet of the first one-way valve is communicated with the first opening 111; the second valve 152 is a second one-way valve, and an inlet of the second one-way valve is communicated with the second opening 112. So that the oil can only pass through the valve and can not flow back, for example, the oil can enter the piston cavity 11 through the first opening 111 and then enter the metering tank 12 through the second opening 112, and the oil can hardly flow back to the piston cavity 11 from the metering tank 12, thereby ensuring the accuracy of the measurement data of the pressure measuring device.

Alternatively, the number of the piston rods 161 is two. During the process that the oil applies a vertical upward pressure to the first piston 162 and drives the first piston upward, the piston rod 161 may shake due to uneven oil composition. If the number of the piston rods 161 is too small, the first piston 162 may shake violently during ascending, and the reading of the pressure sensor 132 in the pressure sensing assembly 13 connected to the other end of the piston rod 161 may not be accurate enough. If the number of the piston rods 161 is too large, the weight of the piston rods 161 is too large, and the oil is subjected to a large pressure from the piston rods 161 and 162 and rises slowly while the oil drives the first pistons 162 and 161 to rise. Therefore, the number of the piston rods 161 is two, which not only increases the stability of the first piston 162 during the ascending process, but also ensures the data accuracy of the pressure sensing assembly 13.

Optionally, the telescopic mechanism 131 further comprises a hydraulic cylinder 1312, the rod 1311 being mounted in the hydraulic cylinder 1312. The hydraulic cylinder is a hydraulic actuating element which converts hydraulic energy into mechanical energy and enables a rod in the hydraulic cylinder to do linear reciprocating motion, the hydraulic actuating element is simple in structure and reliable in operation, a speed reducing device can be omitted when the hydraulic actuating element is used for achieving reciprocating motion, and the motion process is stable. When the hydraulic cylinder 1312 receives an external hydraulic signal, the rod 1311 installed in the hydraulic cylinder 1312 extends to drive the pressure sensor 132, the pad 133 and the piston rod 161 to move downward, and the first piston 162 extrudes the oil in the piston cavity 11 into the metering tank 12 through the second opening 112, the connecting pipe 14 and the third opening 121 under the pressure of the rod 1311.

The piston rod 1311 of the telescopic structure 131 may be a multi-stage piston rod, which has a long extendable total length and a short total length after being retracted into the hydraulic cylinder, so that the hydraulic cylinder has a small size in the axial direction. The pressure measurement device with the structure can reduce the total volume and increase the convenience of the device.

Optionally, the pressure measuring device 1 further comprises a tank 17, and the piston chamber 11, the metering tank 12, the pressure sensing assembly 13, the connecting tube 14, the valve assembly 15 and the piston structure 16 are all located in the tank 17. As shown in fig. 1, one end of the liquid inlet pipeline S is communicated with the oil liquid, and the other end is communicated with the piston cavity 11.

Alternatively, piston chamber 11 is mounted to the bottom of tank 17 and cylinder 1312 is attached to the top of tank 17, as shown in FIG. 1, cylinder 1312 being located opposite piston chamber 11. When the hydraulic cylinder 1312 receives an external hydraulic signal, the rod 1311 in the hydraulic cylinder 1312 extends out to drive the pressure sensor 132 to move downwards, in the process, the rod 1311 applies vertical downward pressure to the pressure sensor 132, the pressure may cause shaking of the rod 1311, the hydraulic cylinder 1312 is fixed to the top of the box body 17, shaking of the rod 1311 can be reduced, the rod 1311 can stably drive the pressure sensor 132 to move downwards, oil in the metering tank 12 can stably rise, and accuracy of the data is improved when oil rising height in the metering tank 12 is obtained subsequently.

Optionally, the metering tank 12 has a strip-shaped transparent window 123 arranged along the height direction of the metering tank 12, and the scale 122 is located at the strip-shaped transparent window 123. Fig. 2 is a structural diagram of the metering tank of the apparatus shown in fig. 1, and as shown in fig. 2, the oil enters the metering tank 12 through the connecting pipe 14, the liquid level rises continuously, when the liquid level does not rise any more within 30S, the reading can be performed through the scale 122 on the bar-shaped transparent window 123, and the second pressure of the oil provided by the liquid inlet pipe S can be obtained through the difference between the reading and the initial reading (the initial reading is the liquid level in the metering tank 12 after the second valve 152 is closed).

Wherein, the material of this transparent window 123 can select glass or resistant oily plastics for use, so can guarantee in the ascending in-process of fluid in the measuring tank 12, this transparent window 123's stability is good.

Optionally, the metering tank 12 further has a fourth opening 124, and the valve assembly 15 further includes a third valve 153, the third valve 153 being mounted to the fourth opening 124. As shown in fig. 1, a third valve 153 is installed at the fourth opening. The third valve 153 is used for controlling the outflow of the oil in the metering tank 12, and after the oil enters the metering tank 12 through the connecting pipe 14, the second pressure of the oil can be obtained through the height difference of the pressure scale 122 on the transparent window 123. Then, the third valve 153 is opened, and the oil in the measuring tank 12 can flow out of the tank 17 through the four ports 124.

Optionally, the fourth opening 124 may be connected to an external recovery device, so that the tested oil is effectively recovered, and the pollution is reduced.

Optionally, fourth opening 124 is located at the bottom of metering tank 12. With the structure, the tested oil flows out through the fourth opening 124 under the action of gravity as much as possible, so that an environment can be provided for the next pressure measurement.

Alternatively, metering tank 12 has a second piston 124 and a spring 125, one end of spring 125 being connected to second piston 124 and the other end of spring 125 being connected to the top of the inner wall of metering tank 12. As shown in fig. 2, after the oil enters the metering tank 12, the liquid level in the metering tank 12 continuously rises, one end of the spring 125 is connected to the top of the metering tank 12, and the other end of the spring is connected to the second piston 124, so that the oil is subjected to a vertical downward pressure given by the second piston 124 in the rising process, the oil can reach a balance as soon as possible and is highly stable, and thus, not only is the measurement time reduced, but also the measurement efficiency is improved. Meanwhile, the pressure given to the oil by the spring 125 and the second piston 124 can also relieve the rising speed of the oil, and the size of the metering tank 12 in the vertical direction is effectively shortened.

Optionally, the height of the third opening 121 in the vertical direction is greater than the height of the second opening 112 in the vertical direction. When the first valve 151 and the second valve 152 are opened, the oil may enter the metering tank 12 through the connection pipe 14 when the oil enters the piston chamber 11 due to the high oil pressure. The height of the third opening 121 in the vertical direction is greater than the height of the second opening 112 in the vertical direction, so that oil entering the metering tank 12 can be reduced by the height difference, and the oil can enter the piston cavity 11 as much as possible.

Optionally, the pressure measurement device 1 further comprises a support 18. As shown in fig. 1, the seat 18 is located at a lower portion of the tank 17, the seat 18 allows a construction space for the oil to flow out of the metering tank 12 through the fourth opening 124, and the seat 18 may increase the robustness of the pressure measuring device.

The pressure measurement device provided by the embodiment of the application can be used for measuring the pressure through the following steps:

1. when the first valve 151 and the second valve 152 are opened, the oil flows into the piston chamber 11 through the liquid inlet pipe S, and the first piston 162 in the piston chamber 11 moves upward in the vertical direction under the pressure of the oil, thereby driving the piston rod 161 connected thereto to move upward.

2. When the pressure sensor 132 connected to the other end of the piston rod 161 contacts the telescopic mechanism 131 installed at the top of the tank 17 and generates a reading, the first valve 151 and the second valve 152 are closed, the reading on the pressure sensor 132 is continuously increased until the reading is stable, and the first pressure of the oil supplied from the liquid inlet pipeline S can be obtained through the reading and the self-weight of the piston rod 161 and the first piston 162.

3. The second valve 152 is opened, the rod 1311 installed in the hydraulic cylinder 1312 is moved towards the pressure sensor 132 by the hydraulic cylinder 1312, the rod 1311 drives the pressure sensor 132, the piston rod 161 and the first piston 162 to move downwards, in the moving process, the oil in the piston cavity 11 enters the metering tank 12 through the second opening 112, the connecting pipe 14 and the third opening 121, the liquid level in the metering tank 12 continuously rises, when the liquid level does not change within 30 seconds, reading is performed through a pressure scale, and then the second pressure of the oil provided by the liquid inlet pipeline S can be obtained through the rising height of the liquid level (namely, the difference between the liquid level in the metering tank 12 and the liquid level in the metering tank after the second valve 152 is closed at this time). Then, the third valve 153 is opened, and the measured oil flows out through the fourth opening 124.

4. The obtained first pressure and the second pressure are mutually verified, and the accuracy of the first pressure can be judged through the second pressure, namely whether the piston cavity 11 has the problems of liquid leakage and air leakage is judged; if the difference between the first pressure and the second pressure is too large, the tightness of the piston chamber 11 can be checked and calibrated.

In summary, the embodiment of the present application provides a pressure measurement apparatus, which includes a piston cavity, a metering tank, a pressure sensing assembly, a connecting pipe, a valve assembly, and a piston structure, wherein a first valve and a second valve in the valve assembly are opened, a test oil enters the piston cavity and drives a first piston and a piston rod to move upward, then the first valve and the second valve are closed, and a first pressure value of the test oil is obtained through a pressure sensor in the pressure sensing assembly; and opening the second valve, driving the first piston to move downwards through a rod in the hydraulic cylinder, and enabling the oil liquid to enter the metering tank through the connecting pipe so as to obtain the second pressure of the tested oil liquid through the difference value of the pressure scales on the metering tank. The first pressure and the second pressure are mutually verified, so that the accuracy of the obtained pressure data can be improved, and the pressure measurement can be completed. The problem of the lower accuracy that produces through piston pressure gauge measurement oil pressure force among the correlation technique is solved, the effect of efficiency and the accuracy of improvement oil pressure force measurement has been reached.

In this application, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. The term "plurality" means two or more unless expressly limited otherwise.

The present application is intended to cover various modifications, alternatives, and equivalents, which may be included within the spirit and scope of the present application.

Claims

1. A pressure measurement device, characterized in that the pressure measurement device comprises: the device comprises a piston cavity, a metering tank, a pressure sensing assembly, a connecting pipe, a valve assembly and a piston structure;

the valve assembly comprises a first valve positioned at the first opening and a second valve positioned on the connecting pipe;

the pressure sensing assembly comprises a telescopic mechanism, a pressure sensor and a cushion block, and the cushion block is provided with two opposite surfaces;

2. The pressure measurement device of claim 1, wherein the first valve is a first one-way valve, and a liquid outlet of the first one-way valve is communicated with the first opening;

3. A pressure measuring device as claimed in claim 2, wherein the telescopic mechanism further comprises a hydraulic cylinder in which the rod is mounted.

4. A pressure measurement device as claimed in claim 3, further comprising a housing in which the piston chamber, metering tank, pressure sensing assembly, connecting tube, valve assembly and piston arrangement are located.

5. A pressure measuring device as claimed in claim 4, wherein the piston chamber is mounted at the bottom of the tank and the hydraulic cylinder is connected to the top of the tank.

6. The pressure measuring device of claim 1, wherein the metering tank has a strip-shaped transparent window arranged along the height direction of the metering tank, and the scale is located at the strip-shaped transparent window.

7. The pressure measurement device of claim 6, wherein the metering tank further has a fourth opening therein, the valve assembly further comprising a third valve mounted to the fourth opening.

8. The pressure measurement device of claim 7, wherein the fourth opening is located at a bottom of the metering tank.

9. The pressure measurement device of claim 6, wherein the metering tank has a second piston therein and a spring, one end of the spring being connected to the second piston and the other end of the spring being connected to the top of the inner wall of the metering tank.

10. A pressure measuring device as claimed in any one of claims 1 to 9, characterized in that the height of the third opening in the vertical direction is greater than the height of the second opening in the vertical direction.