JPH0526985Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention relates to differential pressure and pressure transmitters that measure the flow rate of process fluid based on the pressure difference between two points, and measure gauge pressure and absolute pressure. In particular, this invention relates to improvements in corrosion-resistant differential pressure and pressure transmitters used to measure the flow rate of fluids corrosive to metals.

[Conventional technology]

Conventionally, when measuring the flow rate of fluid in a pipe, an orifice is provided in the pipe to create fluid resistance, the pressure difference between the upstream side and the downstream side is measured, and the flow rate is calculated and measured from this pressure difference. A differential pressure transmitter used for this type of differential pressure measurement generally has a corrosion-resistant structure as shown in FIG. 2 or 3, especially when the fluid to be measured is a metal corrosive fluid such as acidic or alkaline fluid. That is, the differential pressure transmitter, which is generally designated by the reference numeral 1 in FIG.
It has a disc-shaped main body 2 formed by integrally joining A and 2B.

The body main body 2 is made of stainless steel or the like, and has both sides, that is, pressure receiving sides 3a, 3.
A pressure receiving diaphragm 4 on the high pressure side and a pressure receiving diaphragm 5 on the low pressure side are arranged at b with their peripheral edges fixed. Each pressure receiving diaphragm 4, 5 is usually formed in the shape of a corrugated disk from a thin film metal plate made of phosphor bronze, beryum copper, stainless steel or the like. Further, the pressure receiving side surfaces 3a and 3b are also formed in the same waveform as the pressure receiving diaphragms 4 and 5, and back side chambers 6 and 7 are formed between the pressure receiving diaphragms 4 and 5, respectively.

At the center of the interior of the body main body 2, there are two inner chambers 9A defined by a center diaphragm 8.
9B is formed, one of which 9A communicates with the back chamber 6 via a communication path 10, and the other 9B communicates with the back chamber 7 via a communication path 11. Further, the inner chambers 9A and 9B are communicated with a sensor chamber 13 in a sensor housing 12 provided on the upper surface of the body main body 2 via sealed circuits 14 and 15, respectively. The enclosed circuits 14 and 15 are partitioned within the sensor chamber 13 by a pressure sensor 16. The back chambers 6 and 7, the inner chambers 9A and 9B, the communication passages 10 and 11, the sealed circuits 14 and 15, and the sensor chamber 13 are filled with an incompressible inner liquid 1 such as silicone oil.
8 are sealed from the liquid filling passages 19a and 19b, respectively.

20 and 21 are pressure-receiving side surfaces 3a and 3 of the body main body 2 when the fluid to be measured is a metal corrosive fluid.
A base that is closely connected to b via an O-ring 22 and joined by welding 23,
The pressure-receiving sides of these bases 20 and 21, that is, the wetted parts that come into contact with the fluid to be measured, are made of tantalum, monel,
Liquid-contacting diaphragms 24 and 25 are formed of a corrosion-resistant metal such as Hastelloy, Nickel, or titanium, and are each formed into a corrugated disc shape on the outer surface thereof, with their peripheral edges fixed. High pressure on the upstream side of the orifice at 24 and 25
P _H and low pressure P _L on the downstream side of the orifice are respectively applied. The liquid contact portions of the liquid contact diaphragms 24 and 25 that come into contact with the fluid to be measured are also made of the same corrosion-resistant metal as the bases 20 and 21. The bases 20 and 21 have through holes 2 that penetrate through their front and back surfaces.
6 and 27 are formed, respectively, thereby communicating the inner chambers 28 and 29 of the liquid contact diaphragms 24 and 25 with the front side chambers 30 and 31 of the pressure receiving diaphragms 4 and 5, respectively. Then, the through hole 2
6, 27, inner chambers 28, 29 and front chambers 30, 3
1 is also filled with an internal sealing liquid 32, respectively.

33 and 34 are O on the surfaces of the bases 20 and 21.
Process pressure receiving covers (hereinafter abbreviated as covers) that are fitted and fixed through rings 35 respectively have through holes 36 and 37 for supplying the fluid to be measured.

In a differential pressure transmitter with such a configuration,
High pressure P _H and low pressure P _L are connected to the wetted diaphragms 24 and 25.
When applying each, the differential pressure at this time (P _H − P _L )
Accordingly, the diaphragms 24 and 25 are displaced to move the sealing liquid 32, and the movement of the sealing liquid 32 displaces the pressure receiving diaphragms 4 and 5, and the accompanying movement of the sealing liquid 18 causes the pressure sensor to move. The differential pressure measurement by the pressure sensor 16 is performed by distorting the pressure sensor 16 and extracting the amount of distortion as an electrical output. After this electrical signal is amplified by an amplifier, it is recorded and displayed on a meter or remotely transmitted, and is used for accurate measurement of flow velocity, valve control, etc.

In addition, if the fluid to be measured is not a corrosive fluid,
Since the bases 20 and 21 are inconvenient, the covers 33 and 34 are directly fitted and fixed to the respective pressure-receiving sides 3a and 3b of the body main body 2, and high pressure P _H and low pressure P _L are applied to the pressure-receiving diaphragms 4 and 5.

[Problem that the invention attempts to solve]

By the way, the body main body 2 and each base 20, 21
If the welding part 23 is the outer periphery of the joint surface of these two members, the welding direction will be in the radial direction of the body main body 2 as shown by the arrow, and the sensor housing 12 will get in the way. The upper surface of 2 is difficult to weld, so Teig welding is used. However, compared to electron beam welding, Teig welding is difficult to control the penetration depth and penetration shape, and there are problems with stability such as compressive strength and corrosion resistance.

Therefore, as a method to solve this problem, as shown in FIG.
An annular projecting portion 40 that closely contacts the outer peripheral surface of the pressure-receiving side of the body main body 2 is integrally provided on the outer peripheral surface of the joint end with the body main body 2, and from the back surface 41 side of the projecting portion 40, each pressure-receiving side 3a, 3b It is known that each base 20, 21 is fixed to the main body 2 by performing electron beam welding 43 near the outer periphery of the base 20, 21.

In such a structure, since the welding direction can be made oblique to the radial direction of the body main body 2 as shown by arrow A, the sensor housing 12
It has the great advantage of being able to perform electron beam welding without getting in the way, but on the other hand, the base 2
0, 21 becomes smaller than the outer diameter of the main body 2, the diameter R ₁ of the liquid contact diaphragms 24, 25 must be made smaller than the diameter R ₂ of the pressure receiving diaphragms 4, 5. There are drawbacks.

Sealing fluid 1 with a small outer diaphragm
The expansion of the sealed liquid due to the temperature rise in steps 8 and 32 cannot be absorbed, resulting in an increase in the pressure of the sealed liquid. If the outer diaphragm is small, it will be less sensitive to pressure changes from the process fluid. Base 20, 21
If the outer diameter of the differential pressure transmitter is small, it is smaller than the outer diameter of the cover of a normal differential pressure transmitter, and a dedicated cover is required.
When fixing the body main body 2 and the bases 20, 21 by welding, an appropriate jig is required to align the centers. The same can be said of the structure shown in FIG.

Therefore, the present invention solves the above-mentioned problems, allows electron beam welding to be performed without reducing the diameter of the welding diaphragm, and also improves the axial alignment when welding the body main body and the base. The present invention aims to provide a differential pressure and pressure transmitter that does not require any tools and can commonly be used with a cover normally attached to the body.

[Means for solving problems]

In order to achieve the above object, the present invention consists of a body body in which an internal liquid is sealed, and a base whose liquid contact part is made of a corrosion-resistant material is welded and fixed to the pressure-receiving side surface of the measured fluid side. The contact surface with the body main body is provided with a fitting part for the spigot into which the outer circumferential surface of the body main body fits, and a small diameter fitting part on the back side of the fitting recess on the outer circumferential surface of the base is provided on the side of the body main body. A topper portion is formed, and the back surface of the fitting recess is a welding annular plane for welding the base to the body main body.

[Effect]

In the present invention, the back surface of the fitting recess forms a welding plane that enables welding from an oblique direction to the pressure-receiving side surface of the body main body. The main body and the base are aligned by the fitting recess.

〔Example〕

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 is a sectional view showing an embodiment of the present invention applied to a differential pressure transmitter. Components and parts that are the same as those in FIGS. 2 and 3 are designated by the same reference numerals, and their explanations will be omitted. In the same figure, the outer circumferential surface of the side end of each base 20, 21 on the side of the body main body 2 has fitting recesses 50, 5, into which the outer circumferential surface of the side end of the body main body 2 is fitted, respectively.
Fitting portions 51 and 53 having a diameter of 1 are integrally provided in a protruding manner. Further, tapered portions 56 and 57 having a smaller diameter on the body main body 2 side are formed on the outer circumferential surface of each of the bases 20 and 21 on the back surfaces 54 and 55 of each of the fitting portions 52 and 53, respectively. Outer peripheral portions 58, 59 from 57 to the end opposite to the body main body 2 side
is equal to the outer diameter of the body main body 2, and the cover 3 is equal to the outer diameter of the body main body 2.
3 and 34. In this case, in order to reduce the influence of tightening the cover, it is desirable to set the small diameter portion ΦA of the tapered portions 57, 56 to be as large as possible than the inner diameter ΦB of the bases 21, 20, as shown in FIG. The back surfaces 54 and 55 of each of the fitting parts 52 and 53 are connected to each base 2.
0 and 21 are welded and fixed to the main body 2, electron beam welding is performed from the back surface to the outer periphery of each pressure receiving side surface 3a and 3b, thereby forming an annular plane for welding.

In the differential pressure transmitter having such a configuration, welding 43 can be performed from the direction of arrow A due to the formation of the tapered portions 56 and 57, so that the sensor housing 12 does not get in the way, making electron beam welding possible. In addition, the fitting parts 58, 59 of each base 20, 21
has the same outer diameter as the body 2, so not only can the covers 33 and 34 that are attached directly to the body of a normal differential pressure gauge be used as they are, but the diameter of the fitting portion is the same as the body 2. If the diameter is the same as that of the pressure receiving diaphragms 4, 5, the diameter of the liquid contact diaphragms 24, 25 can be made the same as that of the pressure receiving diaphragms 4, 5. Therefore, the pressure increase due to the expansion of the internal liquid 32 due to the temperature rise can be reduced by the deformation of the diaphragms 24, 25. In addition, pressure changes experienced by the process fluid can be sensitively transmitted to the pressure receiving diaphragms 4 and 5. Furthermore, the body main body 2 and the base 20,
21 is joined with the mating portions 52 and 53 by means of the fitting portions 52 and 53, so there is no need to use an alignment jig during welding.

Although this invention has been described in the case where it is applied to a differential pressure transmitter in which both sides constitute the pressure-receiving side of the fluid to be measured, the present invention is not limited to this, and the invention is not limited to this. It can also be applied to flange-type differential pressure gauges and pressure transmitters (gauge pressure, absolute pressure transmitters) in which other process pressure reference pressure is applied to the other pressure-receiving side. For this purpose, the liquid-contacting parts of the base that come into contact with the fluid to be measured (that is, the pressure-receiving side surface of the base and the liquid-contacting diaphragm) may be made of a corrosion-resistant material.

[Effect of idea]

As explained above, according to the differential pressure and pressure transmitter according to the present invention, the base made of a corrosion-resistant material can be electron beam welded to the pressure-receiving side of the main body with a simple structure, and the base can be welded to the pressure-receiving side of the body. Since the body and the main body are fitted with a ferrule, there is no need for alignment using a jig, and the diameter of the upper liquid diaphragm can be made equal to that of the pressure receiving diaphragm, so the pressure increase due to the temperature rise of the inner liquid can be reduced. Its practical effects are extremely large, as it absorbs water, reacts sensitively to changes in process fluid pressure, and can perform highly accurate flow rate measurements.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the present invention applied to a differential pressure transmitter, and FIGS. 2 and 3 are cross-sectional views of conventional differential pressure transmitters. 1...Differential pressure transmitter, 2...Body main body, 3a,
3b...Pressure receiving side, 4, 5...Pressure receiving diaphragm, 8...Center diaphragm, 14,15...
... Enclosed circuit, 16 ... Pressure sensor, 18 ... Sealing liquid, 20, 21 ... Base, 24, 25 ... Wetted diaphragm, 32 ... Sealing liquid, 33, 34 ...
Cover, 43... Welding, 50, 51... Fitting recess, 52, 53... Fitting part, 54, 55... Annular plane for welding, 56, 57... Taper part.

Claims (1)

[Scope of utility model registration request] A base whose liquid contact part is made of a corrosion-resistant material is welded and fixed to the pressure-receiving side surface of the measured fluid side of the body body in which an internal liquid is sealed, and the body is attached to the contact surface of the base with the body body. A fitting recess for fitting is provided on the outer circumferential surface of the main body, and a tapered portion having a smaller diameter on the side of the body is formed on the back side of the fitting recess on the outer circumferential surface of the base. A differential pressure/pressure transmitter, wherein a back surface of the recess forms a welding annular plane for welding the base to the body main body.