DE102005040238A1 - Device for determining and / or monitoring a process variable - Google Patents

Abstract

The invention relates to a device for determining and / or monitoring a process variable with a sensor (2) arranged in the process, which provides measurement data about the process variable, with an electronics housing (3) in which a control / evaluation unit (3a ) is included, and with a connecting part (17) with a tubular outer wall (27), which is arranged between the sensor (2) and the electronics housing (3), wherein in the connecting part (17) a bushing (7) for at least one between the sensor (2) and the electronics housing (3) arranged connecting line (12) is provided. According to the invention, it is proposed that an outlet opening (9) is provided in the outer wall (27) of the connecting part (17), that the bushing (7) is movably mounted in the connecting part (17) and is designed so that it covers the electronics housing (3 ) seals towards the process that the bushing (7) is arranged up to a predetermined critical process pressure in a first position in which it closes the outlet opening (9), and that when the predetermined critical process pressure is exceeded, the bushing (7) is in a second position is arranged, in which the outlet opening (9) is released, whereby the critical process pressure is reduced via the outlet opening (9).

Description

The The invention relates to a device for determination and / or monitoring a process variable with a sensor arranged in the process, which provides measurement data about the process variable, with an electronics housing, in which a control / evaluation unit is included, and with a connection part with a tubular Exterior wall, the is arranged between the sensor and the electronics housing, wherein in the connection part a passage for at least a connecting line arranged between the sensor and the electronics housing is provided.

Measuring devices, the used in process measurement and automation technology, are common sealed against the process with the sufficient quality. Depending on the application is it about it In addition, the meter is also necessary against a remote control point safe and reliable encapsulate. Particularly important is this sealing or encapsulation, when in the container an aggressive or explosive atmosphere is located. Penetrates e.g. a explosive gas mixture in the housing the transmitter of the meter a, so exists by the direct contact with the electrical or electronic components of the transmitter of the meter a acute danger of explosion. Furthermore, there is a risk that in If the meter is not encapsulated, it is explosive and aggressive or toxic gas mixture from the process via the connecting lines gets into the remote checkpoint and causes damage there.

Out a variety of publications has become known to counter this problem by that in the case penetrating medium is detected by means of different sensors and that subsequently suitable countermeasures - e.g. an immediate shutdown of the meter - seized become. About that In addition, the use of the so-called 'Dual Seal' - known solution become, with which a double fuse of the electronics space to the Control point is realized. The solution is necessarily pretty expensive and expensive. In addition, the meter must after a Error case be exchanged, since the detection of the error case automatically leads to a failure of the first security level, which in the case of dual-seal requirements, the desired security requirements not fulfilled anymore are. A shutdown or failure of the meter in a process with high security requirements inevitably stops the ongoing process and is therefore highly undesirable.

Of the Invention is based on the object, a device with a To propose a safety device which is based on an error occurring in the process reacted reversibly.

The Task is solved by that in the outer wall the connection part is provided an outlet opening that the implementation movably mounted in the connecting part and configured so that they are the electronics housing towards the process that seals up to a given performance critical process pressure is arranged in a first position, in which they have the outlet closes, and that when crossing the predetermined critical process pressure the implementation in a second position is arranged, in which the outlet opening released is, which degrades the critical process pressure through the outlet opening.

The 'traveling' implementation according to the invention works in a similar way a pressure relief valve and is with every meter or for each technical component used, in which a first Range, e.g. a sensor space or a connection space, from a second Range, e.g. the electronics room, the special protection needs, is to be separated. Normally, the implementation takes over the Task of process separation: it separates the first area, e.g. the process, from a second area, e.g. the electronic part of the transmitter a measuring device. Occurs the emergency or a critical overpressure in the first area on, that may be to burst the meter or the technical component or in the worst case would trigger an explosion, so will the overpressure already in the first area immediately and automatically dismantled. By yielding to the implementation and the consequent release of the outlet becomes a critical Process pressure derived directly from the meter or the technical component.

By the design of a wandering 'implementation can be a cost and component reduction reach as a component for different functions - process separation and security function - used becomes. In particular, can be with the inventive solution, the Requirements that result from Dual Seal in a simple way realize. Another advantage of the solution according to the invention is to be seen in that through the relatively large area of implementation, on the one possible overpressure acts, a response of the implementation of an increase in pressure already at a relatively low level pressure change possible is.

When Particularly advantageous is the embodiment of the device according to the invention considered in the implementation is stored in the connector so that they fall below the predetermined critical process pressure in the first position returned and the exit opening seals to the process. Due to the reversible designed Execution, there is no interruption of the ongoing process: as soon as the overpressure through the outlet has degraded, the implementation wanders back to normal again.

According to one preferred embodiment of the device according to the invention is in the Area between the execution and the electronics housing at least one spring element is arranged, whose spring force so It is measured that when crossing the predetermined critical process pressure is compressed in such a way that the outlet opening is released. about the spring force of the spring element can be due to the increased process pressure forced axial movement of the implementation in dependence from the bursting pressure of the meter or the technical component. In particular, it is at the at least one spring element to a plate spring to a Spiral spring or around a leaf spring. Alternatively, it can be too to act a bellows, which is preferably made of metal.

In an alternative embodiment of the device according to the invention is at least in an area between the bushing and the electronics housing a Scheerstift arranged, whose stability is dimensioned so that he when crossing of the predetermined critical process pressure breaks, thereby performing in the second position is moved and the exit opening releases. Thus, in this variant, an automatic return movement of the implementation in their starting position ensured is, should a reset element be provided.

According to one advantageous development of the device according to the invention is provided that the movable passage is stored pressure and / or gas-tight in the implementation. In this context can be on the appropriate and for movable parts are resorted to suitable seals. By the Gas and / or pressure-tight Abkapslung is especially in applications With high security requirements, that process medium ensures not with critical parts, e.g. with electronic parts, in contact comes. As possible sealing elements can O-rings and / or Membrane made of materials based on the prevailing process conditions are used.

When it is advantageous in connection with the present invention viewed when in the outlet a closure member arranged so placed in the outlet opening is that when crossing the predetermined critical pressure, the outlet opening is free. Normally is the exit opening secured and locked by the closure part. If an overpressure occurs in the process leading to a falling out or destroying the Closure element leads, so the error is over the operating personnel are directly visible. In addition, it is also possible that Fall out to detect the closure element electronically and report the error to a remote inspection body.

Farther is proposed in connection with the inventive solution that in the Connecting part is provided a switching element, which in approaching the execution to the second position or when reaching the second position Signal generated, which can be used as an error message. hereby will it be possible faults to recognize and record, which in turn makes it possible to Conclusions on to take the process and fix any detected errors. In which Switching element is, for example, a proximity switch or a button.

Around ensure that in a major incident where a critical Process pressure occurs, a rapid reduction of overpressure occurs, are in the connecting part a plurality of outlet openings provided in Direction of movement of execution Seen in a row. With little effort can be so that in case of a large leak or a high Process pressure also a correspondingly rapid pressure reduction due the multiple blow-off amount is achieved.

The The invention will be explained in more detail with reference to the following figures. It shows:

1 : a schematic representation of an ultrasonic flowmeter with flow sensor and electronic part,

2 : a longitudinal section through the in 1 shown flow meter, in which a first embodiment of the implementation of the invention is used,

3 : a longitudinal section through the in 1 shown flow meter, in which a second embodiment of the implementation of the invention is used,

4 : a longitudinal section through the in 1 shown flow meter, in which a third embodiment of the invention Implementation is used,

4a : the section X out 4 in an enlarged view,

5 A fourth embodiment of the device according to the invention

5a : the section Y out 5 in an enlarged view,

6 : a fifth embodiment of the device according to the invention,

6a : the cut Z out 6 in an enlarged view,

7 a sixth embodiment of the device according to the invention,

7a : a perspective view of the in 7 shown embodiment, when installed in the connecting part,

7b : a top view of the in 7a shown embodiment,

7c : a side view of the in 7a shown embodiment,

7d : a longitudinal section according to the marking AA in 7b and

7e : the section X out 7d in an enlarged view.

1 shows a schematic representation of an ultrasonic flowmeter with flow sensor 2 and transmitters 3 in which the inventive 'wandering' implementation 7 is preferably used. As already mentioned, the device according to the invention can be used in any device used in measurement and process automation technology. It is also applicable to any other engineering component where critical pressures can negatively impact functionality.

For the sake of simplicity, following in the 1 illustrated ultrasonic flowmeter 1 received. Ultrasonic flowmeters are widely used in process measurement and automation technology to detect the volume or mass flow of a medium through a pipeline 25 used. The medium may be a gaseous, vaporous or liquid medium.

In terms of mounting options, there are two types of ultrasonic flowmeters: in-line ultrasonic flowmeters, which are typically mounted to the piping via flanges, and clamp-on flowmeters, which are externally mounted on the piping to control volume and flow rates . Mass flow through the pipe wall - so non-invasive measure. Clamp-on flowmeters are for example in the EP 0 686 255 B1 , U.S. Patent 4,484,478, DE 43 35 369 C1 . DE 298 03 911 U1 . DE 4336370 C1 or U.S. Patent 4,598,593.

With regard to the measuring methods, two principles can be distinguished: Flowmeters 1 , which determine the flow over the transit time difference of ultrasonic measuring signals in the flow direction S and counter to the flow direction S (in 1 shown), and flowmeters that obtain the flow information from the Doppler shift of the ultrasonic measurement signals. In the case of ultrasonic measuring devices, which operate according to the transit time difference method, the ultrasonic measuring signals at a predetermined angle via a coupling element in the pipeline 25 , in which the medium flows, irradiated or out of the pipeline 25 broadcast. Here are the ultrasonic sensors 4 Usually arranged so that the traversed sound paths through the central region of the pipeline 25 or the measuring tube are guided. The determined flow value thus reflects the average flow of the medium in the pipeline 25 ,

This in 1 illustrated ultrasonic flowmeter 1 is composed of the flow sensor 2 and the transmitter 3 , in which among others the control / evaluation unit 3a is arranged. The sensor connection space 6 and the electronics connection room 5 are about a connecting part 17 connected with each other. In the outer wall 27 of the connecting part 17 are two outlet openings 9 brought in. The inventive 'wandering' implementation 7 is in the connection part 17 arranged.

2 shows a longitudinal section through the in 1 shown flow meter 1 in which a first embodiment of the implementation according to the invention 7 is used. Shown is the so-called first position, which in the normal case of the implementation 7 is taken, so if no pressure in the sensor connection space 6 prevails. In the 2 illustrated implementation 7 works reversibly, so it is characterized by the fact that it automatically returns to the 'default' moderately set first starting position after the occurrence of an overpressure case.

The implementation 7 serves the gas- and / or pressure-tight implementation of the connection cable 12 , the corresponding electrically driven components of the sensor 2 , here the ultrasonic sensors 4 , connects to the electrical or electronic components in the electronics housing 3 or are housed in the transmitter. The implementation 7 with the two at the periphery of the implementation 7 provided O-rings 12 accomplishes the process separation - and thus the strict encapsulation - of sensor 2 and transmitters 3 , Process isolation typically prevents the medium from potentially transmitting very negative, harmful properties into the transmitter 3 penetrates and causes damage there. Alternatively or in combination may also be another implementation 7a between the electronics housing 3 and the control body 20 be provided. This implementation 7a is in the 2 not shown separately.

The implementation 7 is between the two attacks 18a . 18b of the connecting part 17 stored. In the normal case, if so no critical process pressure in the sensor connection space 6 there is the execution 7 in the first position shown, where it is firmly attached to the stop 18a is applied. Approaches the process pressure a predetermined critical process pressure - which by the spring force of the spring element 10 is defined - so is the spring element 10 squeezed and carrying 7 migrates axially against the spring force upwards. Once the critical process pressure has been achieved, it has to be carried out 7 the exit opening 9 happens, the closure element 21 gets out of the outlet 9 pushed out and the overpressure can be over the outlet opening 9 dismantle. A destruction of the meter 1 due to bursting or penetration of the process medium into the transmitter 3 is thereby effectively avoided.

The removal or destruction of the closure element 21 Signaled in a known manner visually or electronically the error case. Once the overpressure has dissipated, the execution returns 7 under the action of the spring force of the spring element 10 back to the first position shown.

In 3 is a longitudinal section through the in 1 shown flow meter 1 to see in which a second embodiment of the implementation of the invention 7 is used. The main difference to the in 2 shown embodiment is that in 3 embodiment shown is not reversible configured: When a critical process pressure occurs break the two Scheer pins 11 , thereby carrying out 7 moved axially upwards and the outlet opening 9 is released. Now, the critical process pressure across the outlet opening 9 dismantle. Whether this or a reversible variant of the implementation 7 is used depends on the respective safety concept of the measuring point.

In 4 is a longitudinal section through the in 1 shown flow meter 1 illustrated in which a third embodiment of the implementation of the invention 7 is used. 4a shows the section X from 4 in an enlarged view. At the in 4 embodiment shown seals an O-rings 8th axially, while the second O-ring 8th as in the aforementioned embodiments radially tight. Furthermore, at the in 4 illustrated embodiment, two outlet openings 9 provided, which are substantially diametrically opposed to each other, whereby the reduction of an overpressure in the sensor connection space 6 time can be accelerated. Moves the implementation 7 out of its normal position, the switching element 13 pressed and the overpressure case is displayed or as an error message to the control point 26 eg output via a fieldbus.

• – die Verwendung eines Faltenbalgs 14 als Federelement 10, wobei der Faltenbalg 14 den Sensor-Anschlussraum 6 und den Elektronik-Anschlussraum 5 metallisch voneinander trennt;
• – die Verwendung von nur einem axial dichtenden O-Ring 8, was aufgrund der Doppelfunktion des Faltenbalgs 14 als Federelement 10 und als Dichtelement 8 möglich ist;
• – eine Öffnung 15 im Bereich des Verbindungsteils 17, in dem der Faltenbalg 14 angeordnet ist.

5 shows a fourth embodiment of the implementation of the invention 7 ; in 5a is the section Y off 5 to see in an enlarged view. Significant differences from the embodiments described above are:

• - the use of a bellows 14 as a spring element 10 , where the bellows 14 the sensor connection space 6 and the electronics connection room 5 separated from each other metallically;
• - The use of only one axially sealing O-ring 8th , which is due to the double function of the bellows 14 as a spring element 10 and as a sealing element 8th is possible;
• - an opening 15 in the area of the connecting part 17 in which the bellows 14 is arranged.

Remains to mention that the use of a metallic bellows 14 in its function as a spring element 10 and seal 8th is extremely favorable, since it allows a pressure increase to be detected very precisely.

6 shows a fifth embodiment of the device according to the invention; in 6a is the cut Z out 6 to see in an enlarged view. The essential difference to those in the figures 2 or 5 described embodiments can be seen in that as a sealing element 8th and as a spring element to the electronics connection space 5 towards a membrane 16 is used.

In the figures 7 . 7a . 7b . 7c . 7d . 7e a sixth embodiment of the device according to the invention is shown in different views. This is a preassembled and / or verifiable execution 7 that works reversibly: after the Reduction of the overpressure according to one of the methods described above reverses the implementation 7 returns to the starting position, in which she perceives a pure sealing function.

The hiking implementation 7 or the piston has three spring elements 10 on who's performing 7 in the connection part 17 position. The connecting part 17 can on the sensor 2 For example, be welded, or it is an integral part of the sensor 2 ,

The implementation 7 has a Überströmandrehung 24 on which a build-up pressure can be reduced very effectively. This allows the stroke, the implementation 7 due to overpressure until the discharge opening is released 9 minimize. By the overflow rotation 24 can thus reduce the installation space for the implementation.

A seal 8th is on the process-facing planar surface of the bushing 7 arranged. At the seal 8th it is an O-ring, which takes over the sealing function towards the process and axially, ie in the direction of movement of the implementation 7 , poetry. This achieves a better sealing function and a smaller hysteresis. In particular, the aging process of the O-ring has 8th in this arrangement of the O-ring 8th no influence on the pressure with which the passage is moved in the case of a critical overpressure to the second position, in which the outlet opening 9 is released.

Between the execution 7 and the hold-down 18 are spacers 23 provided, which the leadership of the spring elements 10 take. At the same time can be over the length of the spacers 23 the set pressure of the spring elements 10 which has the advantage that the set pressure can be set and checked before final assembly. This makes it possible to carry out 7 with connection part 17 pre-assemble by the fully assembled bushing 7 subsequently from above into the connecting part 17 is inserted.

The connecting screws are preferably used 19 between execution 7 and hold downs 18 Standard screws or standard shoulder screws, where the set pressure can be set to the desired defined value via the length of engagement or over the length of the shoulder. In particular, it is provided that the screws 19 , via which the critical pressure can be set in a defined manner, after the calibration of the response pressure with screw locking lacquer or with other commercially available products. It is further provided that the response pressure and thus the bias of the spring elements 10 is determined by the depth of the mounting hole. This achieves a partial reduction.

Between the execution 7 and the hold-down 18 is a switching element 13 provided, which outputs a signal or an error message when the distance between the implementation 7 and the hold-down 18 changed. This is, as already mentioned several times, at a critical pressure increase in the sensor connection space 6 the case.

Without further ado, in this embodiment, the number of outlet openings 9 vary, whereby the blow-off can be optimally adapted to the particular application. In particular, the positions of the outlet openings 9 to find axially in different heights. As a result, the increase in the amount of leakage with the traveled stroke of implementation 7 correlated.

1

gauge

2

sensor

3

electronics part or transmitter

4

ultrasound transducer

5

Electronics terminal compartment

6

Sensor terminal compartment

7

execution

8th

sealing element

9

outlet opening

10

spring element

11

Scheer pen

12

connection cable

13

switching element

14

bellows

15

opening

16

membrane

17

connecting part

18

Stripper plate

18a

attack

18b

attack

19

screw

20

potting compound

21

closing part

22

circlip

23

Stand Off

24

Overcurrent Andre Hung

25

pipeline

26

control Authority

27

outer wall

Claims (9)

Device for determining and / or monitoring a process variable with a sensor arranged in the process ( 2 ), which provides measurement data about the process variable, with an Elek electronics housing ( 3 ), in which a control / evaluation unit ( 3a ), and with a connection part ( 17 ) with a tubular outer wall ( 27 ) between the sensor ( 2 ) and the electronics housing ( 3 ) is arranged, wherein in the connecting part ( 17 ) an implementation ( 7 ) for at least one between the sensor ( 2 ) and the electronics housing ( 3 ) connecting line ( 12 ) Is provided, characterized in that (in the outer wall 27 ) of the connecting part ( 17 ) an outlet opening ( 9 ), that the implementation ( 7 ) movable in the connecting part ( 17 ) and is configured so that the electronics housing ( 3 ) on the process that the implementation ( 7 ) is arranged up to a predetermined critical process pressure in a first position, in which the outlet opening ( 9 ) and that when the predetermined critical process pressure is exceeded, the execution ( 7 ) is arranged in a second position, in which the outlet opening ( 9 ), whereby the critical process pressure via the outlet opening ( 9 ) degrades. Apparatus according to claim 1, characterized in that the implementation ( 7 ) so in the connection part ( 17 ) is stored, that it moves back below the predetermined critical process pressure in the first position and the outlet opening ( 9 ) seals to the process. Device according to claim 1 or 2, characterized in that in a region between the bushing ( 7 ) and the electronics housing ( 3 ) at least one spring element ( 10 ) is arranged, whose spring force is dimensioned such that it is compressed when the predetermined critical process pressure is exceeded such that the outlet opening ( 9 ) is released. Apparatus according to claim 3, characterized in that it is in the at least one spring element ( 10 ) is a diaphragm spring, a coil spring or a leaf spring. Device according to claim 1, characterized in that in an area between the bushing ( 7 ) and the electronics housing ( 3 ) at least one scissors pin ( 11 ) whose stability is such that it breaks when the predetermined critical process pressure is exceeded, whereby the execution ( 7 ) is moved to the second position and the outlet opening ( 9 ) releases. Apparatus according to claim 1, 3 or 5, characterized in that the movable passage ( 7 ) pressure and / or gas-tight in the connecting part ( 17 ) is stored. Apparatus according to claim 1, 2 or 3, characterized in that in the outlet opening ( 9 ) a closure part ( 21 ) arranged in such a way in the outlet opening ( 9 ) is placed, that when the predetermined critical pressure is exceeded, the outlet opening ( 9 ) are free. Apparatus according to claim 1, characterized in that in the connecting part ( 17 ) a switching element ( 13 ) is provided, which at the approximation of the implementation ( 7 ) Generates a signal to the second position or upon reaching the second position, which is usable as an error message. Apparatus according to claim 1, characterized in that a plurality of outlet openings ( 9 ) are provided, which are parallel to the direction of movement of the implementation ( 7 ) in the outer wall ( 27 ) of the connecting part ( 17 ) are arranged.