DE3436184C1

DE3436184C1 - Pressure relief device for pressure measuring systems

Info

Publication number: DE3436184C1
Application number: DE19843436184
Authority: DE
Inventors: Walter 2872 Hude Labohm
Original assignee: LABOM MESS und REGELTECHNIK GM
Current assignee: LABOM MESS und REGELTECHNIK GM
Priority date: 1984-10-03
Filing date: 1984-10-03
Publication date: 1985-12-12

Abstract

The invention relates to a pressure relief device for pressure measuring systems, in which the measuring pressure is transferred via a working diaphragm (5) to a pressure medium fluid (8). For the purpose of pressure relief, a pressure relief diaphragm (6) is provided, one side of which is in connection with a gas cushion (9) and is supported there against on a diaphragm bed (12), and the other side of which is in connection with the pressure medium fluid (8). <IMAGE>

Description

Der Druck des Gaspolsters wird zweckmäßigerweise geringfügig über den maximal vorgesehenen Meßdruck angesetzt, damit Volumendehnungen durch Temperaturschwankungen nicht zu einer zu frühzeitigen Begren- zung führen. Die erfindungsgemäße Lösung hat den Vorteil, daß unterhalb des eingestellten Druckes des Gaspolsters keinerlei Verfälschungen des in die Druckmittlerflüssigkeit übertragenen Meßdruckes erfolgen, daß aber oberhalb des eingestellten Gasdruckes die Druckmittlerflüssigkeit in das Volumen des Gaspolsters ausweichen kann und somit auch überlastungsempfindliche Drucksensoren keinen Schaden nehmen können.The pressure of the gas cushion is expediently slightly above the maximum intended measuring pressure is set, so that volume expansions due to temperature fluctuations not to an early limit lead. The inventive Solution has the advantage that below the set pressure of the gas cushion no falsifications of the measuring pressure transmitted into the pressure transmitter fluid take place, but above the set gas pressure the diaphragm seal liquid can escape into the volume of the gas cushion and thus also sensitive to overload Pressure sensors cannot be damaged.

Vorteilhafte Ausgestaltungen der Erfindung sind den Unteransprüchen zu entnehmen. Advantageous refinements of the invention are set out in the subclaims refer to.

Die Erfindung wird nachfolgend anhand zweier Ausführungsbeispiele mit Bezug auf die Zeichnungen näher erläutert. The invention is explained below using two exemplary embodiments explained in more detail with reference to the drawings.

Es zeigt F i g. 1 einen Längsschnitt durch einen mit einer Überdrucksicherung versehenen Druckmittler in einem gemeinsamen Gehäuse gemäß der Erfindung in normaler Arbeitsstellung, F i g. 2 eine Darstellung der Anordnung nach F i g. 1 bei Überdruck, und F i g. 3 eine Schnittzeichnung einer anderen Ausführungsform gemäß der Erfindung, bei der die Überdruck sicherung getrennt angeordnet ist Das in den F i g. 1 und 2 in zwei verschiedenen Arbeitsstellungen dargestellte Druckmeßsystem mit integrierter Überdrucksicherung besteht aus einem Grundkörper 1, auf dem beidseitig je ein Abschlußdeckel 2 bzw. 3 dicht abschließend befestigt ist Der Grundkörper 1 weist auf beiden Seiten je ein Membranbett 11 bzw. 12 auf, die durch einen Verbindungskanal 13 miteinander verbunden sind. Über jedem Membranbett ist je eine Arbeitsmembran 5 bzw. Überdruckmembran 6 angeordnet, deren Form mit der Oberfläche des zugehörigen Membranbettes übereinstimmt, um eine wirkungsvolle Abstützung zu erreichen. Mit dem Verbindungskanal 13 ist ein quer liegender Verbindungskanal 14 verbunden, der einerseits zu einer Öffnung 15 führt, in der ein Drucksensor 4 eingesetzt ist, und andererseits mit einer Einfüllöffnung 16 verbunden ist, die nach Einfüllen einer Druckmittlerflüssigkeit 8 verschlossen wird. It shows F i g. 1 shows a longitudinal section through one with an overpressure protection device provided diaphragm seal in a common housing according to the invention in normal Working position, F i g. 2 shows a representation of the arrangement according to FIG. 1 at overpressure, and F i g. 3 shows a sectional drawing of another embodiment according to the invention, in which the overpressure protection is arranged separately. 1 and 2 shown in two different working positions pressure measuring system with integrated Overpressure protection consists of a base body 1 on which a cover plate on each side 2 or 3 is fastened tightly. The base body 1 points on both sides each have a membrane bed 11 and 12, which are connected to one another by a connecting channel 13 are connected. A working diaphragm 5 or overpressure diaphragm is located above each diaphragm bed 6 arranged, the shape of which corresponds to the surface of the associated membrane bed, to achieve effective support. With the connecting channel 13 is a transversely lying connecting channel 14, which on the one hand leads to an opening 15 leads, in which a pressure sensor 4 is inserted, and on the other hand with a filler opening 16 is connected, which is closed after filling a pressure transmitter fluid 8 will.

Der (in der Zeichnung) untere Abschlußdeckel 2 trägt einen Druckanschluß 21, dem die Meßflüssigkeit 7 zugeführt wird, deren Druck gemessen werden solL Oberhalb der Überdruckmembran 6 befindet sich ein Gaspolster 9, das durch Einfüllen eines Gases mit bestimmtem Druck durch eine Einfüllöffnung 17 erzeugt wird; die Einfüllöffnung 17 wird anschließend verschlossen. The (in the drawing) lower cover 2 carries a pressure connection 21, to which the measuring liquid 7 is fed, the pressure of which is to be measured above the overpressure membrane 6 is a gas cushion 9, which by filling a Gas is generated at a certain pressure through a filler opening 17; the filling opening 17 is then closed.

Nachfolgend soll die Funktion der erfindungsgemäßen Überdrucksicherung in Verbindung mit den F i g. 1 und 2 beschrieben werden. The function of the overpressure safety device according to the invention is described below in connection with the F i g. 1 and 2 are described.

Die vom Druckanschluß 21 kommende Meßflüssigkeit 7 trifft auf die untere Seite der Arbeitsmembran 5, die sich entsprechend durchbiegt und den gleichen Druck auf die Druckmittlerflüssigkeit 8 überträgt, deren Druck wiederum von dem Drucksensor 4 gemessen wird. Die Überdruckmembran 6 wird hingegen durch den Druck des Gaspolsters 9 belastet und liegt an dem Mebranbett 12 an, solange der Druck der Meßflüssigkeit 7 und damit der Druckmittlerflüssigkeit 8 den Druck des Gaspolsters 9 nicht überschreitet Der Gasdruck des Gaspolsters 9 ist zweckmäßigerweise auf etwa 10% oberhalb des maximalen Meßbereiches des Druckmeßsystems eingestellt, um einerseits innerhalb des Meßbereiches keine Druckverfälschungen zu bewirken und andererseits eine gewisse Sicherheit gegen Volumenänderungen aufgrund von Temperaturschwankungen zu gewährleisten. The measuring liquid 7 coming from the pressure connection 21 meets the lower side of the working diaphragm 5, which bends accordingly and the same Pressure on the pressure transmitter fluid 8 transmits, the pressure in turn of the Pressure sensor 4 is measured. The overpressure membrane 6, however, is due to the pressure of the gas cushion 9 is loaded and rests on the membrane bed 12 as long as the pressure the measuring fluid 7 and thus the pressure transmitter fluid 8 the pressure of the gas cushion 9 does not exceed the gas pressure of the gas cushion 9 is expediently at about 10% above the maximum measuring range of the pressure measuring system, on the one hand not to cause any pressure falsifications within the measuring range and on the other hand some security against volume changes due to temperature fluctuations to ensure.

Überschreitet der Druck in der Meßflüssigkeit 7 jedoch den Druck des Gaspolsters 9, so hebt sich die Überdruckmembran 6 von dem Membranbett 12 ab und weicht nach oben aus. Hierdurch wird bewirkt, daß der Drucksensor 4 keinen höheren Druckbelastungen ausgesetzt wird. Steigt der Druck in der Meßflüssigkeit 7 weiter an, so stützt sich die Arbeitsmembran 5 irgendwann auf dem Membranbett 11 ab. However, if the pressure in the measuring liquid 7 exceeds the pressure of the gas cushion 9, the overpressure membrane 6 is lifted from the membrane bed 12 and dodges upwards. This has the effect that the pressure sensor 4 is no higher Is exposed to pressure loads. If the pressure in the measuring liquid 7 continues to rise on, the working diaphragm 5 will at some point be supported on the diaphragm bed 11.

Während die Überdrucksicherung nach den F i g. 1 und 2 integral mit dem Druckmeßsystem kombiniert ist, zeigt F i g. 3 eine Anordnung, bei der der Druckmittler und die Überdrucksicherung in getrennten Gehäusen angeordnet und durch eine Rohrleitung miteinander verbunden sind. Der Druckmittler besteht wiederum aus einem Grundkörper 10 mit einem Membranbett 11 für eine Arbeitsmembran 5 und einem Abschlußdeckel 20. Einem Druckanschluß 21 wird die Meßflüssigkeit 7 zugeleitet. Die auf der anderen Seite der Arbeitsmembran 5 stehende Druckmittlerflüssigkeit 8 gelangt zu einem Druckmesser 40, der eine C-förmige Meßfeder 41 aufweist Solche Druckmesser sind allgemein bekannt. While the overpressure protection according to FIGS. 1 and 2 integral with is combined with the pressure measuring system, FIG. 3 an arrangement in which the diaphragm seal and the overpressure protection arranged in separate housings and through a pipeline are connected to each other. The diaphragm seal in turn consists of a base body 10 with a membrane bed 11 for a working membrane 5 and a cover 20. The measuring liquid 7 is fed to a pressure connection 21. The one on the other Side of the working diaphragm 5 standing pressure transmitter fluid 8 reaches a pressure gauge 40, which has a C-shaped measuring spring 41 Such pressure gauges are generally known.

Diese Kombination aus Druckmittler und Druckmesser ist über eine Rohrleitung 33 mit einer entfernt angeordneten Überdrucksicherung 30 verbunden. Diese Überdrucksicherung besteht wiederum aus einem mit einem Membranbett 12 versehenen Grundkörper 31, auf dem ein Abschlußdeckel 32 befestigt ist Eine Überdruckmembran 6 trennt die von der Verbindungsleitung 33 kommende Druckmittlerflüssigkeit 8 von dem Gaspolster 9. An dem Druckmesser 40 ist noch eine verschließbare Einfüllöffnung 42 für die Druckmittlerflüssigkeit 8 und in dem Abschlußdeckel 32 eine Einfüllöffnung 34 für das Gas des Gaspolsters vorgesehen. This combination of diaphragm seal and pressure gauge is via a Pipeline 33 is connected to a remotely arranged overpressure protection 30. This overpressure protection in turn consists of a membrane bed 12 provided Base body 31 on which a cover 32 is attached. An overpressure membrane 6 separates the pressure transmitter fluid 8 coming from the connecting line 33 from the gas cushion 9. There is also a closable filling opening on the pressure gauge 40 42 for the pressure transmitter fluid 8 and in the cover 32 a filling opening 34 is provided for the gas in the gas cushion.

Die Vorrichtung nach F i g. 3 arbeitet in der gleichen Weise wie die Vorrichtungnach den F i g. 1 und 2; sie hat den VorteiL daß konventionelle Druckmeßsysteme nachträglich mit einer über die Rohrleitung 33 angeschlossenen Überdrucksicherung 30 versehen werden können. The device according to FIG. 3 works in the same way as the device of Figs. 1 and 2; it has the advantage that conventional pressure measuring systems subsequently with an overpressure safety device connected via the pipeline 33 30 can be provided.

Statt der in den Fig. 1, 2 und 3 gezeigten Arbeitsmembran 5 bzw Überdruckmembran 6 können auch andere Trennfolien wie zum Beispiel Balgmembranen, Kapselfedern oder Membranbalglieder eingesetzt werden. Als Druckmittlerflüssigkeit wird zweckmäßigerweise Silikonöl verwendet - Leerseite - Instead of the working diaphragm 5 or overpressure diaphragm shown in FIGS. 1, 2 and 3 6 other separating films such as bellows diaphragms, capsule springs or Membrane bellows are used. As a pressure transmitter fluid, it is expedient to use Uses silicone oil - blank page -

Claims

Claims 1. Overpressure protection for pressure measuring systems with a Working diaphragm, one side of which is connected to a pressure measuring connection and when a certain limit pressure is exceeded against the measuring pressure supported by a membrane bed and the other side via a diaphragm seal fluid is in communication with a pressure gauge, characterized by an overpressure membrane (6), one side of which is connected to a gas cushion (9) and is against it supported on a membrane bed (12), and the other side with the pressure transmitter fluid (8) is connected to 2 overpressure protection according to claim 1, characterized that the pressure of the gas cushion (9) measured slightly above the maximum provided pressure is 3. Overpressure protection according to claim 1 or 2, characterized in that that diaphragm seal (5, 11) and overpressure protection (6, 12, 9) in one common Housing are arranged 4. Overpressure protection according to claim 3, characterized in that. that a pressure sensor (4) is arranged in the same housing (1, 2, 3) 5. Overpressure protection according to claim 3 or 4, characterized by a base body (1) with one another opposite sides of the membrane beds (11, 12), which are connected by connecting channels (13) are connected to each other 6. Overpressure protection according to claim 5, characterized by two essentially identically designed cover plates (2, 3) on both Sides of the base body (1).

7. Overpressure protection according to claim 1 or 2 d a d u r c h g e k It is noted that the pressure transmitter (5, 11) and overpressure protection (in separate Arranged housings and through a pipeline leading to the pressure transmitter fluid (8) (33) are connected to each other 8. Overpressure protection according to claim 7, characterized in that that the diaphragm seal (5.11; 10.20) and pressure gauge (40) form a unit.

The invention relates to an overpressure protection device for pressure measuring systems with a working diaphragm, one side of which is connected to a pressure measuring connection stands and when a certain limit pressure is exceeded against the measuring pressure supported on a membrane bed. and the other side via a diaphragm seal fluid with a pressure gauge m is connected. In such pressure measuring systems, the The pressure to be measured is not fed directly to a pressure gauge or pressure sensor, but rather this is done by means of a pressure transmitter that transfers the measuring pressure to a pressure transmitter fluid Separating membrane, on the one hand, to remove the possibly aggressive measuring liquid from the Keep pressure gauges or pressure sensors away and, on the other hand, take precautions against overload of the pressure gauge or pressure sensor, but also these intermediate ones The membrane must be protected against pressure overloads that are significantly above the measuring range Such an overload protection is z. B. from US-PS 38 08 890 and DE-OS 1947533 known and is carried out by a membrane supporting the measuring pressure Membrane bed that is adapted to the shape of the membrane as soon as a certain pressure is exceeded becomes, the membrane rests against the shape of the membrane bed and cannot move bend more further.

A pressure limit is only achieved here when the volume completely recorded under the working diaphragm by the connected pressure gauge and the membrane is supported on the membrane bed The working volume of the pressure gauge must therefore be matched to the amount of diaphragm seal fluid to be absorbed. An adjustment of the volume that the pressure gauge has to accommodate is carried out at the Arrangement according to DE-OS 1947 533 through a volume under the working diaphragm Changing, adjustable pistons are, however, pressure transducers or pressure gauges used that have only a very small volume of work, such as B. piezo-resistive Systems, no matter how small a volume of the diaphragm seal fluid that has to be absorbed, leads to it under the working diaphragm to overload the pressure gauge before a system on the membrane bed takes place From FR-PS 761 812 it is also known in diaphragm seal systems to use a gas cushion for the transmission of a measuring mechanism.

Finally, from DE-AS 12 33 644 en temperature control system known that an expansion tank (heat sensor), a working cylinder for actuation a valve or the like and a safety device with a gas cushion to avoid it of overloads also has a device for adjusting the Setpoint temperature provided with an adjustable bellows that understands the liquid volume is working. As with this device it depends, depending on the measured Adjusting the temperature of the piston of a working cylinder, this can and must with a pressure gauge comparable working cylinder a relatively large volume record in order to lead to a corresponding work movement before overloading entry.

So in a pressure measuring system of the generic type, a pressure gauge is intended are used, which has a working volume of practically zero, so the previously known measures fail.

The setting of the volume of the pressure transmitter fluid in such a way that that although the full measuring range is transmitted unadulterated above this measuring range however, the limit values for the pressure sensors with a small working volume are not exceeded is very critical and comes in handy at larger working temperature ranges not possible.

The invention is based on the task of an overpressure protection for To propose pressure measuring systems with an effective limitation against overpressure takes place without setting the limit pressure above the end of the measuring range is critical This object is achieved according to the invention by an overpressure membrane, one side of which is connected to a gas cushion and is against it a membrane bed is supported, and the other side with the diaphragm seal fluid communicates.