EP2476955A2 - Valve combination with improved test routine - Google Patents

Abstract

A line section with a pressure monitoring device is provided between the valves (15,16), and a control device is attached to the pressure monitoring device. The valves are opened or closed depending on the opening signal and closing signal, to open or close the gas path from the gas source. The leak testing of two valves is performed in time successively, by monitoring the pressure in the line section. The sealing examination of valve is performed upon receipt of the inhibit signal in two different shutdown sequences, by delayed closing of the valves. Independent claims are included for the following: (1) gas valve combination; and (2) control device of gas valve combination.

Description

The invention relates to a method for leak testing a gas valve combination, a corresponding gas valve combination and the control device.

For the control of fluids, in particular gases, valve devices are used for safety reasons, in which two valve closure members are arranged in the gas flow, which can interrupt the gas flow in each case. To check the tightness of the two valve closure members, the pressure in the space enclosed between the two valves can be monitored.

This reveals the US 3,344,807 a double seat gas valve with a differential pressure sensor. The valve is a double-seat valve with two valve plates and a fixed, the first valve plate and a spring-mounted, the second valve plate associated seat. The intermediate space between the valve plates is divided by a bellows. The first subspace is closed by the first valve plate, while the second subspace is closed by the second valve plate. The differential pressure sensor detects pressure differences between the two subspaces and uses them to deliver an alarm signal.

From the DE 42 11 681 C2 a method for controlling valves of a gas turbine plant is known, which includes checking the valves for leaks. The enclosed space between the valves is monitored for pressure changes. A dedicated pressure detector switch is connected to a control unit which also controls the valves. For pressure testing, the downstream valves are closed and the upstream valves are opened and closed again for a short time. From the self-adjusting pressure curve in the valve gap is closed on valve leakage.

From the DE 196 30 875 A1 For example, a valve unit having two valves is known wherein a pressure sensor monitors the space trapped between the valves. This pressure sensor is connected to a leak test unit. When Brennerinbetriebnahme first the presence of fuel is tested. If the pressure sensor reports a signal, the commissioning program will continue. If it does not signal, the input side valve is briefly opened to direct the fuel pressure to the sensor. If the pressure sensor still does not signal, the inlet valve is closed and waiting time is waited.

From the DE 198 31 067 C2 a method for leak testing of gas valves is known. It is based on a pressure switch arranged between two valves. When starting or stopping the burner, the gas valves are checked individually. When the burner is switched on (heat request), the upstream valve is first briefly opened and closed again, the downstream gas valve remaining closed. The pressure rise between the valves is monitored by the pressure switch. Provided after a predetermined time such a pressure drop arises that the pressure switch opens again, the downstream gas valve is leaking. However, if such a pressure drop does not occur, the downstream (burner side) gas valve is considered to be tight. The inspection of the upstream valve takes place after elimination of a heat request. It is first closed the upstream valve and then the downstream. The gas pressure in the space enclosed between the two valves is thus small. The pressure switch is thereby open. If the upstream valve is not tight, the pressure gradually increases, eventually closing the pressure switch. If it does not close, the upstream valve is tight.

In this method, relatively large pressure changes are required to distinguish between leaks and leaks, resulting in large test times.

In addition, the pressure test of the burner-side valve upon heat request and the examination of the upstream, i. Source-side valve when switching off, lead to systematic errors, because the conditions when switching on a burner and switching off a burner are fundamentally different.

Basically, the goal of the development is to minimize the number of valve plays. However, the integration of the check routine in the normal valve operating cycle, as in the DE 198 31 667 C2 , lead to falsifications.

In order to make the leak test more sensitive to small leaks, the DE 102 47 167 A1 before, the time course of the pressure in between the To monitor valves enclosed space to calculate from various pressure readings a trend by which the tightness and the leak can be estimated. However, performing such check routines does not minimize the number of required valve latches.

It is an object of the invention to provide a concept with which a quick valve test can be achieved with a long valve life.

• Erfindungsgemäß wird die Dichtheitsprüfungsroutine in den normalen Regelzyklus einer Ventilsteuereinrichtung integriert. Dabei wird beim Abschalten des Gasstroms, vorzugsweise bei jedem Abschalten, die Hälfte eines vollständigen Ventilprüfungszyklus im Rahmen einer Abschaltroutine durchgeführt. Die Ventileinrichtung umfasst mindestens zwei Ventile, zu denen ein erstes und ein zweites Ventil gehören. Die Ventile sind in einer Gasleitung hintereinander, d.h. in Serie, angeordnet. Bei einer Abschaltsequenz ersten Typs wird zunächst das erste und dann das zweite Ventil geschlossen. Bei einer Abschaltsequenz zweiten Typs wird zuerst das zweite und dann das erste Ventil geschlossen. Die Steuereinrichtung wählt nun bei jedem beispielsweise von einem Temperaturregler oder einer sonstigen Regeleinrichtung geforderten Abschalten, d.h. bei Empfang eines Schließsignals eine der beiden alternativen Abschaltsequenzen, d.h. eine Abschaltsequenz ersten Typs oder einer Abschaltsequenz zweiten Typs. Vorzugsweise wechselt die Steuereinrichtung dabei jeweils zwischen einer Abschaltsequenz ersten Typs und einer Abschaltsequenz zweiten Typs ab. In dem darauffolgenden Schließzeitraum wird dann der Druck in dem zwischen den Ventilen liegenden Volumen ein- oder mehrfach oder ständig überprüft und daraus auf Dichtheit oder Leckage geschlossen. Zur Durchführung dieser Prüfung stehen meist ausreichend lange Zeitspannen zur Verfügung.

This object is achieved with the measures according to claim 1, 7 or 13:

• According to the invention, the leakage test routine is integrated into the normal control cycle of a valve control device. In this case, when switching off the gas flow, preferably at each shutdown, half of a complete valve test cycle is performed as part of a shutdown routine. The valve device comprises at least two valves, which include a first and a second valve. The valves are arranged in a gas line one behind the other, ie in series. In a shutdown sequence of the first type, first the first and then the second valve is closed. In a shutdown sequence of the second type, first the second and then the first valve is closed. The control device now selects one of the two alternative shutdown sequences, ie a shutdown sequence of the first type or of a shutdown sequence of the second type, for each shutdown demanded, for example, by a temperature controller or other control device, ie upon receipt of a closing signal. In this case, the control device preferably alternates between a shutdown sequence of the first type and a shutdown sequence second type. In the subsequent closing period, the pressure in the volume lying between the valves is then checked one or more times or constantly, and from this conclusions are drawn about leakage or leakage. To carry out this test are usually sufficiently long periods of time available.

The time interval between the closing of the first and the second valve is as short as possible in the shutdown sequence of both types. The period of time may be slightly more than a second or, as is preferred, also significantly less. Closes first the first and then the second valve, ambient pressure will be present in the line section enclosed between the valves. If the upstream first valve is tight, this pressure will not rise. If it is leaking, it rises. For the measurement, the entire period until the next restart of the burner or other gas consumer is available.

When the second type shutdown sequence is run, the valves also close within a very short period of time, preferably less than one second. However, in the line section between the two valves now a gas volume is trapped, which is below the nominal pressure of the gas line. Is the gas consumer side, i. the second gas valve tight, it remains. If the pressure drops, it is leaking. For checking purposes, the entire period until the next time the burner is switched on again is available.

It can be seen that the integration of the density check routine according to the invention by alternating the passage of two alternative types of Shutdown sequences the number of valve actuations only from the gas requirements of the gas consumer, ie the control cycles is determined. The leak test routine does not create additional valve actuations and thus spares the valve life. In addition, for the performance of the leak test long periods, namely at least the times from switching off the gas consumer until it is switched back on. These may be periods of time that are significantly in the range of minutes or more. This makes it possible to achieve a very sensitive leak test because of the large time available. Especially in off-peak hours, in heaters, for example, low heat demand pauses between the gas consumption cycles are relatively large and can reach hours or days. Especially in these periods, the leak tester is particularly sensitive to gas leakage of the two valves involved.

Should the shutdown cycles be so long that they exceed predetermined valve verification periods, the leak test routine may be modified. After passing through a shutdown sequence of one type, one of the two valves is checked for leaks. However, the complete test routine is not completed until the shutdown sequence of the other type has been passed with subsequent pressure test. If a predetermined time limit is reached within which the leak test routine must be completed, the leak test routine can be completed by briefly opening and closing one of the two valves. Which of the two valves is opened and closed again for a short time depends on which shutdown sequence was previously run through. If the first shutdown sequence has last been executed, then now open the first valve briefly to check the second valve for leaks. If, on the other hand, the second shutdown sequence was last run through, the second valve is now briefly lifted in order to check the first valve for leaks. Passing through the modified shutdown sequence does not release the gas flow because only one of the two valves is briefly opened, but the other remains closed.

In a variation of the invention, the controller may inhibit reconnection of the gas consumer after passing a shutdown sequence for a certain minimum time required to register a significant pressure change in the conduit section between the two valves. This period of time may be, for example, a fixed or variable time in the minute range. Further modifications are possible. For example, the shutdown sequence followed by a leak test can be carried out at each shutdown or even occasionally, depending on the requirements with regard to safety and duty cycle or other conditions. In addition, it is possible to set up the control device to the processing of gas request signals of different priority. If, for example, a request signal of low priority occurs, the opening of the valves can be delayed until sufficient time has elapsed since the last shutdown sequence to be able to evaluate leakage-related pressure changes. It is also possible for the control device to be designed in such a way that, upon receipt of higher prioritized request signals, it aborts the waiting period provided for the pressure evaluation from passing through the last shutdown sequence until it is switched on again and immediately releases the gas path. Such measures may be useful where delaying gas release can cause hazards.

• Figur 1 eine Gasventilkombination und ihre Steuereinrichtung in schematisierter Darstellung,
• Figur 2 bis 4 Zeitverläufe von Temperatur, Gasfreigabe und Druck als Diagramm.

Further details of advantageous embodiments of the invention will become apparent from the drawings and the description below. Show it:

• FIG. 1 a gas valve combination and its control device in a schematic representation,
• FIGS. 2 to 4 Time curves of temperature, gas release and pressure as diagram.

In FIG. 1 a gas valve combination 10 is shown, which is controlled by a control device 11. The gas valve combination 10 controls the gas flow to a burner 12 or another gas consumer. The gas flow comes from a gas source 13, which may be a gas reservoir or a gas supply line. The gas valve combination 10 is arranged in a line 14 leading from the gas source 13 to the gas consumer, for example burner 12. An upstream portion of the conduit 14 connects the gas source 13 to the gas valve combination 10. A downstream portion of the conduit 14 connects the gas valve combination 10 to the gas consumer or burner 12th

The gas valve combination 10 comprises a first source-side valve 15 and a second consumer-side valve 16. Between the two valves 15, 16, a line section 17 is present. The two valves 15, 16 may be separate by the line section 17 spaced valves. They may just as well be connected directly to one another, the line section 17 then being formed by the channel delimited between the two valve closure elements of the valves 15, 16. The two valves 15, 16 can also be combined with each other in a common housing, wherein the line section 17 in turn is the space enclosed between the two valve closure members.

At the line section 17 or the space corresponding thereto, a pressure sensor 18 can be arranged directly or via a channel or also a stub line. The pressure sensor 18 serves to detect the pressure in the line section 17. The pressure sensor 18 is in the simplest case a pressure switch which provides a signal this indicates whether gas trapped in the conduit section 17 has a pressure exceeding or differentiating a pressure limit. The pressure switch can be hysteresis-afflicted. In the preferred case, however, the pressure sensor is an analog or digital sensor which outputs signals to a sensor line 19, which characterize the pressure detected in the line 17. The signals may be proportional to the pressure (linear sensor) or otherwise dependent thereon, for example with a logarithmic or s-shaped or otherwise optimized characteristic. Two or more pressure sensors can also be used. For example, a first pressure sensor may be provided which has a particularly high resolution (slope) at pressures in the vicinity of the ambient pressure. A second sensor can be provided, which has a particularly high resolution (slope) at pressures in the vicinity of the gas pressure. The first sensor can be queried after passing through a shutdown sequence of the first kind. The second sensor can be queried after passing through a shutdown sequence of the second kind. The two sensors can be designed so that their measuring range is smaller than the pressure difference between ambient pressure and gas pressure.

The sensor line 19 leads to the control device 11, which actuates the two valves 15, 16. For this purpose, the control device 11 is connected via electrical lines 20, 21 with electric valve drives 22, 23, preferably in the form of tension magnets or other magnetic drives.

The control device 11 preferably has an input 24 at which it can receive a gas request signal. In the simplest case, the control device 11 receives at this input 24 on and Switch-off signal, to which the gas flow to the gas consumer (burner 12) is enabled or disabled. But it is also possible to make the control device 11 so that it receives a size at its input 24 on the basis of which in the control device 11, for example by comparison with a desired size, it is decided whether the valves 15, 16 are open or Not. In this case, the control device 11 operates as a control loop. This is in FIG. 1 by way of example illustrates a temperature sensor 25, which detects the temperature in a conduit 26, for example a water pipe. This can come from a not further illustrated heat exchanger, which is heated by the burner 12. A signal line 27 connects the temperature sensor 25 to the input 24.

• Es wird zunächst davon ausgegangen, dass die beiden Ventile 15, 16 geschlossen sind. Der Brenner 12 arbeitet nicht. An der Leitung 26 erfasst der Temperatursensor 25 eine niedrige Temperatur. Die Steuereinrichtung 11 arbeitet nun als Regler und vergleicht dazu diese niedrige Ist-Temperatur mit einer gewünschten Soll-Temperatur, die beispielsweise höher liegt. Die Abweichung zwischen dem höheren Temperatur-Sollwert und dem niedrigeren Temperatur-Istwert wird als Abweichung erkannt. Die Steuereinrichtung 11 öffnet deshalb die beiden Ventile 22, 23. In Figur 2 ist dies zu einem Zeitpunkt t1 veranschaulicht. Beide Ventile 15, 16 öffnen vorzugsweise gleichzeitig oder leicht zeitversetzt. Der Brenner 12 nimmt daraufhin seine Arbeit auf. Die Temperatur ϑ beginnt zu steigen bis ein oberer Temperaturgrenzwert erreicht ist. Die als Zweipunktregler arbeitende Steuereinrichtung 11 schaltet nun den Gasfluss ab, indem sie eine Abschaltsequenz ersten Typs I durchläuft.

This in FIG. 1 illustrated system works as follows:

• It is initially assumed that the two valves 15, 16 are closed. The burner 12 does not work. On the line 26, the temperature sensor 25 detects a low temperature. The controller 11 now works as a controller and compares this low actual temperature with a desired target temperature, which is higher, for example. The deviation between the higher temperature setpoint and the lower actual temperature value is detected as a deviation. The control device 11 therefore opens the two valves 22, 23. In FIG. 2 this is illustrated at a time t1. Both valves 15, 16 preferably open simultaneously or slightly delayed. The burner 12 then takes up his work. The temperature θ begins to increase until an upper temperature limit is reached. The control device operating as a two-position controller 11 now turns off the gas flow by going through a first type I shutdown sequence.

The shutdown sequence type I is that at a time t2, at which a contained in the control unit 11 switching block 28 receives an inhibit signal at an input 29, first the first valve 15 and then the second valve 16 is closed. The closing of the first valve 15 is in FIG. 2 indicated by a dashed line. The closing of the second valve 16 is in FIG. 2 indicated by a dotted line. The two valves 15, 16 close in short succession, for example, at a time interval of less than one second. With the closing of the first valve 15, the gas supply to the gas consumer 12 stops. The pressure in the line section 17 drops very quickly. If the second valve 16 closes at a time t2 ', it has already dropped to a low value, which corresponds for example to the ambient pressure.

FIG. 3 illustrates the switching of the valves 15 and 16 at the time t2, t2 'in a time-expanded representation. If both valves 15, 16 are tight, the pressure P in the line section 17 remains constantly low even after closing both valves 15, 16. However, if the first valve 15 is not completely sealed, the pressure P gradually increases after closing the second valve 16, as in FIG FIG. 3 is illustrated by a line 30. When the switch block 28 detects this, it can generate an error signal and, for example, pass it on to other blocks of the control device 11 or to the outside.

In the following period of time, the gas consumer 12 is out of service. The temperature temp that the Temperature sensor detected, falls off until a lower limit is reached. The comparator 31 provides a corresponding desired / actual difference signal, from which a switching signal is in turn derived by the block 32. The switching block 28 generates from this a turn-on signal, which causes the opening of the two valves 15, 16 at the time t3. The valves 15, 16 can now open at the same time or, if desired, also with a time delay. From this point on, the temperature temp detected by the temperature sensor 25 begins to increase again.

If the upper limit is reached, the block 32 again gives a blocking signal to the switching block 28. This happens at a time t4. At this time, the second type shutdown sequence II is started. In the context of this, the first valve 15 is closed at the time t4, first the first valve 16 and then shortly thereafter at a time t4 '. The time interval between times t4 and t4 'is short. It is preferably less than a second or at most a few seconds. The shutdown sequence II of the second type is in FIG. 4 shown time-stretched. Between the times t4 and t4 ', the line section 17 is charged with a gas volume whose pressure substantially corresponds to the pressure of the gas source 13. If the second valve 16 is not completely tight, the pressure detected by the pressure sensor 18 gradually drops after closing both valves 15, 16, as does the line 33 in FIG FIG. 4 suggests.

Until the next restart of the gas flow, the gas pressure can now be monitored.

It is possible to set up the switching block 28 to operate upon receipt of a turn-on signal at the input 29 first checks whether the time taken to carry out the last shutdown sequence I or II was sufficiently long to detect a possible increase in pressure ( FIG. 3 ) or possible pressure drop ( FIG. 4 ) to recognize. If not, the block 28, if necessary, the reconnection, ie delay the opening of the valves 15, 16 until the minimum period is reached.

It is also possible to design the switching block 28 so that it receives switch-on signals from a plurality of signal sources. In addition, it is possible to design inputs of the switching block 28 so that there receive activation signals have a high priority and lead to the opening of the valves 15, 16, even if the time required to monitor the pressure drop or pressure increase test time is not reached. The switching block 28 shifts the due pressure test to a next switching cycle in such a case.

In the exemplary embodiments explained above, the tightness test of the valves 15, 16 is based on the fact that the valve closing actuations occurring in the context of the normal control operations are passed through two different types of shutdown sequences I and II and the pressure in the line section 17 is monitored in the following time. Preferably, in the shutdown, the shutdown sequences I and II from each other. If desired, however, other schemes may be used. For example, the shutdown sequence I or II can be selected randomly or else according to other criteria.

By integrating the leak test in the normal control operations is achieved that the number of valve clearance in the system according to the invention is not increased must be, although in addition to the control task and sealing tests are carried out. By dividing the test cycle into two shutdown sequences I and II of different types, which are alternatively carried out in chronologically successive cycles, the tightness test of both valves 15, 16 takes place under comparable conditions. Pressure fluctuations, for example due to burner reactions, such as may occur when igniting burners, thus have no influence on the leak test.

In the concept according to the invention, in the case of a two-point controller which controls the gas flow to a gas consumer 12 by means of two valves 15, 16, the tightness of the valves 15, 16 is checked alternately by alternately passing through different shutdown sequences I and II. This minimizes the number of valve latches and makes a very sensitive leak test possible.

LIST OF REFERENCE NUMBERS

10

Gas valve combination

11

control device

12

burner

13

gas source

14

management

15

First valve

16

Second valve

17

line section

18

pressure sensor

19

sensor line

20, 21

Electric lines

22, 23

Electric valve actuators

24

entrance

25

temperature sensor

26

management

27

signal line

I

Shutdown sequence of the first type

II

Shutdown sequence of the second type

28

switching block

29

Sperrsignel input

30

Curve

31

comparator

32

block

Claims (15)

Method for leak testing a gas valve combination (10),
to which a first valve (15) arranged in a duct (14) leading from a gas source (13) to a gas consumer (12), and
a second valve (16) arranged in the conduit (14) and arranged in series with the first gas valve (15), so that between the two valves (15, 16) a line section (17) is fixed,
with a pressure monitoring device (18) and with a control device (11), which is connected to the pressure monitoring device (18) and which controls the valves (15, 16), depending on an opening signal, the gas path from the gas source (13) to the gas consumer (12) to release and, depending on a closing signal to block the gas path from the gas source (13) to the gas consumer (12),
wherein the control device (11) closes the two valves (15, 16) one after the other in order to carry out a leak test while monitoring the pressure in the line section (16),
characterized,
that the density test on receipt of the blocking signal (29) in the context of two different shutdown sequences I and II by time-delayed closing of the two valves (15, 16) is executed. A method according to claim 1, characterized in that the density test is carried out exclusively upon receipt of the inhibit signal (29). A method according to claim 1, characterized in that the closing of the valves (15, 16) in a first shutdown sequence (I) comprises first closing the first valve (15) and then closing the second valve (16) and closing the Valves (15, 16) in a second shutdown sequence (II), first closing the second valve (16) and then closing the first valve (15). A method according to claim 3, characterized in that the two shutdown sequences (I, II) are carried out alternatively. A method according to claim 3, characterized in that the two alternative shutdown sequences (I, II) are carried out alternately at successive blocking times (t2, t4). A method as claimed in claim 1, characterized in that the control means (11) detects the time between the last inhibit signal and the reclosing and modifies the alternative shutdown sequence alternative to the last shutdown sequence without receiving a disable signal if the time elapsed since the last shutdown sequence Limit exceeds, by only one of the valves (15, 16) opens briefly and then the pressure in the line section (17) is monitored. Gas valve combination (10),
to which a first valve (16) arranged in a duct (14) leading from a gas source (13) to a gas consumer (12), and
a second valve (16) arranged in the conduit (14) and arranged in series with the first gas valve (15), so that between the two valves (15, 16) a line section (17) is fixed,
with a pressure monitoring device (18) and with a control device (11), which is connected to the pressure monitoring device (18) and which controls the valves (15, 16), depending on an opening signal, the gas path from the gas source (13) to the gas consumer (12) to release and, depending on a closing signal to block the gas path from the gas source (13) to the gas consumer (12),
wherein the control device (11) is designed in such a way that, in order to carry out a leak test, it closes the two valves (15) one after the other while monitoring the pressure in the line section (17),
characterized,
that the control device (11) upon receipt of the disable signal (29) performs the leak test by delayed closing of the two valves (15, 16). Gas valve combination according to claim 7, characterized in that the control device (11) in such a way is designed so that it performs the leak test only upon receipt of the inhibit signal. Gas valve combination according to claim 7, characterized in that the control device (11) is designed such that the closing of the valves (15, 16) in a first shutdown sequence (I), first closing the first valve (15) and then closing the second Valve (16) and that the closing of the valves (15, 16) in a second shutdown sequence (II) comprises first closing the second valve (16) and then closing the first valve (15). Gas valve combination according to claim 9, characterized in that the control device (11) is designed such that the two shutdown sequences (I, II) are carried out alternatively. Gas valve combination according to claim 10, characterized in that the control device (11) is designed such that the two alternative shutdown sequences (I, II) are carried out alternately in successive blocking signals. Gas valve combination according to claim 7, characterized in that the control device (11) is designed such that it delays the opening of the valves (15, 16) after receiving a blocking signal and subsequent receipt of a switch-on until sufficient for carrying out the leak test by pressure monitoring Minimum time has elapsed. Control device (11) for a gas valve combination (10),
to which a first valve (15) arranged in a duct (14) leading from a gas source (13) to a gas consumer (12), and
a second valve (16) arranged in the conduit (14) and arranged in series with the first gas valve (15), so that between the two valves (15, 16) a line section (17) is fixed,
with a pressure monitoring device (18) which is connected to the control device (11),
wherein the control device (11) controls the valves (15, 16) to release the gas path from the gas source (13) to the gas consumer (12) depending on an opening signal and the gas path from the gas source (13) dependent on a closing signal to block the gas consumer (12),
wherein the control device (11) closes the two valves (15, 16) one after the other in order to carry out a leak test, thereby monitoring the pressure in the line section (17),
wherein the tightness test in the context of the two-step control required opening and closing of the valves (15, 16) in each case when locking the valves (15, 16) by time-delayed closing of the two valves (15, 16) and subsequent pressure monitoring is performed. Control device according to claim 13, characterized in that the control device (11) includes a two-position controller (32), the gas consumer (12) by actuation of the valves (15, 16) turns on and off to turn off the blocking signal generates the Control means (11) carries out the leak test only at and after receiving the inhibit signal. Control device according to claim 13, characterized in that it causes the closing of the valves (15, 16) in a first shutdown sequence (I) first by the closing of the first valve (15) and subsequent closing of the second valve (16) and that they Closing the valves (15, 16) in a second shutdown sequence (II) first by the closing of the second valve (16) and subsequent closing of the first valve (15) causes and that it executes the two shutdown sequences (I, II) alternatively.

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