DE102007041766B4 - Leakage monitoring of systems with at least two media circuits, in particular heat exchangers - Google Patents

Abstract

Method for detecting leaks in a heat exchanger (1) with at least two media circuits separated from one another by at least one wall each, with a first media circuit (3) of the media circuits carrying a medium at high pressure and a second in an operating state of the heat exchanger (1) Media circuit (4) of the media circuits carries a medium with a lower pressure, and the method is carried out in the operating state of the heat exchanger (1) and comprises the steps: measuring a respective absolute pressure in the first media circuit (3) and in the second media circuit (4) and / or in at least one of the first and second media circuits (3, 4) and in a closed space between the first and second media circuits (3, 4), determining a differential pressure between the first and second media circuits (3, 4) and / or one Differential pressure between the at least one of the first and second media circuits (3, 4) and the closed space from the respective absolute pressures of the first and second media circuits (3, ...

Description

The invention relates to a method for detecting leaks in a heat exchanger with at least two separate from each other by at least one wall media circuits and a heat exchanger with at least two separate from each other by at least one wall media circuits.

Heat exchangers, which are also called heat exchangers, are used, for example, in heating systems. In the generic heat exchangers, a thermal coupling of a primary circuit with a secondary circuit without a media exchange takes place.

The problem with these heat exchangers is the monitoring and protection of leaks resulting from internal leaks in the heat exchanger. Such leaks can be that the medium of the primary circuit penetrates into the secondary circuit or vice versa. Such leaks are critical, among other things, because not only a loss of media and destruction of not sufficiently pressure-resistant plant components, but also a health risk can be associated with the media transfer. More rare are leaks on the outer shell of heat exchangers. These may also be associated with media loss and material and health damage in the environment of an outwardly leaking heat exchanger.

For example, in hot water preparation via a district heating network, the primary circuit is coupled via a heat exchanger with a secondary circuit that leads to drinking water. Thus, with an internal leakage of the heat exchanger, the risk of contamination of the drinking water through the provided with additives medium of the primary circuit as well as the risk of penetration of drinking water in the primary circuit, whereby the properties of the primary medium can be changed so that corrosion occurs and / or the efficiency of the heat transport in the primary circuit is reduced. Above all, this danger of a media transfer exists because the primary and secondary circuits are operated at different pressures. Thus, the pressure of the primary circuit is about 8 to 25 bar, while the pressure of the drinking water circuit is about 4 to 10 bar.

Furthermore, leakages of the outer shell of the heat exchanger or of the adjacent media circuits can lead to the discharge of primary and / or secondary medium into the installation space, which is associated with the risk of extensive water damage.

So far, there have been various approaches to detect leaks between the circuits inside a heat exchanger and to limit their consequences.

One solution has been to design an intermediate circuit (such as in DE 10 2007 040 629 A1 described), but also causes an increased design effort, since two heat exchangers are necessary here, to an internal circulation pump, an expansion vessel, a pressure relief and a complex control in the primary and intermediate circuit. Particularly negative is the constant to be overcome double temperature difference at both heat exchangers on the overall process. To avoid this, larger heat transfer surfaces are required, up to more than six times a single apparatus. In addition, an intermediate circuit requires increased operating costs due to the permanent use of electrical energy for the circulation pump as well as the maintenance and servicing of the additional components, without which the reliability of the system would be reduced.

DE 10 2007 040 629 A1 discloses a safety heat exchanger having a primary circuit with drinking water, a secondary safety circuit or intermediate circuit with a health-endangering substance as antifreeze and a tertiary circuit with a refrigerant. In the safety circuit, a pressure switch with two points of contact is provided and in the tertiary circuit, a pressure switch is provided in parallel with control technology. The pressure switch is control technology with solenoid valves connected such that are closed at a loss of pressure in the primary circuit or tertiary cycle of the inlet and the flow of drinking water to the drinking water supply system.

Another possibility is to make the heat exchanger double-walled, so that the primary circuit and the secondary circuit are separated by an outwardly open or closed shrouded cavity and a media transfer could occur only after the unlikely event of simultaneous leaks in both walls, with previously the Pressure drop in one of the two media, the leakage of a medium from an outwardly open leakage chamber or the increase in pressure in a closed cavity indicate a possible leakage. At these solutions, as z. In DE 199 60 462 A1 or DE 197 05 216 A1 are described, however, is disadvantageous that with the double sheath an increased cost of materials and accordingly higher costs of the heat exchanger are connected. In addition, an increased design effort must be operated be ensured in order to ensure sufficient heat coupling of the two circuits despite the double-walled design. In addition, it can be difficult to prove the onset of the medium low pressure in a closed space just as reliably as the entry of the medium much higher pressure at very different media pressures on the two sides.

In DE 199 60 462 A1 a method described for the temporary shutdown of a non-testable, designed to the full nominal pressure of the higher pressure medium leakage switch in possibly two-stage design with possibly associated with him manometer from a leakage chamber of a double tube Sicherheitswärmeübertragers means three-way valve for the time of a repeat pressure test with a flowable test medium , In this method, the internal pressure of the leakage chamber is monitored for constancy in a repetitive pressure test. For leakage monitoring, a separate, flowable test medium is used and not the flow media themselves.

According to DE 197 05 216 A1 In operation, the intermediate space of a double-pipe safety heat exchanger can be acted upon by the overpressure of a neutral medium or can be kept at negative pressure, and a stage of a leakage warning device can be responded to a change in the overpressure or underpressure in the intermediate space.

So far, leaks on single-walled and without intermediate circuit running heat exchangers, which can lead to exceeding the allowable pressure in the secondary circuit, usually hedged with a special maximum pressure switch that can only be unlocked on site. For larger thermal outputs and the corresponding higher possible severity of the consequences of leakage, the redundant design of the maximum pressure switch is prescribed. The maximum pressure switches lead to the shutdown of the media supply in the primary circuit by closing the valve equipped with a corresponding drive, which locks even in the event of a power failure. The disadvantage of this solution is that it does not always come in operation to sufficiently high pressures of the medium on the primary side, which would be sufficient to cause such a pressure increase in the secondary circuit as a result of leakage, which would also lead to a response of / the maximum pressure switch. Leakage can go unnoticed for a long time. In parallel, the maximum pressure switch also protects against other system errors, eg. B. against unacceptable heat in case of lack of heat loss.

Furthermore, it is customary to protect against water shortage on the secondary side by means of a minimal pressure switch. If an adjustable minimum pressure is not reached, the circulation pump is switched off on the secondary side to prevent it from running dry. Such a minimum pressure switch releases the circulation pump again when the predetermined minimum pressure is again exceeded by a certain hysteresis. Such a lack of water can z. B. occur due to the temporary unannounced shutdown of the water supply. Another way of using minimal pressure switches is the secondary side z. B. to protect from decoction by further heat, as soon as the secondary-side pressure drops so much that he approaches the potential point of evaporation dangerously. A used for such purposes minimal pressure switch blocks and can only be unlocked on site by hand when the predetermined minimum pressure was exceeded by a certain hysteresis.

The disadvantage of both solutions is that separate pressure switches must be used for the minimum as well as the maximum pressure monitoring. This is associated with an increased effort in the creation and maintenance, but without being able to reliably detect any leakage in any case.

A similar effect has and for the same purpose a water shortage protection is used by level monitoring in the system or outside, if the pressure in the system or outside despite water shortage barely changed or water shortage in the system can also occur as a result of causes other than leakage, z. B. by insufficient media replenishment.

From the DE 10 2004 035 298 B4 a hot water heating system with a hydraulic protection circuit and a method for operating the same is known in which it is proposed to monitor the dynamic pressure curve in an internal heating circuit with a control unit and abnormal course, ie when the pressure in the internal heating circuit in a short time falls by a predetermined value, to conclude a leak. A predetermined pressure curve can be stored as a characteristic curve in the control unit. However, it is not always predictable how the course of a pressure change in the case of leakage behaves. Thus, this form of leakage monitoring is limited to a narrow range of applications. When coincidence of a change in the pressure curve with a failure of the electrical voltage or during a targeted shutdown of the control / regulating unit leakage monitoring is not present and can after the return of electrical voltage or targeted reconnection of the control unit can not be reconstructed if the pressure change is already completed during the absence of voltage. Despite the presence of a leak, it would not be detected in such a case.

EP 1 390 706 B1 describes a detection method for leakage between two circuits of a plate heat exchanger of the type according to which a fluid is filled under a different pressure for each of the two circuits, wherein the pressure development in the two circuits is monitored by means of pressure transducers and automatically approximates the observed pressures in the two circuits from there to a given threshold is detected. The observation involves the periodic calculation of the difference between the two pressures, signaling a leak as this difference falls below the threshold.

DE 40 07 228 A1 discloses a heating center with a pressure sensor, which measures the pressure in a buffer tank, and another pressure sensor or a differential pressure box, which measures the water level in front of a pump.

The invention relates to systems in which the media circuits in the operating state media carry different pressures.

The invention has for its object to provide a method for detecting leaks in a heat exchanger with at least two separate from each other by at least one wall media circuits and a heat exchanger with at least two separate from each other by at least one wall media circuits so that improved detection security and detecting speed for leaks between the media circuits is ensured.

This object is achieved by a method according to claim 1 and a heat exchanger according to claim 13. Advantageous developments are specified in the respective dependent claims.

The invention is based on the finding that leakage can be detected particularly easily if the differential pressure between the medium circuits is monitored. For this purpose, only a small design effort is required, but allows a reliable leakage monitoring. Between the medium circuits, in particular a primary and the secondary circuit, there is a certain pressure difference, which is dependent on the pressures of the circuits themselves. For example, in the above-mentioned water heating systems with a district heating circuit (primary circuit) at 8 to 25 bar and the drinking water circuit ( Secondary circuit) at 4 to 10 bar this difference -2 to +21 bar. As soon as a leakage has occurred in the heat exchanger, a pressure equalization takes place here, which lowers the differential pressure, as a result of which such leakages can be easily detected.

The method according to the invention is therefore characterized in that the differential pressure between the medium circuits, namely a first circuit with a medium of higher pressure and a second circuit with a medium of lower pressure is monitored, whereby also the absolute pressure of at least one circuit is monitored.

The terms primary and secondary medium are derived from the heat source and the heat sink, ie the direction in which the heat flows in the heat exchanger. It is quite possible that the primary medium has a lower pressure than the secondary medium. In this case, it is advantageous - in addition to the differential pressure - to monitor the absolute pressure of the primary side. In the event that - as stated above - the primary medium has the higher pressure, it is advantageous to monitor the absolute pressure of the secondary side in addition to the differential pressure.

In a preferred embodiment, upon reaching a certain differential pressure or sweeping over a certain absolute pressure, an optical or acoustic signal is given. Alternatively or additionally, upon reaching a certain differential pressure or sweeping over a certain absolute pressure, a protective function can be triggered, such as, for example, at least one of the circuits being blocked in order to perform an automatic backup in addition to the detection and indication of a leakage.

In conventional medium circuits of the set as the set value the differential pressure Ap is _s = 0 bar, in which appears a leak or fused. Alternatively, different positive as well as negative or absolute values can be defined by Δp = 0 bar in order to indicate a leak earlier, namely when it forms and therefore the pressure difference is not yet Δp = 0 bar. By establishing a pressure difference Δp _s not equal to 0 bar, possible measurement errors of the measuring means used can also be taken into account. On the other hand, a differential pressure differing from 0 makes sense even if the design pressures of the medium circuits deviate greatly from one another or the pressures can fluctuate greatly in the operating state. The differential pressure should therefore be adjustable at least to greater than 1 bar, with any other value is useful between the difference Design pressures of the media circuits and 0 bar is.

In order additionally and alternatively to detect a leakage in the second circuit, which has a lower pressure than the first circuit, the pressure increase in the second circuit with respect to a maximum value is interpreted as a control value as a sweep.

Additionally or alternatively, in the second cycle as a sweep, the pressure reduction with respect to a minimum value can be interpreted as a control value. This minimum value is preferably used to reliably detect an emptying of this second circuit, that is to say a leakage to the outside or a medium lacking other reasons. For automatic protection of idling is advantageously provided that when sweeping the minimum value, the circulation pump of this second circuit is turned off to prevent at least the dry running of the circulation pump. At the same time it can also be provided that a shutdown of the first circuit takes place, for example, to prevent boiling in heat exchangers, and / or that a shutdown of the media replenishment in the second cycle takes place in order to avoid major damage in uncontrolled media leakage.

During operation, the pressure difference between the media can also be negative, at least at times, so that a maximum pressure monitoring device does not always detect a leak, but only prevents it from exceeding the design pressure (by blocking etc.). In this case, however, a differential pressure monitoring is reliable, so that other negative consequences of media exchange via a leak (corrosion, damage to health, etc.) can be reliably prevented. It is therefore again pointed out that the differential pressure switching value Δp _{s can} be a negative, a positive or also the absolute value of a pressure difference which is correspondingly compared with a negative, a positive or also the absolute value of a pressure difference measured value.

In addition to monitoring a static differential or absolute pressure value, it may be advantageous to follow the dynamic development of the differential and / or absolute pressure value in order to be able to conclude an ev. Leakage even before a switching value, for example the differential pressure of Δp _s = 0 bar is reached.

It may be useful to trigger an optical and / or acoustic signal before triggering a protective device upon reaching a first control value of a differential pressure and / or an absolute pressure. For this purpose, it is advantageous to deposit not only one but at least two control values of a differential pressure and / or an absolute pressure in the memory and to compare them with the measured value.

In a preferred embodiment, it is provided that automatic safety measures with respect to a measured variable are not removed until the corresponding measured variable, ie the differential pressure or the absolute pressure in the second circuit, by more than 1 bar, in particular more than 0.75 bar, preferably more than 0.5 bar exceeds or falls below the set control value. For example, it may be provided that, when the pressure is increased again, the circulating pump of the second circuit is only switched on again when the minimum value has exceeded by more than +1 bar, in particular more than +0.75 bar, preferably more than +0.5 bar becomes.

It is advantageously provided that, prior to continued operation of the system, a time reconnection block of, in particular, a few seconds, preferably a few minutes, must be overcome. This takes into account that it may be possible that the manipulated variable is repeatedly or repeatedly swept over at short intervals.

Instead of the automatic restart of the system with respect to one or more of the measured variables differential pressure, maximum and minimum pressure can be provided to further increase the security that for continued operation of the system an acknowledgment by a supervisor on site, ie at the site of the system is required ,

In a further advantageous embodiment, a switching delay is provided before giving the signal, the blocking of a media circuit, for example by blocking the circuit by a valve or switching off a corresponding circulation pump, or switching off the media refueling, which is in particular a few minutes, preferably a few seconds , This makes sense if it is always possible to override the switching states under certain operating conditions during operation of the system. B. in heat exchangers during hot water differential pressures of Δp = 0 bar in the expansion of drinking water in a closed system (without hot water) by heating possible, or the maximum pressure can be achieved by hydraulic shocks on the secondary side, as they are known by so-called single-lever or Can be caused.

To check for leaks / leaks, it may be appropriate to put the system regularly in hibernation, so for example the Turn off circulation pumps or close the valves to give the system the ability to assume a steady state static pressure, from the safe with the inventive method can be closed on the state, for example, the heat exchanger.

A device has means for measuring the differential pressure between the medium circuits.

At least one absolute pressure sensor for determining the absolute pressure in at least one medium cycle is advantageously provided.

In a preferred embodiment, the differential pressure measuring means or the differential pressure measuring means and the absolute pressure sensor but corresponding switches are connected to an optical and / or acoustic signaling system. Thus, if a leak occurs, a clearly audible signal can be given immediately to indicate the malfunction and initiate follow-up by the monitoring personnel.

It is particularly preferred if the differential pressure measuring means or the differential pressure measuring means and the absolute pressure sensor are connected via the switch in switching relation with at least one protective device, in particular with a valve for blocking the first circuit, since then automatically switching off this first circuit, so that another Penetration of the medium of this circuit is automatically prevented in the medium of the second circuit and vice versa.

When the pressure sensor for measuring the absolute pressure in the second circuit is connected via a pressure value switch in switching relation with a circulating pump of the second circuit. Dry running of the circulation pump of the second circuit can be prevented in case of lack of water.

In particular, if gaseous media are contained in a circuit, compressors may continue to be required, which can also be configured to be switched off via a scarfing device.

Advantageously, a specific differential pressure can be set as a stall value at the differential pressure switch, in which the signaling system and / or the valve is switched, wherein preferably a differential pressure control value of Δp _s = 0 bar is provided. Alternatively, a value different from 0 bar can also be provided in order, for example, to adapt to possible measurement errors.

It is also advantageous for the pressure value switch, a certain pressure adjustable as a control value, when exceeded, the signal system and / or the valve and or the circulation pump is switched. In this way, for example, for heat exchangers in which the primary circuit has a higher pressure than the secondary circuit, additionally a penetration of primary media into the secondary circuit safely detected and limited their consequences. This type of Leckageübarwachung on the secondary side alone, for example, is advantageous if the differential pressure Ap for reasons such. B. the pressure losses occurring in operation on the heat exchanger on both sides can not assume the control value Δp _s = 0 (but only at standstill), or if a design of the entire secondary system to the higher nominal pressure of the primary system z. B. is not desirable for cost reasons. For this reason, it may also be advantageous to attach the differential pressure measuring means at the respective outlet of the primary or secondary circuit of the heat exchanger.

Further advantageous for the pressure value switch, a certain pressure is adjustable as a control value, below which the signal system and / or the valve and or the circulation pump is switched. Thus, dry running and / or leakage to the outside can be reliably detected and their consequences limited. Due to the adjustability of the differential pressure or the pressure, the leakage monitoring of the system can be precisely adapted to different conditions.

In order to increase the accuracy of the differential pressure to be determined and / or the absolute pressure value to be determined, it may be advantageous to use different measured value transmitters of different measured value ranges adapted to the respectively occurring operating pressure ranges in the various media spaces.

To increase safety, the measuring devices and the connected switching devices can be designed in a safety-oriented manner (in the sense of the term introduced in the art and the measures usually required for this purpose, eg by redundant design, hardware wiring, self-monitoring electronic circuits, (TUV) ) tested software routines, etc.).

To increase the security can be provided that after an interruption and subsequent return of the electrical voltage, the restoration of the previous situation by retrieving all thresholds and switching states is made possible from a non-volatile memory of the device. The same purpose can also serve an uninterruptible power supply.

In the case of double-walled heat exchangers, it may make sense to set the absolute pressure of a closed gap and / or to measure the / the differential pressures between the / the media spaces and the closed space. For this purpose, a variant of a leakage monitoring device with at least three absolute pressure sensors, one in each room is conceivable, but a maximum of two differential pressure or four absolute pressure sensors.

Although individual features and benefits have been described only in terms of the process or equipment, it will be understood that they apply to both. In addition, it is clear that each manipulated variable monitoring can be coupled with each securing means in order to perform safety measures.

The features and further advantages of the present invention will now be apparent from the preferred embodiment described below in conjunction with the sole FIGURE.

The figure shows purely schematically a heat exchanger according to the invention 1 in a graphic representation. The heat exchanger 1 has a container 2 on, through which a primary circuit 3 and a secondary circuit 4 are guided The secondary circuit 4 is through tubes 5 in the container 2 guided, with the medium of the primary circuit 3 at the tubes 5 as a heat transfer surface flows past. This is done via the tubes 5 between the two media of the primary 3 and the secondary circuit 4 a heat transfer, while at the same time a media separation is ensured. Alternative to the tubes 5 For example, plates can also be provided.

In the example shown, the hot water preparation by district heating is the primary circuit 3 the district heating circuit, which is operated at about 80 ° C to 125 ° C and at 8 to 25 bar by a district heating circulation pump (not shown). At the secondary circuit 4 it is a drinking water circuit, which at about 55 ° C to 60 ° C and 4 to 10 bar by means of the circulation pump 6 is operated.

For the detection of leaks are means 7 for storing and determining the differential pressure between the primary 3 and the secondary circuit 4 intended. These funds 7 have a pressure sensor (not shown) for measuring the absolute pressure in the secondary circuit 4 and a pressure sensor (not shown) for measuring the absolute pressure in the primary circuit 4 on and a differential pressure switch 7 , which determines the differential pressure and in which a control value for the differential pressure can be set. As a result, only two sensors for monitoring the differential, maximum and minimum pressure are required. In addition, in the case of hedging several to a primary 3 or secondary circuit 4 connected heat exchangers 1 to at least one pressure measuring means per further heat exchanger 1 be waived.

Furthermore, funds 8th . 9 for storing and switching with respect to a maximum pressure value and a minimum value, namely a pressure maximum value switch 8th and a pressure minimum value switch 9 , The differential pressure switch 7 is with a check valve 10 in the primary circuit 3 connected to this check valve 10 to switch. In addition, the differential pressure switch 7 also connected to an acoustic and / or optical signaling system (not shown) to signal leaks. The maximum pressure switch 8th is also with the check valve 10 and the signaling system connected The pressure minimum value switch 9 is next to the check valve 10 and the signaling system additionally with the circulation pump 6 connected.

The heat exchanger according to the invention 1 is now operated as follows to detect and limit the consequences of leaks. For leaks within the heat exchanger 1 would in the container 2 through a hole or a crack inside the tubes 5 a media transfer take place, so that the medium of the district heating cycle 3 into the drinking water of the secondary circuit 4 invade and pollute the drinking water. On the other hand, drinking water could also enter the primary circuit 3 penetration. In such a media transfer inevitably takes place a pressure equalization.

At the differential pressure switch 7 is set a differential pressure control value Δp _s = 0 bar. As soon as the differential pressure switch 7 detects a differential pressure of Δp = 0 bar, an optical signal is given, possibly supported by an acoustic signal to indicate the leakage. The display may be on an LCD panel (not shown), for example. In addition, the check valve 10 switched so that the primary circuit 3 opposite the container 2 is locked and no further medium of the primary circuit in the drinking water of the secondary circuit 4 can penetrate. In addition to the check valve on the inlet side of the primary circuit 3 to the container 2 may also be another check valve (not shown) on the drain side of the primary circuit 3 on the container 2 be provided.

In addition, the leakage is also via the absolute pressure sensor in connection with the set maximum pressure value of the secondary circuit 4 at the pressure maximum value switch 8th detected. For example, here are according to the design pressure of the secondary circuit 4 of 10 bar set as the maximum value 9.5 bar. This value is due to a leakage due to penetration of the primary circuit medium due at least temporarily higher primary circuit pressure exceeded, causing the pressure maximum value switch 8th even before reaching a differential pressure of Δp = 0 bar triggers an optical and / or acoustic signal and a blocking of the check valve 10 causes.

Since the secondary pressure with 10 bar, at least temporarily, but can also assume higher values than the pressure of the medium on the primary side with z. B. 8 bar, a detection of leakage with a maximum value switch would not be possible in this case. Here, however, the protection takes place via the differential pressure setpoint Δp _s = 0 bar.

Gegenfüber a dry running of the circulation pump 6 secured is the heat exchanger 1 dddurch that at the pressure minimum value switch 9 a minimum pressure of, for example, 1 bar is set, when it falls below the circulation pump 6 is automatically turned off. In addition, an optical and / or acoustic signal is given and it can be provided that the check valve 10 for blocking the primary circuit or for switching off an automatic media replenishment of the second medium cycle 4 (not shown) is actuated to safely prevent Auskochen or greater media loss in the event of leakage to the outside.

To further increase the safety is provided that after switching the check valve 10 and the circulation pump 6 by differential pressure switch 7 , Maximum pressure switch 8th and / or pressure minimum value switch 9 the switching states of the check valve 10 and the circulation pump 6 can only be reversed on the spot by the acknowledgment of a person, namely by monitoring personnel, so that so before restarting the heat exchanger 1 a safety query is provided and a cause determination is possible.

Alternatively, however, it can also be provided that after the switching of the check valve 10 and the circulation pump 6 by differential pressure switch 7 , Maximum pressure switch 8th and / or pressure minimum value switch 9 upon detection that one of the measured values is related to the respectively set value of the differential pressure measuring switch 7 , the pressure maximum value switch 8th and / or the pressure minimum value switch 9 has changed by more than a certain amount, the check valve 10 or the circulation pump 6 in relation to the corresponding measured value again - by hand or automatically - is released. It is with respect to the differential pressure switch 7 and the pressure minimum value switch 9 provided as an amount +0.5 bar, for example, +0.75 bar or +1 bar can be used to increase the security. With respect to the maximum pressure switch 8th is provided as an amount corresponding to -0.5 bar, which can be verwenadet -0.75 bar or -1 bar, for example, to increase the security. In addition, a switch-on delay as well as a switch-on delay of a few seconds to minutes are provided in order to ignore only brief sweeping of the control values.

So if about the check valve 10 was closed because of the differential pressure switch 7 detected a differential pressure corresponding to the differential pressure switching value Δp _s = 0 bar, and because the pressure maximum value switch 8th exceeding the maximum pressure value detected in the secondary circuit of 10 bar, so the check valve 10 be released again when the differential pressure has risen to at least Δp = 0.5 bar and additionally the secondary circuit pressure has fallen below P = 9.5 bar.

This automatic restart of the heat exchanger 1 but is appropriate only for the circulation pump 6 provided, ie that, for example, after a pressure drop in the secondary cycle 4 below 1 bar, the circulation pump 6 through the pressure minimum value switch 9 is turned off and that a reconnection of the circulation pump 6 then automatically takes place when the pressure in the secondary circuit 4 has risen above 1.5 bar.

With regard to the switching states, it is preferably provided that differential pressure switches 7 , Maximum pressure switch 8th and pressure minimum value switch 9 each independently the check valve 10 in the blocking position and the signaling system in the signal position switch. These switching states of check valve 10 and signal conditioning can preferably be canceled on the spot only when all measures are normalized again. In case of damage, however, the heat exchanger 1 remain in safe condition, taken out of service and repaired or replaced.

In addition to the electronic version of the leakage monitoring system is also a fully or partially mechanical (hardware) execution z. B. on the basis of absolute pressure and / or differential pressure manometers with self or manually unlockable limit contacts possible.

From the foregoing it has become clear that by the present invention, a heat exchanger 1 is provided, the leaks reliably detected without special design effort and thus required high costs in the various possible operating conditions and is also prepared for automatic protection in the occurrence of these leaks.

While the invention has been explained on a heat exchanger for hot water, it can also be used for example in heat exchangers for the heating of the house connection station in the leakage monitoring. Here it is advantageous to detect the pressure on the primary side only with a pressure sensor, and with a further pressure sensor, the pressure on the heating side and the pressure on the hot water side. In general, it can be said that the present invention can be used universally wherever two media of different pressure can be safely separated from each other by a wall. The media will usually be liquids, but other media, such as gases, are also conceivable.

LIST OF REFERENCE NUMBERS

1

Heat exchanger

2

container

3

Primary circuit

4

Secondary circuit

5

roar

6

circulating pump

7

Differential pressure measuring equipment

8th

Pressure maximum value switch

9

Pressure switch minimum value

10

Check valve.

Claims (17)

Method for detecting leaks in a heat exchanger ( 1 ) with at least two of each other by at least one wall separated media circuits, wherein in an operating state of the heat exchanger ( 1 ) a first media cycle ( 3 ) of the medium cycles a medium with high pressure leads and a second medium cycle ( 4 ) the media circuits a medium with lower pressure leads, and wherein the method in the operating state of the heat exchanger ( 1 ) and comprising the steps of measuring a respective absolute pressure in the first medium circuit ( 3 ) and in the second media cycle ( 4 ) and / or in at least one of the first and second medium circuits ( 3 . 4 ) and in a closed space between the first and second medium circuits ( 3 . 4 ), Determining a differential pressure between the first and second medium circuits ( 3 . 4 ) and / or a differential pressure between the at least one of the first and second medium circuits ( 3 . 4 ) and the closed space from the respective absolute pressures of the first and the second medium circuit ( 3 . 4 ) or the respective absolute pressures of the at least one of the first and second medium circuits ( 3 . 4 ) and the closed gap, simultaneously comparing the determined differential pressure with a predetermined differential pressure and the absolute pressure of the second medium circuit ( 4 ) with a predetermined maximum pressure, determining a leakage between the first and the second medium circuit ( 3 . 4 ) and / or the at least one of the first and second medium circuits ( 3 . 4 ) and the closed gap, when the determined differential pressure reaches the predetermined differential pressure, determining a leakage between the first and the second medium circuit ( 3 . 4 ), when the absolute pressure of the second medium cycle ( 4 ) exceeds the maximum pressure, and triggers a protective function upon determination of a leak. Method according to claim 1, wherein an optical and / or acoustic signal is given as part of the protective function. Method according to claim 1 or 2, wherein, within the scope of the protective function, a device for circulating the medium of the second medium circuit ( 4 ) provided circulating pump ( 6 ) and / or the first media cycle ( 3 ) and / or an automatic media replenishment of the second medium cycle ( 4 ) are switched off. Method according to one of claims 1 to 3, wherein as a predetermined differential pressure, a differential pressure control value (Δp _s ) is set, which in the range between 0 bar and the pressure difference of the media of the first and the second medium cycle ( 3 . 4 ) is in the operating state. The method of claim 4, wherein the differential pressure control value (Δp _s ) is 0 bar. Method according to one of claims 1 to 5, wherein the absolute pressure of the second medium circuit ( 4 ) is compared with a predetermined minimum pressure and, if the absolute pressure of the second medium cycle ( 4 ) falls below the minimum pressure, one for circulating the medium of the second medium cycle ( 4 ) provided circulating pump ( 6 ) is switched off and / or an automatic media replenishment of the second medium cycle ( 4 ) is switched off. Method according to one of claims 3 to 6, wherein in a renewed pressure reduction, the circulation pump ( 6 ), the first media cycle ( 3 ) and / or the automatic media replenishment of the second medium cycle ( 4 ) are only switched on again when the minimum value is exceeded by more than -1 bar, in particular more than -0.75 bar, preferably more than -0.5 bar. A method according to claim 6, wherein at a pressure increase the circulating pump ( 6 ), the first media cycle ( 3 ) and / or the automatic media replenishment of the second medium cycle ( 4 ) are only turned on when the minimum value is exceeded by more than +1 bar, in particular more than +0.75 bar, preferably more than +0.5 bar. Method according to one of claims 3 to 8, wherein before the further operation of the plant ( 1 ) a time reconnection block of a few seconds, preferably a few minutes must be overcome. Method according to one of claims 3 to 9, wherein for further operation of the plant ( 1 ) a safety acknowledgment, preferably at the site of the plant is required. Method according to one of claims 3 to 10, wherein before giving the signal or triggering the protective function, in particular the blocking of the media circuits ( 3 . 4 ) and / or switching off the media replenishment of the second medium cycle ( 4 ), a switching delay is provided, which is in particular a few minutes, preferably a few seconds. Method according to one of the preceding claims, wherein before the leak detection, the system ( 1 ) is put into a state of rest, in which the circuits ( 3 . 4 ) have their resting pressure. Heat exchanger ( 1 ) with at least two medium circuits separated from each other by at least one wall, wherein a first medium circuit ( 3 ) of the medium cycles a medium with high pressure leads and a second medium cycle ( 4 ) of the media circuits a medium with lower pressure leads, and means for monitoring leaks between the first and second medium circuits ( 3 . 4 ), the apparatus comprising: an absolute pressure sensor in each of the first and second medium circuits ( 3 . 4 ) or an absolute pressure sensor in each of the first and second medium circuits ( 3 . 4 ) and in a closed space between the first and second medium circuits ( 3 . 4 ) for determining respective absolute pressures, differential pressure measuring means, which are adapted to derive from the respective absolute pressures of the first and second medium circuits ( 3 . 4 ) Determining a differential pressure between the medium circuits ( 3 . 4 ) and / or from the respective absolute pressures of at least one of the first and second medium circuits ( 3 . 4 ) and the closed gap determining a differential pressure between the at least one of the first and second medium circuits ( 3 . 4 ) and the closed space, wherein the differential pressure measuring means are arranged to compare the determined differential pressure with a predetermined differential pressure and to perform a switching operation when the determined differential pressure reaches the predetermined differential pressure, a pressure value switch ( 8th ) connected to the absolute pressure sensor of the second medium circuit ( 4 ) and which is set up, simultaneously with the provided in the differential pressure measuring means comparing the determined differential pressure with the predetermined differential pressure, the absolute pressure of the second medium circuit ( 4 ) with a control value of the pressure value switch ( 8th ) preset maximum pressure, and wherein the pressure value switch ( 8th ) is arranged to perform a switching operation when the absolute pressure of the second medium circuit ( 4 ) exceeds the maximum pressure, and wherein the device is arranged so that the differential pressure measuring means and the pressure value switch ( 8th ) trigger a protective function when a switching operation is performed. Heat exchanger ( 1 ) according to claim 13, wherein the device is a check valve ( 10 ), which in the first medium cycle ( 3 ) and that with the differential pressure measuring means and the pressure value switch ( 8th ), and wherein the device is arranged such that the differential pressure measuring means and the pressure value switch ( 8th ) when a switching operation, the check valve ( 10 ), so that the first medium cycle ( 3 ) is locked. Heat exchanger ( 1 ) according to claim 13 or 14, wherein the differential pressure measuring means a differential pressure switch ( 7 ) adapted to store a desired differential pressure setpoint (Δp _s ). Heat exchanger ( 1 ) according to claim 15, wherein the differential pressure control value (Δp _s ) is 0 bar. Heat exchanger ( 1 ) according to one of claims 13 to 16, wherein the device comprises a further pressure value switch ( 9 ) connected to the absolute pressure sensor of the second medium circuit ( 4 ) and which is set up, the absolute pressure of the second medium cycle ( 4 ) with a control value of the further pressure value switch ( 9 ) preset preset minimum pressure and to perform a switching operation when the absolute pressure of the second medium cycle ( 4 ) falls below the minimum pressure, and wherein the further pressure value switch ( 9 ) with a for circulating the medium of the second medium cycle ( 4 ) provided circulating pump ( 6 ) is connected, so that when making a switching operation by the other Pressure value switch ( 9 ) the circulation pump ( 6 ) is switched off.

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