DE9402496U1 - Sampling device for taking liquid samples - Google Patents

Description

: . . . · < · · ·· 3612.4&mdash;b IU:- ·..·.·. ..* : 29.12.1993

The invention relates to a sampling device for taking liquid samples from a container, in particular a main line, with - a sampling line which connects the main line to a first controlled valve,

- a first switching unit for actuating the first valve,

- a time-controlled clock generator to control the first switching unit and

- a sample collection container for collecting individual liquid samples.

Sampling devices of the above type are used to take individual samples from a main fluid line at specific time intervals and to collect the individual samples in a sample collection vessel. The contents of the sample collection vessel can then be removed and analyzed in order to determine the properties of the fluid flowing in the main line averaged over a longer period of time. The purpose of sampling devices of the above type is therefore not a momentary or continuous analysis or the extraction of individual samples, but the provision of a total sample quantity from many individual samples in order to determine the time-averaged properties of the fluid in the fluid line.

A known sampling device of the above type is disclosed in DE-AS 29 15 931. The sampling device here has a switching unit that controls a valve in a sampling line that connects the fluid line to a collecting vessel provided with a sampling connection. Simple sampling devices of the above type have the disadvantage that

3612.4&mdash;b .r. ^: 3..*- *..'.:.&diams;··" ^: 29.12.1993

that when there are pressure fluctuations in the main line, different flow rates occur in the collecting vessel during the opening time of the valve in the extraction line. Due to the different pressures in the main line, the sample collected in the collecting vessel is no longer an exact time-averaged image of the amount of liquid in the main line, but the size of the individual liquid samples is different due to the pressure differences. DE-AS 29 15 931 therefore teaches that a counter with a pulse generator should be arranged in the fluid line for flow-proportional extraction, which sends a flow-proportional pulse sequence to the switching unit during a measuring period. Such a solution can take the effects of different pressures in the main line into account to a large extent, but the entire arrangement with a counter, a pulse generator and a correspondingly complicated control and switching unit is very complex.

The invention is therefore based on the object of creating a sampling device which takes individual liquid samples for collection in a sample collection container, the size of which is largely independent of the respective pressure in the main line and which can nevertheless be operated using only a simple time control.

This object is achieved according to the invention in that

- a second controlled valve operated by a second switching unit is connected on one side via an intermediate line to the first controlled valve and on the other side to the sample collection container,

- where a single sample container is inserted into the intermediate line and

—3—

3612.4&mdash;b 5- S !-*··· ..' : 29.12.1993

- the first and second switching units are connected to the time-controlled clock generator in such a way that

- that the individual sample container is cyclically filled with an individual liquid sample by opening the first controlled valve,

- separated from the main line by closing the first controlled valve and

- is connected to the sample collection container by opening the second controlled valve, - so that the individual liquid sample essentially reaches the sample collection container in its entirety.

Preferably, the time-controlled clock generator is connected to the first controlled valve via the first switching unit and to the second controlled valve via the second switching unit in such a way that it cyclically opens the first controlled valve to fill the individual sample container with an individual liquid sample and closes the second controlled valve or leaves it in the closed state; after a filling time T1, the first controlled valve closes; after a waiting time T2, which can also be 0, the second controlled valve opens to empty the individual sample container; after an emptying time T3, the second controlled valve closes; and then during a pause time T4, which can also be 0, the time-controlled clock generator does not actuate the first and second controlled valves.

The solution according to the invention therefore provides a sampling device in which an individual sample volume is created cyclically between the first controlled valve and the second controlled valve in the interior of the intermediate line and the individual sample container, which after it has been filled from the sampling line, is separated from the main line and the content of which is essentially

3612.4&mdash;b

: 29.12.1993

is completely emptied into the sample collection container. The sample collection container is therefore never directly connected to the main line. Fluctuations in the pressure in the main line therefore only have a minor effect on the size of the individual liquid sample.

This is achieved in particular if, according to an advantageous development of the invention, the filling time Tl is dimensioned such that, under the respective operating conditions, the filling process of the individual sample container is completely finished after the expiry of the filling time Tl.

An advantageous development of the invention provides that the sample collection container has an outlet connection, in particular a coupling. This enables easy removal of the collected individual samples.

An advantageous development of the invention is characterized in that the sample collection container and/or the intermediate line and/or the individual sample container is connected to a vent and/or overflow line. The vent and/or overflow line connected to the intermediate line and/or the individual sample container has a third controlled valve arranged adjacent to the first controlled valve, which opens or closes this line, whereby the time-controlled clock controls this third controlled valve so that it is closed while the individual sample container is being filled and open while the individual sample container is being emptied. The vent and/or overflow lines ensure a defined venting of the sampling device and a controlled drainage of any excess liquid that may arise. If the main line contains toxic, environmentally harmful or otherwise questionable liquids,

3612.4&mdash;b :_·55_r': · · ..· : 29.12.1993

This development of the invention allows for quick and easy provision to be made to properly collect and drain any small amounts of liquid that may arise. In this case, it is particularly recommended, according to an advantageous development of the invention, to insert an automatic safety valve into the ventilation and/or vent line(s), which automatically closes when liquid passes through. This reliably prevents liquid from escaping from the vent and/or overflow line.

The first and/or the second and/or possibly the third controlled valve are preferably designed in the form of solenoid valves. The first and the third controlled valve can advantageously be combined in a controlled three-way valve, which makes the structure of the sampling device more compact and reduces the number of components required and thus also the possible sources of error.

In the simplest case, the individual sample container is conveniently formed only by the interior of the intermediate line. According to an advantageous development of the invention, the individual sample container and/or the sample collection container can also be designed to be exchangeable using detachable connections. Although this requires a slightly higher construction effort, it enables the sampling device to be easily and quickly adapted to the parameters required by the operator in terms of size and number of individual samples. The maximum number of samples that can be taken without emptying the sample collection container in the meantime can be calculated in a simple way from the internal volume of the individual sample container and the intermediate line in relation to the internal volume of the sample collection container.

3612.4&mdash;b V-'.&bgr;'- ··.:.. ..* : 29.12.1993

The maximum number of individual samples to be obtained multiplied by the duration T of a cycle, consisting of the filling time T1, the waiting time T2, the emptying time T3 and the pause time T4, gives the total measuring time T of the sampling device. The total measuring time T can generally be easily adapted to the operating requirements by changing the setting of the time-controlled clock generator. The advantageous further development of the invention makes it possible to change at least one of the two other parameters, volume of the individual container and volume of the sample collection container, in addition to the cycle time T parameter. This makes it possible to easily adapt the sampling device to a wide variety of application requirements and wishes.

The sampling device advantageously has a level measuring device with a level indicator, e.g. a visually readable riser pipe made of glass or a transparent plastic or a riser pipe provided with a corresponding glass or plastic insert. This makes it easy to check the amount of liquid already collected in the sample collection container.

A further advantageous development of the invention provides that the sampling device has a compressed gas device for transferring the individual liquid samples from the individual sample container into the sample collection container by means of a compressed gas, preferably a chemically neutralized gas. Such a compressed gas conveying device is particularly advantageous for sampling viscous liquids, e.g. oil products. In this case, the transfer process from the individual sample container into the sample collection container is carried out by the compressed gas, e.g.

Nitrogen N2 is supported.

3612.4&mdash;b IV*I-' : S ·! "" ^: *'&Ggr; 29.12.1993

The sampling device has valves controlled by the timer to control the flow of compressed gas. The compressed gas can also be used to speed up the emptying of the sample collection container. The lines required for this can be opened and closed easily using manual valves; partial or fully automatic control is not necessary.

The time-controlled clock generator conveniently contains a radio-, quartz- or mains frequency-controlled clock.

The time-controlled clock generator is advantageously connected to a time-controlled timer or to a counting device that counts the cycles of the time-controlled clock generator to switch off the time-controlled clock generator. In this way, the sampling device can be switched off fully automatically after a predetermined total measurement time or after a predetermined number of individual clock cycles. In this advantageous further development of the invention, the taking of further individual samples is automatically stopped after a certain period of time or number of clock cycles.

A further advantageous development of the invention provides that all electrical devices of the sampling device are designed to be explosion-proof. This is particularly advantageous if the main line contains explosive or flammable liquids.

The power supply of the electrical equipment can advantageously be provided permanently or temporarily using electrical storage devices such as accumulators, batteries or capacitors. The temporary use of electrical

3612.4&mdash;b I SsV ^: .. ^: .:!. "" ^: ":' 29.12.1993

Storage devices can be used to bridge periods of power failure, so that even in this case the continuous collection of individual samples is ensured. A permanent power supply using accumulators, batteries or capacitors will be considered in particular if the sampling device is used far away from a possible power supply, e.g. on overland pipelines far away from settlements.

It is advantageous to provide a bypass to the main line by connecting the sampling line to the main line via an additional return line. This ensures a constant flow of liquid through as large a part of the sampling line as possible, which increases the representativeness of the individual samples.

It is advisable to insert a filter into the sampling line, especially if the liquid in the main line is or may be contaminated, in order to ensure safe operation of the sampling device.

Another advantageous development of the invention provides that a pressure reducer and/or a pressure indicator is inserted into the sampling line. A pressure reducer is preferably used when the main lines are under high pressure. If the pressure reducer is equipped with pressure indicators for the inlet and/or outlet pressure, this also enables easy monitoring of the pressure in the sampling line and/or in the sampling device. The use of a pressure indicator is advantageous in any case, since a constant pressure on the outlet side of the pressure reducer compensates for the already small fluctuation in the size of the individual samples in the sampling device.

3612.4&mdash;b :-:9:-: : .* · "'·*"·' 29.12.1993

receiving device is further reduced.

A further advantageous development of the invention provides that a safety pressure relief valve is arranged in the sampling line adjacent to the first controlled valve. Such a safety pressure relief valve serves to protect the sampling device from pressure peaks or other excessive pressures in the sampling line. As an additional safety measure, the sampling device can be designed to be pressure-resistant.

The components of the sampling devices are conveniently arranged in a housing into which the sampling line is led. For visual control of the various displays of the level measuring device, time-controlled clock or similar, the housing can conveniently have a door with a viewing window.

The invention is explained in more detail below using two exemplary embodiments. The accompanying drawings show:

Fig. 1 is a schematic flow diagram of a first embodiment of the sampling device according to the invention;

Fig. 2 is a schematic representation of the position of the valves in the embodiment of Fig. 1; 30

Fig. 3 is a schematic flow diagram of the valve arrangement in a second embodiment of the sampling device according to the invention.

In the case of the device shown in Fig. 1 and generally designated 1,

- 10 -

3612.4&mdash;b Ml(J-: : .''" ^: 'T 29.12.1993

In the sampling device according to an embodiment of the present invention, all components are arranged within a housing 22. A sampling line 3 is led into the housing and a return line 20 is led out. Parts of the sampling line 3 and the return line 20 form a bypass to the main line 2 through which the liquid to be tested flows. A pressure reducer 21 is inserted into the sampling line 3 and has a pressure indicator 28 for the outlet-side pressure - i.e. the pressure on the side of the sampling device. The first controlled valve 4 and the third controlled valve

16 are combined in this embodiment in a controlled, electromagnetically operated three-way valve 17. The individual sample container 10 is filled with water through the interior of the intermediate line 11, which is located between the three-way valve

17 and the second controlled valve 6, also a solenoid valve, is inserted. The two solenoid valves 6 and 17 are used in explosion-proof design. Below the second controlled valve 6 there is a replaceable sample collection container 12 into which the individual liquid samples from the intermediate line 11 are emptied after the second controlled valve 6 is opened. In this embodiment the replaceable sample collection container 12 has an internal volume of 3 l. Parallel to the sample collection container there is a riser pipe 19 made of glass with a visually readable level indicator that shows the liquid level inside the sample collection container.

The intermediate line 11 is vented via a vent and/or overflow line 15, and the sample collection container via a vent and/or overflow line 14. The two vent and/or overflow lines 14, 15 are further combined to form a common vent and/or overflow line 27. In this

- 11 -

3612.4&mdash;b &igr;-&agr;&idigr;:-: : .· · *''":' 29.12.1993

An automatic safety valve 18 is inserted into the common vent and/or overflow line 27, which immediately interrupts the flow of media in the event of an extreme increase in flow or a sudden change in the viscosity of the medium - e.g. when liquid passes through instead of gas. The common vent and/or overflow line 27 is then led out of the housing 22.

The two solenoid valves 17 and 6 are controlled via their respective switching units 5, 7 by a time-controlled clock generator 8, which contains a quartz clock and is also explosion-proof. To initiate the filling of the intermediate line 11, a voltage pulse is applied to the two solenoid valves 17 and 6, whereby the first controlled valve 4 is opened, the second controlled valve 6 is closed and the third controlled valve 16 is closed. (The first controlled valve 4 and the third controlled valve 16 are, as already mentioned, combined in the form of a solenoid valve in the three-way valve 17.) Fig. 2 shows schematically the position of the valves 17 and 6 during the filling time T 1 and during the emptying time T 3.

At the end of the filling time T 1, the time-controlled clock interrupts the voltage pulse, causing the first controlled valve 4 to close, the second controlled valve 6 to open and the third controlled valve 16 to open. In the subsequent emptying time T 3, the individual liquid sample from the intermediate line 11 passes into the sample collection container under the effect of gravity. The waiting time T 2 and the pause time T 4 are 0 in this embodiment of the invention, the cycle time T results from the sum of the filling time T 1 and the emptying time T 3. The duration of the times T 1 and T 3

- 12 -

3612.4&mdash;b £3.2&Idigr;-&iacgr; .S .· ..· : 29.12.1993

can be easily set using push buttons on the time-controlled clock generator. The housing 22 has a door (not shown in the drawing) with a transparent window, through which the liquid level in the riser pipe 19, the display of the pressure indicator 21 and the times T 1 and T 3 set on the time-controlled clock generator 8 can be read visually.

The time-controlled clock generator 8 is switched off after a period of time preset on the timer 9 has elapsed, so that no further individual samples are taken. Cycle time T, internal volume of the intermediate line 11 and internal volume of the exchangeable sample collection container 12 are sensibly coordinated with one another in such a way that the desired total measurement time is achieved. The embodiment shown can, for example, be designed so that the volume of the sample collection container 12 is filled to 3 liters after a total measurement time of 12 hours. The timer 9 is started by means of a control switch 25 in an explosion-proof design.

In this embodiment, the electrical equipment is supplied with power via a power supply cable 26 that is fed into the housing; power failure protection using accumulators or batteries has been dispensed with. Instead, this embodiment contains a thermostat 23 that allows temperature control of the entire sampling device within the housing 22 by means of an explosion-proof electrical heater 24 controlled by the thermostat 23. The housing 22 is thermally insulated from the environment by means of molded foam and aluminum foil.

- 13 -

VVVV V V V V VVV

3612.4&mdash;b - 13.:- ^: .. ^: * ^: .. ^: .:i. * ."S9 ^# 'l2.1993

The intermediate line forming the individual sample container 10, the sample collection container 12 and all line connections of the sampling device are made of stainless steel in this embodiment. The vent and/or overflow lines 14 and 27 are stainless steel pipes with an outside diameter of 12 mm, the other connecting lines are made of stainless steel pipes with an outside diameter of 6 mm. The riser pipe 19 consists of a pipe made of high-strength glass in a stainless steel housing. In this way, not only is the material of the sampling device highly resistant to aggressive media, but at the same time the entire sampling device is also designed to be high-pressure resistant. This means that even if the pressure reducer 21 fails, no liquid will leak into the interior of the housing 22 or into the environment. The use of a safety pressure relief valve was therefore deliberately omitted.

The second embodiment of the sampling device according to the present invention, generally designated 1, shown in Fig. 3 has a compressed gas device, generally designated 30, with which the transfer process from the individual sample container 10 into the sample collection container 12 is accelerated. Since this second embodiment of Fig. 3 differs from the first embodiment of Fig. 1 only in the number and arrangement of the valves, the other components have not been shown. Fig. 3 therefore only contains a schematic representation of the arrangement of the controlled valves 4, 6 and 16 as well as the controlled valves 32 and 35 of the compressed gas device 30.

Also in this second embodiment of the inventive

_ 14 _

3612.4&mdash;b - JAls-·..· ·..*.:.. .."29:12.1993

In the sampling device 1 according to the invention, the two controlled valves 4 and 16 are again combined in a controlled, electromagnetically operated three-way valve 17. In addition to the individual sample container 10, which in turn is formed by the interior of the intermediate line 11, this second embodiment contains a compressed gas container, which is formed by the interior of a compressed gas line section 34. The compressed gas line section 34 is closed at both ends by valves 32, 35, which can be actuated by the time-controlled clock generator 8 via their respective switching units 33, 36. The valve 32 is connected to the third controlled valve 16 via a compressed gas supply line 31. In this second embodiment of Fig. 3, the pressurized gas supply line 31 takes the place of the venting and/or overflow line 15 from the first embodiment of Fig. 1. The pressurized gas, which is nitrogen N2, is supplied to the pressurized gas device 30 via a pressurized gas supply line 38.

The switching behavior of the three-way valve 17, in which the first controlled valve 4 and the third controlled valve 16 are combined, is identical to the first embodiment of Fig. 1 (see the illustration in Fig. 2). At the same time as the opening of the second controlled valve 6, the closing of the first controlled valve 4 and the opening of the third controlled valve 16 at the beginning of the emptying time T3, a signal from the time-controlled clock generator 8 also opens the valve 32 in the compressed gas device 30. As a result, not only gravity acts on the individual liquid sample in the intermediate line 11, but also the pressure of the nitrogen compressed gas in the compressed gas line section 34. The emptying of the

- 15 -

3612.4&mdash;b

The individual liquid sample from the individual sample container 10 into the sample collection container 12 is thereby significantly accelerated. After the emptying time T3 has elapsed, the second controlled valve 6 closes, the first controlled valve 4 opens at the beginning of the filling time Tl, and the third controlled valve 16 closes. Signals from the timer 8 simultaneously close the valve 32 and open the valve 35, whereby new nitrogen gas flows from the compressed gas supply line 38 into the compressed gas line section 34 and builds up a new gas pressure there. Before or at the beginning of the emptying time T3, the valve 35 is closed by a signal from the time-controlled timer 8.

The interior of the compressed gas line section 34 thus forms a buffer volume for the compressed gas, which - suitably timed by the time-controlled clock generator 8 - acts on the individual liquid sample located in the interior of the intermediate line 11 and accelerates its transfer into the sample collection container 12.

In order to prevent the pressure or liquid in the extraction line 3 or in the intermediate line 11 from having a reaction on the compressed gas device 30, a check valve 37 is inserted into the compressed gas supply line 31.

· · Z

3612.4&mdash;b - &igr; i : :·: : .· · "2^:12.1993

List of reference symbols

1 sampling device

2 Main line

3 Extraction line

4 first controlled valve

5 first switching unit

6 second controlled valve 7 second switching unit

8 time-controlled clock

9 Timer

10 individual sample containers

11 Intermediate line

12 sample collection containers

13 Clutch

14 Vent and/or overflow line

15 Vent and/or overflow line

16 third controlled valve 17 three-way valve

18 automatic safety valve

19 Riser pipe

20 Return line

21 Pressure reducer
22 Housing

23 Thermostat

24 Heating

25 control switches

26 Power supply line

27 Vent and/or overflow line

28 Pressure indicator

30 Pressure gas device

31 Pressurized gas supply line

32 Valve

33 Switching unit

3612.4&mdash;b - 2 -i : :*: : .* · · ^# &dgr;5*;&idiagr;2.&idiagr;993

34 Pressure gas pipeline section

35 Valve

36 Switching unit

37 Check valve

38 Compressed gas supply line

Claims (26)

VVVV V V V V WVV 3612.4&mdash;b - 1 &tgr;:.·..· ·..*.:.. ..29.iL2.1993 Protection claims: 1. Sampling device for taking liquid samples from a container, in particular a main line, with - a sampling line connecting the main line to a first controlled valve, - a first switching unit for actuating the first controlled valve, - a time-controlled clock generator to control the first switching unit and - a sample collection container for collecting individual liquid samples,
characterized in that - a second controlled valve (6) operated by a second switching unit (7) is connected on one side via an intermediate line (11) to the first controlled valve (4) and on the other side to the sample collection container (12), - wherein a single sample container (10) is inserted into the intermediate line (11) and - the first (5) and the second (7) switching unit are connected to the time-controlled clock generator (8) in such a way, - that the individual sample container (10) is cyclically filled with an individual liquid sample by opening the first controlled valve (4), - separated from the main line (2) by closing the first controlled valve (4) and - is connected to the sample collection container (12) by opening the second controlled valve (6), - so that the individual liquid sample is essentially completely transferred into the sample collection container (12). VVVV V V V V VVV 3612.4&mdash;b - 2 T.W.· *..'.:.. ..29 .Jl2.1993 2. Sampling device according to claim 1, characterized in that the time-controlled clock generator (8) is connected to the first controlled valve (4) via the first switching unit (5) and to the second controlled valve (6) via the second switching unit (7) in such a way that it cyclically opens the first controlled valve (4) to fill the individual sample container (10) with an individual liquid sample and closes the second controlled valve (6) or leaves it in the closed state; after a filling time T1 the first controlled valve (4) closes; after a waiting time T2, which can also be 0, the second controlled valve (6) opens to empty the individual sample container (10); after an emptying time T3 the second controlled valve (6) closes; and then during a pause time T4, which can also be 0, the time-controlled clock generator (8) does not actuate the first (4) and the second (6) controlled valve. 3. Sampling device according to claim 2, characterized in that the filling time Tl is dimensioned such that under the respective operating conditions of the sampling device (1), the filling process of the individual sample container (10) is completely finished after the expiration of the filling time Tl. 4. Sampling device according to one or more of the preceding claims, characterized in that the sample collection container (12) has an outlet connection, in particular a coupling (13) having. 5. Sampling device according to one or more 3612.4&mdash;b -3,-&iacgr;.·..· ·..·.:.. .. -29:12.1993 of the preceding claims, characterized in that the sample collection container (12) is provided with a vent and/or overflow line (14)
connected is.
05 6. Sampling device according to one or more
of the preceding claims, characterized in that the intermediate line (11) and/or the individual sample container (10) is provided with a venting and/or overflow line (15) which is opened or closed by a third controlled valve (16) arranged adjacent to the first controlled valve (4), wherein the time-controlled clock
(8) controls the third controlled valve (16) so that it is closed during filling of the single sample container (10) and open during emptying of the single sample container (10). 7. Sampling device according to claim 5 or 6,
characterized in that in the Vent and/or overflow line (14, 27) and/or into the ventilation and/or overflow line (15, 27)
an automatic safety valve (18) is inserted, which closes automatically when liquid passes through. 25 8. Sampling device according to one or more
of the preceding claims, characterized in that the first (4) and/or second (6) and/or optionally third (16) controlled valve is a solenoid valve. 9. Sampling device according to claim 6, characterized
characterized in that the first (4) and the third controlled valve (16) are combined in a controlled three-way valve (17). 3612. 4&mdash;b - 4 .j. ^: .. ^: ' ^: .. ^: .:!. * " ^: 2*9*;*12.1993 10. Sampling device according to one or more of the preceding claims, characterized in that the individual sample container (10) is formed by the interior of the intermediate line (11). 11. Sampling device according to one or more of the preceding claims, characterized in that the individual sample container (10) is designed to be exchangeable by means of detachable connections. 12. Sampling device according to one or more of the preceding claims, characterized in that the sample collection container (12) is designed to be exchangeable by means of detachable connections. 13. Sampling device according to one or more of the preceding claims, characterized in that the sample collection container (12) has a level measuring device with a level indicator. 14. Sampling device according to claim 13, characterized in that the level measuring device is a visually readable riser pipe (19) made of glass or a transparent plastic or a riser pipe (19) provided with a corresponding glass or plastic insert. 15. Sampling device according to one or more of the preceding claims, characterized in that the sampling device (1) has a compressed gas device (30) for transferring the individual liquid samples from the individual sample container (10) 3612.4-b - 5 .-:.:..:' :..:. _s :. ""1^I ₂ .1993 into the sample collection container (12) by means of a compressed gas, preferably a chemically inert gas. 16. Sampling device according to claim 15, characterized in that the sampling device (1) has valves (32, 35) controlled by the time-controlled clock generator (8) for controlling the compressed gas flow. 17. Sampling device according to one or more of the preceding claims, characterized in that the time-controlled clock generator (8) contains a radio-, quartz- or mains frequency-controlled clock. 18. Sampling device according to one or more of the preceding claims, characterized in that the time-controlled clock generator (8) is connected to a time-controlled timer (9) or to a counting device that counts the cycles of the time-controlled clock generator for switching off the time-controlled clock generator (8). 19. Sampling device according to one or more of the preceding claims, characterized in that all electrical devices are designed to be explosion-proof. 20. Sampling device according to one or more of the preceding claims, characterized by a permanent or temporary power supply of the electrical devices by means of electrical storage devices such as accumulators, batteries or capacitors. 3612.4&mdash;b - 6 r..''..''' :..:.::. ' :?3'£2.1993 21. Sampling device according to one or more of the preceding claims, characterized in that the sampling line (3) is connected to the main line (2) by an additional return line (20), whereby a bypass to the main line (2) is achieved. 22. Sampling device according to one or more of the preceding claims, characterized in that a filter is inserted into the sampling line (3). 23. Sampling device according to one or more of the preceding claims, characterized in that a pressure reducer (21) and/or a pressure indicator (28) is inserted into the sampling line (3). 24. Sampling device according to one or more of the preceding claims, characterized in that a safety pressure relief valve is arranged in the sampling line (3) adjacent to the first controlled valve (4). 25. Sampling device according to one or more of the preceding claims, characterized in that the components of the sampling device are arranged in a housing (22) into which the sampling line (3) is guided. 26. Sampling device according to claim 25, characterized in that the housing (22) has a door provided with a viewing window.