EP1556647A1

EP1556647A1 - Method and device for the removal of liquid samples from pressurised containers

Info

Publication number: EP1556647A1
Application number: EP03772253A
Authority: EP
Inventors: Marcel G. F. Kroll; Nicolaas Augustinus Van Hoof; Uwe Bier; Enrico Dietzsch; Michael Krusche; Thomas Richter
Original assignee: Amtec Anwendungszentrum fur Mikrotechnologien Chemnitz GmbH
Current assignee: Amtec Anwendungszentrum fur Mikrotechnologien Chemnitz GmbH
Priority date: 2002-10-24
Filing date: 2003-10-23
Publication date: 2005-07-27
Also published as: AU2003279314A1; WO2004038281A1; DE10249771A1

Abstract

The invention relates to a method and device for the removal of liquid samples from one or more pressurised containers and a device for carrying out said method. The aim of the invention is to achieve an automatic extraction of samples from containers under pressure, whereby the pressure in the original container remains essentially unchanged and only the actual required sample amount is extracted from the container. Said aim is achieved, whereby the sample is introduced from the pressurised container into a sample loop as a buffer store, which is firstly sealed relative to the sample container, said seal only being released after the connection between the pressurised container and the buffer store is broken. A device is disclosed for the above with a sample loop (3) provided in the line system, connected to the pressurised container (1) and the sample container (2) by means of two valves and a further valve (V3) is provided on the sample loop (3) supplied with an inert gas or a process gas.

Description

Method and device for taking liquid samples from pressure vessels

The invention relates to a method for taking liquid samples from one or more pressure vessels and a device for carrying out this method.

For various types of technical applications, it is necessary to take liquid samples from pressurized containers, which are mainly conducted into sample vessels or into analysis systems. A typical example of this are reactors, which are used in chemical research for the development of new chemical compounds and materials (e.g. catalysts) and for process optimization.

These devices usually (e.g. according to US 6,306,658 B1) consist of several closed reaction containers for simultaneously carrying out a corresponding number of reactions. For this, e.g. the temperature, the pressure and the gas supply in the individual reaction vessels can be set and changed in a program-controlled manner. The contents of the container can be stirred using stirring systems with adjustable speeds. The reaction vessels (e.g. according to WO 98/56 506 A1) often have fluidic connections in the lids, which are used for automated gas supply and for building up pressure in the reaction vessels. In this case, the same pressure is predominantly applied to a group of reaction vessels via a common gas supply.

However, the previously known single and multiple reactors have the disadvantage that automatic sampling of liquid from the container is not possible while the reaction is carried out under pressure. For this, the pressure in the container has to be reduced significantly, but this affects the reaction. Such a reduction in pressure is therefore largely undesirable.

If the pressure in the container is to be maintained largely unchanged, manual sampling can be carried out. the container. However, this alternative variant is also problematic. For manual sampling protrudes with one Filter-secured tube into the liquid in the respective reaction container. This tube is connected to a sample container via a valve (preferably with a variable opening cross section). For taking a sample, the valve - depending on the current pressure in the reaction container - is carefully opened to drain a certain amount of liquid into the sample container. Due to the pressure difference between the reaction and sample container, the procedure must be very sensitive, the amount of sample taken and the resulting reduction in pressure in the - container largely dependent on the experience of the person performing it. These manual sampling are therefore subject to considerable subjective influences and are therefore difficult to reproduce or automate.

Another disadvantage of such. manual sampling by means of a directly connected valve consists in the fact that liquid remains in the pipeline between the reaction container and the drain valve which is no longer available to the reaction system. For further sampling at later times, this liquid must first be disposed of in a waste container until the "current" liquid is available at the outlet from the reaction container. As a result, an additional quantity of liquid is removed from the second sampling in addition to the actually necessary sample quantity, which disadvantageously affects the reaction system being affected.

The object of the invention is to provide a method for automatic sampling of liquids from pressurized containers, the pressure in the outlet container being to be maintained largely unchanged and only the amount of sample actually required being taken from the pressure container. Furthermore, an apparatus for performing this method is to be created.

The object is achieved in that the sample is fed from the pressure vessel to a buffer store which is initially blocked off from the sample container and this barrier is only lifted after the connection between the pressure vessel and the buffer store has been interrupted. For this purpose, a device is proposed in which a sample loop is assigned to the line system and is operatively connected to the pressure container and the sample container via two valves. Advantageous refinements are described in the respective dependent subclaims. The method according to the invention is characterized in that in a system comprising one or more pressure containers under pressure (or working), one or more sample containers under normal pressure, several valves and a sample loop, a first valve V , is opened, which is arranged between a pressure vessel 1, a connection point 19 and the sample loop 3, and in a second stage a liquid sample quantity is pressed into the sample loop 3 by the container pressure p. of the pressure vessel 1, and the valve V, is closed is, and through a third valve V ₃ , which is arranged downstream of the pressure vessel 1 behind the sample loop 3, inert or process gas with a pressure p ₃ , which is higher than the normal pressure, and thereby the sample amount in the sample loop 3 is supplied after opening a second valve V ₂ , which between the sample loop 3 and the sample container age 2 is arranged, is pressed into the sample container 2, and in a third stage after closing the second valve V ₂ and opening the first valve V _1, the residual liquid quantities remaining in the lines or in the sample loop 3 due to the higher pressure p ₃ in the Pressure vessel 1 are returned.

The technical solution according to the invention is suitable for various applications in which an automatic sampling of liquids from pressure vessels is advantageous. Such sampling is now largely independent of subjective influences, such as the care and experience of the staff. The test conditions and results achieved are thus reproducible. The preferred field of application is multiple reactors, which are used in chemical research for the development of new chemical compounds and materials as well as for process optimization. The main advantage over previously known technical solutions is that the pressure in the outlet container is maintained largely unchanged and consequently there is no impairment of the reactions in the pressure container. Furthermore, only the amount of sample actually required is taken from the pressure vessel, which is very important for microreactors and multiple sampling. According to the invention, this amount of sample is very small due to the special procedure and essentially only corresponds to the volume of the sample loop. It is also possible to take samples directly into sample vessels, which are listed below Normal pressure and where the sample liquid can be analyzed under these conditions.

The invention also relates to a device for carrying out the method for taking liquid samples from pressure vessels, the device comprising

- one or more pressure vessels,

one or more sample containers which are connected to the pressure container (s) via a first valve V,

- A sample loop which is connected to the pressure vessel (s) via a branch point and a second valve V ₂ , and

- After the sample loop downstream of the pressure vessel and the branch point 19 arranged third valve V ₃ , which is connected to a compressed gas supply.

The principle of the solution according to the invention is explained below with reference to the drawing. Show it:

Fig. 1 shows the basic structure of a device for performing the method. Fig. 2 shows an embodiment of the device for use with several pressure vessels

With the arrangement shown in FIG. 1, a defined amount of liquid is taken as a sample from a container 1 under pressure p. This sample is filled via a line system into a sample container 2, which is under normal pressure p ₂ . A filter 4 is preferably assigned to the line system in the area of the pressure vessel 1. It should be achieved that the pressure p- remains largely unchanged in the pressure vessel 1 despite taking the sample and only the actually required amount of sample is taken from the pressure vessel.

For this purpose, the arrangement has a sample loop 3. The sample loop 3 is preferably interchangeable, so that it can be adapted to different operating conditions with different shapes and volumes (for example 100, 200 or 500 μl) with little effort. The sample loop 3 is operatively connected to the pressure container 1 and the sample container 2 via a first valve V and a second valve V ₂ . The connection of sample loop 3, valve V, to the pressure container 1 and valve V ₂ to the sample container 2 can be designed in various ways. As a preferred variant, which is also shown in the drawing, this connection is designed as a T-branch. In the further A third valve V ₃ , preferably with a variable opening cross section, is arranged downstream of the sample loop 3. An inert gas or a process gas is present at this valve V ₃ . The gas has a pressure p ₃ which is at least somewhat greater than the pressure p 1 in the pressure vessel 1. The pressure at the opposite end of the sample loop 3 is identified as p ₄ in the drawing. The following procedure is implemented with this arrangement according to FIG. 1:

In the initial state, valves V and V _{3 are} closed, valve V ₂ is open. The entire pipe system is free of liquid. The pressure in the flow path between the valves V. ,, V ₂ and V ₃ is lower due to the connection to the sample container 2 than in the pressure container 1 and in the line between the pressure container 1 and valve V, in this state the valve V _{2 is} closed.

If the valve V ₁ is now opened, liquid flows through the filter 4 and the valve V into the sample loop 3 due to the pressure difference p.> P _4. This flow process lasts until the same pressure in the sample loop 3 as in the pressure vessel 1 prevails. Due to the small volume of sample loop 3 and line system compared to the pressure vessel 1, this pressure is only slightly smaller than the initial value of p-. When filling the sample loop, the gas in the line system is compressed in the line between the sample loop 3 and the valve V ₃ .

Now valve V. is closed and then valve V _{2 is} opened. Due to the pressure difference p ₄ > p ₂ , a large part of the liquid in the sample loop 3 flows into the sample container 2. Now the valve V ₃ is additionally opened by a small value and the inflowing inert or process gas presses the rest of the sample liquid likewise in the sample container 2. The sample loop 3 and the line system between the valve V ₃ and the sample container 2 are pressed free of liquid. Subsequently, valve V _{2 is} closed, valve V _{3 is} completely opened and, after p ₄ = p ₃ is reached again, valve V. is opened. Due to the overpressure of the inert or Process gas compared to the pressure p ₁ in the pressure vessel 1, the liquid located in the line system between the branch valve V ₁ / valve V ₂ / sample loop 3 (T-connection) and the pressure vessel 1 is pressed back into the pressure vessel 1. An outlet pressure p _{n is} produced again. As a last step, valve V _n is first closed, then valve V _{3 is} also closed and finally valve V _{2 is} opened. Here, the pressure ^escapes' in the sample loop 3 by the output of the sample container 2. In this operating state, further by integrating valves, the sample loop 3 and the associated piping system are rinsed with cleaning fluid, wherein the output of the valve V ₂ previously away from the sample container 2 and a waste container must be moved: For reasons of clarity, such additional valves and a related waste container are not shown in detail in FIG. 1.

The filter 4 assigned to the line system is adapted to the respective work situation and can e.g. be a sintered body with a defined pore size.

The sample containers used can preferably be changed automatically.

An application for several pressure vessels is to be expected more frequently than the use for individual pressure vessels described with reference to FIG. 1. A related embodiment is shown in Fig. 2 as a block diagram and is also explained in more detail below.

The device shown in FIG. 2 consists of several pressure vessels 1. The pressure vessels 1 are separately connected by connecting lines secured with filter 5, each with a sample system 6 as a container selection and a valve system called a gas 7 selection. The valve systems are preferably constructed from multi-port valves. In the present case, a valve corresponding to valve V is integrated in sample 6 container selection. In the container selection sample 6 there is a program-controlled fluidic connection between a selected one. Pressure vessel 1 and a sample line 8, in the container selection gas 7 between a selected pressure vessel 1 and a pump line 9. The connection options to the sample line 8 and to the pump line 9 are independent of one another. The connection to the sampling system 10 is established by the sample line 8, the connection to the liquid supply 11 by the pump line 9. The sampling system 10, in which one or more valves can also be designed as a multiport valve, consists here of a 6-port valve V ₄ with two switching positions and a further valve V ₅ . The branch point 19 and the valve V _{2 are} integrated in the valve V ₄ . The two switching positions of the valve V ₄ are: connection between port 1 and 2, port 3 and 4, port 5 and 6 (dashed in Fig. 2) or connection between port 2 and 3, port 4 and 5 and port 6 and 1 (in Fig. 2 fully drawn).

The valves V ₅ and V ₆ correspond to the valve V ₃ of FIG. 1. The sampling system 10 is connected to a filling robot 12 for filling sample containers 2 or alternatively to an online analysis system 13. Optionally, the sampling system 10 can be operatively connected to a waste container 14. Further connections exist to a pump 15 for the supply of cleaning liquid and via a further valve V ₆ to the gas supply 16 for the inert or process gas. The following method variant thus represents a preferred embodiment of the invention, namely if the valve V is integrated in a container selection sample 6; the valve V ₂ and the branch point 19 are replaced by a multi-port valve V ₄ ; and the valve V _{3 is} replaced by the valves V ₅ and V ₆ , which are connected to the gas supply 16 as well as to the different ones via a common line Ports 3 and 6 of the multiport valve V ₄ ; and in the second stage of the method in the multiport valve V ₄ a connection between port 1 and port 2 is established when the sample amount is pressed into the sample loop 3 and a connection is established between port 4 and port 5 when the sample amount is pressed into the sample container 2.

The sampling system 10 enables the passage of gases from the gas supply 16 to the individual pressure vessels 1 as well as the passage of liquid samples from the individual pressure vessels 1 to the filling robot 12 or to the online analysis system 13 via the container selection sample 6. The sampling system 10 reduces the pressure between the individual. Pressure vessel 1 and the sample container 2 or the online analysis system 13 and the determination of the sample amount.

The liquid supply 11 has at least one liquid supply. 2, for example, three such feeds for different liquids are shown, each of which is stylized as a simple line. Furthermore, the liquid supply 11 connected to the gas supply 16. The liquid supply 11 is used to provide selected liquids on the pump line 9 with a predetermined amount, to pass gases for emptying the lines and to readjust the pressure in the containers after the liquid has been supplied.

The gas supply 16 is connected to one or more gas inlets. 2, for example, three such feeds are shown, each of which is stylized as a simple line. Furthermore, the gas supply 16 is connected to an outlet 17 for gaseous waste products. A valve circuit realizes a fluidic connection between one or more selected gas inlets with the connections to the liquid supply 1 t and to the sampling system 10. In conjunction with a mass flow controller, a pressure measuring device and the associated control technology, pressure build-up up to a predetermined setpoint is made possible. Furthermore, the pressure in the pressure vessels 1 can be reduced to predetermined target values by the gas supply 16. Such setpoints are referred to as "nominal tank pressure".

With this arrangement according to FIG. 2, sampling is carried out, which is characterized by a specific pressure control variant, a sequence of steps, a rinsing process and a push-back procedure, as shown below:

First the valves V ₅ and V _{6 are} closed, the valve V ₄ is in the position in which port 1 is connected to port 6! The sample loop 3 is in fluidic operative connection to the filling robot 12 or to the online analysis system 13, which ensures that the pressure prevailing in the sample loop 3 is significantly lower than the nominal container pressure.

A selected pressure container 1 is connected to the pump line 9 and the gas supply 16 via the container selection gas 7. The tank pressure (working pressure) in the selected pressure tank 1 and the activated line system is measured by the pressure measuring device of the gas supply 16. Alternatively, the tank pressure can also be determined continuously by individual pressure measuring devices in the individual pressure tanks. This tank pressure forms together with a nominal tank pressure, the basis for the pressure control within the process, which can be done in three different pressure control variants.

A first pressure control variant is characterized in that the container pressure is initially only measured and a backpressure procedure to be carried out after the sample has been taken is carried out with the aid of the nominal container pressure. A second pressure control variant is characterized in that the container pressure is reduced by a certain amount compared to the nominal container pressure with the aid of components of the gas supply 16 and the above-mentioned push-back procedure is carried out again using the nominal container pressure. Finally, a third pressure control variant is characterized in that the container pressure is initially only measured and the subsequent push-back procedure is carried out with a pressure greater than the nominal container pressure. In this variant, however, a subsequent lowering of the container pressure to the nominal container pressure is required.

If the measured tank pressure falls below a certain lower threshold value required for the method to be carried out successfully, then in all three pressure control variants, the selected pressure tank 1 is pressurized with gas via the gas supply 16 and the pump line 9 until the tank pressure exceeds the lower threshold value. After completion of this phase of the container pressure measurement or setting in accordance with the selected pressure control variant, the connection between the selected pressure container 1, the pump line 9 and the gas supply 16 in the container selection gas 7 is disconnected.

The selected pressure vessel 1 is then connected to the sample line 8 via the vessel selection sample 6. A sequence of steps then begins such that a fluidic connection between the pressure vessel 1, the sample line 8, the sample loop 3 and the valve V _{5 is} established by switching the valve V ₄ to position 2 (shown in broken lines in FIG. 2). Due to the pressure difference in the pressure vessel 1 and the line system consisting of sample line 8 and sample loop 3, the gas in the line system is compressed by inflowing sample liquid in the direction of the closed valve V ₅ until pressure equalization between pressure vessel 1 and the line system has taken place. The valve V _{4 is then switched} to position 1 (shown in solid lines in FIG. 2). tion between the sample loop 3 and the sample line 8 interrupted. Now the sample loop 3 is in fluidic connection to the filling robot 12 or the online analysis system 13. Due to the overpressure prevailing in the sample loop 3, the content of the sample loop 3 is derived in the direction of the filling robot 12 or the online analysis system 13 and a sample vessel or sent directly to an analysis.

According to the invention, this sequence of steps is carried out at least once. In a further method variant, this can also be done several times. To reduce impurities in the sample, a repeated execution of the sequence of steps is a component of the method according to the invention. If the sequence of steps is carried out n times, where n> 1, the content of the sample loop 3 is fed to a waste container 14 until the (n-1) test is carried out by special switching devices in the filling robot 12 or the online analysis system 13 In each case, the nth execution of the sample liquid reaches the sample container 2 or the online analysis system 13. In addition, if the sequence of steps is carried out n times (where n> 1), the content of the sample loop 3 becomes the (n-1) th Execution in the waste container 14 with the help of gas, which can flow from the gas supply 16 via the open valve V ₆ into the sample loop 3, completely emptied.

If a dilution of the sample is necessary, for example to provide a sufficient amount of liquid for subsequent analyzes, even with the smallest sample amounts, a pump 15 at port no. 6 of valve V ₄ , which is in position 1, defines one in a rinsing process amount of dilution liquid pumped through the sample loop 3 in the direction of the ^{Füllroboters'} 12 or the online Analysesys-tems 13 so that thereby the sample liquid is completely purged from the sample loop. 3 After the supply of dilution liquid has ended, the remaining amount of dilution liquid is pressed out of the sample loop 3 by opening the valve V ₆ with the aid of gas from the gas supply 16, so that the sample loop 3 is completely emptied of liquid. Finally, the connection to the gas supply 16 is interrupted again by closing the valve V ₆ .

In the meantime, a pressure was built up for the push-back procedure by the gas supply 16 in front of the closed valve V ₅ , which pressure depends on the selected one Pressure control variant is greater than or equal to the nominal tank pressure. By opening the valve V ₅ , gas flowing into the sample line 8 causes the liquid in the sample line 8 to be pushed back into the pressure vessel 1. During this push-back procedure, the tank pressure is set to nominal tank pressure (first or second pressure channel variant) or a value above the nominal tank pressure (third pressure channel variant) by the inflowing gas, depending on the selected pressure control variant. After the pressure build-up, the valve V _{5 is} closed and the connection of the sample line 8 to the selected pressure vessel 1 in the container selection sample 6 is disconnected. If the third pressure control variant was selected, the selected pressure container 1 is then connected to the gas supply 16 by means of the container selection pump 7 and the container pressure is reduced to the nominal container pressure. Finally, the connection of the gas supply 16 to the selected pressure container 1 in the container selection gas 7 is disconnected.

For cleaning the sample loop 3, with position 1 of the valve V ₄ (shown in solid lines in FIG. 2) and the closed valve V _6, cleaning liquid is pumped through the sample loop 3 by means of the pump 15, this being brought into fluidic connection with the waste container 14 has been. By subsequently opening the valve V ₆ , the cleaning liquid is completely emptied from the sample loop 3 into the waste container 14 by inflowing gas. The valve V _{6 is then} closed.

In order to reduce contamination in the individual samples from the pressure vessels 1, the sample line 8 can be cleaned in two variants according to the invention before the next sampling is carried out. In a first variant, a. Sampling as just described is carried out from a cleaning container 18 which is arranged parallel to the pressure containers 1, is filled with a cleaning liquid and is under pressure. In this case, the sample liquid obtained, which consists of cleaning liquid and possibly impurities, is fed to the waste container 14 in any case.

In a second variant, the sample line 8 is brought into operative connection with the container selection sample 6 with the cleaning pressure container 18, which is empty for this variant and is open under normal pressure. Then, after opening valve V _5, a certain amount of cleaning liquid is passed through with the aid of liquid supply 11 the sample line 8 is pumped to the cleaning container 18. After the pumping process has ended, the amount of cleaning liquid remaining in the line system is completely emptied into the cleaning container 18 by inflowing gas with the aid of the gas supply 16.

List of reference numbers

1 pressure vessel

2 sample containers

3 sample loop

4 filters (Fig. 1)

5 filters (Fig. 2)

6 Sample container selection

7 Gas tank selection

8 sample line

9 pump line

10 sampling system

11 Liquid supply

12 filling robots

13 Online analysis system

14 waste container

15 pump

16 gas supply

17 Gaseous waste outlet

18 cleaning pressure vessels

19 branch point

Pi pressure in the pressure vessel p ₂ normal pressure in the sample vessel

Ps pressure after valve V ₃ p ₄ pressure in sample loop

V _1; V _2; V ₃ valves (Fig. 1) V ₄ . V ₅ . V ₆ valves (Fig. 2)

Claims

claims

1. A method for taking liquid samples from pressure vessels, characterized in that in a system comprising one or more pressure vessels under container (working) pressure, one or more sample containers under normal pressure, several valves and one

Sample loop, in a first stage for sampling a first valve (V,) is opened, which is arranged between a pressure vessel (1), a connection point (19) and the sample loop (3), and in a second stage a liquid sample quantity through the Container pressure (p.,) Of the pressure vessel (1) is pressed into the sample loop (3), and the valve (V,) is closed by a third valve (V ₃ ), which is downstream of the pressure vessel (1) behind the sample loop ( 3) is arranged, inert or process gas with a pressure (p ₃ ), which is higher than the normal pressure, is supplied and the amount of samples in the sample loop (3) after opening a second valve (V ₂ ) which between the Sample loop (3) and the sample container (2) is arranged, is pressed into the sample container (2), and in a third stage after closing the second valve (V ₂ ) and opening the first valve (V,) in the lines or remained in the sample loop (3) Any residual liquid quantities are returned to the pressure vessel (1) by the higher pressure (p ₃ ).

2. The method according to claim 1, characterized in that to produce the initial state after closing the valves (V,) and (V ₃ ), the second valve (V ₂ ) is opened and is closed again after pressure equalization.

3. The method according to claim 1, characterized in that additional amounts of liquid in the lines between the sample container (2) and pressure vessel (1) and sample loop (3) via a pump (15) and a liquid supply (11) with the supply of Inert or process gas is connected, for purging the system.

4. The method according to claim 1, characterized in that the container pressure is initially only measured and the third stage to be carried out after the sample is taken (push-back procedure) is carried out with the aid of the nominal container pressure.

5. The method according to claim 1, characterized in that the container pressure is reduced by a certain amount compared to the nominal container pressure with the aid of components of the gas supply and a push-back procedure to be carried out after the sample is taken is carried out using the nominal container pressure.

6. The method according to claim 1, characterized in that the container pressure is initially only measured and the subsequent push-back procedure is carried out with a pressure greater than the nominal container pressure, with a subsequent reduction in the container pressure to the nominal container pressure.

7. The method according to claim 1, characterized in that the steps for reducing impurities are carried out two or more times.

8. The method according to claim 1, characterized in that the valve (V,) is integrated in a container selection sample (6); the valve (V ₂ ) and the branch point 19 are replaced by a multiport valve (V ₄ ), and the valve (V ₃ ) is replaced by the valves (V ₅ and V ₆ ), which are connected to the gas supply (via a common line) 16) are also connected to the different ports 3 and 6 of the multiport valve (V ₄ ), and in the second stage of the method in the multiport valve (V ₄ ) when the sample quantity is pressed into the sample loop (3) a connection between port 1 and Port 2 is established and a connection between port 4 and port 5 is established when the sample quantity is squeezed into the sample holder (2).

9. The method according to claim 1, characterized in that the sample liquid with the gas or the flushing liquid from the sample loop (3) in a waste container (14) or in a sample container (2) or in an online analysis system (13) is emptied ,

10. The method according to claim 1, characterized in that the sample line (8) is cleaned between the sample taking, in that the sample line is arranged with a pressurized cleaning container (18) arranged parallel to the pressure vessels (1) and filled with a cleaning fluid. is brought into operative connection, one or more samples are taken from the cleaning container (18) and the sample liquid obtained, which consists of cleaning liquid and possibly impurities, is fed to a waste container (14).

11. The method according to claim 1, characterized in that a cleaning of the sample line (8) between the sampling takes place in that the sample line (8) is brought into active connection with an empty cleaning container (18), wherein first a certain amount of cleaning liquid through the sample line (8) pumped to the cleaning container (18) and, after the pumping process has ended, the amount of cleaning liquid remaining in the line system is completely emptied into the cleaning container (18) by inflowing gas.

12. The device for performing the method for taking liquid samples from pressure vessels according to claim 1, characterized in that it consists of

- one or more pressure vessels (1),

one or more sample containers (2) which are connected to the pressure container (s) (1) via a first valve (V,),

- A sample loop (3), which is connected to the pressure vessel (s) (1) via a branch point (19) and a second valve (V ₂ ), and

- A downstream of the sample loop downstream of the pressure vessel (1) and the branch point (19) arranged third valve (V ₃ ) which is connected to a compressed gas supply (16).

13. The apparatus according to claim 12, characterized in that the sample loop (3) is designed to be interchangeable and has different volumes.

14. The device according to claim 12, characterized in that the valve (V,) is integrated in a container selection sample (6); the valve (V ₂ ) and the branch point 19 are replaced by a multiport valve (V ₄ ), and the valve (V ₃ ) is replaced by the valves (V ₅ and V ₆ ), which are both connected via a common line to the gas supply (16) and to the different ports 3 and 6 of the multiport valve (V ₄ ), whereby the multiport valve (V ₄ ) can be switched such that port 1 and 2, port 3 and 4, port 5 and 6 or port 2 and 3, port 4 and 5 and port 6 and 1 are connected.

15. The apparatus according to claim 12, characterized in that a plurality of pressure vessels

(I) are provided, each pressure vessel (1) being connectable to a pump line (9) and a sample line (8) via a program-controlled fluidic connection, and the pump line (9) being connected to a central liquid supply

(II) and the sample line (8) is in operative connection with a sample system (10) containing the sample loop (3), the multiport valve (V ₄ ) and the pump (15) with the corresponding supply and discharge lines.

16. The apparatus according to claim 15, characterized in that the sampling system (10) with a filling robot (12) for filling the sample container (2) or with an online analysis system (13) and with a pump (15) for supplying cleaning and / or dilution liquid and via a further valve (V ₆ ) to a central gas supply (16).