The present invention is a procedure for taking a liquid sample and determining the characteristics of this sample, as well as an instrument to be used for this procedure.

For production companies using a liquid in a product-or manufacturing a liquid product-it may be essential to know e. g. the exact purity, the turbidity and the colour, as well as similar characteristics of the liquid.

To gain sufficient knowledge of a liquid in the processing plant a sample is taken and analysed. A liquid in a production line goes through certain process stages. These stages may include fermentation of the liquid and the consequent emission of certain gasses (e. g. carbon dioxide, ammonia), and transportation/filtration of the liquid which makes it whirl around, thus creating gas bubbles which will be carried with the liquid in the processing plant.

When measuring one of the characteristics of the liquid it is important that the liquid contains no gas bubbles that may interfere with the measurement. Till now the gas bubbles have been removed from the liquid by taking a sample from a pipe section of the processing plant in a test tube.

The liquid sample is then exposed to ultrasound to remove the gas bubbles. A treatment with ultrasound will make the pressure of the liquid sample fluctuate with the frequency of the sound. This will liberate microscopic gas bubbles from the liquid. The gas bubbles will merge, until they have a sufficient volume to overcome the inertia of the liquid and they will then ascend to the surface of the liquid. Subsequently the chosen characteristic of the liquid can be measured.

However, there are a number of drawbacks by taking a liquid sample in this way, e. g.: - the liquid sample is taken into a test tube that has to be transported to a laboratory for treatment and subsequent measurements. This means that each measurement requires time as well as staff, - a certain delay when using the results of the liquid sample for monitoring the process, as some time will elapse from taking the sample until the result will reach an operator in a control room, and this may result in slow process control, - using the known methods for removal of gas bubbles requires ultrasound equipment, and this is expensive - risk of work-related injuries when handling dangerous liquids - after measuring, the liquid sample must be disposed off, and this may be inappropriate in case of costly special liquids or environmentally harmful liquids.

The purpose of this invention is to produce an instrument for taking samples and determining characteristics of a liquid in a closed system, to remove the gas bubbles mechanically, to analyse the characteristics of the liquid continuously and quickly, and, subsequently, to use the data obtained, for instance, for the control of the production process.

This may be achieved by a method of taking the samples into a by-pass system, comprising the following steps: - a pump will draw a liquid sample from a pipe section of a processing plant into a, mainly, vertical pipe section of the by-pass system, - the first test valve is shut off, and by means of the pump a vacuum is created in the sample, - a second test valve is shut off, and the sample in the pipe section will be compressed by a piston, - a measuring device will determine the characteristics of the sample, - the sample may then be returned to the pipe section of the processing plant from where it was taken.

To remove the gas bubbles in the liquid sample, the pressure in the sample is changed, as this will make the gas bubbles of the liquid sample dissolve. This is possible, as-according to Henry's law-the amount of

dissolved gas of a liquid is proportional to pressure and temperature. As an example, this means that at 1 bar pressure 1 litre of air may be dissolved in 1 litre of water, and at 2 bar pressure 2 litres of air may be dissolved etc. This means that in 1 litre liquid containing 1 litre dissolved air plus 1 litre of gas bubbles, it is possible to convert the gas bubbles into liquid by increasing the pressure of the liquid to 2 bar.

When converting gas bubbles in a liquid into pure liquid, the processing speed can be increased, for instance, by increasing the pressure by a factor of 10-instead of increasing the pressure to a level corresponding to the pressure necessary for dissolving the amount of gas bubbles-as this will make the liquid free of bubbles in a few seconds, allowing measuring of the characteristics of the liquid.

To make a liquid sample free of bubbles, the liquid sample must remain totally or partly still. Therefore, a liquid sample is drawn from a pipe section of a processing plant into a mainly vertical pipe section of the by- pass system, in which the liquid sample can remain. In the first phase the pump will establish a vacuum in the liquid sample when the first test valve is being shut off, and the bigger gas bubbles will ascend to the surface, as the vacuum will draw the bubbles from the liquid sample. After this the liquid sample is isolated when the second test valve is shut off.

To remove the smaller gas bubbles still floating around in the liquid, the sample is compressed by a piston in the mainly vertical pipe section, and, according to Henry's law, the gas bubbles will be dissolved and turn into liquid.

Now the measurement of the liquid sample can be taken, and this will give a very precise picture of the real characteristics of the sample. Subsequently the two test valves are opened, allowing the sample to be either discharged or destroyed or to be returned to the processing plant.

As not all liquids have the same characteristics at different temperatures, it may be important to know, for instance, the components of the liquid, and how it reacts at a certain temperature. Another step has therefore been added to the above sampling method: The liquid sample will be warmed up/cooled down before and after, respectively, determining the characteristics of the sample. The warming up/cooling down of the sample must be made with a certain speed so that the time used for measuring will not be considerably prolonged.

For example, the qualities of a liquid may be destroyed if the temperature has risen above a certain level, and this may be ascertained by comparing the qualities with that of a control sample before heating.

After determining the characteristics-such characteristics being, for instance, turbidity, colour, temperature and composition-of the liquid sample, such data can be stored in a control and communication unit. To use the characteristics of the sample for e. g. process control it is possible to transmit the relevant data from this unit directly to e. g. the process control room. Vice versa it is possible from the process control room, via the control and communication unit, to initiate the measurement of selected characteristics at any time.

The following is a description of a device, which has been invented on the basis of the methods and -principles described above, and which is suitable for taking samples and determining different characteristics of a liquid in the pharmaceutical industry. The invention can also be used in other industries where purification of liquids is involved, and where great accuracy in measuring different liquid characteristics is essential, such as paper mills, food processing, cleaning and other industries affecting the environment.

The device includes a by-pass system, consisting of: - a mainly vertical pipe section, - at least two shutoff valves, - a first and a second test valve, - at least one outlet for at least one measuring device, - at least one piston and - at least one pump.

The shutoff valves are placed in the by-pass system adjacent to a pipe section of a processing plant. The outlet for the device and the piston are placed in the vertical pipe section between the test valves, and the pump is placed in the by-pass system after the second test valve and before one of the shutoff valves.

The first and the second test valve are placed at the ends of the vertical pipe section. When shutting off these test valves the liquid sample is isolated in the vertical pipe section.

The two shutoff valves are placed at the inlet and the outlet of the by-pass system. They are used for shutting of the entire by-pass system for e. g. cleaning and replacing various measuring devices.

A number of outlets for the measuring devices have been mounted on the vertical pipe section. In a preferred versions of the invention, a flange is mounted at one or more of these outlets, as this facilitates both installation and replacement of measuring devices depending on which characteristics are to be measured.

It is important that the mainly vertical pipe section is installed in such a way that its inlet is considerably below its outlet. This will enable gas bubbles of a certain size to overcome the inertia of the liquid and ascend to the surface of the liquid, where they can leave the pipe section. If the pipe section is horizontal, the gas bubbles will gather in the entire pipe section.

Furthermore, the liquid flow in the by-pass system should run from the lower inlet and up through the vertical pipe section, as gas bubbles that are released, before the piston is pressed down, will ascend.

The piston is placed in such a way that it may be pressed down into the liquid sample in the vertical pipe section and thus create pressure in the liquid sample.

In an alternative version of the invention more outlets for measuring devices may be made available. In this case it must be ascertained that these outlets are not placed too closely, as probes or similar plug-in parts for the liquid sample may interfere with the measuring made in adjacent outlets.

In order to create a vacuum in the liquid sample, the pump is installed after the second test valve, and in such a way that the liquid sample is drawn into the by-pass system. The by-pass system is so designed that the liquid will flow from below and upwards into the mainly vertical pipe section.

For heating or cooling the liquid, the by-pass system is equipped with a heat exchanger at each of the outlets with a section on each side of it. These two sections are connected in order to ensure a uniform heating/cooling of the liquid sample around the outlet.

As previously mentioned, the characteristics of a liquid may vary depending on its temperature. It may therefore be necessary, for instance, to prepare a curve of certain liquid characteristics at a fluctuation of temperature between, for instance, 0 and 20 C. A number of liquid samples are taken, and are then warmed up/cooled down to the desired temperatures. On the basis of the data recorded it is then possible to draw a curve of the different-characteristics of a liquid at different-temperatures.

If several outlets have been made available in the mainly vertical pipe section, each is equipped with a heat exchanger unit with a section on each side of it. A shutoff valve may be placed between each outlet and its heat exchanger, as this will make it possible simultaneously to measure the characteristics of a liquid at different temperatures. The alternative to a long vertical pipe may be a by-pass system with a number of parallel vertical tube sections, each equipped with an outlet for a measuring device and a heat exchanger.

The heat exchanger is designed for connection to a heating and/or cooling medium. It is necessary that both a heating and/or cooling medium can be connected, as the process temperature of a liquid. may fluctuate considerably from the desired temperature. Furthermore, in a processing plant the piping may not always carry the same liquid.

The heating and/or cooling media are either air, liquid or electric power. In one version of the invention the heating and/or cooling medium is air, mainly compressed air, led into the side of a vortex pipe, whereby the compressed air rotates rapidly, thus separating into a cold and a warm air stream. The cold/warm air stream is now led to the primary side of the one section of the heat exchanger, then to the other side through a transition pipe from where it leaves the system.

By using compressed air in a vortex pipe, the production of cold/warm air will result in an air volume of opposite temperature, meaning that the excess compressed air, e. g. when using hot air, will be cold and vice versa. It is possible that the flow of compressed air may be used somewhere else in the processing plant to reduce the consumption of compressed air and/or reduce energy consumption.

The compressed air for heating/cooling the liquid sample in an air/liquid heat exchanger can be between minus 40-35 C and up to 100-110 C ; this will typically be sufficient for warming up or cooling down a specific liquid sample during a relatively short period.

In another version of the invention the heat exchanger is a liquid/liquid heat exchanger, in which the heat supply can be made by a boiler and/or as waste heat from the process, and cooling may be made by a condensing unit/compressor.

The alternative to air/air, air/liquid, liquid/liquid heat exchangers will be to use electric power as heating or cooling medium. The electric power is fed to a cooling unit directly mounted on the mainly vertical pipe section, or a heating unit-either piso-electric elements, electrically heated pads or the like-directly mounted on the vertical pipe section.

In one version of the invention the by-pass system including the vertical pipe section is constructed for flange installation in a pipe section of a processing plant. If the by-pass system is mounted on a separate pipe section, with flanges it is possible to produce and supply the device in a standard version, in which the process pipe section is of a certain specified length allowing the user to install the device in the processing plant, merely by replacing a pipe section of the plant. Alternatively, the device can be produced with different lengths of the pipe sections.

An alternative to flange installation is a pipe section of the device directly welded onto a pipe of the processing plant.

In devices with a flange installed at the outlet, it is possible to connect different types of gauges for measuring the turbidity, colour, temperature or composition of a liquid.

In a preferred version of the invention, the measuring device for determining the turbidity of a liquid, is a device for determining the purity of the liquid or the contents of impurities in the liquid sample.

In another version of the invention ; the-measuring device will determine the colour of the liquid, as it may be important to ascertain the colour of a liquid before or after mixing-it--with-another product, or at the end of the production process.

In yet another version the measuring device can be a device for analysing the composition of the liquid. This could be a gas chromatograph, a spectrometer or the like, by which the chemical composition of the liquid is analysed. Such a measuring device may be used for tracing for instance undesirable heavy metals in the liquid.

In order to use all these measurements of the characteristics of a liquid sample, the device is furthermore equipped with an electronic control unit comprising sensors, a communication unit and a display.

The electronic control unit is connected to the different components of the device. This unit can, for instance, be connected to the two shutoff valves, the two test valves, the piston, the pump, the heat exchangers and the cooling/heating element, making it possible to electronically control the sampling from

either the display on the spot or by a connection by cable, infrared connection or the like from a control room.

Furthermore, this electronic control unit is connected to a number of sensors attached to the different components. As an example, pressure-sensitive switches for measuring the pressure to which the liquid sample is exposed when the piston is pressed into the vertical pipe. There is also a temperature sensor, e. g. a PT100 probe, for measuring the temperature of the liquid when it enters the by-pass system, so as to control/monitor the amount of heat/cold necessary in the heat exchanger.

By using such a by-pass system it will be possible to make a number of measurements in rapid succession, and almost continuously in the process, and it will, thus, function as a unit for optimising the process.

An example of an application of this invention is the cleaning of liquids through for instance filters. The device enables this cleaning process to be controlled by the turbidity of the liquid by monitoring that the value of turbidity drops according to the mesh size of the filters used.

Furthermore the flow velocity through the filters is adjusted in accordance with the measured turbidity values, and it is, therefore, important that the pumping pressure through the filters can be adjusted accurately. It has, however, not been possible to measure the turbidity inline in a flow process with the desired accuracy due to the bubbles generated, when the liquid is cleaned in the filters, as these bubbles disturb the measuring results and these can, therefore, not be used for the adjustment of the processes.

In the further description we refer to the drawing, in which figure 1 shows an installation of the invented device.

Figure 1 shows a device 1 consisting of a by-pass system 2, which in this set-up, is installed in a section 3 of a process pipe installed in a process plant with flange 4. At the in) et and outlet of the by-pass system 2 the shutoff valves 5 are connected. In this version these shutoff valves are manually operated and are used for shutting off the by-pass system or for cleaning the pipe systems of the by-pass system.

In order to lead the liquid further in the by-pass system 2, an approximately horizontal pipe section 15 is placed after the first shutoff valve 5, and this horizontal pipe section is connected to the first test valve 7 forming the first part of the vertical pipe section 16. Right after the first test valve 7 the first section 8A of heat exchanger 8 is placed.

Outlet 17 is mounted between the heat exchanger sections 8A and 8B. This outlet is provided with a flange 9 designed for installation of different types of gauges (not shown). After the upper section 8A of the heat exchanger 8 a piston 10 is placed in such a way that it can compress the volume of liquid between itself and the first valve 7.

A second test valve 11 is placed after the piston 10. This valve ensures that a specific amount of liquid will remain still in the vertical pipe section-16 of-the by-pass system 2. Immediately after the valve 11 a pump 6 is installed. This pump will ensure that the liquid sample is drawn into the lower pipe section 15 of the by- pass system 2, up into the vertical pipe section 16 and further up to the second test valve 11.

After the first test valve 7 is closed, the pump will create a vacuum in the liquid in the vertical pipe section 16, and all gas bubbles in this liquid will thereby be extracted and will disappear into the process pipe 3.

Subsequently the second test valve 11 will close, and the piston 10 will then compress the test liquid between the piston and the first test valve.

For cooling/heating the liquid sample, the sections 8A and 8B of the heat exchanger are each connected to a vortex pipe 13, into which compressed air is fed, circulated and thus separated into a cold and a hot fraction. In this version it is possible to cool the air down to-35 C and heat the air to 100'C for circulation in the heat exchanger 8. The two sections 8A and 8B are connected by pipe 14.

The cupboard 17 also contains the control and communication unit (not shown) as well as different sensors, valves and connections. Furthermore on the front of cupboard 17 should be a display unit (not shown), from which device 1 for sampling liquid can be controlled on site, or from which measurement data may be communicated to e. g. a process control room.

The invention is not limited to what is shown on the drawing nor to the above mentioned manufacturing options. Other versions with other types, gauges, pistons, pumps and piping are foreseeable within the framework of this invention and the patent claims.