Abstract: A seal forming a fluid tight connection between a gas chromatography column and a sample inlet assembly is disclosed. The seal is formed by a metal injection molding process. The seal has a first surface adapted for sealing with the sample inlet assembly and a second surface adapted for sealing with the column. The seal has an aperture extending between the first and second surfaces. A method of sealing a connection between a gas chromatography sample inlet assembly and a gas chromatography column is also disclosed. The method includes providing a seal as described above, compressing the first surface of the seal against an end of the inlet assembly, positioning the column in fluid communication with the aperture, and engaging the column with the second surface.

Abstract: A self-contained chromatography system is provided and includes a chromatography column, a carrier gas reservoir containing a carrier gas and an analyte stream processing device, wherein the carrier gas reservoir is disposed upstream from the chromatography column and wherein the analyte stream processing device is disposed downstream from the chromatography column. A method for implementing the self-contained chromatography system is also provided and includes generating a first system pressure upstream from the chromatography column and a second system pressure downstream from the chromatography column to cause the carrier gas to flow between the carrier gas reservoir and the analyte stream processing device. The method further includes combining a sample material with the carrier gas, introducing the combined sample to the chromatography column to generate the analyte stream and processing the analyte stream via the analyte stream processing device.

Abstract: The present invention relates to a three dimensional preconcentrator and inlet heater. The preconcentrator consists of a substrate with passageways, a conductive material coated to the top and the bottom of the substrate and an adsorbent coating covering the entire substrate. This substrate is suspended in a holding frame by a connecting bridge. The preconcentrator may also include a resistor and a proportional-integral-differential controller. The device may be used inline with a detector and can be retrofitted to existing devices. An array of preconcentrators may also be formed. The invention also relates to methods of use of the preconcentrator and methods of manufacture. A method of use includes contacting an analyte and a preconcentrator, allowing the analyte to adsorb to the preconcentrator and then desorbing the analyte. A method of manufacture involves applying the adsorbent coating by misted chemical deposition.

Abstract: The present invention is directed to an apparatus and a method for continuously removing water vapor from a closed loop, re-circulated gas flow in an ion mobility spectrometer using a water permeable membrane, having a first side and a second side opposite the first side. The gas flow is disposed adjacent and carried past the first side to deposit water vapor that passes through the membrane to the second side. An exhaust flow is disposed adjacent and carried passed the second side of the membrane to remove the water vapor from the system. Therefore, the water removal apparatus continuously regenerates in-situ. Heaters, heat sinks and additional treatment systems including charcoal filters can also be included in the system to enhance its performance.

Abstract: A multi-purpose modular pyrolysis and thermal processing system (MPMPTPS) for pyrolyzing and/or vaporizing liquids and solids to create an evolved vapor suitable for introduction into a gas-chromatography and/or vapor detection system, thereby allowing detection, classification and/or identification characteristics of threat agents. The MPMPTPS system is capable of pyrolyzing and/or vaporizing liquid (in solution, suspension or colloidal form) and solid (in aerosol or powder form) form of biological and chemical threat agents in a manner that the evolved vapor may be introduced into Gas-Chromatography systems and/or vapor detection systems, without the use of any reagents and/or bottled gases.

Abstract: A hand-held, ultra-sensitive gas chromatograph which provides real time detection and analysis of chemical compounds or impurities is disclosed. The detection sensitivity ranges from parts per trillion to parts per million with an average retention time ranging from thirty to forty-five seconds. Optimum calculated effective plate number is 55,000, with a response time on the order of two minutes. The self-contained apparatus operates on twenty-four watts, weighs twelve pounds, and measures 8?×6?×13.

Abstract: An inlet seal assembly for sealing an injection port member in a chromatography instrument , comprising an injection port member having a raised metal ring, an inlet seal member with an upper surface, a peripheral groove formed in the inlet seal member upper surface, a soft resinous plastic material ring positioned in the peripheral groove opposite the raised metal sealing ring, a reducing nut holding the inlet seal member against the injection port member, and threads connecting the reducing nut to the injection port member whereby to press the soft ring against the raised metal sealing ring to form a seal. The inlet seal assembly also may have a bottom seal between the inlet seal member and the reducing nut. A method of making and using the inlet seal assembly.

Abstract: An analyte pre-concentrator for gas chromatography is disclosed generally comprising a tube having a restricted outlet and packed with an adsorbent, wherein the tube serves as the liner of a chromatographic injector, as an adsorbent trap coupled to a chromatographic column, and/or as an adsorbent trap coupled to a headspace sampler. Preferably, a heating device allows the tube to be heated. In a preferred embodiment, the analyte pre-concentrator further comprises a column isolating accessory so that a chromatographic column can be temporarily isolated from substances flowing through the tube.

Abstract: The present invention relates to a three dimensional preconcentrator and inlet heater. The preconcentrator consists of a substrate with passageways, a conductive material coated to the top and the bottom of the substrate and an adsorbent coating covering the entire substrate. This substrate is suspended in a holding frame by a connecting bridge. The preconcentrator may also include a resistor and a proportional-integral-differential controller. The device may be used inline with a detector and can be retrofitted to existing devices. An array of preconcentrators may also be formed. The invention also relates to methods of use of the preconcentrator and methods of manufacture. A method of use includes contacting an analyte and a preconcentrator, allowing the analyte to adsorb to the preconcentrator and then desorbing the analyte. A method of manufacture involves applying the adsorbent coating by misted chemical deposition.

Abstract: The invention relates to a gas chromatography apparatus with a cooling device, wherein the cooling device includes a closed cooling circuit containing a refrigerant, so that no refrigerant is wasted.

Abstract: A portable multi-dimensional gas chromatograph, the gas chromatograph including a carrier gas container, a regulator fluidly connected to the carrier gas container, a dopant chamber containing a reference chemical, at least one pre-concentrator which is fluidly connected to the regulator and the dopant chamber, a first separation column fluidly connected to the at least one pre-concentrator, a second separation column fluidly connected to the at least one pre-concentrator, a first detector fluidly connected to the first separation column, and a second detector fluidly connected to the second separation column.

Abstract: Disclosed are systems and methods that include a thermal desorption unit, a chromatographic column, and an interface device between the unit and the column. The interface device controls the fluid flowing into the column, such as by providing additional carrier gas to maintain a substantially constant gas flow or velocity, by proving a controlled temperature increase, or by venting a portion of the gas received from the thermal desorption unit, thereby removing the dependence on the thermal desorption unit for such control. In some embodiments, the interface is a chromatographic injector. In certain embodiments, a transfer line from the desorption unit is coupled to the same port of the interface device as the chromatographic column. In some of these embodiments, this is accomplished by employing a special adaptor.

Abstract: An inlet includes a bottom assembly and a top assembly. The bottom assembly includes at least one male unit, and the top assembly has at least one beveled surface and includes at least one female unit and a lateral driving unit. The top assembly is placed inside the bottom assembly by aligning the female unit of the top assembly with the male unit of the bottom assembly. The lateral driving unit laterally drives the top assembly and causes the beveled surface of the top assembly to rise against the male unit of the bottom assembly, allowing the top assembly to seal with the bottom assembly.

Abstract: A gas chromatography/mass spectrometry system includes two sample introduction parts, a gas chromatography part having two columns, a column oven for housing the two columns in a parallel configuration, an interface part through which an outlet end of each of the two columns is inserted, and a mass spectrometry part. The mass spectrometry part has an ionization chamber to which the outlet ends of the columns inserted through the interface part are connected, a mass separation part, an ion detector, and a vacuum chamber for housing the ionization chamber, the mass separation part, and the detector. Because the outlet ends of the parallel columns are both connected to the ionization chamber, the carrier gas flow and line velocity are the same as though there is one column, thereby avoiding line stagnation. Since analyses can be performed selectively with a single system, results having high reliability and precision can be obtained.

Abstract: A fluidic switching device is particularly for use in chromatography is described. The device allows a rapid switching between chromatographic columns; particularly, in gas chromatography.

Abstract: The invention relates to an apparatus for sample preparation and/or sample delivery for an injection system of a chromatograph, having a magazine (1), which can be moved in steps, for juxtaposed sample tubes (2), and having a lifting device (6) which can be moved between two end positions perpendicular to the transport direction of the magazine (1) via a motor (11) and bears a gripper (7) for a sample tube (2), as well as having a transfer device for a sample tube (2), the lifting device comprising at least one telescopic threaded cylinder (8) which bears the gripper (7) and has a plurality of nested threaded cylinders with an inner threaded cylinder (8a) and an outer threaded cylinder (8d) of which one is arranged non-rotatably relative to the magazine (1), while the other can be rotated by the motor (11).

Abstract: A sealing mechanism for a gas chromatograph machine includes a weldment attachment mountable at the weldment assembly of the machine. The attachment has a passage therethrough for gas communicated to the weldment assembly. An actuator imparts a direct force on the weldment attachment to move it linearly towards an injection port of the machine and to sealingly clamp the weldment attachment onto the port. Torsional forces are not applied on the weldment attachment by the actuator.

Abstract: An analyte pre-concentrator for gas chromatography is disclosed generally comprising a tube having a restricted outlet and packed with an adsorbent, wherein the tube serves as the liner of a chromatographic injector, as an adsorbent trap coupled to a chromatographic column, and/or as an adsorbent trap coupled to a headspace sampler. Preferably, a heating device allows the tube to be heated. In a preferred embodiment, the analyte pre-concentrator further comprises a column isolating accessory so that a chromatographic column can be temporarily isolated from substances flowing through the tube.

Abstract: This invention concerns a method and apparatus for vaporization injection of large volumes of liquid sample (substance to be analysed+solvent) introduced by a syringe needle into a heated vaporization chamber which is part of an injector coupled operatively to a device for gas chromatographic analysis. The sample is sent in the form of a liquid band traveling through the vaporization chamber at high speed until it reaches a stopping and vaporization device positioned adjacent to the inlet of a capillary to collect the vapors. In order to inject large volumes without modifying the vaporization chamber and without partial losses of the samples, the sample vapors, in splitless mode, are drawn up from the vaporization chamber into the capillary by virtue of the local action of volume contraction caused by recondensation of at least the solvent vapors in the capillary.

Abstract: A thermal conductivity detector includes separate sample gas and reference gas chambers. Each chamber has a gas inlet and a gas outlet and a sensor. The chambers are connected by at least one passageway. For example, a passageway can extend from the sample gas chamber to the reference gas chamber adjacent the gas inlets. As a further example, a passageway can be provided adjacent the gas outlets. More specifically, an exhaust passageway extends from the first passageway to the additional passageway and there is an exhaust outlet connected to the additional passageway.

Abstract: A purge and trap concentrator and a method for drying a stream of sample gas in a gas analysis instrument. A dryer tube has an inlet that receives a stream of sample gas during a drying interval and receives a stream of dry gas during a regeneration interval. The dryer tube also has an outlet and an interior passageway between the inlet and an outlet. Support material comprising polymer sorbent is placed in the interior passageway and provides a support surface area for a hygroscopic coating comprising lithium chloride. A controller controls a heater to increase the temperature of the dryer tube to between 100 and 300 degrees centigrade during the regeneration interval and controls the heater to decrease the temperature of the dryer tube to below 100 degrees centigrade during the drying interval.

Abstract: A uniform fluid distribution system (2) for use with a liquid transfer system (100) for maintaining an interface between liquid phases within a large scale separator system including a cell into which liquid may be introduced as discrete phases at an inlet zone occupying a first approximately transverse cross-sectional region of said cell and outputted at an outlet zone occupying a second approximately transverse cross-sectional region of said cell. Said distribution system comprises at least one liquid inlet (24) and at least two distribution outlets (32), which are connected by an internal flow connection system (36).

Abstract: An analyte pre-concentrator for gas chromatography is disclosed generally comprising a tube having a restricted outlet and packed with an adsorbent, wherein the tube serves as the liner of a chromatographic injector, as an adsorbent trap coupled to a chromatographic column, and/or as an adsorbent trap coupled to a headspace sampler. Preferably, a heating device allows the tube to be heated. In a preferred embodiment, the analyte pre-concentrator further comprises a column isolating accessory so that a chromatographic column can be temporarily isolated from substances flowing through the tube.

Abstract: This invention concerns a method and apparatus for vaporization injection of large volumes of liquid sample (substance to be analysed + solvent) introduced by means of the needle of a syringe onto a heated vaporization chamber which is part of an injector applied to a device for gas chromatographic analysis, the sample being sent in form of a liquid band travelling through said vaporization chamber at high speed until reaching stopping and vaporization means positioned adjacent to the inlet of a capillary to collect the vapours.

Abstract: Apparatus for chromatography, featuring a composite chromatography column including a tubular member having an inlet end and an outlet end, where the tubular member includes an innermost first layer comprised of a first material and a second layer comprised of a second material. The chromatography apparatus can also include a first intermediate layer formed from a third material, where at least a portion of the first intermediate layer is disposed between the innermost first layer and the second layer. A second intermediate layer formed from a fourth material, can further be included in the chromatography apparatus, where at least a portion of the second intermediate layer is disposed between the innermost first layer and the second layer. A portion of the second intermediate layer can be disposed between the second layer and the first intermediate layer.

Abstract: A method and an apparatus for sample injection in gas chromatography increases the injecting volume of a sample, and can analyze any of high-boiling-point compounds, low-compounds boiling-point compounds, and compounds decomposed by heat. A sample is injected into a vaporizing chamber 6 having curved or crooked outer wall 6G and sample path S and formed of continuous inner walls 6H; the sample is temporarily held in the vaporizing chamber 6; then an objective compound is vaporized, and introduced into a separation column 17.

Abstract: This invention concerns a method and apparatus for vaporization injection of large volumes of liquid sample (substance to be analysed+solvent) introduced by means of the needle of a syringe onto a heated vaporization chamber which is part of an injector applied to a device for gas chromatographic analysis, the sample being sent in form of a liquid band travelling through said vaporization chamber at high speed until reaching stopping and vaporization means positioned adjacent to the inlet of a capillary to collect the vapours. In order to inject large volumes without modifying the vaporization chamber and without samples parts losses, in splitless mode, a drawing up of the sample vapours from the vaporization chamber into said capillary is made by means of a local action of volume contraction, caused by recondensation of at least the solvent vapours in this capillary, said capillary being in the form of a pre-column with no stationary phase, maintained at low temperature at least during the injection.

Abstract: A sub- to super-ambient temperature programmable microfabricated gas chromatography column enables more efficient chemical separation of chemical analytes in a gas mixture by combining a thermoelectric cooler and temperature sensing on the microfabricated column. Sub-ambient temperature programming enables the efficient separation of volatile organic compounds and super-ambient temperature programming enables the elution of less volatile analytes within a reasonable time. The small heat capacity and thermal isolation of the microfabricated column improves the thermal time response and power consumption, both important factors for portable microanalytical systems.

Abstract: To provide a method and an apparatus for sample injection in gas chromatography that can significantly increase the injecting volume of a sample, and can analyze any of high-boiling-point compounds, low-boiling-point compounds, and compounds decomposed by heat at a high accuracy.

Abstract: A temperature programmable microfabricated gas chromatography column enables more efficient chemical separation of chemical analytes in a gas mixture by the integration of a resistive heating element and temperature sensing on the microfabricated column. Additionally, means are provided to thermally isolate the heated column from their surroundings. The small heat capacity and thermal isolation of the microfabricated column improves the thermal time response and power consumption, both important factors for portable microanalytical systems.

Abstract: An assembly for desorbing sampling tubes comprises a gas chromatograph known per se provided with an injector. The sampling tubes are provided with an inflow opening and an outflow opening. The assembly comprises an adapter which is placed in the injector and which is provided with a chamber which is bounded by a heat conducting housing. The adapter is arranged for placing a sampling tube in the chamber thereof, while in a condition of a sampling tube wherein it is placed in the adapter, the inflow opening thereof is in fluid communication with a first carrier gas supply duct, while the outflow opening of the sampling tube is in fluid communication via the injector with a gas chromatography column disposed in the gas chromatograph.

Abstract: A new class of miniaturized gas chromatographic columns has been invented. These chromatographic columns are formed using conventional micromachining techniques, and allow packed columns having lengths on the order of a meter to be fabricated with a footprint on the order of a square centimeter.

Abstract: The present invention relates to an autosampler device useful in high pressure liquid chromatography (HPLC), and more particularly to a device useful for the automated introduction of small sample volumes into a HPLC system. Methods of analyzing low abundant protein samples using such a device are also included.

Abstract: An analyte pre-concentrator for gas chromatography is disclosed generally comprising a tube having a restricted outlet and packed with an adsorbent, wherein the tube serves as the liner of a chromatographic injector, as an adsorbent trap coupled to a chromatographic column, and/or as an adsorbent trap coupled to a headspace sampler. Preferably, a heating device allows the tube to be heated. In a preferred embodiment, the analyte pre-concentrator further comprises a column isolating accessory so that a chromatographic column can be temporarily isolated from substances flowing through the tube.

Abstract: A vaporization injector for gas chromatography analysis instruments, of the type including a vaporization chamber, heated or which may be heated, with a longitudinally elongated shape, a device for hermetically inserting the needle of a syringe containing the sample (substance to be analysed and solvent) into the chamber, a connection for feeding a carrier gas into the chamber and a gas chromatography capillary column with an upstream end open inside the vaporization chamber. In order to allow the vaporization of large sample volumes, the upstream end of the gas-chromatography column and the injection point of the sample into the vaporization chamber are both arranged adjacent to one of the longitudinal ends of the vaporization chamber and the feed connection for the carrier gas is located adjacent to the other end.

Abstract: An extraction device for liquid—liquid extraction of at least one analyte from a sample and on-line transfer of the analyte(s) to a gas chromatography extraction unit, a sample inlet, a sample outlet, and an organic liquid inlet, wherein the extraction device also includes a needle to be connected with a gas chromatography apparatus injector for the on-line transfer of the analyte(s) from the membrane-based extraction unit to the gas chromatography apparatus via the needle, an organic liquid being immobilized as a stagnant phase in a volume of less than 20 &mgr;l in the membrame-based extraction unit.

Abstract: A separation column for analyzing a gas includes a capillary which is filled with a separation material. In order to be able to use the separation column in a microsystem technology, spheres are used as the separation material. The spheres all have the same diameter. The diameters of the spheres are slightly smaller than the internal diameter of the capillary or are matched to the internal diameter of the capillary. The spheres are provided inside the capillary in a row one behind the other.

Abstract: A replaceable injection liner for a gas chromatograph is disclosed having a laterally extending external flange at its input end against which an injection septum is placed. A closure cap is positioned over and around the external flange and the injection septum to seal the septum against the flange, the septum closing and sealing the input end of the injection liner. The liner has a seal positioned beyond the flange to seal the interior surface of the injector and isolate it from the atmosphere and the injector's internal pressure.

Abstract: An apparatus and method for separating and analyzing a component of a fluid sample that is considered to be a contaminant, and particularly, that is or may be an organic material. The invention is predicated on the introduction of the sample fluid in a pulsed manner via a first carrier fluid into a feed chamber. A membrane is located between the feed chamber and an exit chamber, and in fluid registry therewith. When the sample enters the feed chamber, the component to be separated and analyzed can permeate the membrane, and thus passes through the membrane to the exit chamber, and then enters a second carrier fluid which carries it to a detector for analysis. The detector may be a gas chromatograph (GC), mass spectrometer (MS) or the like.

Abstract: A sample inlet liner includes a novel matrix that serves to retain an injected sample. The preferred inert matrix is polytetrafluoroethylene (PTFE) that serves to retain an injected sample and is provided in lieu of a conventional packing material. The contemplated inert matrix may be selected from a range of configurations of PTFE so as to provide a supporting material capable of retaining an ample quantity of injected sample in the sample inlet liner. The contemplated matrix nonetheless provides a tortuous path for the retained quantity of injected sample so as to facilitate known injection techniques such as split/splitless injection and large volume injections.

Abstract: The present disclosure relates to a gas chromatograph having a plurality of layers or channels. The chromatograph typically comprises an inlet that receives a sample to be analyzed, a column disposed in each of the plurality of chromatograph layers, each column being in fluid communication with and downstream from the inlet and having a stationary phase coating its inner surfaces, and a detector in fluid communication with and downstream from at least one of the columns. In a preferred arrangement, the chromatograph includes a pre-column disposed in each of the chromatograph layers upstream of the columns, each pre-column being in fluid communication with the inlet and having a stationary phase coating its inner surfaces.

Abstract: An extraction device for liquid-liquid extraction of at least one analyte from a sample and on-line transfer of said analyte(s) to a gas chromatography extraction unit, a sample inlet, a sample outlet, and an organic liquid inlet, wherein it also comprises a needle to be connected with a gas chromatography apparatus injector for the on-line transfer of the analyte(s) from the membrane-based extraction unit to the gas chromatography apparatus via the needle, an organic liquid being immobilized as a stagnant phase in a volume of less than 20 &mgr;l in the membrame-based extraction unit.

Abstract: A gas chromatography split injector including a housing having a carrier gas inlet port and a vent port and an injector liner is provided. The injector liner includes a substantially cylindrical outer liner member disposed within the housing and an inner liner member disposed within the outer liner member. The inner liner member has substantially cylindrical upper and lower portions and a constriction therebetween. The constriction includes an inner surface having an inner diameter smaller than a diameter of inner surfaces of the upper and lower portions. The injector also includes a chromatographic column passing through the lower portion of the inner liner member and is in sealing engagement with the constriction of the inner liner member. A transfer line passing through the upper portion of the inner liner member and has an end located proximate to the constriction of the inner liner member.

Abstract: An apparatus and method for selectively concentrating an analyte on an apparatus by evaporating solvent from the analyte. Concentration is performed by heating or by flowing a gas stream over the analyte to evaporate solvent from the analyte. The invention also provides a method to be used in conjunction with the apparatus.

Abstract: The invention relates to a method and device for preparing samples for gas chromatography, the sample material being guided through a liquid chromatograph (1) by a solvent and being monitored by a detector (2), and, on the basis of the detector (2) recognizing a chromatographic region of interest, the sample material of this region being removed from the stream of sample material leaving the liquid chromatograph (1) and being analyzed by gas chromatography. In this case, the stream of sample material leaving the liquid chromatograph (1) is guided through a flow-through cuvette (4), and the removal is carried out, until the end of the chromatographic region of interest, via a syringe (18) which, when the sample material of the region of interest reaches the flow-through cuvette (4), is introduced into the stream of sample material guided through the flow-through cuvette (4) and is drawn upwards at a predetermined ratio to the transport rate of the stream of sample material.

Abstract: To switch gas flows between gas sources and gas sinks, a gas flow switching device includes gas passages, which communicate with one another and which have connecting points for the gas sources and the gas sinks. Furthermore, the gas flow switching device has a device for setting different pressures. To simplify the construction of the gas flow switching device and to achieve precisely defined pressure and flow conditions without the need for calibration, the gas flow switching device has two plates (9, 10), which are positioned on top of one another and joined together. The two plates (9, 10) have congruent channels (11) on their respective sides that face one another. These channels (11) have semicircular cross sections and form gas passages (4 to 8). In addition, at their lateral exit points from the plates (9, 10), the channels (11) form connecting points (12 to 17).

Abstract: An assembly for desorbing sampling tubes comprises a gas chromatograph known per se provided with an injector. The sampling tubes are provided with an inflow opening and an outflow opening. The assembly comprises an adapter which is placed in the injector and which is provided with a chamber which is bounded by a heat conducting housing. The adapter is arranged for placing a sampling tube in the chamber thereof, while in a condition of a sampling tube wherein it is placed in the adapter, the inflow opening thereof is in fluid communication with a first carrier gas supply duct, while the outflow opening of the sampling tube is in fluid communication via the injector with a gas chromatography column disposed in the gas chromatograph.

Abstract: A preferred sample introduction apparatus includes a wall that defines a channel, with the channel being configured to receive a sample and being adapted to engage in fluid communication with the separation column of a chromatographic apparatus. Preferably, a coating of semi-conductive material is arranged adjacent to at least a portion of the wall. Additionally, a heater controller is provided which electro-magnetically communicates with the coating. So configured, the coating, in response to receiving energy from the heater controller, increases in temperature, thereby increasing a temperature of the sample.

Abstract: A gas chromatograph or other analytical instrument requiring controlled fluid flow incorporates a manifold assembly that eliminates the need for many of the external fittings and connections required in the instrument. A manifold block has plural fluid flow paths formed therethrough to route fluids to selected components. A collar mates to the block and adapts to a rotary injection valve to provide the continued fluid paths from the block to the injector valve and the other components of the instrument.

Abstract: The invention relates to a gas chromatograph having a temperature-controlled injector for containing a vaporizer tube with chemical substances, thereon to be analyzed via a gas chromatography column, which temperature-controlled injector and vaporization tube can be heated by an electric resistance coil type of heating unit and can be cooled by a cooling unit, wherein the cooling unit has a cooling coil (7) which surrounds the heating unit and which is provided via a feedline and a return line (8, 9) with an external source of liquid, cooled coolant, with provision of a pump (11) for circulating the coolant and of a drain valve for draining the cooling coil.