Laminar-Flow im Visier
Flow sensors for the LF-monitoring whether in the semiconductor manufacturing or in the Pharmaproduktion, which is portion of the hochklassig pure or sterile pure areas still in the increase understood, because ever more production process thereafter calls. In order to limit the expenditure for the preservation of the purity one changed over no more the whole area than defining highly pure to put on but special � environments � then than mini Environment,� Glovebox, insulator or RABS (Restricted ACCESS Barrier system) to be called. All these pure areas it is common that within as small and against accesses protected a range as possible high-clean processes take place, for example liquid drugs is filled up, or special semiconductor processes accomplished. The term couples laminar flow closely with this high purity is. Among them one understands with low turbulences air flow, which is characterised by a very small flow rate of air. One too� supervising parameter � particularly during high-sterile filling up processes (so-called zone A) � thereby the flow rate of air is in the range of the laminar flow. Of the FDA published rules of the Good Manufacturing Practices (GMP) it specifies that the flow rate within a range from 0,45 m/s has to move + � 20%. For farm-acre-grant to the zone A require the GMP a continuous monitoring of the flow rate of air and of it outgoing the term of � the laminar flow monitoring � or briefly LFMonitoring nationalized itself. Actually, then one would like to think a simple venture. One sets up a flow sensor in a suitable place in the current and closes him to the process monitoring system on � finished. That some requirements of the FDA and the user oppose, which would like to point out this report and prove at the same time, how a new sensor becomes fair from the house Schmidt Technology these requirements. A measuring range of 1 m/s was established requirements at flow sensors for the LF-MonitoringMessbereichAuf reason of the monitored area of 0,36 � 0.54 m/s quasi as standard. Thus all at present usual operating conditions are cover measuring range initial those ISO 14644 specify that the measuring range must begin with 0,1 m/s. This requirement comes also from the user range, because it is usual meanwhile to throttle outside of the production times or during the disinfection the air agitation which leads to flow rates around 0,2 m/s. _ since measure the Messunsicherheit a sensor around the beginning particularly high be, be valid the rule, that a sensor the good be suitable be, the deep its beginning lie. The best sensors at the market are today about 0,05 m/s. For this reason to the LF-monitoring practically only thermal flow sensors are used. Impellers cannot do with Str�mungsgeschwindigkeitenum or under 0,2 m/s no more assigned werden.GenauigkeitDa the GMP a flow tolerance of + � 20% give mean this that the sensor must be better in each case. That sounds itself first simply, is it however not. Since such small currents in wind tunnels to manufacture only very with difficulty are must one with currents under 0,5 m/s with relatively large Messunsicherheiten live. That shows up in the fact that the sensor offerers always indicate the measurement inaccuracy as combination value e.g. as %-value of the measured value plus a %-value of the measuring range or an absolute value. If one takes for example the indication of a measurement inaccuracy of 3% of the measured value plus to a fixed value of 0,04 m/s, then this means a measurement inaccuracy of 0,0535 m/s with a measured value of 0,45 m/s and those are then already 11.9% of the measured value! Estimate yourselves thus happy, if your LF-sensor is better with 0,45 m/s, as 15% of the Messwert.MaterialienEs may only materials be used, which separate no pollutants and to any cleaning and disinfecting processes resist. The industry familiarly above all high-grade steel, plastics are accepted only if they do not separate particles. For the employment in pharmacy additionally a stability is required against alcohols and the frequently used disinfectant hydrogen peroxide. If a sensor cannot prove its resistance against the assigned disinfectants, then it must require fair DesignDie requirements at sterility during the disinfection process developed or taken off werden.GMP that the sensor possesses as smooth and behind-cut-free a surface as possible, which can be cleaned problem-free. Hidden cavities are too avoid calibrationcertificate of the FDA accepted results of measurement presuppose that for the sensors a calibration certificate is submitted, which is restorable on national standards i.e. a restorable work calibration certificate or a DKD certificate is necessity long-term stability sensors for the continuous monitoring is according to the desire of the users as for many years as possible without an interference their service to do. They become in 6 - until 12-monatigen rhythm by mobile measurements examined and could are on this occasion also readjusted. This work is however avoidable, particularly since experts advise against urgently to adjust inserted flow sensors in the field. The Messunsicherheit of such an arrangement is worse around factors than with an alignment in the wind tunnel of the sensor manufacturer. Therefore those sensors are clear in the advantage, whose measuring signal possesses as high a long-term stability as possible, so that no readjusting is necessary locally. The conversion of the requirements with new SensorDer of Schmidt Technology on the market flow sensor brought for laminar flow monitoring calls itself again SS 20,415 and for the employment in pure areas was developed. How well this sensor fulfills the tasks placed before is examined, in the following: The sensor offers a measuring range of 1 m/s as standard, whereby the sensor can already measure starting from 0,05 m/s. Each sensor is adjusted separately by a multipoint alignment in the highly exact wind tunnel, therefore it offers a very good accuracy. Those� Measurement inaccuracy is indicated as 3% by the measured value plus 0,04 m/s. This means a maximum measurement inaccuracy of 0,0535 with a measured value of 0,45 m/s m/Sek. = 11.9% Design fair of the Messwert.GMP: Into the pure area only the perfectly smooth feeler pipe (only 9 mm strongly) at its front end rises up the sensor element is, which is built in a chamber head protected from mechanical loads. Thus only smooth surfaces, without hid cavities and easily to clean. The feeler pipe and the assembly parts on pure space side consist of high-quality high-grade steel 1.4571. Only the very small sensor head and the sensor element contained in it consist of other materials. The stability against alcohol and H2O2 was confirmed after extensive laboratory tests by the manufacturer. Each sensor is supplied when desired the customer with a restorable work calibration certificate. The highly exact wind tunnel of Schmidt is subject to the monitoring of a quality assurance system according to ISO 9001:2000. The manufacturer calls this sensor long-term stable (over several years) and therefore no alignment potentiometers attached. Beyond these characteristics the sensor can book still further pluses. As at present only LF-sensor at the market the SS 20,415 can detect and alternatively also in the R�ckw�rtsbetrieb measure the direction of flow of air. It is possible to supervise several filter units and to recognize a any back flow in case of failure an exhaust clearly. Unique is also the contamination recognition. If the sensor cannot measure for example in consequence of a Reinigungsfl�ssigkeit on the sensor element any longer correctly, then it emits an error signal. This error signal disappears, as soon as the sensor is ready for use again drying and thus. Additionally to the analogue output the sensor has two switching exits, which are applicable for threshold value monitoring as direction exit or. There the response time within the range of 10 mSek. � 10 sec. is adjustable, can any turbulence effects be eliminated, which arise, if the sensor is installed for example too close under perforated plates. Complete electronics of the transducer is built in the feeler pipe. Thus both removement and replacement of the sensor are simplified noticeably. If one wants to send the sensor in for work calibration, then simply the feeler pipe with the central screw is unscrewed and the lead is marked out - more not. One is particularly proud with Schmidt on the pure space rapid assembly system. This consists of a photograph sleeve and a central screw attached at the sensor. First the photograph sleeve is installed the lead let in wall or cover, thereafter, then the sensor is connected with the cable, inserted into the sleeve and fastened with the screw in the desired angle. These work procedures are settled in minutes. The photograph sleeve gives it in 5 different variants and thus suitably each usual pure space floor scheme. If the sensor is embodied in the cover, then a feeler pipe bent around 90 � presents itself. Like that it is in a simple manner ensured that the feeler point keeps the correct distance to the filter discharge opening and also for the framework of the filter. In this mounting method the sensor element is also automatically correctly aligned for air flow and the correct installation thus a children's game. As the second variant there is a straight feeler pipe for the installation of the sensor in Wand.FazitDer flow sensor SS 20,415 fulfilled almost any user desire to a flow sensor for laminar flow monitoring in pure areas. It and further sensors of this modern series are suitable in the best way for the employment in pure areas. Typical applications are e.g. the monitoring of the space rushing over, the volume flow measurement in and exhaust air ducts or the volume flow measurement for Coating plant article conditions 2006�
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