Measuring and testing – Fluid pressure gauge – Diaphragm
Reexamination Certificate
2001-12-12
2003-10-28
Lefkowitz, Edward (Department: 2855)
Measuring and testing
Fluid pressure gauge
Diaphragm
C073S730000, C073S732000
Reexamination Certificate
active
06637272
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a device for pressure measurement on a line of various installations. It relates more particularly to a manometer whose design makes it possible, on the one hand, to avoid any dead space in the driving element, and on the other hand to offer very easy cleaning without the need to disconnect the measuring instrument from the process line or even dismantle it.
BACKGROUND OF THE INVENTION
Manometers of conventional design, whether of the Bourdon tube, capsule, or bellows type, etc., have driving elements containing a relatively large dead space, in which the fluid to be measured remains trapped.
In manometers of this type, it is in fact very difficult, if not impossible, to clean the said driving element, which is at a real dead end that is impossible to reach. Finally, the fluid whose pressure is being measured remains permanently trapped inside the driving element. For certain industries and applications, this phenomenon may be troublesome, because undesirable germs and bacteria can grow and multiply inside this dead end. Moreover, it is obvious that by virtue of its very shape, a Bourdon tube or bellows—whether it is drawn without welding, or rolled and welded then drawn—cannot have a perfect internal surface condition whatever treatments are applied to it.
Assuming that the internal surface condition is correct, the welds produced—at the end of the tube and for fixing the tube to the connector—give rise to the presence of impurities inside the tube.
Treatments such as electropolishing, treatment in the “extrudom” or other treatments, may claim to improve the internal surface condition of a really small part of the Bourdon tube, but in no case can they make it sufficiently clean and free from all impurities.
Conventional driving elements, of whatever form (Bourdon tube, bellows, capsule, etc.), prove to be real pockets for particles, which are impossible to clean efficiently, and whose internal surface condition in contact with the medium to be measured is incompatible with industries requiring high degrees of cleanliness and purity.
Furthermore, during changes in manufacture, the user may wish to clean the lines and the measuring instruments that are installed on the latter. In the case of manometers, such cleaning is impossible, unless the manometer is separated from the installation by means of an intermediate component, called a separator. This separator makes it possible to isolate the measuring instrument from the line, and serves as a “buffer”. The separator is equipped with a diaphragm that is in contact with the fluid to be measured, whilst a filling liquid (generally an oil) provides transmission of the pressure existing in the installation between this diaphragm and the driving element of the manometer.
The use of a separator may give rise to problems and is not always ideal. The performance of a separator largely depends on the mechanical characteristics of the diaphragm itself (its response curve), on the quality of the filling liquid, its thermal stability, its viscosity, the filling conditions, etc. In addition, hermeticity between this diaphragm and the line of the installation is provided by a seal, which also offers retention zones where germs, bacteria and microbial flora can develop.
Furthermore, the use of a filling liquid in the separator means there is a risk of contaminating the entire installation equipped in this way, if diaphragm rupture occurs.
In addition, a separator is an added item, independent of the manometer, which adds an extra cost to the final product.
Even so, manometers, whether or not they are mounted on a separator, are reliable instruments for measuring pressure, whose performance meets the requirements of the majority of industrial applications.
There are fields of application or industries where the drawbacks mentioned above become preponderant. This applies in particular to the food and agricultural industries, fine chemicals, the pharmaceutical industry, the semiconductor manufacturing industry, industries producing or using pure, rare and toxic gases, industries where pressure measuring instruments are used in painting processes, etc.
In all these industries or applications, the use of pressure measuring instruments demands very stringent precautions, especially with regard to the presence of impurities, germs, dust etc. The measuring instruments used in these types of processes must be able to be cleaned very easily.
In food and agricultural industries, for example, the processors need to measure the pressure of foodstuff liquid or pastes intended for human or animal consumption. Consequently, equipment for carrying out these measurements must never under any circumstances allow the growth and development of germs or bacteria that might alter or contaminate the foodstuffs whose pressure is being measured. Therefore the measuring instruments must be designed in such a way that the retention zones are almost non-existent, and in such a way that they are easy to clean (i.e. they must be designed in such a way that they can easily be cleaned by passing cleaning products, hot water, or other decontaminating products through the lines of the installation).
Similar problems arise in the pharmaceutical industry, fine chemicals industry, etc.
In the field of gas distribution in the semiconductor industry, manometers are mainly used for measuring the pressure of two groups of gases:
Gases that are called “pure gases”, which have extremely exacting requirements in terms of purity: ultrapure nitrogen; argon; helium; etc. These are generally gases for which the degrees of purity may reach or exceed 99.99999%.
Gases called “doping gases”—generally highly toxic gases (arsine, boron—gallium, etc.)—for doping the silicon wafers on which electronic components are produced, such as memories (RAM, DRAM), microprocessors, etc.
In this industry it is necessary to employ measuring instruments that have been made following very rigorous procedures in terms of cleanliness, so that there is no risk of contaminating the gases that are used.
Furthermore, all retention zones are forbidden, because, in this case too, they promote the development of undesirable germs or bacteria.
Moreover, for example in pressure measurement on lines for painting processes, depending on the operations being carried out, the pressure measuring instruments have to measure the pressure of paints of different colours. Between two manufacturing operations, the manometers must be easy to clean and must not have any retention zones where paint from the previous manufacturing operation might contaminate the next manufacturing operation.
The examples given above are not limiting. There are many other manufacturing processes where the measuring instruments installed on the production lines must be as easy to clean as possible, with a design that does not permit any retention zones promoting the development of germs, bacteria and other substances that could contaminate the production process or the constituents that are involved in the said production process, such as, in particular, liquids, gases, etc.
It is clear from the foregoing that these instruments must, as far as possible, be able to be cleaned or rinsed. In this context, it can be seen that conventional manometers do not offer this facility by any means, and that their use poses enormous problems, unless they are combined with separators.
To overcome these drawbacks, the main manufacturers of pressure measuring instruments have in recent years developed devices called “full-bore pressure transmitters” which avoid these contamination problems. In fact, various technologies derived from recently developed technologies in electronics have made it possible to devise pressure measuring instruments in which the driving element (the element that makes it possible to transform a physical quantity—pressure—into an electrical signal) is quite simply a tube, and the “fluid” whose pressure is to be measured circulates inside this tube. There are, for example, pressure transmitters
Bourdon S.A.
Jenkins Jermaine
Lefkowitz Edward
Nixon & Vanderhye PC
LandOfFree
Manometer with direct passage does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Manometer with direct passage, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Manometer with direct passage will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3112429