Measuring and testing – Sampler – sample handling – etc. – Capture device
Reexamination Certificate
1999-03-15
2002-03-26
Noland, Thomas P. (Department: 2856)
Measuring and testing
Sampler, sample handling, etc.
Capture device
C073S864520, C073S864630, C166S264000
Reexamination Certificate
active
06360620
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method for the extraction of intact liquid samples, in particular, from a well sunk into the ground, by submersion of a compressible hollow flexible body fitted in supporting means which, subsequent to submersion to the sample extraction depth, is acted upon to effect liquid entry through an inlet, as well as a sample extractor for performing the method.
2. Description of Related Art
Such a sample extractor is known from U.S. Pat. No. 4,461,186 which comprises a sterile flexible body in the form of a tubular bag, the openings of which are fitted by means of compression rings to two rigid endpieces, the upper of which comprising an inlet being releasably fitted to the console of a sample extractor, and the lower being fitted in the vertically displaceable console of the sample extractor which is forced away from the upper endpiece by elastic means. The lower endpiece comprises a vertical pin projecting up into the bag volume and fitting into said inlet in such a manner that the endpieces are placed at a certain distance from another in the starting position, corresponding to the length of the pin, whereby air will be present in the bag at the commencement of sample extraction.
The inlet in the upper endpiece is covered by a hose which is connected to a glass tube fixed in a crunching mechanism. The sample extraction is activated in that a weight is dropped when the sample extracted with a bag fitted is placed at the desired depth, said weight falling on the crunching mechanism which fractures the glass tube whereby the inlet opening is uncovered, and liquid may flow through it. The same mechanism is further connected to a release mechanism which releases the lower endpiece so that this, due to the influence of the downward directed elastic means, is displaced such that sample material is sucked through the inlet in the upper endpiece. The sample extraction is terminated in that the lower endpiece acts on a spring loaded valve via a rod-and-spring which blocks the inlet in the upper endpiece. Subsequently the sample extractor is hoisted up and the fluid sample collected in the bag volume may be removed from the sample extractor along with the endpieces. The sample extraction hence occurs using the bellows principle, where an elastic influence on one endpiece away from the upper, fixed endpiece causes surrounding fluid to be sucked into the bag volume.
This known sample extractor would be adapted to use in extraction of samples in predetermined depths where the requirements for the method used are not particularly rigid, i.e., where it is known beforehand that the subsequent results of analyses are reasonably removed from the detection limit of the substances in question. Examples might be the extraction of water samples in marine areas in the sea or in lakes, and in wells and large-diameter wells, where sufficient room is available for the submersion of the complete sample extraction equipment.
The extraction of fluid or water samples in order to detect substances endangering the environment in the course of evaluation of, e.g., the extent and distribution of ground water pollution is commonly performed. The extraction of the water samples directly at the filter of a well as well as in the water claiming area, where the water samples are extracted in pipes placed in the ground for this purpose.
Since the concentrations of the substances endangering the environment in, e.g., drinking water wells and water claiming areas are often near the detection limit, it is of a large importance that the samples are extracted in such a way that it is representative of the actual water quality in a given level at the particular sample extraction site.
Hence rigid requirements are put on the cleanliness of the equipment used for the sample extraction, while it is of a large importance that the samples may be extracted in different depths in the well, such that these are representative, and to enable the extraction of samples which are non-oxidised and which have not been subjected to atmospheric air, whereby gasses which may have been dissolved in the water sample might escape.
It would be impossible to use the sample extractor described in U.S. Pat. No. 4,461,186 for the extraction of the mentioned intact liquid samples which have to be analysed for substances occurring in concentrations very close to the detection limit. There are several reasons for this, e.g., atmospheric air will be present in the bag volume at commencement of the sample extraction. Lowering of the sampling equipment will cause turbulence and mixing of layers possibly occurring within the well, due to the construction and size of the equipment. This situation is further aggravated by dropping weight in order to crunch the glass tube which initiates the sample extraction.
Alternatively intact water samples may be extracted by means of a vacuum pump situated on the ground by the well, which sucks the water sample into a sample bottle. However, it may be difficult to determine the precise depth from which the sample is pumped, and there may be doubts as to possible contamination by substances present in the higher water layers in the well. Furthermore, there remains the fact that the pumped water sample cannot avoid, however briefly, to be in contact with air when it is fed to a sample container, which is undesired as described above. The problem with using a vacuum pump is furthermore that it hardly functions at depths exceeding 10 m. However, in order to solve this problem, pumps are known which are so small that they may be sunk into the well and pump the samples up. If such a pump is to be used in other locations, it must be cleaned first which is a time consuming and hence cost creating work which sometimes makes one use one pump per well which is costly in acquisition but often necessary, but even here remains the problem of the sample's contact with air.
SUMMARY OF THE INVENTION
It is the purpose of the present invention to provide a method for the extraction of intact fluid samples, in particular from a well sunk into the ground, by submersion of a compressible hollow flexible body fitted in supporting means comprising an inlet which, subsequent to submersion to the sample extraction depth, is filled with fluid, and a sample extractor to perform the method which alleviates the disadvantages concerning the use of the known pumps and which permits the extraction of intact and representative water samples without allowing the extracted samples to contact the atmosphere during sample extraction.
It has been realised in the invention that this purpose is obtainable in that the hollow flexible body is held in support means in the form of a pressure vessel during lowering to the desired sample extraction depth and filly compressed by means of a pressurised gas inside the pressure vessel, whereupon the pressure in the pressure vessel is caused to change in such a way that a surrounding fluid seeps into the hollow flexible body.
Due to the fact that the hollow flexible body is fully compressed until the seeping of the fluid is effected by releasing the pressure in the pressure vessel it is obtained that the collected fluid sample does not contact the atmosphere which means that the sample remains intact and hence un-influenced, until it is analysed.
For the performance of the methods, a sample extractor is provided of the kind in which the support means are constituted by a leak-proof container in which is placed the compressible hollow flexible body in the form of a bag of a suitable clean and resistant material, the open end of which is connected to the inlet in an air- and fluid tight manner, and which container is connected to a hose, at the other end of which means are provided for controlling the pressure between the wall of the container and the outside of the bag, which inlet is preferably provided at a bottom end of the container, viz. a removable tightly fitting plug, to which is fitted the flexible body and which has a through pas
Nixon & Peabody LLP
Noland Thomas P.
Rotek A/S
Safran David S.
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