Measuring and testing – Sampler – sample handling – etc. – With heating or cooling
Reexamination Certificate
2000-07-18
2001-09-18
Raevis, Robert (Department: 2856)
Measuring and testing
Sampler, sample handling, etc.
With heating or cooling
C073S863860
Reexamination Certificate
active
06289752
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to sampling systems and techniques suitable for sampling a media in a flowing pipeline. More particularly, the present invention relates to a spot sampling technique for periodically filling a cylinder or a portion of a sample cylinder with a hydrocarbon-containing gas in the flowing pipeline at selected time intervals for subsequently analyzing the constituents of the sample and assuming that the sample constituents represent the flowing media.
BACKGROUND OF THE INVENTION
Those familiar with the technology of sampling a hydrocarbon-containing media, such as natural gas, in a flowing pipeline recognize that there are two well-known sampling techniques:
(1) “Spot sampling” involves the taking of a sample of media at one or more points in time and assuming that the sample accurately represents the composition of the media over some defined substantially long period of time, e.g. one sample per week or once per month. The spot sampling method may thus involve simply filling a sample cylinder containing a vacuum with the media, with the decision to spot sample requiring interaction by a sampler technician. More typically, a sample cylinder may be conditioned by a series of fill and empty actions to remove all air and then finally fill the cylinder to take the samples.
(2) “Composite sampling” differs from spot sampling in that in composite sampling method, the media in a flowing pipeline collects the sample media slowly over some defined long period of time. Prior to starting the composite cycle, the sample cylinder may thus be conditioned using a repeating, fill and empty method, and the sample cylinder then left at ambient pressure. The composite cycle is typically performed by a positive displacement sample pump that samples a fixed volume or “bite” of media at a rate proportional to the flow, e.g., taking a selectively sized sample “bite” once every several thousand cubic feet of flowing gas. Less accurately, a sample of a fixed size may be taken once every several minutes, and typically from once every two minutes to once every sixty minutes. In yet another composite sampling technique, a small sample slowly “leaks” to the sampler bottle using a motorized regulator. The point is that the sampling equipment, not a sampling technician, determines when a sample bite is obtained.
Both the spot sampling and composite sampling techniques have historically been performed without regard to the ambient temperature of the sampling equipment or the dew point of the gas being sampled. During the act of obtaining a sample, the gas may be brought below its dew point by coming into contact with sampling equipment that is at a temperature below the dew point of the flowing gas. In this situation, components of the sampled gas will tend to condense out and cling to the walls of the sampling equipment. Since the condensed components of the gas are commonly the heavy ends that are rich in BTU content, and since these condensed components never get into the sample cylinder because they cling to the walls of the equipment or drip back into the pipeline, the sample which is taken is biased “lean”, meaning that the BTU content of the gas flow into the pipeline is actually greater than that represented by the sample.
The above deficiencies in sampling equipment have long been recognized by the American Petroleum Institute (API). API has recently enacted a sampling standard that requires heating of the sampling equipment to a temperature above the dew point of the flowing gas while the sample is being taken. Cost effective and efficient solutions to the heating requirement are formidable, since typically electrical power is not available at the sampling point. Gas is plentiful and infra-red heater solutions are possible with composite samplers because they must be kept warm over an extended period of time. The sampling speed required with spot sampling, however, makes the infra-red heater solutions inefficient because of their long start-up cycle times. A prior art sampling pump with a pressure regulator is disclosed in U.S. Pat. No. 5,498,136.
The disadvantages of the prior art are overcome by the present invention, and an improved sampling system and method particularly applicable for spot sampling is disclosed. The present invention thus overcomes many of the difficulties and shortcomings of the prior art, which have long been recognized in the industry.
SUMMARY OF THE INVENTION
The sampling system and technique of the present invention is primarily directed to spot sampling, not composite sampling. The technique of the present invention is cost effective since only the probe must be purchased for each spot sampling site. A heater/sampler attachment is thus necessary only for each sample technician, who reuses this equipment at each sample point. Cross-contamination may be substantially reduced if not entirely eliminated by a simple cleaning operation between samples. Only a short section of a straight small diameter hole connecting the probe to the sample cylinder need be cleaned for most applications.
The power for heating may be obtained from the gas being sampled and the heat is generated in an intrinsically safe manner using a vortex heater. Most components of the system are fabricated from a hard annodized aluminum which provides both excellent corrosion resistance and quick heat up times, since aluminum is an excellent heat conductor. Alternatively, pressurized gas to the vortex heater may be supplied by a portable pressurized gas vessel, such as a compressed air bottle.
It is an object of the present invention to provide an improved technique for sampling that satisfies the desire that the sampling equipment be heated to a temperature above the dew point of the flowing gas while the sample is being taken.
A related object of the invention is a sampling system which utilizes a vortex device responsive to the fluid in the pipeline to heat the sample probe and sampler bottle. The heating/sampling device may be manually oriented and connected to a permanently installed hot gas circulating probe.
It is a further object of the invention to provide an improved method of sampling wherein the probe and sampler bottle are heated with the medium being circulated in the pipeline. A sampler bottle is exposed to externally circulating hot gas constrained to an annulus about the OD of the sampler bottle.
Yet another object of the invention is an improved method of heating a sample probe and bottle prior to taking a spot sample, with a method utilizing hot fluid from the flowing media to heat the sampling equipment while the sample is being taken.
It is a feature of the invention that the sampler bottle may thus be mounted directly to the sampler body.
The sampling equipment may include a removable bottle sheath with a slot running the length of the sheath and containing a split pliable material to provide hot gas sealing while allowing the sheath to be placed over the sampler bottle in the presence of valves on either end of the bottle.
A feature of the present invention is that the sampling equipment and method may be reliably used by sampling personnel with little training and experience.
Yet another feature of the invention is the substantially improved sampling accuracy and the resulting savings realized when conducting spot sampling of a medium, such as natural gas, flowing in a pipeline.
Still another feature of the invention is that the components of the sampling equipment may be easily manufactured to have a relatively long life. The system is highly reliable and cost effective. Only the probe must be purchased for each spot sampling site.
Yet another feature of the invention is that cross contamination of the sampled fluid may be substantially reduced if not entirely eliminated.
Yet another feature of the invention is that the power source for obtaining heat is generated in an intrinsically safe manner.
Yet a further feature of the invention is that most of the components of the sampling system may be fabricated from aluminum.
These and furth
Cessac Kevin J.
Nimberger Spencer M.
Browning Bushman
PGI International Ltd.
Raevis Robert
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