Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N1/00—Sampling; Preparing specimens for investigation
  • G01N1/02—Devices for withdrawing samples
  • G01N1/10—Devices for withdrawing samples in the liquid or fluent state
  • G01N1/20—Devices for withdrawing samples in the liquid or fluent state for flowing or falling materials
  • G01N1/2035—Devices for withdrawing samples in the liquid or fluent state for flowing or falling materials by deviating part of a fluid stream, e.g. by drawing-off or tapping

Definitions

• This invention relates to apparatus for obtaining samples of flowing fluid streams substantially identical in composition to the composition of the flowing streams.
• a sampling loop apparatus for sampling the composition of fluid flowing through a fluid flow conduit comprising a sampling conduit having a first end disposed inside said fluid flow conduit and lying on a plane transverse to the path of the fluid flow in the flow conduit and having a second end connected to and communicating with said fluid flow conduit downstream of said first end, and a means for sampling fluid from the sample conduit.
• the sampling conduit is sized in relation to said fluid flow conduit to cause isokinetic withdrawal of fluid from said fluid flow conduit into said sampling conduit.
• the diameter of said fluid flow conduit between said first end and said second end of said sampling conduit is greater than the diameter of said sampling conduit. More preferably, both the length and diameter of the fluid flow conduit are larger than said sampling conduit.
• the present invention provides means to produce the same or substantially the same average flow velocity at the inlet of the sampling conduit and at points upstream of the inlet in the undisturbed flow of the flow conduit.
• This flow velocity relationship may be obtained by adjusting the length and/or diameter of the fluid flow conduit or the sampling conduit between the points where the two conduits are in communi ⁇ cation with each other.
• the diameter adjustment may be ma ⁇ e at any point along the length of the conduits. For example, the
• OMPI diameter of the sample conduit or the fluid flow conduit may be ⁇ adjusted only at the plane of sampling, hence the diameter of either conduit does not need to be uniform.
• a practical means of obtaining isokinetic sampling is to adjust the length of one of the conduits without changing the diameter of either conduit.
• Another technique is to alter the roughness of either or both conduits, thereby changing the friction factor of said conduits.
• the method of sampling using the present apparatus is also an aspect of the present invention.
• An advantage of the present invention is the absence of any outside pump means to obtain an isokinetic sampling system.
• a particularly significant advantage is that isokinetic sampling is maintained over a broad range of fluid properties and flow conditions without recourse to appended servome.chanical systems.
• FIG. 1 is a schematic representation of the present apparatus showing a sample conduit as a shunt across a loop of fluid flow conduit.
• FIG. 2 is a schematic representation of one embodiment of the present invention.
• FIG. 3 is a graph illustrating the effect of sampling velocity on sampling error of sand in water.
• FIG. 4 is an alternate schematic embodiment of the apparatus of FIG. 1.
• FIG. 5 is a graph illustrating the ability of one embodiment of this invention to maintain isokinetic sampling conditions over a broad range of operating conditions.
• the central feature of the present invention is an apparatus and method for obtaining a sample of a fluid from a fluid flow conduit in which the sample has the same composition as the fluid in the conduit.
• the manner of analyzing the fluid sample in the sampling conduit is not a primary concern of this invention. For example, physical samples of fluid may be
• PI recovered by providing two solenoid gates to close off a portion of the sampling conduit so that fluid can be drained into a collection vessel. This can be repeated at intervals to deter ⁇ mine the composition of the fluid flowing through the fluid flow conduit for any given period of time.
• a representative sample of a dispersion flowing through a flow conduit can only be obtained if the sample is withdrawn isokinetically, Isokinetic withdrawal or isokinetic sampling occurs when the fluid streamlines in and around the sampling conduit inlet are congruent with the streamlines describing the dispersed particle trajectories in and around the sampling conduit inlet. Such congruence of the fluid and particle streamlines may be further termed isokinetic flow. Isokinetic flow occurs only when the average fluid velocity at the sampling conduit inlet is equal to the average fluid velocity at points upstream of the inlet in the undisturbed flow of the flow conduit.
• dispersed particle inertia will carry a disproportionate number of particles past the inlet while the fluid streamlines will converge into the inlet.
• a sample so obtained will contain a lower concentration of dispersed particles than the fluid in the flow conduit.
• dispersed particle inertia will carry a disproportionate number of particles into the inlet as the fluid streamlines diverge past the inlet.
• a sample obtained in this way will contain a higher concentration of dispersed particles than the fluid in the flow conduit.
• the dispersed particles in question may be gas bubbles, liquids immiscible with the predominant fluid, or solids.
• Isokinetic flow is obtained according to the present invention by adjusting the sampling inlet diameter, the fluid flow conduit diameter at the point of sampling, the two conduit lengths and the two conduit diameters.
• Isokinetic sampling by the present invention is insensitive to the velocity in the fluid flow conduit provided the flow in the sampling and flow conduits are both laminar or both turbulent.
• the size of the sample obtained in the sampling conduit may be first determined by sizing the sampling conduit to produce the desired sample volume and then, for example, adjusting the sampling inlet diameter and the fluid flow conduit length between the two ends of the sampling conduit to obtain the same flow in both conduits.
• the relationships between the diameter and length of the conduits may be readily determined by trial and error, however, it is preferred to use suitable equations to approximate the appropriate relationships and then make the necessary adjustments to obtain the desired isokinetic flow. Because the characteristics of the flow regimes for turbulent and laminar flow are different, equations for any such regime must be developed separately.
• the frequency of vibration becomes a function of the mass of the fluid. If the density of the fluid increases, the effective mass of the U-tube increases.
• the frequency of vibration can be sensed and converted to AC voltage which is a function of the density or specific gravity of the flowing fluid.
• means is provided for capture of a sample in the sampling conduit.
• capture as used herein is understood to include physical capture or recovery of a sample and subsequent analysis and/or in situ conduit analysis or evaluation of the sample.
• the present apparatus may be used to sample homogeneous and heterogeneous system of fluids, solids, gases, mixtures of fluids and solids, and mixtures of gases and liquids.
• the present apparatus has been found to be particularly useful for the sampling of liquids containing entrained particulate solids such as sand.
• FIG. 1 shows a schematic representation of the appara ⁇ tus wherein the fluid flow path through fluid flow conduit 10 is shown by the arrow.
• a sampling conduit 12 has hollow probe
• sampling conduit has an ingress or inlet end 15 and a outlet or egress end 13 communi ⁇ cating with said conduit 10 downstream of said inlet end 15.
• the fluid flow proceeds through conduit 10 and sampling conduit
• Flow meters 18 and 19 are attached to conduits 10 and 12, respectively, to measure the flow rate in the conduits.
• a capture or analysis means, as described above, is illustrated by the numberal 14.
• the inlet 15 of probe 11 is positioned away from the wall 16 of conduit 10 in a plane perpendicular to the path of fluid flow. This positioning aligns the inlet 15 to capture fluid and minimizes the distur ⁇ saye of the fluid at the point of sample entry into the sampling conduit 12.
• inlet 15 should lie on a plane transverse to the flow path of fluid in conduit 10; this invention does not require that inlet 15 lie on a plane perpendicular to the path of fluid flow as generally shown in FIG. 1.
• FIG. 1 shows the inlet end 15 approximately at the center of the conduit 10, it need not be at the center because the disturbance of the flow in conduit 10 caused by probe 11 occurs after the sample enters inlet 15.
• the inlet is preferably spaced away from the wall 16 to avoid any channeling effect that may occur along the wall.
• the inlet 15 is located on an extension 17 of probe 11, this extension lies in a plane parallel to the longitudinal axis of fluid flow conduit 10.
• conduit 10 and sampling conduit 12 are ⁇ adjusted as described above to obtain isokinetic sampling. It should be appreciated that the probe 11 and the extended portion 17 terminating in inlet 15 could be an arcuate shape and the same considerations discussed above regarding placement in conduit 10 would apply.
• FIG. 2 illustrates one capture means wherein sampling conduit 112 extends into conduit 110 by use of probe 111 and extension 117.
• a fluid flows through conduit 110 and into inlet 115, into sample conduit 112, and hence through conduit 112 and outlet 113 into conduit 110 downstream of inlet 115.
• Located at each end or at any two points in sampling conduit 112 are two automatically operated valves 114 which when simul ⁇ taneously activated trap the fluid in sampling conduit 112 therebetween.
• a third automatic valve 116 is located on line 118 which communicates with sampling conduit 112 through valve 116. Opening of valve 116 allows the sample in sampling conduit 112 to pass into collection vessel 119 via line 118. It should be appreciated that the valve 116 need not be automatic ⁇ ally actuated.
• a relief valve (not shown) may also be provided to aid the flow out of conduit 112.
• a fluid flow is allowed to stabilize through conduit 110 and sampling conduit 112.
• Valves 114 are activated and immediately thereafter valve 116 is activated to drain the sample into vessel 119.
• the valve 116 is closed and valves 114 reopen and the steps above repeated. These steps may be conveniently preformed by a simple computer programmed to take samples at predetermined intervals.
• FIG. 4 shows an apparatus, in schematic representation, which has the same elements and functionality as that in FIG. 1, however, the elements are arranged in a different spatial configuration. The same designations of these elements have been employed in both figures for that reason.
• the length of the fluid flow conduit 10 between the sampling conduit inlet 15 and outlet 13 is the same as the length of the sampling conduit 12.
• the diameter of the fluid flow conduits and ⁇ the diameter of the sample conduits in FIGS. 1, 2 and 4 are illustrated as being substantially uniform, it should be clear that this is not a requirement of the present invention. Variations in diameter are accounted for in the sample approxi ⁇ mation equation set forth above and may be similarly accounted for in different systems by those persons skilled in the art.
• the essential feature for the valid operation of the apparatus and method of this invention is that the fluid velocity be the same in the entrance of the sample conduit and in fluid flow conduit at the plane corresponding to the entrance of the sampling conduit.
• FIG. 5 An example of the performance of one embodiment of this invention is illustrated in FIG. 5. This apparatus was designed, assembled, and operated in the following manner.
• a sampling device was designed to sample oil containing 0.2% by weight sand flowing through a 1-1/2 inch (0.038/meter) inside diameter conduit at the rate of 1000 barrels (160 cubic meters) per day.
• the general configuration of the device is illustrated in FIG. 1.
• sampling loop was constructed similar to the configuration in FIG. 1 using the L/l ratio determined in the first step (a) .
• the sampling conduit length 1 was selected to be 3 feet (.914 meters), therefore the length 1 of the flow conduit was constructed to be 9.6 feet (2.92 meters).
• Tests were performed using this device which demon ⁇ strates the ability of this invention to maintain isokinetic sampling over a wide range of velocities and fluid properties.
• the viscosity of the fluids was varied from 1.0 to 40 centipoises
• the density of the fluid ranged from 0.86 grams/cubic centimeter to 1.0 gram/cubic centimeter
• the velocity of the fluid in the sampling conduit varied from 5 to 15 ft/sec (1.524 to 4.57 m/sec).
• the result of these tests, shown in FIG. 5 is that the ratio of the velocity in the sampling conduit to the fluid conduit was equal ⁇ to 1.0 over the range of Reynolds number from 4,000 to 60,000.

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• Life Sciences & Earth Sciences (AREA)
• Hydrology & Water Resources (AREA)
• Physics & Mathematics (AREA)
• Health & Medical Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Biochemistry (AREA)
• General Health & Medical Sciences (AREA)
• General Physics & Mathematics (AREA)
• Immunology (AREA)
• Pathology (AREA)
• Sampling And Sample Adjustment (AREA)

Applications Claiming Priority (1)

Publications (2)

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Family Applications (1)

Country Status (8)

Families Citing this family (5)

Citations (5)

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• 1979
  • 1979-09-04 DE DE19792953813 patent/DE2953813A1/de not_active Withdrawn
  • 1979-09-04 WO PCT/US1979/000684 patent/WO1981000766A1/en not_active Ceased
  • 1979-09-04 NL NL7920203A patent/NL176493C/xx not_active IP Right Cessation
  • 1979-09-04 JP JP80500355A patent/JPS6032129B2/ja not_active Expired
  • 1979-09-04 CH CH293181A patent/CH651393A5/de not_active IP Right Cessation
  • 1979-09-04 BR BR7909052A patent/BR7909052A/pt unknown
• 1981
  • 1981-03-23 EP EP80900188A patent/EP0035016A1/de not_active Withdrawn
  • 1981-05-01 DK DK194881A patent/DK194881A/da not_active Application Discontinuation

Patent Citations (5)

Non-Patent Citations (1)

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