GB2042471A - Sampling non-homogenous liquids - Google Patents
Sampling non-homogenous liquids Download PDFInfo
- Publication number
- GB2042471A GB2042471A GB7910313A GB7910313A GB2042471A GB 2042471 A GB2042471 A GB 2042471A GB 7910313 A GB7910313 A GB 7910313A GB 7910313 A GB7910313 A GB 7910313A GB 2042471 A GB2042471 A GB 2042471A
- Authority
- GB
- United Kingdom
- Prior art keywords
- liquid
- vessel
- collecting
- sampling
- collecting vessel
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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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
Abstract
In order to estimate the water content of oil in a pipeline (7), 20 samples are fed in succession to a tank (1) and allowed to settle when the tank is sufficiently full. Most of the water collects in a neck (12) and is drawn off with the mixed oil into a sample bomb (13) for analysis. The remaining contents of the tank are agitated to disperse the water therein as uniformly as possible by circulation by means of a mixing pump (14) and then another sample is taken in the second sample bomb (16) for analysis. The overall water content can then be estimated from the formula <IMAGE> where W is the water content by volume, w1 and w2 are the water contents by volume of the two samples respectively, v1 is the volume of the first sample and V is the volume of liquid collected in the tank. The apparatus includes a second tank (2) which is filled while the contents of the tank (1) settle and are analysed, and a source of flushing oil (18) to clean the system after analysis. <IMAGE>
Description
SPECIFICATION
Sampling non-homogenous liquids
In industries such as the petroleum industry where large quantities of liquids are pumped through pipes it is sometimes necessary for a small representative sample of the liquid passing through the pipe over a long period to be obtained for the purpose of analysis. Although such samples can be obtained manually this is tedious and inconvenient and it is usual for automatic sampling devices to be installed.
Various forms of these devices are in use, but although they are of different forms mechanically they all operate on the principle bf taking a large number of sudden "grabs" of liquid at intervals over a long period, the total quantity "grabbed" being collected in a sample vessel.
These sample devices work very well when the liquid being sampled is more or less homogenous, but considerable difficulty is experienced when they are used with non-homogenous liquids.
The invention is primarily, but not exclusively, directed to the sampling of wet crude oil for the purpose of acurately determining its water content - an operation which has to be performed with great care in connection with the metering of crude oil for royalty purposes. The invention will therefore be described in relation to this particular problem, but it must be understood that it is also applicable to the case where the dispersed phase is less dense than the continuous phase.
The heart of the problem is that the water is hardly ever distributed uniformly in the oil.
The content of water may vary from a fraction of one percent to ten percent or even more, and in these concentrations the water is liable to collect into large globules or even slugs, so that the instantaneous water content of the oil at any one cross-section of the pipe is liable to vary greatly from moment to moment. Whereever possible, samplers are installed in vertical pipes, but in the oil industry this may not be practical, and sampling in a horizontal pipe may be unavoidable; when this happens, the water is likely to concentrate along the bottom of the pipe, and it will often be necessary to install some kind of mixing device just upstream of the sampling probe in an attempt to distribute the water more or less uniformly over the whole cross-section of the pipe.
In an attempt to obtain a representative sample it is therefore necessary to take a very large number of individual "grabs" over a period of, say twenty-four hours. Unfortunately this is not a complete solution, because practical considerations impose a limit on the size of "grab" that can be made: usually a "grab" has to consist of a few ml, and only with difficulty can "grabs" as small as 1 ml be obtained. Consequently, if a very large number of "grabs" is made over the sampling period the sample collected will inevitably be large: for example, a "grab" of 5 ml every five seconds would result in a sample of nearly 100 litres at the end of the twenty-four hour period.
Two alternative approaches are possible. In
Method 1 which is the most usual; the number of "grabs" taken is limited (one thousand "grabs" per day is generally regarded as the minimum number) and a sample container of capacity about ten litres is used. A container of this size can be transported fairly easily to a laboratory, where the contents can be separated into much smaller samples for laboratory analysis.
In Method 2, a much larger number of "grabs" is taken and a much larger sample container is filled. Such a container is too large to transport to a laboratory, and a circulating system is therefore used to mix the contents of this large collecting vessel so that a small and (hopefully) uniform sample can be drawn off into a small container for transport to the laboratory and analysis as in the previous method.
Both methods have their limitations. The trouble with Method 1 is that the "grabs" are too infrequent and large slugs of water can easily shoot past the sampling probe without being caught. In method 2, on the other hand, the difficulty is that, if the water content is fairly high, it is extremely difficult to mix the contents of the collecting vessel sufficiently thoroughly to enable a representative sample to be drawn off into the small container.
According to the invention, there is provided a method of sampling a flowing liquid containing a second liquid dispersed therein comprising the steps of, filling a collecting vessel with a succession of samples from the liquid flow, allowing the contents of the vessel to settle until a predominant amount of the dispersed liquid collects in collecting means within the vessel, measuring the quantity of collected dispersed liquid and removing the measured quantity before or after such measurement, agitating the remaining contents of the collecting vessel to substantially evenly distribute the remainder of the dispersed liquid, drawing off part of the remaining contents of the collecting vessel in a sampling vessel for analysis, and calculating the overall content of the dispersed liquid in the collecting vessel from the quantity of removed dispersed liquid and the analysis obtained from the sampling vessel and a knowledge of the volumes of liquid in the collecting vessel and the sample vessel.
According to the invention also, there is provided a method of sampling a flowing liquid containing a second liquid dispersed therein comprising the steps of, filling a collecting vessel with a succession of samples from the liquid flow, allowing the contents of the vessel to settle until a predominant amount of the dispersed liquid collects in a collecting means within the vessel, drawing off the contents of the collecting means for analysis in a sampling vessel agitating the remaining contents of the collecting vessel to substantially evenly distribute the remainder of the dispersed liquid, drawing off part of the remaining contents of the collecting vessel in a second sampling vessel for analysis, and calculating the overall content of the dispersed liquid in the collecting vessel from the analysis obtained from the two sampling vessels and a knowledge of the volumes of the liquid in the collecting vessel and sampling vessels.
Further according to the invention, there is provided apparatus for sampling a flowing liquid which contains a second liquid dispersed therein, comprising a collecting vessel, means for filling the collecting vessel with a succession of samples of the liquid flow, means within the collecting vessel for receiving dispersed liquid which separates from the liquid body within the collecting vessel, means for measuring the quantity of separated liquid, means for removing the separated liquid from the collecting vessel, means for mixing the liquid content of the collecting vessel, and a sampling vessel to receive part of the contents of the collecting vessel for analysis thereof after removal of the separated liquid.
Also according to the invention, there is provided apparatus for sampling a flowing liquid which contains a second liquid dispersed therein, the apparatus comprising a collecting vessel, means for filling the collecting vessel with a succession of samples of the liquid flow, means within the collecting vessel for receiving dispersed liquid which separates from the liquid body within the collecting vessel, a sampling vessel connectable to the collecting vessel to receive the contents of the said means for collecting separated dispersed liquid so that the liquid content of the said means for receiving the separated dispersed liquid may be analysed, means for mixing the liquid content of the collecting vessel, and a second sampling vessel connectable to the collecting vessel to receive part of the contents of the collecting vessel for analysis after removal of the content of the said means for receiving the separated dispersed liquid.
Preferably the means for receiving the dispersed liquid which separates from the liquid body within the collecting vessel comprises a narrow neck portion at the top or bottom of the collecting vessel.
In one preferred form of the invention for estimating the water content in oil, most of the water in a large collecting vessel is allowed to separate out before any attempt is made to render the remainder of the contents uniform by mixing. A very large number of "grabs" are taken and allowed to enter a large collecting vessel. When the vessel is sufficiently full, no more "grabs" are allowed to enter the vessel and the contents are allowed to stand for a considerable period until most of the oil has settled in a narrow neck at the bottom of the vessel. This neck is preferably provided with a window so that the interface between the oil and the water can be seen. When a sufficient time has elapsed (or when it is observed that the level of the water in the neck no longer rises) the contents of the lower neck are drawn off into a sample bomb for transport to the laboratory and analysis.Then the remaining contents of the large vessel are mixed by circulating with a mixing pump, and a second sample bomb is then filled with the slightly wet oil which has been circulated. The water content W, as a fraction of the volume of the mixture of oil and water, is then given by w1 v1 +w2(V-v1) W=
V
Where w1 and w2 are the water contents by volume of the first and second samples,
Where v, is the volume of the first sample, and
Where V is the total volume collected in the collecting vessel.
A preferred embodiment of the invention will now be described by way of example with reference to the accompanying diagrammatic drawing.
This embodiment includes two collecting tanks 1, 2 connected through three way valves 4, 5 to a pipe line 7 containing oil to be sampled. The oil is fed to the valve 5 by a pump 8. Valve 4 is set so that the samples are fed to either tank 1 or tank 2 as necessary. The valve 5 is operated by solenoids energised by control means (not shown) to deliver the samples required over a preset period, usually 24 hours, and valve 4 is controlled by liquid level sensors 10, 11 in the tanks so that when one tank is filled the samples are automatically fed into the other tank.
Each tank has a narrow neck 12, 22 at its bottom end, each neck having a sight glass so that as the oil and water in the tanks separate, the water level can be seen. At the bottom ends of the necks 12, 22 lines lead to a "wet oil" sample bomb 1 3. Further lines lead to a common mixing pump 14, and back to the upper ends of the tanks by a common return line 1 5 which has a "dry oil" sample bomb connected in parallel, and a line 1 7 from a flushing oil tank 1 8 also tapped into the line 1 5. On/off cocks 30-39 control the flow circuits. Each tank is fitted with a device 40, 41 for indicating the volume of its contents.
The apparatus above described is operated as follows:- Tank 1 is filled and valve 4 then switches to fill tank 2 while the liquid in tank 1 settles.
When settling is finished,i.e. when the water level in neck 1 2 no longer rises the volume indicator 40 is read, valve 30 is opened and valve 31 closed to draw off the contents of the neck into bomb 13, which is then taken to a laboratory for analysis after reclosing valve 30. Valves 31, 35 and 36 are then opened and pump 14 started to mix the remaining contents of tank 1. When mixing is complete valve 35 is closed and valves 38, 39 are opened to fill bomb 1 6. The filled bomb 1 6 is then also removed for analysis after closing valves 38 and 39 again. Thereafter the tank 1 and the circulating system is drained through valve 32 and, if necessary, flushed out with oil from tank 1 8 through valve 34.
During this time samples are collected in tank 2 and the analysis procedure described above with reference to tank 1 can be repeated for tank 2, after the bombs are replaced.
It is sometimes desirable, particularly when the flow of oil is in a horizontal pipe, to check that the samples taken are truly representative. To do this, two sampling feeds are installed, one near the top of the pipe 7 and the other near the bottom of the pipe. One feeds into each of the two collecting tanks. An analysis of the contents of both tanks will show whether or not the water content of the samples from the top of the pipe is the same as that from the bottom of the pipe. If the water contents differ, it is clear that the true water content of the flow is between the two values obtained.
For sampling liquids in which the dispersed phase is the less dense of the two, the apparatus is modified so that the collecting necks 1 2 and 22 are located at the tops of the tanks 1, 2 instead of at the bottom ends of the tanks.
In a simplified form of the invention, only one sample bomb is necessary, the water collected in the neck 12, 22 being measured before the remaining contents are mixed and analysed by the sample bomb as previously described. The necks 12 or 22 can be provided with calibrations for measuring the quantity of water collected, and after measurement the water is then run off before the mixing step. Alternatively the water may be run off into a separate measuring vessel for establishing its volume. In both cases care has to be taken to make sure that only water is run off. Where a calibrated neck is employed, wiper means can be installed to clear the sight glass to detect the water/oil interface accurately, or an electronic detector may be employed.
Claims (14)
1. A method of sampling a flowing liquid cohtaining a second liquid dispersed therein comprising the steps of, filling a collecting vessel with a succession of samples from the liquid flow, allowing the contents of the vessel to settle until a predominant amount of the dispensed liquid collects in collecting means within the vessel, measuring the quantity of collected dispersed liquid and removing the measured quantity before or after such measurement, agitating the remaining contents of the collecting vessel to substantially evenly distribute the remainder of the dispersed liquid, drawing off part of the remaining contents of the collecting vessel in a sampling vessel for analysis, and calculating the overall content of the dispersed liquid in the collecting vessel from the quantity of removed dispersed liquid and the analysis obtained from the sampling vessel and a knowledge of the volumes of liquid in the collecting vessel and the sampling vessel.
2. A method of sampling a flowing liquid containing a second liquid dispersed therein comprising the steps of, filling a collecting vessel with a succession of samples from the liquid flow, allowing the contents of the vessel to settle until a predominant amount of the dispersed liquid collects in a collecting means within the vessel, drawing off the contents of the collecting means for analysis in a sampling vessel, agitating the remaining contents of the collecting vessel to substantially evenly distribute the remainder of the dispersed liquid, drawing off part of the remaining contents of the collecting vessel in a second sampling vessel for analysis, and calculating the overall content of the dispersed liquid samples from the analysis obtained from the two sampling vessels.
3. A method according to claim 2 wherein the calculation follows the formula w,v, +w2(Vv,) W=
V where w, and w2 are the dispersed liquid contents of the two sampling vessels respectively by volume, v, is the volume of the first sampling vessel, and V is the volume of the liquid collected in the collecting vessel, and W is the fraction of dispersed liquid in the liquid flow by volume.
4. Apparatus for sampling a flowing liquid which contains a second liquid dispersed therein, comprising a collecting vessel, means for filling the collecting vessel with a succession of samples of the liquid flow, means within the collecting vessel for receiving dispersed liquid which separates from the liquid body within the collecting vessel, means for indicating the contents of the collecting vessel, means for measuring the quantity of separated liquid, means for removing the separated liquid from the collecting vessel, means for mixing the liquid content of the collecting vessel, and a sampling vessel to receive part of the contents of the collecting vessel for analysis thereof after removal of the separated liquid.
5. Apparatus for sampling a flowing liquid which contains a second liquid dispersed therein, the apparatus comprising a collecting vessel, means for filling the collecting vessel with a succession of samples of the liquid flow, means within the collecting vessel for receiving dispersed liquid which separates from the liquid body within the collecting vessel, means for indicating the contents of the collecting vessel, a sampling vessel connectable to the collecting vessel to receive the separated dispersed liquid from the said means for receiving the dispersed liquid so that the liquid content of the said means for receiving the separated dispersed liquid may be analysed, means for mixing the liquid content of the collecting vessel, and a second sampling vessel connectable to the collecting vessel to receive part of the contents of the collecting vessel for analysis thereof.
6. Apparatus according to claim 4 or 5 wherein the means for receiving the separated dispersed liquid comprises a necked portion of the collecting vessel at the top or bottom thereof.
7. Apparatus according to claim 6 wherein the necked portion has a device for detecting the position therein of an interface between the dispersed liquid which has separated and the remaining liquid.
8. Apparatus according to claim 7 wherein the device is a sight glass.
9. Apparatus according to any of claims 5-8 including a second collecting vessel which is similar to the first-mentioned collecting vessel, and to which both sampling vessels are similarly connectable for receiving portions of the liquid content of the collecting vessels.
10. Apparatus according to any of claims 4-9 wherein the means for mixing the liquid of the or both collecting vessels is a circulating pump having its inlet and outlet connectable to the or'both collecting vessels provided by ducts with on/off valves.
11. Apparatus according to claim 10 wherein the sampling vessel referred to in claim 4 of the second sampling vessel referred to in claim 5 is connectable to one of said ducts through on/off valves as to provide a by-pass circuit for the flow of liquid through the duct.
1 2. Apparatus according to any of claims 5-11 wherein the means for filling the or both collecting vessels includes fluid connections from the or both collecting vessels to diametrically opposite points in a pipe line which carries the flowing liquid, control valves being provided whereby the two collecting vessels may be filled from the respective opposite points.
1 3. A method of sampling a flowing liquid containing a second liquid dispersed therein substantially as hereinbefore described with reference to the accompanying drawing.
14. Apparatus for sampling a liquid flowing through a pipeline and which contains a second liquid dispersed therein constructed and arranged substantially as hereinbefore described and shown in the accompanying drawing.
1 5. A method of determining the water content of oil flowing through a pipe line which comprises obtaining samples of the liquid by a method according to claim 1-3, or 1 3 or by apparatus according to any of claims 4-1 2, or 14 and analysing the samples to obtained substantially as herein before described.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7910313A GB2042471A (en) | 1979-02-23 | 1979-03-23 | Sampling non-homogenous liquids |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7906510 | 1979-02-23 | ||
| GB7910313A GB2042471A (en) | 1979-02-23 | 1979-03-23 | Sampling non-homogenous liquids |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2042471A true GB2042471A (en) | 1980-09-24 |
Family
ID=26270678
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB7910313A Withdrawn GB2042471A (en) | 1979-02-23 | 1979-03-23 | Sampling non-homogenous liquids |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2042471A (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0053322A1 (en) * | 1980-11-24 | 1982-06-09 | BEB Gewerkschaften Brigitta und Elwerath Betriebsführungsgesellschaft mbH | Device for taking representative samples of crude oil |
| EP0066443A1 (en) * | 1981-06-01 | 1982-12-08 | George Levey | Liquid sampling |
| EP0075977A2 (en) * | 1981-09-30 | 1983-04-06 | Shell Internationale Researchmaatschappij B.V. | Process and apparatus for sampling non-homogeneous fluids |
| US4463599A (en) * | 1983-02-28 | 1984-08-07 | Welker Engineering Company | Free water volume analyzer |
| FR2544495A1 (en) * | 1983-04-15 | 1984-10-19 | Hydratec | Method and device for sampling liquids |
| FR2722879A1 (en) * | 1994-07-19 | 1996-01-26 | Commissariat Energie Atomique | DEVICE FOR THE CONTINUOUS SAMPLING AND ANALYSIS OF A LIQUID EFFLUENT |
| CN102183384A (en) * | 2011-03-16 | 2011-09-14 | 李长震 | Online monitoring autosampler of moisture content of crude oil |
-
1979
- 1979-03-23 GB GB7910313A patent/GB2042471A/en not_active Withdrawn
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0053322A1 (en) * | 1980-11-24 | 1982-06-09 | BEB Gewerkschaften Brigitta und Elwerath Betriebsführungsgesellschaft mbH | Device for taking representative samples of crude oil |
| EP0066443A1 (en) * | 1981-06-01 | 1982-12-08 | George Levey | Liquid sampling |
| EP0075977A2 (en) * | 1981-09-30 | 1983-04-06 | Shell Internationale Researchmaatschappij B.V. | Process and apparatus for sampling non-homogeneous fluids |
| EP0075977A3 (en) * | 1981-09-30 | 1983-09-21 | Shell Internationale Researchmaatschappij B.V. | Process and apparatus for sampling non-homogeneous fluids |
| US4463599A (en) * | 1983-02-28 | 1984-08-07 | Welker Engineering Company | Free water volume analyzer |
| FR2544495A1 (en) * | 1983-04-15 | 1984-10-19 | Hydratec | Method and device for sampling liquids |
| FR2722879A1 (en) * | 1994-07-19 | 1996-01-26 | Commissariat Energie Atomique | DEVICE FOR THE CONTINUOUS SAMPLING AND ANALYSIS OF A LIQUID EFFLUENT |
| WO1996002818A1 (en) * | 1994-07-19 | 1996-02-01 | Commissariat A L'energie Atomique | Device for continuously sampling and analysing a liquid effluent |
| US5723093A (en) * | 1994-07-19 | 1998-03-03 | Commissariat A L'energie Atomique | Apparatus for the continuous sampling and analysis of a liquid effluent |
| CN102183384A (en) * | 2011-03-16 | 2011-09-14 | 李长震 | Online monitoring autosampler of moisture content of crude oil |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |