1、Designation: D7829 13Standard Guide forSediment and Water Determination in Crude Oil1This standard is issued under the fixed designation D7829; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in
2、parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide covers a summary of the water and sedimentdetermination methods from the API MPMS Chapter 10 forcrude oils. The purpose of this guide
3、is to provide a quickreference to these methodologies such that the reader can makethe appropriate decision regarding which method to use basedon the associated benefits, uses, drawbacks and limitations.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement ar
4、e included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations p
5、rior to use.2. Referenced Documents2.1 ASTM Standards:2D473 Test Method for Sediment in Crude Oils and Fuel Oilsby the Extraction Method (API MPMS Chapter 10.1)D4006 Test Method for Water in Crude Oil by Distillation(API MPMS Chapter 10.2)D4007 Test Method for Water and Sediment in Crude Oil bythe C
6、entrifuge Method (Laboratory Procedure) (APIMPMS Chapter 10.3)D4057 Practice for Manual Sampling of Petroleum andPetroleum Products (API MPMS Chapter 8.1)D4177 Practice for Automatic Sampling of Petroleum andPetroleum Products (API MPMS Chapter 8.2)D4377 Test Method for Water in Crude Oils by Potent
7、iomet-ric Karl Fischer TitrationD4807 Test Method for Sediment in Crude Oil by Mem-brane FiltrationD4928 Test Method for Water in Crude Oils by CoulometricKarl Fischer TitrationD5854 Practice for Mixing and Handling of Liquid Samplesof Petroleum and Petroleum Products (API MPMS Chap-ter 8.3)2.2 API
8、Standards:3API MPMS Chapter 8.1 Standard Practice for Manual Sam-pling of Petroleum and Petroleum Products (ASTMD4057)API MPMS Chapter 8.2 Standard Practice for AutomaticSampling of Petroleum and Petroleum Products (ASTMD4177)API MPMS Chapter 8.3 Standard Practice for Mixing andHandling of Liquid Sa
9、mples of Petroleum and PetroleumProducts (ASTM D5854)MPMS Chapter 10.1 Standard Test Method for Sediment inCrude Oils and Fuel Oils by the Extraction Method(ASTM D473)MPMS Chapter 10.2 Standard Test Method for Water inCrude Oil by Distillation (ASTM D4006)MPMS Chapter 10.3 Standard Test Method for W
10、ater andSediment in Crude Oil by the Centrifuge Method (Labo-ratory Procedure) (ASTM D4007)MPMS Chapter 10.4 Determination of Water and/or Sedi-ment in Crude Oil by the Centrifuge Method (FieldProcedure)MPMS Chapter 10.7 Standard Test Method for Water inCrude Oils by Potentiometric Karl Fischer Titr
11、ation(D4377)MPMS Chapter 10.8 Standard Test Method for Sediment inCrude Oil by Membrane Filtration (D4807)MPMS Chapter 10.9 Standard Test Method for Water inCrude Oils by Coulometric Karl Fischer Titration (D4928)3. Significance and Use3.1 Theoretically, all of the sediment and water determina-tion
12、methods are valid for crude oils containing from 0 to100 % by volume sediment and water; the range of applicationis specified within the scope of each method. The round robinsfor all methods were conducted on relatively dry oil. Allprecision and bias statements included in the methods arebased upon
13、the round robin data. Analysis becomes more1This guide is under the jurisdiction of ASTM Committee D02 on PetroleumProducts and Lubricants and is the direct responsibility of Subcommittee D02.02 onHydrocarbon Measurement for Custody Transfer (Joint ASTM-API).Current edition approved May 1, 2013. Pub
14、lished July 2013. DOI: 10.1520/D7829-13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from Ameri
15、can Petroleum Institute (API), 1220 L. St., NW,Washington, DC 20005-4070, http:/www.api.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1challenging with crude oils containing higher water contentsdue to the difficulty in obtaining
16、 a representative sample, andmaintaining the sample quality until analysis begins.3.2 Currently, Karl Fischer is generally used for dry crudeoils containing less than 5 % water. Distillation is mostcommonly used for dry and wet crude oils and where separatesediment analysis is available or in situat
17、ions where thesediment result is not significant. The laboratory centrifugemethods allow for determination of total sediment and water ina single analysis. The field centrifuge method is used whenaccess to controlled laboratory conditions are not available.3.3 In the event of a dispute with regard t
18、o sediment andwater content, contracting parties may refer to the technicalspecifications table to determine the most appropriate refereemethod based upon knowledge of and experience with thecrude oil or product stream.4. Procedure4.1 To obtain the total sediment and water results when thetwo are de
19、termined by separate methods: First, add the raw,unrounded results together, and then round the sum to thecorrect significant figure.4.2 It is critically important that the analytical samples arecollected and handled with careful regard to ensure that theyare representative of the entire parcel. The
20、 crude oil or productstream should be homogenous at the sampling point, and thesample properly mixed prior to analysis. Sub-samples shouldnot be allowed to settle prior to transfer into an analyticaldevice such as a centrifuge tube, distillation apparatus, orextraction thimble. Refer to API MPMS Cha
21、pter 8.1 (ASTMD4057) Standard Practice for Manual Sampling of Petroleumand Petroleum Products, API MPMS Chapter 8.2 (ASTMD4177) Standard Practice for Automatic Sampling of Petro-leum and Petroleum Products, API MPMS, and Chapter 8.3(ASTM D5854) Standard Practice for Mixing and Handling ofLiquid Samp
22、les of Petroleum and Petroleum Products forappropriate sample collection and mixing.4.3 It is imperative that every sample is mixed sufficiently toensure that it is homogeneous. However, with prolongedmixing the temperature of the sample will increase. This willdecrease the representative nature of
23、the sample due toevaporative losses. The mixing system must be evaluated todetermine that the mixing time is sufficient without unduetemperature increases.4.4 Sampling error can be a source of bias in analyticalmethods. This is reflected in the precision and bias statementfor each method, but it sho
24、uld be considered when evaluatingmethods. A larger sample size will increase the probability thata sample is representative of the entire parcel and can minimizethe potential bias arising from a less homogenous samplestream. Measuring sample size by weight using an analyticalbalance is not subject t
25、o human error; measuring sample sizeby volume using analytical glassware is a source of humanerror.4.5 When sample size is determined by weight, consider thetype of analytical balance used to weigh the sample. Ensurethat the resolution is appropriate, having sufficient significantfigures, for the an
26、alysis.5. ReportWater Only Determination Methods5.1 MPMS Chapter 10.4, Determination of Water and/orSediment in Crude Oil by the Centrifuge Method (FieldProcedure):NOTE 1ASTM Test Methods D96 for Water and Sediment in CrudeOil By Centrifuge (Field Procedure), the technically equivalent ASTMstandard
27、was withdrawn without replacement in 2000.5.1.1 Range of Application:5.1.1.1 There is no approved precision and bias statementfor this method.5.1.1.2 The practical minimum detection limit is 0.025 %v/v water. Lower concentrations of water should be reported asless than 0.025 % v/v or 0 % v/v.5.1.1.3
28、 This scope of the method indicates that it applies tocrude oil, there is no water content specified in the scope.5.1.2 Interferences, Biases, and Limitations:5.1.2.1 The round robin for this method was conducted forcombined sediment and water, not the sediment or waterfractions separately. Therefor
29、e the precision and bias state-ments do not apply to analysis of water only.5.1.2.2 This method will typically quantify light alcoholssuch as, (but not limited to), methanol and ethanol in the waterfraction, biasing the water result high.5.1.2.3 Centrifuge tubes may be filled directly from asample t
30、ap and analyzed minimizing sample handling. Mini-mizing sample handling helps to maintain the representativenature of a sample.5.1.2.4 A 50 mL sample is used for analysis as measured inthe centrifuge tube.5.1.2.5 The variety of acceptable solvents allows the user tomatch the best solvent to the crud
31、e type. This can minimizebias resulting from precipitated material (asphaltenes or paraf-fins) being measured as sediment.5.1.2.6 This method will not measure dissolved water, thusthe results may be biased low in crudes with dissolved water.In addition, depending upon the efficiency of the emulsionb
32、reaker used, some highly stable emulsions may not fullybreak down which will bias the results low.5.1.2.7 The sensitivity of this method is limited to thedivisions marked on centrifuge tubes. The intervals range from0.025 % to 12.5 % by volume of sediment and water.5.1.2.8 The method is not highly p
33、rescriptive, and lack ofconsistency may be a source of variability in the results.5.1.2.9 Because the user reads the result directly off theglassware, result interpretation is susceptible to human error.5.1.2.10 Because this method is often performed in anuncontrolled environment, maintaining “stopp
34、ered” tubesthroughout the entire analytical process may help maintain therepresentative nature of the sample.5.2 MPMS Chapter 10.2 (ASTM D4006, IP 358/82), Stan-dard Test Method for Water in Crude Oil by Distillation:5.2.1 Range of Application:D7829 1325.2.1.1 The scope of this test method does not
35、indicate arange of water content. The round robin, upon which theprecision and bias statement was developed, ranged from 0.1 %to 1 % water by volume.5.2.1.2 The practical minimum detection limit is 0.025 % byvolume. Lower concentrations of sediment and water should bereported as less than 0.025 % v/
36、v or 0 % v/v.5.2.2 Interferences, Biases, and Limitations:5.2.2.1 This test method will typically quantify light alco-hols such as, but not limited to, methanol and ethanol in thewater fraction, biasing the water result high.5.2.2.2 Volumetric glassware may be filled directly from asample tap. The v
37、olumetric glassware is rinsed with multipleportions of solvent to ensure full transference of sample intothe distillation apparatus. This helps ensure that sample did notsettle prior to collection of analytical portions. If the sample isallowed to settle, the representative nature may be in question
38、.5.2.2.3 Samples used for analysis range from 5 to 200 g ormL, with the smaller sample used for crude oils containing ahigher water content.5.2.2.4 The sensitivity of this test method is limited to thedivisions marked on the distillation trap. The intervals rangefrom 0.125 % to 0.5 % water by volume
39、. The intervals increaseas the water content of the crude oil increases.5.2.2.5 The repeatability for this test method ranges from0.017 for 0.005 volume % of water to 0.08 for 0.130 volume %of water.5.2.2.6 This test method is more time consuming than thecentrifuge or Karl Fischer methods.5.2.2.7 Th
40、is test method requires a laboratory environmentto set up and operate.5.2.2.8 Because the user reads the result directly off theglassware, result interpretation is susceptible to human error.5.3 MPMS Chapter 10.7 (ASTM D4377-00, IP 356/99),Standard Test Method for Water in Crude Oils by Potentiomet-
41、ric Karl Fischer Titration:5.3.1 Range of Application:5.3.1.1 The scope of this test method applies to crude oilscontaining 0.02 to 2 mass or volume % of water.5.3.1.2 The average practical minimum detection limit forthis method is 0.08 mass %. This is based upon oil with arelative density of 0.850
42、and a water equivalence of 4 for thetitration.5.3.2 Interferences, Biases, and Limitations:5.3.2.1 This test method may be appropriate for crude oilsand products which contain light alcohols such as, but notlimited to, methanol and ethanol. However, no samples con-taining alcohols were used in the r
43、ound robin study; conse-quently the precision and bias statements in the test method donot apply.5.3.2.2 Mercaptans in crude oils will bias the results high.This interference is limited with the use of pyridine freereagents. The titration speed and sensitivity settings on KarlFischer units may also
44、mitigate the interference. Refer to themethod for information about mercaptan bias.5.3.2.3 This test method allows the user flexibility withimplementation, the lack of consistency may be a source ofvariability in the results.5.3.2.4 Syringes of sample may be drawn directly from thesample vessel of t
45、hey may be drawn from a subsamplecontainer. The syringe contents are then transferred to thetitration vessel. The use of a subsample container and thesyringe are a source of error.5.3.2.5 The analytical sample size is 1 to5gofcrude oil.5.3.2.6 The resolution for this test method is in the nearesthun
46、dredth 0.08 mass % for relatively dry crude up to thenearest 0.4 mass % for wetter crude oils.5.3.2.7 This repeatability for this test method ranges from0.012 for 0.05 mass % of water to 0.040 mass % for 2.0 mass% of water.5.3.2.8 Due to the non-prescriptive flexibility in selection ofsolvents and t
47、itration parameters, the potentiometric KarlFischer method may have greater interference from mercaptansthan the coulometric method.5.3.2.9 Samples and aliquots in secondary containers, whichincludes syringes, may stratify over time and bias the results.5.3.2.10 This test method requires weighing th
48、e sample, butdoes not include a balance as required equipment.5.3.2.11 This test method allows manual titration usingKarl-Fischer reagent. Because the user reads the result directlyoff the glassware, result interpretation is susceptible to humanerror.5.3.2.12 Top loading balances must be calibrated
49、and certi-fied regularly.5.4 MPMS Chapter 10.9 (ASTM D4928-00, IP 386/99),Standard Test Method for Water in Crude Oils by CoulometricKarl Fischer Titration:5.4.1 Range of Application:5.4.1.1 This procedure is applicable to the determination ofwater in crude oils containing from 0.02 % to 5 % water.5.4.1.2 The practical minimum detection limit is 0.005 %.Lower concentrations of sediment and water should be re-ported as less than 0.005 % v/v or 0 % v/v.5.4.2 Interferences, Biases, and Limitations:5.4.2.1 This test method may be appropriate for crude oilsand products which contain ligh
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