ASTM D1066-2018e1 Standard Practice for Sampling Steam.pdf

1、Designation: D1066 181Standard Practice forSampling Steam1This standard is issued under the fixed designation D1066; 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 parentheses indicates the y

2、ear of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1NOTE3.2.1.1 was editorially corrected in December 2018.1. Scope1.1 This practice covers the sampl

3、ing of saturated andsuperheated steam. It is applicable to steam produced in fossilfired and nuclear boilers or by any other process means that isat a pressure sufficiently above atmospheric to establish theflow of a representative sample. It is also applicable to steam atlower and subatmospheric pr

4、essures for which means must beprovided to establish representative flow.1.2 For information on specialized sampling equipment,tests or methods of analysis, reference should be made to theAnnual Book of ASTM Standards, Vols 11.01 and 11.02,relating to water.1.3 The values stated in SI units are to b

5、e regarded asstandard. The values given in parentheses are mathematicalconversions to inch-pound units that are provided for informa-tion only and are not considered standard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibi

6、lity of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization

7、established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2A269 Specification for Seamless and Welded AusteniticStain

8、less Steel Tubing for General ServiceA335/A335M Specification for Seamless Ferritic Alloy-Steel Pipe for High-Temperature ServiceD1129 Terminology Relating to WaterD3370 Practices for Sampling Water from Closed ConduitsD5540 Practice for Flow Control and Temperature Controlfor On-Line Water Sampling

9、 and Analysis3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this standard, refer toTerminology D1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 isokinetic sampling, na condition wherein thesample entering the port (tip) of the sampling nozzle has thesame velocity

10、vector (velocity and direction) as the streambeing sampled.3.2.1.1 DiscussionIsokinetic sampling ensures a represen-tative sample of dissolved chemicals, solids, particles, chemi-cals absorbed on solid particles, and in the case of saturatedand wet steam, water droplets are extracted from a processs

11、tream.3.2.2 sample cooler, na small heat exchanger designed toprovide cooling/condensing of process sampling streams ofwater or steam.3.2.3 sampling, nthe extraction of a representative portionof the steam flowing in the boiler drum lead or pipeline bymeans of a sampling nozzle and the delivery of t

12、his portion ofsteam in a representative manner for analysis.3.2.4 saturated steam, na vapor whose temperature cor-responds to the boiling water temperature at the particularexisting pressure.1This practice is under the jurisdiction of ASTM Committee D19 on Water andis the direct responsibility of Su

13、bcommittee D19.03 on Sampling Water andWater-Formed Deposits, Analysis of Water for Power Generation and Process Use,On-Line Water Analysis, and Surveillance of Water.Current edition approved Aug. 1, 2018. Published August 2018. Originallyapproved in 1949. Last previous edition approved in 2011 as D

14、1066 11. DOI:10.1520/D1066-18E01.2For 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.Copyright ASTM International

15、, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides a

16、nd Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.13.2.5 superheated steam, na vapor whose temperature isabove the boiling water temperature at the particular existingpressure.4. Summary of Practice4.1 This practice describes the apparatus, design

17、concepts,and procedures to be used in extracting and transportingsamples of saturated and superheated steam. Sampling nozzleselection and application, line sizing, condensing requirementsand optimization of flow rates are all described. Condensedsteam samples should be handled in accordance with Pra

18、cticesD3370 and D5540.5. Significance and Use5.1 It is essential to extract and transport steam in a mannerthat provides the most representative sample of the processsteam in order to accurately determine the amount of allimpurities (dissolved chemicals, solid particles, chemicalsabsorbed on solid p

19、articles, water droplets) in it (1).3Anaccurate measure of the purity of steam provides informationthat may be used to determine whether the purity of the steamis within necessary limits to prevent damage or deterioration(corrosion, solid particle erosion, flow-accelerated corrosion,and deposit buil

20、dup) of downstream equipment, such asturbines and process heat exchangers. The sources of impuri-ties in the steam can include boiler water carryover, inefficientsteam separators, natural salt solubility in the steam and otherfactors. The most commonly specified and analyzed param-eters are sodium,

21、silica, iron, copper, and cation conductivity.6. Hazards6.1 The transport of steam samples may present hightemperature and/or high pressure safety concerns that shouldbe considered and addressed based upon local (site) require-ments.7. Interferences7.1 Sampling of steam presents difficult extraction

22、 andtransport problems that affect the representativeness of thesample. Isokinetic sampling requires that the velocity vector(velocity and direction) of the fluid entering the sample nozzleport (tip) be the same as the stream being sampled at thelocation of the sample nozzle. When the sample is not

23、extractedisokinetically the contaminants in the steam are not properlyrepresented in the sample. The effects of non-isokinetic sam-pling are illustrated in Fig. 1 and can make the sampleunrepresentative. The sample should be removed at a positionaway from the pipe wall, located at a point of average

24、 velocitywhich can be calculated for both laminar and turbulent flows.7.2 Saturated SteamTraditionally, saturated steamsamples with initial steam velocities above 11 m/s (36 ft/s)were considered to provide adequate turbulent flow to ensuretransport of most particulates and ionic components. Morerece

25、nt studies (2, 3) found that because many sample lines arelong and uninsulated, steam samples are frequently fullycondensed prior to reaching the sample station. Partially orfully condensed samples usually have a velocity too low toprevent excessive deposition and the sample becomes nonrep-resentati

26、ve of the source. This condensation can result in longsample lag times (time between the sample entering thesampling nozzle to when it reaches the sample panel) measuredin minutes and hours instead of seconds. Detailed design of the3The boldface numbers given in parentheses refer to a list of refere

27、nces at theend of this standard.FIG. 1 Effect of Non-Isokinetic SamplingD1066 1812sample line to control vapor and liquid velocity can minimizethis interference but cooling of saturated steam samples at thesource is recommended to assure a representative sample. SeePractices D3370 and D5540 for furt

28、her information on factorsthat affect liquid sample transport.7.3 Superheated SteamMost contaminants can be dis-solved in superheated steam. However, as steam pressure andtemperature are reduced the solubility of many contaminants isdecreased and the contaminants precipitate and deposit on theinner

29、surfaces of the sample line (4). This condition has beenfound to be prevalent only in regions of dry wall tube where thetemperature of the tube wall exceeds the saturation temperatureof the steam.7.3.1 Interference also occurs when the transport tube tem-perature is at or below the saturation temper

30、ature. The steamloses superheat and dissolved contaminants deposit on the tubewall. The sample is no longer representative. Superheatedsteam samples shall be cooled immediately after extraction toensure a representative sample. Cooling the sample within thesample nozzle may cause thermal fatigue and

31、 is not recom-mended and could affect the composition of the sample.8. Procedure8.1 This practice concerns equipment design only and notoperating procedures.9. Materials and Apparatus9.1 Extracting the Sample:9.1.1 Saturated and superheated steam are normallysampled as two-phase fluids (steam and sm

32、all droplets of wateror steam and particulate) requiring isokinetic sampling to beemployed. Since steam velocities vary with boiler load itnormally is not practical to sample isokinetically throughoutthe load range. Normally, the load of interest is full load or aguaranteed overload. The sampling sy

33、stem shall be designed toprovide isokinetic sampling under the most critical loadconditions. Once the sampling nozzle is designed, the isoki-netic sampling rate is directly proportional to the mass flowrate of the process stream and independent of operatingpressure.9.1.2 Saturated SteamAt low veloci

34、ties, the moisture inwet steam forms a film along the inside surface of the steamline that entrains impurities (5). Samples should be extracted ata position away from the pipe wall (Fig. 2). See 9.1.4.5.9.1.3 Superheated SteamParticulates are often present insuperheated steam and these particulates

35、can contain solublespecies (Na, Cl, SO4) that are of interest and should besampled (1, 6-8). Therefore, an isokinetic sampling nozzleshould be used for sampling superheated steam in order toobtain a representative sample of both the gas and solid phases.9.1.4 Sampling NozzlesThe design of a steam sa

36、mplingsystem should start with the design of the isokinetic samplingnozzle. The sampling nozzle design will determine the require-ments for the isolation valves and sample line from thesampling nozzle to the primary sample cooler/condenser. Thedesign isokinetic sampling rate should be determined by

37、therequirements of Practices D3370 and the volume of sampleneeded for on-line analyzers and grab samples. This value istypically between 1000 and 1200 cc/min (condensed). Forapplications where the mass flow rate in the process pipechanges significantly during different modes of operation, thesamplin

38、g nozzle should be designed to provide a representativesample for the most critical process conditions or the typicaloperating conditions.9.1.4.1 Stratification of suspended solids and liquid dropletsin horizontal steam pipes can influence the composition of thesteam samples, particularly for lower

39、velocity streams wherethe Reynolds number is not in the fully turbulent regime. Tominimize the effects of stratification it is recommended thatsteam sampling nozzles be located in long vertical pipes. Toensure that all water droplets are carried in the flow stream,downward flow is preferred. Nozzles

40、 which must be located ina horizontal pipe should be near the top of the pipe (2, 7, 8).9.1.4.2 Ideally, the nozzle should be installed at least 35internal pipe diameters downstream and 4 internal pipe diam-eters upstream of any flow disturbance (elbow, tee, valve,orifice, etc.). If this is not poss

41、ible, the nozzle should beinstalled so that the ratio of its distance from the upstreamdisturbance to the downstream disturbance is about 9:1. Ifchoosing between sample points on a horizontal or a verticalpipe, in most cases where fully turbulent flow is present, thelocation with the longer straight

42、 run of pipe is preferred.9.1.4.3 Sampling nozzles shall be adequately supported andshall be designed according to applicable codes to preventfailure due to flow-induced vibration, thermal stress, and otherpossible causes (9). A conical shape rather than cylindrical willreduce the effects of vortex

43、shedding, which can lead to fatiguefailures. Strength of the attachment to the pipe must also beconsidered. Nozzles are most often made of AISI 316 (10) orother austenitic stainless steels or superalloys (1, 2, 7). Lowalloy and carbon steels are not recommended due to thetendency of these materials

44、to form surface oxides that canadsorb and desorb impurities, Weld joints used for dissimilarmetals are subject to high thermal stresses due to differentcoefficients of thermal expansion. Care should be used in weldrod selection and inspection of all weld joints.9.1.4.4 Sample port (tip) shall be dri

45、lled cleanly, using thestandard drill size nearest to the calculated port diameter. Thesmallest recommended port diameter is 3.18 mm (18 in.). Portdiameters of less than 2.38 mm (332 in.) are subject to pluggingand shall not be used. The size of the sample port is determinedby the equation:FIG. 2 Is

46、okinetic Sampling NozzleD1066 1813S 5 ID2v !/4 (1)where:S = sampling rate (by mass) of the steam,ID = size of the sample port,v = velocity of the steam in the pipe being sampled, and = density.9.1.4.5 The center-line of the nozzle tip is most frequentlylocated at a distance from the pipe wall where

47、the actualvelocity equals the average velocity under laminar flow,typically 0.12 times the pipe inner diameter (Fig. 2) (1, 2, 7, 8).This also ensures that the sample is extracted from a flowregion removed from the pipe inner surface. Where laminarflow is not expected or for sampling in small diamet

48、er piping(6 in. NPS or smaller) where space limitations restrict thesampling nozzle dimensions, greater insertion depths may beused.9.1.4.6 At least one shut off valve (commonly referred to asa root valve or isolation valve) shall be placed immediatelyafter the point from which the sample is withdra

49、wn so that thesample line may be isolated. In high pressure applications twoisolation valves are often used. Because of the sensitivity ofsome small bore instrumentation valves to deposition, it istypically recommended to have two isolation valves for allsteam sampling applications. The valve(s) selected should berated for the pressure/temperature of the sample source andhave approximately the same orifice size as the inside diameterof the sampling nozzle. Bleed valves are not recommendedbecause they can introduce impurities into the sampling systemwhen opene