1、Designation: D4778 15Standard Test Method forDetermination of Corrosion and Fouling Tendency ofCooling Water Under Heat Transfer Conditions1This standard is issued under the fixed designation D4778; the number immediately following the designation indicates the year oforiginal adoption or, in the ca
2、se of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method provides directions for fabricating andoperating a test apparatus to simu
3、ltaneously monitor thecorrosion and fouling tendency of real and pilot cooling watersystems under heat transfer conditions.1.2 Interpretation of the results of this test method must beleft to the investigator. Many variables are involved which maynot be easily controlled or fully understood. Variati
4、ons indesign and operating conditions may produce results that arenot comparable from unit to unit.1.3 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not consid
5、ered standard.1.4 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 prior to use.2
6、. Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD2331 Practices for Preparation and Preliminary Testing ofWater-Formed DepositsD2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterG1 Practice for Preparing, Cleaning, a
7、nd Evaluating Corro-sion Test SpecimensG16 Guide for Applying Statistics to Analysis of CorrosionData3. 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 corrosion, nthe deterioration of
8、 the metal by reac-tion with its environment.3.2.2 fouling, ndeposition of organic matter or inorganicmatter, or both, on heat transfer surfaces that result in the lossof heat transfer efficiency.3.2.3 heat flux, nheat transfer per unit area per unit time.4. Summary of Test Method4.1 Water from the
9、system to be tested flows across a heatedtube of the desired metallurgy at a constant flow rate and heatflux. Corrosion rate is determined by weight loss while foulingtendency is determined by the deposit weight.5. Significance and Use5.1 Deposits on heat transfer surfaces reduce efficiency ofthe he
10、at exchanger affected. A method for easily determiningthe corrosion and fouling tendency of a particular water underheat transfer conditions will allow the evaluation of changes inthe various system variables such as heat flux, flow velocity,metallurgy, cycles-of-concentration, and treatment schemes
11、 onheat exchanger performance.6. Apparatus (Fig. 1)6.1 Test SpecimenA metal tube of38 or12 in. (9.5 or 12.5mm) outside diameter with sufficient inside diameter to snug-gly accommodate the cartridge heater. The tube should be cutto a length sufficient to extend12 in. (12.5 mm) from each endof the tes
12、t assembly. If both corrosion and deposition are to bedetermined, metallurgy of the test specimen should match thatof the heat exchanger being modeled.6.2 Cartridge HeaterA14 or38 in. (6.2 or 9.5 mm)diameter. Heated surface should be 4 to 8 in. (10 to 20 cm) longwith a minimum power rating sufficien
13、t to provide 110 % ofthe heat load required (see Eq 7, 8.2.2). The heater should have1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.03 on Sampling Water andWater-Formed Deposits, Analysis of Water for Power Generation an
14、d Process Use,On-Line Water Analysis, and Surveillance of Water.Current edition approved June 1, 2015. Published July 2015. Originally approvedin 1988. Last previous edition approved in 2010 as D4778 10. DOI: 10.1520/D4778-15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orco
15、ntact 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, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1an unheated section o
16、f sufficient length to allow the center ofthe heated section to be placed consistently in the center of thetest specimen.6.3 Power ControllerA device to set and control thepower to the heater, such as a variable transformer, is used toadjust the heat flux in order to maintain the surface temperature
17、of the test specimen consistent with the heat exchanger beingmodeled. The power controller should be rated to maintain atleast 120 %, but not more than 400 % of the power required.6.4 Flow ControlA flow meter or a flow control devicesuch as an orifice, or both, is recommended to maintain aconsistent
18、 flow rate during the test period.6.5 Safety EquipmentA pressure or flow sensor/controlleris necessary to cut power to the heater in the event of a flowinterruption. A high temperature cutoff is recommended foradded protection.6.6 Test AssemblySee Fig. 2.7. Materials7.1 Vapor Phase Inhibitor PaperEn
19、velopes constructed ofvapor phase inhibitor paper.8. Procedure8.1 Installation of Test Device:NOTE 1All pipe is threaded 1 in. (25 mm) PVC. Heater should befused and grounded in accordance with local electrical codes.FIG. 1 Test Apparatus and Parts ListParts List:(1) test specimen (6) acrylic tube,
20、10 in. (25 cm) long by 1 in. (25 mm)outside Diameter(2) tube fitting; nylon (no metal parts) (7) Cartridge type heater (not shown)(3) reduci ng bushing, PVC(4) tee, 1 in. (25 mm) PVC(5) tube fitting, 1 in. (25 mm) tube by 1 in.(25 mm) male pipe thread stainless steelFIG. 2 Test Assembly and Parts Li
21、stD4778 1528.1.1 Placement of the test device with respect to thecooling water system is an important factor in monitoringfouling and corrosion in interpreting the test results. Foulingand corrosion are both affected by temperature. In the case ofcorrosion, the higher the water temperature, the grea
22、ter will bethe corrosivity of the water. Fouling, however, is a far morecomplex phenomenon, involving one or more of several typesof foulants, namely, particulate matter, precipitates, biomass,corrosion products, and contamination. There are five phasesinvolved in the fouling phenomenon: initiation,
23、 attachment,removal, transport, and aging.8.1.2 Several of the foulants are temperature sensitive.Precipitates, such as calcium carbonate, tend to precipitatemore rapidly as temperatures increase. Most biomasses, on theother hand, would agglomerate more rapidly at temperaturesbetween 90 and 105F (32
24、.2 and 40C).8.1.3 The test device may be installed to take its inlet waterfrom one of three locations: cold water supply to a heatexchanger, a heat exchanger outlet, or warm water return to thecooling tower. The choice of location is a function of the typeof fouling problem(s) experienced with the p
25、articular system.No matter where it is placed, the fouling conditions in the testdevice should simulate the plant equipment as closely aspossible. Specifically, the surface or interface temperature andthe shear stress of the water film against the heated surface inthe test device should be the same
26、as in the plant equipmentbeing monitored.8.2 Determination of Setup Conditions:8.2.1 Calculate plant heat exchange conditions as follows:Vp5 0.408Fp!P/D2N! (1)where:V = water velocity, ft/s,p= process,F = water flow rate, gal/min,P = number of passes,D = inside diameter of tubes in process heat exch
27、anger, in.,andN = number of tubes in process heat exchanger.q/A!p5 1910To2 Ti!Fp!/DLN! (2)where:q/A = heat flux on inner tube, Btu/h/ft2,p= process,T = temperature, F,o= outlet water,i= inlet water,F = water flow rate, gal/min,D = inside diameter of tube in process heat exchanger, in.,L = length of
28、heater section, ft, andN = number of tubes in process heat exchanger.8.2.2 Calculate the test device setup as follows:Vt5 Vp# D/d22 d1!#(3)where:V = water velocity, ft/s,t= test device,p= process,D = inside diameter of tube in process heat exchanger, in.,d2= inside diameter of outer tube in test dev
29、ice, in., andd1= outside diameter of inner (heated) tube in test device,in.Ft5 2.45Vtd222 d12! (4)where:F = water flow rate, gal/min,t= test device,V = water velocity, ft/s,d2= inside diameter of outer tube in test device, in., andd1= outside diameter of inner (heated) tube in test device,in.W 5 9.8
30、Ts2 Tb!V0.8L110.096Tb!ford15 0.50! (5)where:W = power supplied to heater, W,T = temperature, F,s= surface or interface,b= bulk water, andV = water velocity, ft/s,L = length of heater section, ft, andd1= outside diameter of inner (heated) tube in test device,in.W 5 7.94Ts2 Tb!V0.8L110.096Tb!ford15 0.
31、375! (6)where:W = power supplied to heater, W,T = temperature, F,s= surface or interface,b= bulk water,V = water velocity, ft/s,L = length of heater section, ft, andd1= outside diameter of inner (heated) tube in test device,in.E 5 WR!0.5(7)where:E = voltage of heater, V,W = power supplied to heater,
32、 W, andR = resistance of heater, ohm.8.3 Preparation of Test Specimen:8.3.1 Remove all metal burrs from each end of the tube witha file or emery belt.8.3.2 Thoroughly degrease the tube inside and out in accor-dance with Practice G1, and brush to remove adherent greaseor metal grit.8.3.3 Dry with a c
33、lean cloth and store in a desiccator untildry.8.3.4 Weigh the clean dry specimen to the nearest milli-gram.8.3.5 Store the weighed specimen in a suitable manner(protective atmosphere) to prevent atmospheric corrosion dur-ing storage and in transit. Vapor phase inhibitor paper issuitable for this pur
34、pose.8.4 Assembly of Test Apparatus:8.4.1 Install earth ground to test apparatus and secure inaccordance with local electrical codes.D4778 1538.4.2 Remove test specimen from protective atmosphere.8.4.3 Insert cartridge heater into test specimen to prescribeddepth.NOTE 1If the fit is not snug, hot sp
35、ots may occur and the heater lifemay be significantly shortened.8.4.4 Assemble test specimen/cartridge heater into test ap-paratus using nylon fittings such as Swagelok. Connect heaterleads to voltage control device.8.4.5 Flush inlet water line for 10 min to remove any foreignmatter.8.4.6 Connect in
36、let and outlet water lines.8.4.7 Turn water on and adjust flow to that calculated in Eq4, 8.2.2.8.4.8 Connect power controller to power source. Turn onpower.8.5 Operation:8.5.1 A minimum test period of 14 days is recommended. Aperiod of 30 to 60 days is preferable in order to more accuratelyevaluate
37、 corrosion and deposition.8.5.2 Maintain flow and power as constant as possibleduring the test period, making frequent small adjustmentsrather than infrequent, but large adjustments when and iffluctuations do occur. Keep a log of all changes and adjust-ments.8.6 Analysis:8.6.1 At the end of the test
38、 period, turn off power anddisconnect power controller from power source. Then slowlyshutdown water flow.8.6.2 Carefully drain water from test apparatus to preventdisruption of deposit film.8.6.3 Remove the test specimen from the apparatus withoutdisturbing deposit film. Note the deposit characteris
39、tics such asvolume, thickness, color, and appearance. Photograph thedeposit where possible.NOTE 2If there is any delay in transporting the test specimen to thelaboratory where the analysis will be performed, then it should be placedin a protective atmosphere in the interim period.8.6.4 Dry the speci
40、men in a desiccator to constant weight.Weigh to the nearest milligram.NOTE 3Deposit may flake off during drying. Place a long sheet ofpaper under the specimen to collect any fallen deposit and add the weightof this deposit to the test specimen weight.8.6.5 If the deposit is to be analyzed for compos
41、ition,remove as much of it as possible with a plastic knife and addto it the deposit collected in 8.6.4. Chemical analysis of thedeposit may be performed in accordance with Practices D2331,but this step is optional.8.6.6 Clean the test specimen as well as possible with aplastic knife. Remove oily de
42、posits in accordance with PracticeG1. Remove remaining loose deposits from the specimen bywiping with a soft cloth or bristle brush. If the test specimen isclean, proceed to 8.7. If adherent deposits remain, remove thedeposits in accordance with Practice G1.8.6.6.1 Dry with paper towels followed by
43、warm air drying.8.6.6.2 Subject a weighed blank coupon of the same metal-lurgy to the identical cleaning procedure used for the testspecimen and reweigh to determine the blank correction factorto be applied to the weight losses.8.7 After drying, reweigh a clean tube to the nearestmilligram.9. Calcul
44、ation9.1 Calculate the deposit weight by subtracting the weightof cleaned test specimen from the weight of specimen withdeposit as follows:Wd5 W22 W1(8)where:Wd= weight gain due to deposition, mg,W2= weight of test specimen with deposit, mg, andW1= initial weight of test specimen, mg.9.2 Calculate t
45、he metal weight loss by subtracting theweight of the cleaned test specimen from the initial specimenweight and correcting for the change in weight of a blank aftercleaning as follows:Wc5 W11 2W42 W5!/W4#2 W2(9)where:Wc= weight loss due to corrosion, mg,W1= initial weight of test specimen, mg,W4= ini
46、tial weight of blank specimen, mg,W5= weight of cleaned blank specimen, mg, andW2= weight of test specimen with deposit, mg.9.3 Calculate the average corrosion rate for the test speci-men as follows:Xc57.09Wc!/d1LeZt! (10)where:Xc= average corrosion rate, mills/yr,Wc= weight loss due to corrosion, m
47、g,d1= outside diameter of test specimen, in.,Le= total length of exposed test specimen, in.,t = exposure time, days, andZ = density of metal (see Table 1), g/cm3.9.4 Calculate the average rate of fouling for the test speci-men as follows:Xd50.0493Wd!/d1Lht! (11)where:Xd= average rate of fouling, mg/
48、cm2/day,Wd= weight gain due to deposition, mg,d1= outside diameter of test specimen, in.,Lh= length of heated section, in., andt = exposure time, days.TABLE 1 Density of MetalMetallurgy ZAdmiralty brass 8.52Copper 8.94Carbon steel 7.86304 stainless steel 7.94D4778 15410. Precision and Bias10.1 The p
49、recision and bias of this test method are asspecified in Practice G1. The precision and bias statementcontained in Practice G1 is repeated in Appendix X1 for thebenefit of the reader.10.2 Because this standard is for a continuous samplingmethod, it is exempt from the requirement of a round-robin testin accordance with Practice D2777, paragraph 1.3.3.11. Quality Control11.1 The test specimens should come from a reliable andconsistent source. The alloy must meet ASTM specifications.11.2 All handling steps of the test specimens before
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