1、Designation: D 4778 05Standard Test Method forDetermination of Corrosion and Fouling Tendency ofCooling Water Under Heat Transfer Conditions1This standard is issued under the fixed designation D 4778; the number immediately following the designation indicates the year oforiginal adoption or, in the
2、case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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 s
3、imultaneously 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. Vari
4、ations 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 the standard. The values given in parentheses are providedfor information only.1.4 This standard does not purport to address all of the
5、safety 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. Referenced Documents2.1 ASTM Standards:2D 1129 Terminology Relating
6、to WaterD 2331 Practices for Preparation and Preliminary Testing ofWater-Formed DepositsD 2777 Practice for Determination of Precision and Bias ofApplicable Methods of Committee D19 on WaterG1 Practice for Preparing, Cleaning, and Evaluating Cor-rosion Test SpecimensG16 Practice for Applying Statist
7、ics to Analysis of Corro-sion Data3. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology D 1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 corrosionthe deterioration of the metal by reactionwith its environment.3.2.2 foulingdeposition of org
8、anic matter or inorganicmatter, or both, on heat transfer surfaces that result in the lossof heat transfer efficiency.3.2.3 heat fluxheat transfer per unit area per unit time.4. Summary of Test Method4.1 Water from the system to be tested flows across a heatedtube of the desired metallurgy at a cons
9、tant 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 heat exchanger affected. A method for easily determiningthe corrosion and fouling t
10、endency 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 onheat exchanger performance.6. Apparatus ( Fig. 1)6.1 Test SpecimenA metal tube
11、 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 test assembly. If both corrosion and deposition are to bedetermined, metallurgy of
12、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 sufficient to provide 110 % ofthe heat load required (see Eq 7, 8.2.2). The heater should
13、 havean unheated section of 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 mainta
14、in the surface temperatureof the test specimen consistent with the heat exchanger being1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.03 on Sampling of Water andWater-Formed Deposits, Analysis of Water for Power Generati
15、on and Process Use,On-Line Water Analysis, and Surveillance of Water.Current edition approved Jan. 1, 2005. Published January 2005. Originallyapproved in 1988. Last previous edition approved in 1999 as D 4778 94 (1999)e1.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact
16、 ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.modeled. The power contro
17、ller 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 flow rate during the test period.6.5 Safety EquipmentA pressure or flow sensor/contro
18、lleris 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 Paperenvelopes constructed ofvapor phase inhibitor paper.8. Procedure8.1 Installation of Test
19、 Device:8.1.1 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 greater
20、 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, at
21、tachment,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 (32.2
22、and 40C).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, 10 in. (25 cm) long by 1 in. (25 mm)outside Diameter(2) tube fitting; nylon (no metal
23、 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 ListD47780528.1.3 The test device may be installed to take its inlet waterfrom one of t
24、hree 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 particular system.No matter where it is placed, the fouling conditions in the testdevice
25、 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 as in the plant equipmentbeing monitored.8.2 Determination of Setup Conditions:8.2.1 Ca
26、lculate plant heat exchange conditions as follows:Vp5 0.408 Fp!P/D2N!(1)where:V = water velocity, ft/s,p= process,F = water flow rate, gal/min,P = number of passes,D = number of tubes in process heat exchanger, in., andN = number of tubes in process heat exchanger.q/A!p5 1910 To2 Ti! Fp!/DLN!(2)wher
27、e: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 heater section, ft, andN = number of tubes in process heat exchanger.8.2.2 Calculate the test d
28、evice 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 device, in., andd1= outside diameter of inner (heated) tube in test device,in.Ft5 2.45 Vtd222 d12!
29、(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 Ts2 Tb!V0.8L 1 1 0.096 Tb! for d15 0.50! (5)where:W = power supplied to heater, W,T = temperat
30、ure, 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 7.94 Ts2 Tb! V0.8L1 1 0.096 Tb! for d15 0.375! (6)where:W = power supplied to heater, W,T = temperature, F,s= surface or in
31、terface,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, W, andR = resistance of heater, ohm.8.3 Preparation of Test Specimen:8.3.1 Remov
32、e all metal burrs from each end of the tube witha file or emery belt.8.3.2 Throughly 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 clean cloth and store in a desiccator untildry.8.3.4 Weigh the clean dry specimen t
33、o 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 purpose.8.4 Assembly of Test Apparatus:8.4.1 Install earth ground to test apparatus a
34、nd secure inaccordance with local electrical codes.8.4.2 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 spots may occur and the heater lifemay be significantly shortened.8.4.4 Assemble test specime
35、n/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 inlet and outlet water lines.8.4.7 Turn water on and adjust flow to that calculated in Eq4, 8
36、.2.2.8.4.8 Connect power controller to power source. Turn onpower.D47780538.5 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 corrosion and deposition.8.5.2 Maintain flow and power as constant as possibleduri
37、ng 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 period, turn off power anddisconnect power controller from power source. Then slow
38、lyshutdown 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 characteristics such asvolume, thickness, color, and appearance. Photograph thedeposit where p
39、ossible.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 specimen in a desiccator to constant weight.Weigh to the nearest milligram.NOTE 3Deposit
40、 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 composition,remove as much of it as possible with a plastic knife and addto it the deposi
41、t collected in 8.6.4. Chemical analysis of thedeposit may be performed in accordance with PracticesD 2331, but this step is optional.8.6.6 Clean the test specimen as well as possible with aplastic knife. Remove oily deposits in accordance with PracticeG1. Remove remaining loose deposits from the spe
42、cimen 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 warm air drying.8.6.6.2 Subject a weighed blank coupon of the same metal-lurgy to
43、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. Calculation9.1 Calculate the deposit weight by subtracting the weightof cleaned test spe
44、cimen 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 the metal weight loss by subtracting theweight of the cleaned test specimen from th
45、e initial specimenweight and correcting for the change in weight of a blank aftercleaning as follows:Wc5 W11 2 W42 W5!/W4# 2 W2(9)where:Wc= weight loss due to corrosion, mg,W1= initial weight of test specimen, mg,W4= initial weight of blank specimen, mg,W5= weight of cleaned blank specimen, mg, andW
46、2= weight of test specimen with deposit, mg.9.3 Calculate the average corrosion rate for the test speci-men as follows:Xc5 7.09 Wc!/d1LeZt!(10)where:Xc= average corrosion rate, mills/yr,Wc= weight loss due to corrosion, mg,d1= outside diameter of test specimen, in.,Le= total length of exposed test s
47、pecimen, 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:Xd5 0.0493 Wd!/d1Lht! (11)where:Xd= average rate of fouling, mg/cm2/day,Wd= weight gain due to deposition, mg,d1= outside diameter of test sp
48、ecimen, in.,Lh= length of heated section, in., andt = exposure time, days.10. Precision and Bias10.1 The precision and bias of this test method are asspecified in Practice G1. The precision and bias statementcontained in Practice G1is repeated in the Appendix for thebenefit of the reader.10.2 Becaus
49、e this standard is for a continuous samplingmethod, it is exempt from the requirement of a round-robin testper Practice D 2777, paragraph 1.3.3.11. Keywords11.1 cooling water; corrosion; deposits; fouling; heattransferTABLE 1 Density of MetalMetallurgy ZAdmiralty brass 8.52Copper 8.94Carbon steel 7.86304 stainless steel 7.94D4778054APPENDIXX1. PRECISION AND BIAS STATEMENT FROM PRACTICE G1X1.1 The factors that can produce errors in mass lossmeasurement include improper balance calibration and stan-dardization. Generally, modern analytic
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