NACE SP0189-2013 Online Monitoring of Cooling Water Systems (Item No 21041).pdf

1、NACE SP0189-2013 (formerly RP0189) Item No. 21041 Standard Practice Online Monitoring of Cooling Water Systems This NACE International standard represents a consensus of those individual members who have reviewed this document, its scope, and provisions. Its acceptance does not in any respect preclu

2、de anyone, whether he or she has adopted the standard or not, from manufacturing, marketing, purchasing, or using products, processes, or procedures not in conformance with this standard. Nothing contained in this NACE International standard is to be construed as granting any right, by implication o

3、r otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by Letters Patent, or as indemnifying or protecting anyone against liability for infringement of Letters Patent. This standard represents minimum requirements and should in no way be interpreted as

4、 a restriction on the use of better procedures or materials. Neither is this standard intended to apply in all cases relating to the subject. Unpredictable circumstances may negate the usefulness of this standard in specific instances. NACE International assumes no responsibility for the interpretat

5、ion or use of this standard by other parties and accepts responsibility for only those official NACE International interpretations issued by NACE International in accordance with its governing procedures and policies which preclude the issuance of interpretations by individual volunteers. Users of t

6、his NACE International standard are responsible for reviewing appropriate health, safety, environmental, and regulatory documents and for determining their applicability in relation to this standard prior to its use. This NACE International standard may not necessarily address all potential health a

7、nd safety problems or environmental hazards associated with the use of materials, equipment, and/or operations detailed or referred to within this standard. Users of this NACE International standard are also responsible for establishing appropriate health, safety, and environmental protection practi

8、ces, in consultation with appropriate regulatory authorities if necessary, to achieve compliance with any existing applicable regulatory requirements prior to the use of this standard. CAUTIONARY NOTICE: NACE International standards are subject to periodic review, and may be revised or withdrawn at

9、any time in accordance with NACE technical committee procedures. NACE International requires that action be taken to reaffirm, revise, or withdraw this standard no later than five years from the date of initial publication and subsequently from the date of each reaffirmation or revision. The user is

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11、81-228-6200). Revised 2013-06-22 Revised 2002-10-11 Revised 1995 Approved 1989 NACE International 1440 South Creek Dr. Houston, Texas 77084-4906 +1 281-228-6200 ISBN 1-57590-159-5 2013, NACE International SP0189-2013 NACE International i _ Foreword This NACE standard describes a variety of devices u

12、sed for online monitoring of fouling, corrosion, and other parameters in cooling water systems. Methods are presented for collecting test data to determine fouling and corrosion rates that may be used for, but are not limited to, (1) predicting the expected service life of heat-exchange equipment, (

13、2) optimizing the cooling water system operation, (3) detecting operating problems and upset conditions, (4) monitoring corrective actions taken when such conditions occur, (5) assisting in problem solving, and (6) evaluating alternate chemical treatment programs. This standard is intended for use b

14、y operators of cooling water systems and those organizations that supply treatment materials and consulting services to them. This standard was originally prepared in 1989 by NACE Task Group (TG) T-3T-1, a component of Unit Committee T-3T, “On-Line Monitoring Technology,” and revised in 1995 by TG T

15、3T-4. It was revised in 2002 and 2013 by NACE TG 241, “On-Line Monitoring of Cooling Waters and Cooling Water Test Units.” TG 241 is administered by Specific Technology Group (STG) 11, “Water Treatment.” This standard is issued by NACE International under the auspices of STG 11. In NACE standards,

16、the terms shall, must, should, and may are used in accordance with the definitions of these terms in the NACE Publications Style Manual. The terms shall and must are used to state a requirement, and are considered mandatory. The term should is used to state something good and is recommended, but is

17、not considered mandatory. The term may is used to state something considered optional. _ SP0189-2013 ii NACE International _ NACE International Standard Practice Online Monitoring of Cooling Water Systems Contents 1. General 1 2. ApparatusFouling/Deposit Monitors . 1 3. ApparatusCorrosion Monitors 7

18、 4. ApparatusIntegrated Online Monitors 8 5. Application Criteria 9 6. Data Collection, Handling, and Interpretation 9 References 13 Bibliography . 14 Appendix A: Heat Transfer Nomenclature and Equations (Nonmandatory) 16 FIGURES Figure 1: Schematic Diagram of Typical Electrically Heated MonitorAnnu

19、lar Flow 2 Figure 2: Schematic Diagram of Typical Electrically Heated MonitorTubular Flow 3 Figure 3: Typical Pressure-Drop Monitor for Biofouling . 5 Figure 4: Typical Two-Tube Heat Exchanger Test Unit . 6 Figure 5: Schematic Diagram of an Integrated Online Monitor 10 Figure A1: Schematic Diagram o

20、f the Temperature Profile of a (a) Clean Tube and (b) Deposit-Fouled Tube . 17 Table A1: Nomenclature . 16 _ SP0189-2013 NACE International 1 _ Section 1: General 1.1 The purpose of this standard is to describe technologies applicable to the online monitoring of cooling water systems. The standard f

21、ocuses on those technologies that provide data on a short-term basis (minutes to hours) and provide output in a form that may be used by the operator to deal with changing conditions in real time. 1.2 For the purpose of this standard, an online monitor for a cooling water system is defined as a devi

22、ce, or combination of devices, that measures corrosion rates and determines changes in heat transfer coefficients (fouling factors) by measuring pertinent parameters under steady-state conditions that simulate critical conditions in an operating heat exchanger in a reliable and objective manner and

23、with acceptable precision and accuracy. 1.3 References to Existing Publications 1.3.1 ASTM (1)G 96 1covers two techniques for monitoring the corrosion rates of metals(1) electrical resistance method, and (2) linear polarization resistance (LPR) method. Of the two, the LPR method, which determines in

24、stantaneous corrosion rates, has found considerable acceptance compared with other methods for monitoring corrosion rates of metals exposed to cooling waters. 1.3.2 NACE Publication 3T199 2 covers techniques for both direct and indirect monitoring of corrosion and related parameters in field applica

25、tions. 1.3.3 EPRI (2) Report TR-112024 3 covers online monitoring techniques used by utility end users. 1.4 This standard covers simulation of plant heat exchangers with cooling water on the tube side where the monitor incorporates (1) a test surface heated by high-purity steam or an electrical resi

26、stance heater of constant heat flux, or (2) pressure-drop methodology, generally unheated to evaluate microbiological growth. However, other heating media such as hot water or a heat transfer fluid have been used as the heat source. When numerical results are given for fouling, they represent only w

27、hat occurred under a specific set of heat exchanger operating conditions and cooling water quality. Online monitors, such as those covered in this standard, are not designed to model operational problems such as localized hot spots, changing heat flux, localized low-velocity areas, hydraulic shocks,

28、 or mechanical cleaning that may occur in operating plant heat exchangers. As with most process modeling, online monitors cannot replicate the total process heat exchanger at one time. Thus, the user must choose the section of the heat exchanger (e.g., inlet, middle, outlet) to be modeled. 1.5 Appen

29、dix A (nonmandatory) includes heat transfer nomenclature and equations used in this standard. _ Section 2: Apparatus Fouling/Deposit Monitors 2.1 Electrically Heated Monitors 2.1.1 Principles of Operation 2.1.1.1 Online monitors are often designed for easy use and simplicity, using an electrical res

30、istance heating element to impose a heat load on the metal surface and measuring the rate of heat transfer from that metal surface into a cooling water stream passing by it (see Figure 1). This enables the heat transfer efficiency and overall cleanliness to be determined. This heat transfer rate is

31、relatively constant as long as the surface remains free of foulant. However, as substances (e.g., hardness salts, oxides and hydroxides of iron, silt, biomass, and process contamination) form deposits on the heated surface, they decrease the overall cleanliness and reduce heat transfer. The heat loa

32、d is supplied by an electrically heated element that is located near or directly in contact with the metal probe surface. 2.1.1.2 Fouling is a function of cooling water temperature, viscosity, flow characteristics (Reynolds number and shear stress), geometry, materials of construction, and temperatu

33、re of the heat transfer surface. The levels of dissolved and (1)ASTM International (ASTM), 100 Barr Harbor Dr., West Conshohocken, PA 19428-2959. (2)Electric Power Research Institute (EPRI), 3420 Hillview Ave., Palo Alto, CA 94304. SP0189-2013 2 NACE International suspended solids, microbiological m

34、atter, and process contamination are the most important cooling water characteristics, while the velocity, shear stress, and fluid viscosity are the determinant flow characteristics. 2.1.1.3 Certain parameters must be measured to find the accurate rate of heat dissipation into the cooling water. Sen

35、sors are located between the surface and the heat source to determine the wall or surface temperature. Temperatures of the influent and effluent cooling water streams may also be measured. Depending on the particular design, these temperatures can be continuously or intermittently recorded or analyz

36、ed by a computer system. For safety, the heating element usually has an automatic shutoff, which is activated under no flow and/or high wall temperature conditions. Figure 1: (3)Schematic Diagram of Typical Electrically Heated Monitor Annular Flow 2.1.1.4 Two types of monitoring devices are commonly

37、 used. In one device, cooling water flows in an annular space, thus making possible the use of a combination of visual determination and heat transfer computations (see Figure 1). 4-8(Other geometries that permit visual observation and heat transfer measurement are available.) Visual observations ar

38、e qualitative; they can be made using a transparent test section. These observations should show the type and quantity of deposit build-up as well as allow the observer to judge the rate of deposit formation in the monitor. Observations also may be made offline through disassembly and inspection of

39、the heat transfer surface. In some designs, a heat transfer tube is separate from the heat source. By weighing a heat transfer tube prior to installation and then weighing the exposed tube (after careful removal and drying), it is possible to estimate the approximate total deposit mass and average m

40、ass per unit surface area. Afterward, accumulated deposits should be removed and analyzed. 2.1.1.5 The second device uses an electrical heating element that applies heat to the outside of the tube and the cooling water circulates through the inside of the tube (see Figure 2). 9With this type of devi

41、ce, the tube alloy and dimensions may be selected to match the process equipment and the cooling water velocity may be controlled to duplicate the shear stress and/or velocity profile at the metal surface. Fouling is determined by changes in the calculated heat transfer resistance; visual observatio

42、n is not possible. However, observations may be made offline through disassembly and inspection of the inside tube surface. On completion of the test, accumulated deposits should be removed and analyzed. 2.1.1.6 Usually, the effects of fouling are expressed in one of the following three ways: foulin

43、g factor, cleanliness factor, or a change in overall heat transfer coefficient. (See Appendix A.) 2.1.1.7 To ensure that data are taken under steady-state flow conditions, typically a minimum of 12 to 15 equivalent diameters must be allowed after a change in flow path and ahead of measurement to per

44、mit full flow development. Such measurement should also be a minimum of four to six equivalent diameters ahead of any changes in flow path. (3)Figure 1 is reprinted with permission from Ashland Inc., from K.W. Herman, J.G. Knudsen, “The Use of a Novel Portable Fouling and Corrosion Monitor Recorder

45、in Industrial Cooling Water Systems,” paper presented at the Industrial Water Conference, Pittsburgh, PA, November 1979. (Copyright Drew Chemical Corp., Boonton, NJ 07005.) SP0189-2013 NACE International 3 The equivalent diameter is four times the cross-sectional area divided by the wetted perimeter

46、 for an annular duct. For internal tubular flow, the equivalent diameter is equal to the diameter of the tube. Figure 2: (4)Schematic Diagram of Typical Electrically Heated Monitor Tubular Flow 2.1.2 Examples of Devices 2.1.2.1 A number of different device designs and models are currently available.

47、 Most have many similarities with a few distinct design differences. Among the possible control parameters are cooling water velocity, heat input, cooling water temperature, and surface temperature. Depending on the particular model, a number of parameters, including cooling water flow, wall tempera

48、ture, bulk cooling water temperature, influent cooling water temperature, and effluent cooling water temperature, may be measured. Some designs incorporate measurement of additional parameters such as corrosion rate, pH, and conductivity. Supplemental monitors may be used with the fouling monitor to obtain a more complete picture; however, when doing so, care should be taken to ensure that these devices do not disturb the cooling water flow across the h