1、Item No. 24233 NACE International Publication 46107 This Technical Committee Report has been prepared by NACE International Task Group 157* on Buildings: Corrosion and Scale Control in Circulating Water Systems. Control of Corrosion, Deposition, and Microbiological Growth in Recirculating Water Syst
2、ems in Buildings September 2007, NACE International This NACE International technical committee report represents a consensus of those individual members who have reviewed this document, its scope, and provisions. Its acceptance does not in any respect preclude anyone from manufacturing, marketing,
3、purchasing, or using products, processes, or procedures not included in this report. Nothing contained in this NACE International report is to be construed as granting any right, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by
4、 Letters Patent, or as indemnifying or protecting anyone against liability for infringement of Letters Patent. This report should in no way be interpreted as a restriction on the use of better procedures or materials not discussed herein. Neither is this report intended to apply in all cases relatin
5、g to the subject. Unpredictable circumstances may negate the usefulness of this report in specific instances. NACE International assumes no responsibility for the interpretation or use of this report by other parties. Users of this NACE International report are responsible for reviewing appropriate
6、health, safety, and regulatory documents and for determining their applicability in relation to this report prior to its use. This NACE International report may not necessarily address all potential health and safety problems or environmental hazards associated with the use of materials, equipment,
7、and/or operations detailed or referred to within this report. Users of this NACE International report are also responsible for establishing appropriate health, safety, and environmental protection practices, in consultation with appropriate regulatory authorities if necessary, to achieve compliance
8、with any existing applicable regulatory requirements prior to the use of this report. CAUTIONARY NOTICE: The user is cautioned to obtain the latest edition of this report. NACE International reports are subject to periodic review, and may be revised or withdrawn at any time without prior notice. NAC
9、E reports are automatically withdrawn if more than 10 years old. Purchasers of NACE International reports may receive current information on all NACE International publications by contacting the NACE International FirstService Department, 1440 South Creek Drive, Houston, Texas 77084-4906 (telephone
10、+1 281228-6200). FOREWORD This technical committee report applies to water-using cooling and heating systems in buildings. It provides information for minimizing system damage and operational interference because of corrosion, scale, fouling, and microbiological growth in building heating, ventilati
11、on, and air conditioning (HVAC) systems. This includes low-pressure steam boilers and hot water “boilers” (see Glossary). The document also addresses thermal energy storage (TES) systems, but does not address potable water systems. Control of Corrosion, Deposition, and Microbiological Growth in Reci
12、rculating Water Systems in Buildings is intended for use by building owners and engineering,maintenance, and operations management personnel. It is also intended for use by those involved in the design and construction of building HVAC systems so that corrosion, scale, fouling, and microbiological g
13、rowth problems described above can be understood, anticipated, and minimized through appropriate design decisions. This report was prepared by Task Group (TG) 157 on Corrosion and Scale Control in Circulating Water Systems in Buildings. This TG is administered by Specific Technology Group (STG) 46,
14、Building Systems. It is also sponsored by STG 11, Water Treatment, and STG 61, Inhibition: Corrosion and Scaling. It is issued by NACE International under the auspices of STG 46. NACE technical committee reports are intended to convey technical information or state-of-the-art knowledge regarding cor
15、rosion. In many cases, they discuss specific applications of corrosion mitigation technology, whether considered successful or not. Statements used to convey this information are factual and are provided to the reader as input and guidance for consideration when applying this technology in the futur
16、e. However, these statements are not intended to be recommendations for general application of this technology, and must not be construed as such. _ * Chair Anthony Selby, Water Technology Consultants, Inc., Evergreen, Colorado. NACE International 2 NACE International Publication 46107 Control of Co
17、rrosion, Deposition, and Microbiological Growth in Recirculating Water Systems in Buildings Contents Introduction 5 Types of Systems 5 Open Recirculating Cooling Systems . 5 Closed Recirculating Systems 4 Medium- and High-Temperature Hot Water Systems . 7 Steam Heating Systems 7 Ambient Cooling (Fre
18、e Cooling) 8 Thermal Energy Storage Systems 9 System Materials . 10 System Problems 10 Corrosion 10 Microbiological Growth 11 Mineral Scale 11 Fouling (Suspended Solids Deposition) 11 Environmental Considerations 11 New System Startup and Startup after Layup 11 Introduction. 11 New Construction . 12
19、 Cleaning New Cooling Towers 12 Cleaning to Avoid White Rust . 12 Startup after Layup . 13 System and Equipment Layup 13 Cleaning 14 Introduction. 14 Typical Methods Used to Determine Whether Cleaning is Needed 14 Typical Methods Used to Determine Whether Cleaning is Applicable 14 Cleaning Technique
20、s 15 Mechanical Cleaning. 15 On-line Chemical Cleaning . 15 Off-line Chemical Cleaning . 15 Combination of Above Methods 15 Cleaning Enhanced Tubes in Chillers . 15 Typical Precautions 15 Open Recirculating Systems 16 Introduction. 16 Systems 16 Cooling Tower Systems 16 Evaporative Condensers/Cooler
21、s . 16 Problems That Lead to Water Treatment 16 Microbiological Deposits . 16 Corrosion 16 Mineral Scaling . 17 General Deposition . 17 Keeping Cooling Systems Clean 18 Microbiological Control . 18 Oxidizing Microbiocides 18 Feeding Oxidizing Biocides. 19 Nonoxidizing Microbiocides. 19 NACE Internat
22、ional 3 Biodispersants 19 Corrosion Control 19 Overview. 19 Water Chemistry . 19 Corrosion Inhibitors in Open Cooling Water Systems . 19 Mineral Scale Control 20 Overview. 20 Operational Methods for Mineral Scale Control 20 Chemical Treatment for Mineral Scale Control . 20 Suspended Solids Control.
23、21 Makeup Water Treatment . 22 Sidestream Treatment of Circulating Cooling Water . 22 Cooling Tower Cleaning 22 Control of Cycles of Concentration 22 Use of Polymeric Dispersants. 24 Special Concerns in Chemical Treatment. 24 Nonchemical Water Treatment Devices . 24 Closed Recirculating Systems . 24
24、 Introduction. 24 Primary and Secondary Closed Systems . 25 Closed System Corrosion Control. 25 Chilled and Low Temperature Closed Systems 26 Medium and High Temperature (177oC 350oF) Closed Systems 27 Monitoring Performance in Closed Systems. 27 Ambient Cooling Systems (Free Cooling) 27 Introductio
25、n. 27 Microbiological Growth in Ambient Systems. 27 Control of Scale 27 Thermal Energy Storage Systems 28 Introduction. 28 System Design 29 Corrosion Control 29 Fouling/Deposit Control 30 Microbiological Control . 30 Steam Heating Boilers in Buildings 31 Introduction. 31 Types of Boilers 31 Tube Boi
26、lers 31 Sectional Boilers . 32 Electric Boilers 32 Boiler Systems 32 Pretreatment of Boiler Makeup . 32 Deaeration to Removed Dissolved Oxygen 32 Softening to Remove Hardness (Calcium/Magnesium). 33 Dealkalization to Remove Alkalinity 33 Internal Chemical Treatment 34 Corrosion Control in Boilers 34
27、 Carbonate Treatment 34 Phosphate Treatment 34 All-Organic Treatment. 34 Corrosion Control in Condensate Systems. 35 Boiler Controls and Safety 35 Water Level Control and Low Water Protection 35 Pressure Relief . 35 Firing Controls. 36 Boiler Inspections 36 Testing and Monitoring . 36 Monitoring Req
28、uired to Meet Performance Objectives . 36 Cooling Tower Evaporation 36 Cycles of Concentration (COC) 36 Scale and Corrosion Inhibitor Control. 37 NACE International 4 Microbiological Control . 37 Corrosion Monitoring 37 Deposition Monitoring. 38 Closed System Treatment Control 39 Glossary . 39 Refer
29、ences . 41 Appendix A . 42 Determining System Volume Appendix B . 42 Cleaning Approach Outline Appendix C . 43 Preparing an Open Cooling System for Layup NACE International 5 INTRODUCTION Types of Systems In a typical commercial HVAC design, chilled water is generated in the evaporator section of a
30、refrigeration unit and is circulated around the facility in a closed loop. Heat from the refrigeration unit is exhausted to a cooling tower via the condenser section. This arrangement is shown in Figure 1. FIGURE 1. Conventional HVAC Chiller System Open Recirculating Cooling Systems The open recircu
31、lating system (condenser loop) contains the chiller condenser, cooling tower, and associated equipment. Cooling tower systems are open to the air and operate under conditions of continuous water loss (evaporation and blowdown) and replacement (makeup). These systems are contaminated to some extent w
32、ith bacteria and suspended material scrubbed from the air. This contamination can result in fouling and corrosion because of microbiological growth and suspended solids (silt) accumulation. Open recirculating systems are discussed in detail later in this report. Closed Recirculating Systems The clos
33、ed recirculating system can include recirculating loops used for both heating and cooling. A simple recirculating closed loop is shown in Figure 2. This system can be a cooling loop, a chilled water loop, or a low temperature (82 to 121C 180 to 250F) heating hot water loop. When a closed loop both h
34、eats and cools, it is commonly known as a dual temperature system. In any case, each system consists of circulating pumps, terminal units that account for cooling or heating load, an expansion tank, and heat exchangers that can be chillers/evaporators or hot water boilers/steam converters. Steam con
35、verters are steam to water heat exchangers while terminal units are fan coil units, air handling units, or induction units. Other important components include pump seals, air purgers, air separators, valves, fittings, etc. A typical makeup water system for a closed loop usually consists of a small-d
36、iameter city water pipe line connected to the expansion tank, a pressure regulating valve for automatic makeup when system water pressure drops, and a check valve or a back flow preventer to prevent contamination of city water with system water. However, makeup systems for large closed loops usually
37、 are each equipped with an emergency makeup connection, a storage tank with transfer pumps, and a large enough expansion tank to permit flushing of piping. Figure 3 represents a basic building block of more complex closed recirculating water systems. It is often labeled as a two-pipe (a supply and a
38、 return header) chilled water or hot water heating system. The simple two-pipe configuration is usually modified for large building and dual temperature operations. The modifications typically include: NACE International 6 (a) Adding a secondary, two-pipe, dual temperature system to a simple two-pip
39、e primary chilled water system via direct injection for secondary chilled water operation and a hot water heat exchanger for heating operation in winter. See Figure 4. This configuration also applies to district cooling systems and TES systems. See the TES section in this report for more information
40、. (b) Seasonally converting an open cooling tower loop into a closed two-pipe hot water loop in winter by activating a standby hot water boiler in winter. This design is for packaged heat pump condenser loops. (c) Seasonally converting a closed chilled water loop into an open free cooling loop witho
41、ut incorporating a plate-and-frame heat exchanger. See the Ambient Cooling Systems section in this report for more information. (d) Use of a three-pipe system (two supply and one common return headers). This means that the terminal units can receive either chilled water or hot water from either of t
42、he two supply headers. The water is returned through the common return header. (e) Use of a four-pipe system (two supply and two return headers). The four pipe systems have separate circulating pumps for chilled water and hot water. The only common components are the terminal units. The circulating
43、medium is usually water. The water can be softened or deionized (demineralized), and mixed with inhibited glycol for freeze protection. In the case of glycol systems, the makeup systems include a softened or deionized water line connected to an open or vented storage tank with a transfer pump(s) for
44、 feeding glycol into the system. Chemical treatment of closed systems is discussed later in this report. FIGURE 2. Closed Cooling/Heating System FIGURE 3. Complex Closed System NACE International 7 Medium- and High-Temperature Hot Water Systems These are hot water heating systems with water temperat
45、ure of 121to 204C (250 to 400F) and pressure ranging from 20 to 240 psig (138 to 1,656 kPag). These systems are sometimes referred to as hot water heating boilers, although no boiling occurs and no steam is generated. They are different from low-temperature hot water heating systems in that the make
46、up water is deaerated and softened, and the expansion tanks are either nitrogen blanketed or steam cushioned. System piping usually consists of feed water makeup piping, boiler circulation piping, and service distribution piping. See Figure 4. FIGURE 4. Medium- and High-Temperature Hot Water System
47、These designs are usually found in large district or campus heating systems. Underground or aboveground piping systems are often used, and secondary low-temperature hot water systems are often at the end of the service distribution. The boilers can be high-temperature hot water (HTHW) generators or
48、high-pressure steam boilers that are equipped with a cascade heater to generate high-temperature hot water. The former is called a direct system while the latter is called an indirect system. Steam Heating Systems A steam heating system generates steam in a boiler, and the steam is used for space he
49、ating or in an absorption chiller. The steam may be produced by an on-site boiler or by an off-site central steam plant (outside steam). A simple steam heating system is shown in Figure 5. NACE International 8 FIGURE 5. Steam Heating System The steam boiler can also be used to transfer heat to a closed hot water loop via a converter. This is shown in Figure 6. FIGURE 6. Steam or Hot Water Boiler With ConverterAmbient Cooling (Free Cooling) Under certain ambient conditions, the cool water from the cooling tower has a low enough temperature to satisfy build
