1、LONG TERM RESISTANCE OF AWWA C906 POLYETHYLENE (PE) PIPE TO POTABLE WATER DISINFECTANTS TN-44/2015 2 Foreword This technical note was developed and published with the technical help and financial support of the members of the PPI (Plastics Pipe Institute, Inc). The members have shown their interest
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6、 obtained by contacting PPI directly or visiting the web site. The Plastics Pipe Institute, Inc. www.plasticpipe.org November 2015 3 LONG TERM RESISTANCE OF AWWA C906 POLYETHYLENE (PE) PIPE TO POTABLE WATER DISINFECTANTS PPI TN-44 1. INTRODUCTION The operational service life of a piping system depen
7、ds on many factors. Resistance to disinfectants is one of these factors. Polyethylene (PE) pipes intended for potable water applications contain additives to provide resistance to the long term oxidizing effects of water disinfectants. Research programs conducted on PE piping compounds resulted in t
8、he development of a model that projects the performance of PE pipes in chlorinated (i.e. free chlorine and chloramine) potable water distribution and transmission systems.1 The model is based on testing in accordance with ASTM F2263, “Test Method for Evaluating the Oxidative Resistance of Polyethyle
9、ne (PE) Pipe to Chlorinated Water” and projects the performance of PE pipes due to specific end use conditions. PE pipe compounds intended for potable water applications are classified for oxidative resistance in accordance with ASTM D3350. The oxidative resistance categories include CC1, CC2 and CC
10、3 (highest performance). CC1, CC2 and CC3 PE pipe compounds provide long term resistance to disinfectants in most potable water service applications. Table 1 shows a selection of utility specific conditions and the resultant resistance to disinfectants of pipes produced from PE4710 CC1 compounds. Ta
11、ble 1: Resistance to Disinfectants at Selected Utilities for AWWA C906 Pipe Average US Utility Indiana Utility-1 Indiana Utility-2 North Carolina California Utility-1 California Utility-2 Disinfectant type Chloramine Chlorine Chlorine Chloramine Chlorine Average Disinfectant Residual (ppm) 1.6 1.4 0
12、.9 1.9 0.9 Average pH 7.7 8.8 8.6 9.0 7.9 Estimated ORP (mV)2 650 650 740 680 650 750 Average Annual Water Temperature (oF)3 57 57 54 68 61 64 Pipe DR and Pressure Class, PC (psi) DR21 PC100 DR21 PC100 DR21 PC100 DR21 PC100 DR21 PC100 DR21 PC100 Average Working Pressure (psig) 70 70 70 70 65 77 Proj
13、ected Oxidative Resistance under the specific operating conditions (years) 100 100 100 100 100 100 This technical note provides a method to determine the resistance to disinfectants for different conditions than those shown above. 1 Jana Technical Report, “JP 916: Jana Mode 3 Shift Functions”, March
14、 2012 2 Oxidative Reduction Potential (ORP) is a measure of the ability of a chemical substance to oxidize. 3 The Average Annual Water Temperature (AAWT) is a weighted average of the daily water temperature, not the highest temperature observed in the system. 4 2. DETERMINE THE PIPE DISINFECTANT IND
15、EX (PDI) Based on ASTM F2263 test data, a Pipe Disinfectant Index (PDI) has been developed and normalized to reflect resistance to disinfectants. The PDI has been normalized to reflect a resistance to disinfectants of at least 50 years for a PDI 1, and at least 100 years for a PDI 2. A PDI 1 indicat
16、es acceptable service in the presence of disinfectants. The procedure is outlined below along with figures, curve fit equations, tables and examples. 1. Obtain the following data: Average annual water temperature, AAWT (F). If AAWT is not available from the water utility Appendix A may also be used
17、to estimate this value. Pipe Pressure Class (PC) Average system working pressure Average Disinfectant residuals (ppm) Average Water pH, Pipe Material Chlorine Category CC1, CC2, or CC3 2. Determine the following: Temperature Factor, FTemp from Figure 1 Pressure Ratio Factor, FPress from Figure 2 Wat
18、er Quality Factor, FWQ = 8.0 for chloramines; for chlorine FWQ refer to Table 2 Pipe Material Factor, FMat from Table 3 Pipe Size Factor, FSize from Table 4 3. Calculate the Pipe Disinfectant Index (PDI): PDI = FTemp x FPress x FWQ x FMat x FSize y = 189e-0.07x 012345678950 60 70 80Temperature Facto
19、rAverage Annual Water Temperature AAWT, deg F Figure 1 Temperature Factor FTemp y = x3.5 01234567891011121314151 1.25 1.5 1.75 2 2.25Pressure Ratio FactorPE4710 Pressure Class (PC) Average Working Pressure Figure 2 Pressure Ratio Factor, FPress This may also be used for PE3608, and will be conservat
20、ive 5 Table 2: Water Quality Factor FWQ4 Average Water pH 6.5 6.75 7 7.25 7.5 7.75 8 8.25 8.5 8.75 9 AverageDisinfection withChlorineResidual (ppm)0.5 2 2.1 2.3 3 3.9 6.1 10 10 10 10 10 0.7 1.5 1.7 2 2.4 2.9 3.8 5 6.9 9.8 10 10 1 1.2 1.3 1.5 1.7 2.1 2.6 3.4 4.6 6.1 8.9 10 1.5 1 1.1 1.2 1.4 1.6 2 2.6
21、 3.4 4.4 6.4 9.1 2 0.8 1 1.1 1.2 1.4 1.8 2.3 3 3.9 5.7 8.2 2.5 0.8 0.8 0.9 1.1 1.3 1.6 2 2.7 3.5 4.9 7.2 3 0.8 0.8 0.9 1.1 1.3 1.5 1.9 2.5 3.2 4.4 6.4 4 0.7 0.7 0.8 0.9 1.1 1.3 1.7 2.2 2.7 3.8 5.5 If the pH and residual Chlorine values are in-between the values shown above, select FWQ by rounding th
22、e value of residual chlorine and/or pH to the nearest tabulated number. Table 3: Pipe Material Factor FMat5 Chlorine Category Material Factor, FMat CC1 0.16 CC2 0.45 CC3 1.0 Table 4: Pipe Size Factor FSize Nominal Pipe Size Size Factor, FSize 4” 1.0 4” Data Under Development6; use 1.0 as a conservat
23、ive value 4 The Water Quality Factor, FWQ has not been determined for HDPE pipes used in the presence of chlorine dioxide as a secondary disinfectant. The use of chlorine dioxide as a secondary disinfectant is rare and estimate to be used in 4” FSize = 1 Calculate Pipe Disinfection Index, PDI PDI= P
24、DI =2.12.53.40.161 = . Example 1 Result: PDI 2, therefore the pipe is resistant to the disinfectant conditions for at least 100 years. Example 2: 12” IPS DR17 (PC125) PE4710 CC2 category Average Annual Water Temperature, AAWT = 78oF Average Chlorine disinfection residual = 0.7ppm Average water pH =7
25、.5 Average working pressure = 100psi From Figure 2, for T = 78F, FTemp = 0.8 From Figure 3, = 125100 = 1.25 FPress = 2.2 From Table 2, for pH7.5, chlorine 0.7ppm FWQ = 2.9 From Table 3, for CC2, FMat = 0.45 From Table 4, for Pipe Size 4” FSize = 1 Calculate Pipe Disinfection Index, PDI PDI= PDI =0.8
26、2.22.90.451 = . Example 2 Result: PDI2, therefore the pipe is resistant to the disinfectant conditions for at least 100 years. 7 Appendix A The average annual ground temperature at the pipes burial depth may be used to estimate the value.7 Figure A1 provides ground temperature data at typical pipe b
27、urial depths. Figure A2 represents recent data from USDA regarding annual average soil temperature at selected observation points throughout the U.S. and is consistent with Figure A1. Figure A1: Average Annual Water Temperature Guidance Source: U.S. Environmental Protection Agency (prepared from dat
28、a included in Collins, W.D., 1925, Temperature of Water Available for Industrial Use in the United States, United States Geological Survey, Water Supply Paper 520-F). Figure A2: Soil Temperature at One Meter Burial Depth Source: United States Department of Agriculture (USDA), National Resources Conversation Service (NRCS), Soil Climate Analysis Network (SCAN) data (2014-15). 7 E.J. Mirjam Blokker and E.J. Pieterse-Quirijns, Modeling temperature in the drinking water distribution system, 104 AWWA JOURNAL 11 (2013).
