1、 ANSI/AWWA D104-11 (Revision of ANSI/AWWA D104-04) AWWA Standard Effective date: March 1, 2011. First edition approved by AWWA Board of Directors Jan. 27, 1991. This edition approved Jan. 23, 2011. Approved by American National Standards Institute Dec. 16, 2010. 6666 West Quincy Avenue Advocacy Denv
2、er, CO 80235-3098 Communications T 800.926.7337 Conferences www.awwa.org Education and TrainingScience and TechnologySections The Authoritative Resource on Safe Water Automatically Controlled, Impressed-Current Cathodic Protection for the Interior Submerged Surfaces of Steel Water Storage Tanks SM C
3、opyright 2011 American Water Works Association. All Rights Reserved. ii AWWA Standard This document is an American Water Works Association (AWWA) standard. It is not a specification. AWWA standards describe minimum requirements and do not contain all of the engineering and administrative information
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14、iation. All Rights Reserved. iii Committee Personnel The AWWA Cathodic Protection Task Force, which developed this standard, had the following personnel at the time: David H. Kroon, Chair R.A. Aboyure, Engineered Storage Products Company, Dekalb, Ill. (AWWA) L. Barrett, Gibsonia, Pa. (AWWA) J.R. Con
15、rady, Conrady Consultant Services, Wilsonville, Ala. (AWWA) C.W. Dessens, City of Houston, Houston, Texas (AWWA) R.V.D. Field, Engineered Storage Products Company, DeKalb, Ill. (AWWA) M. Fogata, California Corrosion Specialists, San Diego, Calif. (AWWA) R.A. Gummow, Correng Consulting Services, Down
16、sview, Ont. (AWWA) R.J. Kochilla, City of Cleveland, Parma, Ohio (AWWA) D.H. Kroon, Corrpro Companies Inc., Houston, Texas (AWWA) J. Rog, Corrpro Waterworks, Medina, Ohio (AWWA) L.D. Scott, CB however, the combination of coatings and cathodic protection may be more economical and effective than usin
17、g coatings or cathodic protection alone. II.B. Cathodic Protection. The two major components of an automatically controlled, impressed-current cathodic protection system are the direct current (DC) power supply controller (rectifier) and the anode system. The range of output current capacity require
18、d for an automatically controlled rectifier in a specific application is determined by assuming the area of submerged, bare steel to be protected when the interior tank coating is new and when the interior coating has deteriorated to the point where recoating is necessary. In potable water, current
19、density requirements can range from 0.5 to 5.0 mA/ft 2(5.4 to 53.8 mA/m 2 ) of bare steel surface. Applications involving turbulence, high temperature, or both may require higher current densities. For newly coated tanks, the total current requirement may be as little as 1 percent of the current req
20、uired to protect an uncoated surface. As a rule, rectifiers for newly coated tanks should have sufficient current capacity to protect the anticipated bare submerged surface area before coating repair or replacement. The required operating voltage of a rectifier for a specific tank depends on the cur
21、rent required to provide adequate protection and the total circuit resistance of the system. Automatically controlled rectifier systems should be used for cathodic protection of water storage tanks. Automatically controlled systems use one or more long-life refer- ence electrodes to monitor the prot
22、ection levels maintained on the submerged surfaces. The reference electrode continuously monitors the tank-to-water potential, free of IR (voltage) drop error. IR drop must be eliminated or minimized to accurately determine the voltage between the tank and the reference electrode submerged in the ta
23、nk. The controller instantaneously interrupts the flow of cathodic protection current, providing an IR drop-free measurement, which closely approximates the polarized potential. The controller compares the measured tank-to-water potential to a preset value and auto- matically adjusts the current output of the rectifier. Automatic units include a tank-to- water potential monitoring meter, which can be easily checked by the purchaser. Copyright 2011 American Water Works Association. All Rights Reserved.
