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API 653 In-Service Inspection Report <br /> for <br /> Pacific Ethanol HMT Inspection <br /> Tank No. T-7702 August a,2013 <br /> Stockton, CA Page 16 of 41 <br /> 4.3.3 SHELL CORROSION RATE CALCULATIONS <br /> When the corrosion rate is not known, the maximum interval shall be 5 years (API 653, <br /> Para. 6.3.3.2 a). When the corrosion rate is known, the maximum interval shall be the <br /> smaller of RCA/2N years or fifteen (15) years (API 653, Para. 6.3.3.2 b): <br /> RCA = tart—tm,,, <br /> N= tprev— tact/Y <br /> f UT= tact— tmin/2N <br /> Where: <br /> RCA= See Table = Difference between the measured shell thickness <br /> and the minimum required thickness in inches. <br /> N= See Table = Shell corrosion rate in inches per year <br /> Y= Years in service 6 <br /> fUT= See Table = Inspection interval for the next Ultrasonic (UT) <br /> testing, in years (not exceeding 15 years) <br /> Previous Current Minimum Next <br /> Thickness Measured Material Required Corrosion Ultrasonic(UT) <br /> Course (in.) Average Loss Thickness RCA Rate Thickness <br /> No. (taw)* Thickness (in.) (in.) (in.) (in./yr) Inspection <br /> (in.) (t_) (n1) (years) <br /> r:4, I I I I ►. <br /> 1 0.188 0.177 0.011 0.100 0.077 0.0018 15 <br /> 2 0.188 0.175 0.013 0.100 0.075 0.0021 15 <br /> 3 0.188 0.175 0.013 0.100 0.075 0.0021 15 <br /> * =Assumed Original thickness data to facilitate corrosion rate calculations. <br /> R E C' E 1111 <br /> AUG 14 2014 <br /> APIRPTNE.DOT REV 2 2326286817-7702r(Rev 1) 1116/20132:13 PM <br /> ENVIRONMENTAL HEALTH <br /> DEPARTMENT <br />