Method for extending the time between out-of-service, in-tank inspections using ultrasonic sensor

Abstract

A method and apparatuses to extend the time interval between out-of-service, in-tank inspections while insuring structural integrity using a risk-based, Bayesian statistical approach comprised of a passing leak detection test, determining that the tank is not leaking, estimating a thickness of the tank floor to estimate a corrosion rate, and conducting a risk assessment using the result of the leak detection test, the corrosion rate and thickness of the tank floor, and statistical data of tank failures.

Claims

1. A method for determining if a time until a next scheduled out-of-service internal inspection of a storage tank can be extended while insuring structural integrity of a tank floor, comprising the steps of: (a) performing a leak-detection test; (b) determining that the tank is not leaking based on a result of the leak detection test; (c) estimating a thickness of the tank floor in at least one location of the tank floor, wherein the thickness of the tank floor over at least one location of the tank is measured and used to estimate a corrosion rate and the thickness of the tank floor as a function of a selected time period to determine if a minimum floor thickness can be maintained during said selected time period, and wherein in-tank floor thickness estimates are made using an ultrasonic thickness (UT) measurement sensor; (d) conducting a risk assessment using the result of the leak detection test in (b), the corrosion rate and thickness of the tank floor in (c), and statistical data of tank failures including data related to tank corrosion conditions, thereby assessing whether or not the time until the next scheduled out-of-service internal inspection can be safely extended; and (e) performing an inspection of the tank that includes a thickness measurement of the tank at a time prior to the extended time.

2. The method of claim 1, wherein said in-tank floor thickness estimates are used to estimate a minimum thickness of said tank floor at any location of said tank floor.

3. The method of claim 1, wherein said in-tank floor thickness estimates are used to estimate a maximum corrosion rate of said tank floor at any location of the tank floor.

4. The method of claim 1, wherein an acoustic emission (AE) inspection of said tank floor for active corrosion is used to determine whether the thickness estimate of the tank floor in one location of said tank floor is used to estimate at least one of a thickness and a corrosion rate of another location of said tank floor.

5. The method of claim 4, wherein said thickness estimate of the tank floor in one location of said tank floor is used to estimate at least one of a thickness and a corrosion rate for the entire tank floor.

6. The method of claim 4, wherein said in-tank floor thickness estimates is used to estimate a minimum thickness of said tank floor at any location of said tank floor.

7. The method of claim 4, wherein said in-tank floor thickness estimates is used to estimate a maximum corrosion rate of said tank floor at any location of the tank floor.

8. The method of claim 1, wherein a previous out-of-service inspection of the tank floor thickness is used to estimate the minimum thickness and a maximum corrosion rate from said in-tank floor thickness measurements.

9. The method of claim 8, wherein said in-tank floor thickness estimates is referenced to previous floor thickness estimates made during previous out-of-service inspection in a same region as said in-tank floor thickness measurements and used with said previous out-of-service inspection of said floor to estimate a floor thickness and a corrosion rate at another location on said tank floor.

10. The method of claim 9, wherein a percentage change in said in-tank floor thickness measurements over those measured in said previous out-of-service tank floor inspection is used to compute a percentage change of all other previous measurements of said tank floor from said previous out-of-service tank floor inspection.

11. The method of claim 10, wherein said in-tank floor thickness measurements in one location of said tank floor can be used to estimate a thickness or corrosion rate of another location in said tank floor.

12. The method of claim 10, wherein said in-tank floor thickness measurements in one location of said tank floor can be used to estimate a thickness or corrosion rate for the entire tank floor.

13. The method of claim 10, wherein said in-tank floor thickness measurements are used to estimate a minimum thickness of said tank floor at any location in said tank.

14. The method of claim 10, wherein said in-tank floor thickness measurements are used to estimate a maximum corrosion rate of said tank floor at any location in the tank floor.

15. The method of claim 1, wherein an acoustic emission (AE) inspection of said tank floor for active corrosion is used with a previous out-of-service tank inspection of said floor thicknesses and corrosion rates to estimate the minimum floor thickness and a maximum corrosion rate of said tank floor.

16. The method of claim 1, wherein AE inspection measurements are used to categorize a condition of the floor of the tank in terms of no active corrosion, some active corrosion, active corrosion, moderate corrosion, or severe corrosion.

17. The method of claim 1, wherein results of an acoustic emission (AE) inspection of said tank floor for active corrosion is used to determine a magnitude of said corrosion in the tank floor.

18. The method of claim 1, wherein measurements from a previous out-of-service internal inspection are used to categorize the condition of the floor of the tank in terms of no active corrosion, some active corrosion, active corrosion, moderate corrosion, or severe corrosion.

19. The method of claim 1, wherein results of a previous out-of-service internal inspection of said tank floor for active corrosion is used to determine a magnitude of said corrosion in the tank floor.

20. The method of claim 1, wherein the measurements from an in-tank internal inspection are used to categorize the condition of the floor of the tank in terms of no active corrosion, some active corrosion, active corrosion, moderate corrosion, or severe corrosion.

21. The method of claim 1, wherein results of an in-tank internal inspection of said tank floor for active corrosion is used to determine a magnitude of said corrosion in the tank floor.

22. The method of claim 1, where said measured thickness is made using is an magnetic flux thickness measurement sensor.

23. The method of claim 1, where said thickness estimate is made using a long range ultrasonic test (LRUT) thickness measurement sensor.

24. The method of claim 1, where said thickness estimate is made using an EMAT (Electro Magnetic Acoustic Transducer) thickness measurement sensor.

25. The method of claim 1, where said estimating of thickness is made using an ultrasonic thickness sensor mounted on a robotic crawler.

26. The method of claim 1, where said estimating of thickness is made using an ultrasonic thickness sensor mounted on the end of a pole, which is inserted through an opening at the top of a tank.

27. The method of claim 1, further comprising estimating a corrosion activity on said tank floor with coverage of the entire floor of said tank.

28. The method of claim 1, where said leak detection test is conducted with a mass-based leak detection system.

29. The method of claim 28, where said leak detection test is conducted with the mass-based leak detection system using a long range differential pressure (LRDP) system.

Description

IN THE DRAWINGS

(1) FIG. 1 illustrates the preferred method and apparatus of the present invention with an in-tank floor thickness and an in-tank corrosion assessment system integrated with the mass-based leak detection system.

(2) FIG. 2 illustrates the preferred method and apparatus of the present invention with an in-tank floor thickness and an in-tank corrosion assessment system separated from the mass-based leak detection system.

(3) FIG. 3 illustrates an alternative embodiment of the preferred method and apparatus of the present invention with an in-tank floor thickness system integrated with the mass-based leak detection system and combined with an external walled-mounted corrosion assessment system.

(4) FIG. 4 illustrates an alternative embodiment of the preferred method and apparatus of the present invention with an in-tank floor thickness system separated from the mass-based leak detection system and combined with an external walled-mounted corrosion assessment system.

(5) FIG. 5 illustrates a cumulative frequency distribution (CFD) of floor thickness in an aboveground tank. The distribution is normally distributed and three standard deviations would normally predict the lowest and highest floor thickness.

(6) FIG. 6 illustrates the CFDs of the floor thickness of the five aboveground storage tanks analyzed.

DETAILED DESCRIPTION OF THE INVENTION

(7) The method and apparatuses of the present invention can be used to provide critical data and information about the structural integrity of an aboveground or bulk underground storage tank needed to better prioritize and better schedule out-of-service tank inspections for these tanks, because it can be used to assess the condition of the tank floor, i.e., the thickness of the tank floor, the rate of corrosion of the floor, and whether or not any holes or cracks exist in the floor. If the floor is in good condition, then it is possible to postpone a scheduled inspection or to extend the time between inspections so that the maintenance and repair activities can focus on those tanks with the most need.

(8) The method is comprised of a leak detection test and one or more actual measurements of the thickness and corrosion condition of the bottom floor of the tank in a least one section of the tank. This approach will work well for tanks in which the corrosion is either small or relatively uniform. If not, information about the spatial distribution of floor thickness and corrosion rate is needed to better use these data. This spatial information can be obtained from (1) thickness measurements of the floor of the tank using UT and/or magnetic flux or eddy current measurements made in previous out-of-service inspections according to API 653, AP12R1, or STI SP001, and/or (2) an AE inspection of the tank floor to assess the corrosion condition of the tank floor. The method and the apparatuses of the present invention provide important data to risk-based inspection assessments.

(9) If an API 653 floor inspection was conducted previously, the results of this inspection can be used to increase the confidence in the risk assessment performed to determine if a scheduled tank inspection can be extended without risk of tank failure or a leak. The bottom inspection gives the results of bottom thickness measurements on all plates comprising the floor. Each plate can have a different rate of corrosion or initial thickness. The rate of corrosion can vary because of some inhomogeneity in the soil beneath the tank that accelerates local corrosion on the external or underneath side of the bottom or some local pools of water on the inside of the tank due to deflection in the tank floor. A complete floor inspection according to API 653 will identify such local pockets of accelerated corrosion. This information can be used to make a more conservative estimate of the corrosion rate for future local measurements of bottom thickness on one or a limited number of plates. This is really conservative since once these problem areas are identified, they are usually addressed as part of the API 653 inspection before the tank is brought back into service for another 10-year period. Even so, the UT thickness data provided during the tank test is used to estimate the corrosion rate between the last thickness measurement in the same location can be used to re-estimate the rate of corrosion at all of the previous measurements by the ratio of the local UT measurement and the previous API floor inspection measurements. Thus, if in the previous API 653 Inspection a corrosion rate of 0.035 in./year was estimated and the UT thickness measurement is different (higher or lower), the ratio of the corrosion rate measured with the UT sensor and the previous corrosion rate can be used to forecast the corrosion rate in the tank using the largest rate measurement in the previous API inspection. This corrosion rate can be used to extend the interval between inspections until the minimum plate thickness is met. This computation is really conservative, because it assumes that none of the corrective action taken at the last API 653 Inspection was of any value.

(10) FIG. 1 illustrates the preferred method and apparatus of the present invention. It is comprised of a mass-based leak detection test system 1, such as long range differential pressure (LRDP) inserted into the tank 10 an at convenient opening 72 at the top of the tank, a set of at least three ultrasonic thickness sensors 142, 144, 146 on an arm 130 attached to the leak detection sensor tube 204, 206, and either the results of a previous out-of-service inspection of the tank floor via API 653, API12R1, STI SP001 or other approved inspection method and/or a set of three AE sensors 124, 134, 136 located near the floor 60 of the tank 10 with one of the sensors 124 located at a different elevation from an arm 120 attached to the tube 204 and in a different plane than the other two sensors. FIG. 2 illustrates a very similar but alternative embodiment where the leak detection system 200 is separated from the UT and AE measurement system 1 and is inserted into a different opening 70 at the top of the tank. Both embodiments will produce very similar results. FIGS. 3 and 4 illustrate measurement configurations similar to FIGS. 1 and 2 except the AE sensors 124, 134, 136 are mounted on the outside wall 12 of the tank 10, where one of the sensors 124 is mounted at a different elevation than the other sensors. The elevation difference for AE measurements from both the internal and external sensor location allows for acoustic signals generated on the surface 50/top 40 part of the tank to be distinguished from acoustic signals generated from the floor 60 of the tank. This prevents false alarms on the surface due to condensation drips.

(11) The preferred method of measuring thickness of the tank floor is to use one or more ultrasonic (UT) thickness probes that make contact with the floor and AE sensors that detect the presence of corrosion noise (or leaks) that propagate through the liquid product. The AE sensors can be placed on the external wall of the tank, or inserted in the product inside the tank on the staff used to make the UT floor thickness measurements, where at least one of the sensors is at a different elevation than the other sensors and not in the same vertical plane. The preferred configuration is three sensors mounted in the liquid inside the tank as illustrated in FIG. 1 or 2. Additional floor thickness measurements can be made by adding one or more additional UT sensor systems arm 130 at the bottom of the leak detection system in FIGS. 1 and 3 or to the floor 60 of the staff 104 in FIGS. 2 and 4. Additional UT measurements can be most easily made with any of the two basic configurations by rotating the leak detection tube 204 or the mounting staff 104. This is possible because the UT measurements can be made in less than 1 min.

(12) An analysis of the out-of-service, internal inspection of the floor of the tank obtained using the UT sensor thickness data was performed to determine if a small sample (i.e., 3 to 6) could be used to accurately estimate the minimum thickness and the maximum corrosion rate of the tank floor using a small number of UT measurements obtained in a local area of the tank when there were no local hot spots or high areas of corrosion. Approximately 4 or more UT thickness measurements were made per tank floor panel. We analyzed the inspections from five large USTs with ages ranging from 13 to 15 years old and diameters of 69.7 ft (3 tanks), 37.7 ft (1 tank) and 26.3 (1 tank). Table 4 presents an illustration for one of five cylindrical USTs; the histograms of the data in Table 4 are illustrated in FIG. 5 as a cumulative frequency distribution (CFD). The CFDs of all five tanks in illustrated in FIG. 6. Table 5 presents the results from a 82.5-ft-diameter aboveground storage tank containing 1,040,000 gal that was built in 1976 and last inspected in 2009 (34 years old). The tables summarize the statistics for each panel and for the floor as a whole. The general conclusion is that 3 to 6 UT measurements made on any floor panel or group of floor panels would be sufficient to make a good estimate of the minimum measured thickness and therefore the maximum corrosion rate. This estimate is made from by subtracting 3 times the standard deviation from the mean or median or by just using the minimum UT measurement. This is justified from the Gaussian behavior of the histograms.

(13) The ultimate objective of these measurements is to determine if a scheduled out-of-service inspection should be performed now or can it be postponed so another inspection can be performed. The Extension/Postponement Time Interval will depend on the number of tests conducted and the results of these tests and previous measurements. A passing leak detection result with provides the basis for postponing or extending the time interval of an out-of-service inspection. Without any other tests or information about the condition of the tank, the time interval between inspections can be extended a year, which is the time required between tightness test specified by the EPA for smaller tanks to insure their integrity. With floor thickness measurements and some assessment of the spatial distribution of the thickness and corrosion of the tank floor, longer time intervals are possible depending on the extent of the testing and the results of the testing.

(14) While all of these proposed measurement procedures have been used for tank integrity assessments for many years, they have not been used in combination or for in-service inspections. The proposed method and apparatuses make it possible to prioritize the order for tank inspections and to postpone out-of-service inspections safely for a period of time without taking the tank out of service, by using well understood methods of integrity inspection, and with a high probability that the tank will not structurally fail or leak during the extension period.

(15) TABLE-US-00004 TABLE 4 Summary of the statistics of a UT internal inspection of the tank floor for an 65.6-ft diameter, 733,000-gal UST that is 15 years old. UT UT Reading Plate Reading Number Number (in) Mean StdDev Median Max Min Number 1 1 0.364 0.361 0.006 0.364 0.366 0.352 4 2 1 0.366 3 1 0.352 4 1 0.363 5 1 0.363 0.362 0.005 0.363 0.366 0.351 9 6 1 0.366 7 1 0.359 8 1 0.366 9 1 0.361 10 2 0.358 11 2 0.365 12 2 0.366 13 2 0.351 14 2 0.37 0.366 0.011 0.369 0.380 0.354 6 15 2 0.354 16 2 0.383 17 2 0.354 18 2 0.367 19 2 0.37 20 3 0.361 0.369 0.012 0.367 0.388 0.349 8 21 3 0.383 27 3 0.369 23 3 0.365 24 3 0.365 25 3 0.388 26 3 0.349 27 3 0.368 28 3 0.36 0.366 0.006 0.366 0.374 0.360 4 29 4 0.374 30 4 0.365 31 4 0.366 32 4 0.364 0.361 0.006 0.354 0.367 0.350 12 33 4 0.365 34 4 0.363 35 4 0.354 36 4 0.367 37 5 0.363 38 5 0.366 39 5 0.361 40 5 0.35 41 5 0.364 42 5 0.366 43 5 0.352 14 5 0.365 0.363 0.006 0.365 0.369 0.348 12 45 6 0.367 46 6 0.348 47 6 0.365 48 6 0.356 49 6 0.369 50 6 0.365 51 6 0.362 52 6 0.357 53 6 0.367 54 6 0.365 55 7 0.364 56 7 0.365 0.364 0.003 0.365 0.367 0.356 13 57 7 0.354 58 7 0.366 59 7 0.363 60 7 0.357 61 7 0.356 62 7 0.363 63 8 0.355 64 8 0.363 65 8 0.3652 66 8 0.366 67 8 0.364 68 8 0.367 69 8 0.366 0.364 0.005 0.365 0.373 0.352 13 70 8 0.365 71 8 0.363 72 8 0.373 73 9 0.365 74 9 0.367 75 9 0.352 76 9 0.365 77 9 0.363 78 9 0.364 79 9 0.365 80 9 0.364 81 9 0.365 82 9 0.364 0.354 0.005 0.355 0.369 0.357 4 83 9 0.357 84 9 0.369 85 10 0.367 86 10 0.366 0.366 0.006 0.368 0.371 0.352 8 87 10 0.37 88 10 0.367 89 10 0.352 90 10 0.368 91 10 0.371 92 11 0.368 93 11 0.363 94 11 0.366 0.364 0.005 0.366 0.367 0.355 6 95 11 0.367 96 11 0.355 97 11 0.367 98 11 0.365 99 11 0.363 100 12 0.365 0.362 0.004 0.364 0.366 0.356 8 101 12 0.366 102 12 0.356 103 12 0.363 104 12 0.359 105 12 0.366 106 12 0.356 107 12 0.366 108 12 0.364 0.371 0.005 0.372 0.375 0.364 4 109 13 0.371 110 13 0.375 111 13 0.373 112 14 0.366 0.370 0.005 0.368 0.378 0.366 4 113 14 0.367 114 14 0.378 115 14 0.369 116 14 0.369 0.367 0.002 0.368 0.369 0.364 4 117 14 0.369 118 14 0.367 119 14 0.364 120 15 0.364 Mean StdDev Median Max Min Number Mean 0.365 0.006 0.366 0.372 0.355 0.364 StdDev 0.003 0.003 0.002 0.007 0.006 0.006 Median 0.364 0.005 0.366 0.369 0.355 0.365 Max 0.371 0.012 0.372 0.388 0.366 0.388 Min 0.361 0.002 0.363 0.366 0.348 0.348 Number 16 16 16 16 16 120 3 StDev 0.009 0.008 0.007 0.020 0.017 0.019 Mean ? 0.356 ?0.002 0.359 0.352 0.339 0.345 3 StDev

(16) TABLE-US-00005 TABLE 5 Summary of the statistics of a UT internal inspection of the tank floor for an 82.5-ft diameter, 1,040,000-gal AST that is over 34 years old. READING READING READING READING READING Median ? 3 * Mean ? 3 * 1 2 3 4 5 Mean StDev Median Max Min Min StDev StDev 1 0.362 0.365 0.367 0.373 0.37 0.367 0.0043 0.367 0.373 0.362 0.005 0.0128 0.354 2 0.375 0.378 0.371 0.369 0.368 0.372 0.0042 0.371 0.378 0.368 0.003 0.0126 0.358 3 0.366 0.364 0.363 0.369 0.37 0.366 0.0030 0.366 0.370 0.363 0.003 0.0091 0.357 4 0.375 0.372 0.363 0.371 0.375 0.371 0.0049 0.372 0.375 0.363 0.009 0.0148 0.357 5 0.363 0.365 0.365 0.367 0.368 0.366 0.0019 0.365 0.368 0.363 0.002 0.0058 0.359 6 0.375 0.374 0.378 0.369 0.373 0.374 0.0033 0.374 0.378 0.369 0.005 0.0098 7 0.374 0.373 0.372 0.377 0.374 0.374 0.0019 0.374 0.377 0.372 0.002 0.0056 8 0.373 0.375 0.378 0.369 0.37 0.373 0.0037 0.373 0.378 0.369 0.004 0.0110 0.362 9 0.375 0.377 0.374 0.37 0.371 0.373 0.0029 0.374 0.377 0.370 0.004 0.0086 10 0.362 0.365 0.366 0.369 0.362 0.365 0.0029 0.365 0.369 0.362 0.003 0.0088 0.356 11 0.365 0.364 0.369 0.368 0.37 0.367 0.0026 0.368 0.370 0.364 0.004 0.0078 0.360 12 0.375 0.374 0.369 0.378 0.37 0.373 0.0037 0.374 0.378 0.369 0.005 0.0111 13 0.363 0.366 0.368 0.37 0.372 0.368 0.0035 0.368 0.372 0.363 0.005 0.0105 0.358 14 0.362 0.362 0.362 0.371 0.364 0.364 0.0039 0.362 0.371 0.362 0.000 0.0117 0.350 15 0.365 0.368 0.37 0.37 0.363 0.367 0.0031 0.368 0.370 0.363 0.005 0.0093 0.359 16 0.362 0.365 0.366 0.364 0.369 0.365 0.0026 0.365 0.369 0.362 0.003 0.0078 0.357 17 0.369 0.37 0.378 0.377 0.37 0.373 0.0043 0.370 0.378 0.369 0.001 0.0130 0.357 18 0.37 0.37 0.365 0.372 0.374 0.370 0.0033 0.370 0.374 0.365 0.005 0.0100 0.360 19 0.365 0.366 0.369 0.372 0.375 0.369 0.0042 0.369 0.375 0.365 0.004 0.0125 0.357 Mean StDev Median Max Min Diff Mean 0.368 0.369 0.369 0.371 0.370 0.369 0.0034 0.369 0.374 0.365 0.004 StDev 0.00545 0.00494 0.00504 0.00352 0.00375 0.00344 0.0008 0.00368 0.00370 0.00334 0.00193 Median 0.366 0.368 0.369 0.370 0.370 0.369 0.0033 0.369 0.374 0.364 0.004 Max 0.375 0.378 0.378 0.378 0.375 0.374 0.0049 0.374 0.378 0.372 0.009 Min 0.362 0.362 0.362 0.364 0.362 0.364 0.0019 0.362 0.368 0.362 0.000 N 19 19 19 19 19 19 19 19 19 19 19 Mean ? 3 * 0.352 0.354 0.354 0.360 0.359 0.359 StDev

(17) The tables below summarize the types of tests and the potential Extension Time Interval in years if one or more of the tests are performed and passed. Table 6 summarizes the methods proposed are (1) a third-party approved leak detection test for like Vista's LRDP mass-based system; (2) ultrasonic (UT) measurements of floor thickness (0.001 in.); (3) a previous API inspection with UT and magnetic flux thickness measurements across the entire tank floor; and (4) an acoustic emission (AE) test for assessing active corrosion across the tank floor. A leak detection test can also be performed with the AE system. Its value is to confirm the approved test and to help interpret the AE corrosion measurements. The Extension Time Interval determined from the measurement program is dependent on the results. Only results a Pass leak detection test is shown. If the tank fails a leak detection test, it should be taken out of service and repair after confirming the presence of a leak.

(18) TABLE-US-00006 TABLE 6 In-Service Tank Inspection Method for Prioritizing Out-of-Service Inspections 3.sup.rd Party Inspection Approved Leak UT Thickness at API 653/ AE Corrosion/ Extension Time Method Detection Test One Location STI SP001 Leak Detection Interval (Years) 1 Yes 1 2 Yes Yes 1 or more to 3 or 4 3 Yes Yes 1 or more to 4 4 Yes Yes 1 or more to 3 5 Yes Yes Yes 2 to 5 6 Yes Yes Yes 1 to 4 7 Yes Yes Yes Yes 2 or 3 to 5

(19) It is difficult to make a general statement about the number of years an out-of-service, internal inspection can be extended because it is heavily dependent on the results of the floor thickness estimates. Obviously, a tank floor that has a low rate of corrosion and greatly exceeds the minimum thickness will have a longer extension time than one that is experiencing a high rate of corrosion and is barely meeting the minimum thickness standard. Since all of the measurements made are trying to estimate the condition of the tank from limited data (as compared to a full, out-of-service, internal inspection, it is important to consider the degree of confidence in the spatial estimate of corrosion.

(20) Table 7 illustrates the range of Extension Time Intervals that might be expected for various methods of the current invention for low to moderate corrosion rates. A more detail estimate for 203 implementations is illustrated below. If the rate of corrosion is high, then the Extension Time Interval would be shorted than those proposed in Table 2.

(21) TABLE-US-00007 TABLE 7 In-Service Tank Inspection Method for Prioritizing Out-of-Service Inspections for Low to Moderate Corrosion Rates Unless Otherwise Specified 3.sup.rd Party Inspection Approved Leak UT Thickness at API 653/ AE Corrosion/ Extension Time Method Detection Test One Location* STI SP001* Lesk Detection Interval (Years) 1 Pass 1 2 Pass Floor >0.1 in. 2 3a Pass A, B, C, FU1/2 4 or 5** 3b Pass D, FU3 1 or 2** 4 Pass >0.1 in. 2 or 3** 5 Pass >0.1 in. Floor >0.1 in. 4 or 5** 6a Pass >0.1 in. A, B, C, FU1/2 4 or 5** 7a Pass >0.1 in. Floor >0.1 in. A, B, C, FU1/2 5 6b Pass >0.1 in. D, FU3 1 or 2** 7b Pass >0.1 in. Floor >0.1 in. D, FU3 2** 5 Pass >0.1 in. E, FU4 0 6 Pass >0.1 in. Floor >0.1 in. E, FU4 1 *Thickness is forecast out to Extension Time Interval based on max corrosion Rate **Use the longer year extension if all thickness measurements are safely greater than 0.1 in.

(22) As noted above, the AE test results are reported as either A through E or FU1 through FU4, where E and FU4 are expected to have significant damage, need significant repair, and have a high probability of leaking. A grade of C means no damage or repair required, but some maintenance is needed. A grade of FU3 has more damage than C, but is not likely to be leaking.

(23) The proposed method and apparatuses of the present invention are best used as part of a risk-based inspection procedure, where these measurements can provide a substantive basis for risk mitigation.

(24) The method of the present invention for estimating the Extension Time Interval is based on a Bayesian statistical analysis. There are a variety of probability hypothesis statements that can be made that are essentially equivalent. One example is: What's the probability that that there is adequate thickness in the floor of a tank to extend the time between inspections (a given time interval) given that we have conducted and passed a leak detection test? If we assume that adequate floor thickness is 0.1 in. (0.05 in. for tanks with secondary containment), we can state this probability statement as, What's the probability that that the thickness in the floor of a tank is greater than 0.1 in. (0.05 in.) so that the time between inspections can be extended (a given time interval) given that we have conducted and passed a leak detection test? Another way of stating the hypothesis is What's the probability that that the time between inspections (a given time interval) given that we have conducted and passed a leak detection test and there is adequate thickness in the floor of a tank? In line with the assumption above, this hypothesis can be stated as What's the probability that that the time between inspections (a given time interval) given that we have conducted and passed a leak detection test and the thickness of the floor of a tank is greater than 0.01 in. (0.05 in.)? All of these statements can be made more complex by adding additional a priori information. For example, What's the probability that that the time between inspections (a given time interval) given that (1) we have conducted and passed a leak detection test, (2) there is adequate thickness in the floor of a tank, and (3) the corrosion of the tank floor is low?, or GIVEN that (1), (2), (3), and (4) . . . (n). We can also expand (2) to include additional sensors like those illustrated below in (2a) through (2e). We can add a minimum acceptable floor thickness in (3) like 0.1 in. (0.05 in. for secondarily contained tanks). We can also add state conditions like (4) low corrosion rates, (5) consistency between methods and data collected. (2a) Local UT thickness measurements, (2b) Previous Out-of-Service Floor Thickness Measurements over the nominal thickness at the Initial Installation, (2c) Previous Out-of-Service Floor Thickness Measurements over Previous Out-of-Service Inspection, (2d) An AE Corrosion Activity Measurement and a Previous Out-of-Service Inspection, (2e) An AE Corrosion Activity Measurement where the corrosion rate throughout the tank is low and the previous evaluation of the floor thickness throughout the entire tank floor is more than adequate (i.e., >>the minimum acceptable thickness (e.g., close to the original thickness of the tank floor).

(25) The probability hypothesis can be very complicated. The heart of the Extension Time Interval is a Passing Leak Detection Test and an estimate of the minimum thickness of the tank floor that exceeds 0.1 in. (or 0.05 in.) throughout the extension period. There is a level of uncertainty on this thickness estimate depending on the number of sensors, when the in-tank measurements were made, and what the spatial distribution of the floor thickness is. Thus, a tank with hot spots or local areas of high corrosion would have a shorter Extension Time Interval than a tank with uniform corrosion, knowledge of the spatial distribution of floor thickness, and an up-to-date estimate of floor thickness. It is because of this uncertainty that longer Extension Time Intervals than 4 or 5 years is not recommended.

(26) For the preferred method of the present invention, the probability hypothesis would be, What's the probability that that the thickness in the floor of a tank is greater than 0.1 in. (0.05 in.) so that the time between inspections can be extended a certain time interval (to be specified as a function of the sensor measurements and sensor measurement results) given that (1) we have conducted and passed a leak detection test, (2) we have made several measurements of the local tank floor thickness, (3) we have made an estimate of the spatial distribution of floor thickness and corrosion rate with one or more methods, (4) the thickness and rate of corrosion are Low, Moderate, or High, (5) the floor thickness estimates are correlated and consistent with each other, and (6) the most current in-tank measurements of floor thickness (e.g., a UT sensor) or corrosion activity (e.g., an AE system) and whether or not the thickness and/or corrosion rate/activity are correlated with, consistent with, and/or smaller than the estimates made during previous out-of-service inspection? For simplicity, we can start with only tanks that have Passed a Leak Detection Test and will result in a minimum floor thickness that is adequate or greater than 0.1 in. We can further combine the thickness measurements (items (2) and (3) from the results of the measurement (items (4)-(6)).

(27) As stated above, we can break the probability statement into many parts as a complex statement, or simply combine it into a succinct statement as presented in the illustration below. Typically, one would assign a probability to Bayes Theorem, but one can also use a Confidence Level (from 0 to 10) to describe the Method and Results, and then associate an Extension Time Interval (0 to 5 Years) with each Confidence Level. This is described below.

(28) A simple illustration of the application of this method is presented below. The following hypothesis is tested. What's the probability that the thickness in the floor of a tank is of adequate thickness (i.e., greater than 0.1 (or 0.05 in. for tanks that are secondarily contained)) so that the time interval between inspections can to be safely extended by a certain time interval GIVEN that the tank passes a leak detection test. We consider a Passing Test with third-party evaluated LD Test Method with a P.sub.D?95% and P.sub.FA?5%. A Passing Test indicates that there is a high probability that there are no holes in the tank floor or no holes in the tank floor that are large enough to actually leak due to debris closing the hole or no holes in the tank floor that detected as leaking. For purposes of this illustration, we consider the five different measurement of floor thickness described above in (2a) through (2e) that will support the notion of adequate floor thickness or some pre-determined minimum, desirable floor thickness, i.e., P(W). For this illustration, P(W) incorporates the thickness inferences from one or more of the measurement methods of the present invention. For this illustration, we will assume 0.1 in. (and 0.05 in.).

(29) Mathematically, Bayes' theorem gives the relationship between the probabilities of W and Q, P(W) and P(Q), and the conditional probabilities of Q given W and W given Q, P(Q|W) and P(W|Q). In its most common form, it is:

(30) $P\left(W/Q\right)=\frac{(P\left(Q/W\right)P\left(W\right)}{P\left(Q\right)}$
where this probability statement can also be expressed as

(31) $P\left(W/Q\right)=\frac{(P\left(Q/W\right)P\left(W\right)}{P\left(Q/W\right)P\left(W\right)+P\left(Q/M\right)P\left(M\right)}$
or

(32) $P\left(W/Q\right)=\frac{P\left(Q/W>a\right)P\left(W>a\right)}{P\left(Q/W>0\right)P\left(W>a\right)+P\left(Q/M<a\right)P\left(M<a\right)}$
where
W=adequate floor thickness or FT>a, where a may be 0.0 in. or 0.1 or 0.05 in. or some acceptable thickness, which is estimated from one or more of the five current and previous measurements of the tank floor thickness or tank floor corrosion for this illustration.
Q=Pass a leak detection test with a known P.sub.D, LR, and P.sub.FA
P(Q) is the probability of Passing a Leak Detection Test. We normally define P(Q) for a Leak Rate (i.e., Hole Size) and perform the test such that the probability of detection of a leak of a certain size is at least 95%. If the LR is smaller than the smallest hole that will leak, then this become the P(Q) for all leak rates. If not, then it is possible that a leak may still exist and be too small to detect with a high reliability. Also, a leak of a detectable size can be missed to because of the statistic nature of the test.
P(W)=Probability that the floor is of adequate thickness to extend the time interval between tests.
P(W/Q)=Probability that floor is of adequate thickness to extend the time interval between tests given that a Passing Leak Detection Test.
P(Q/W)=Probability of Passing a Leak Detection test given that the floor has adequate thickness.

(33) $P\left(Q/W>a\right)P\left(W>a\right)+P\left(Q/W<a\right)P\left(W<a\right)P\left(W/Q\right)=\frac{P\left(Q/W>a\right)P\left(W>a\right)}{P\left(Q/W>a\right)P\left(W>a\right)+P\left(Q/W<a\right)P\left(W<a\right)}=\frac{\left(95\%\right)\left(80\%\right)}{\left(95\%\right)\left(80\%\right)+\left(5\%\right)\left(20\%\right)}=98.7\%$
where the test was originally conducted with a probability of passing of 95%. While 95% is very good, 98.7% is even better. The added reliability is provided by the a priori information about the expectations of conducting a test with information about the tank thickness. We have assumed the application of different measurement systems and incorporate one type of result, i.e., whether or not the measured corrosion rate is high or low.

(34) Tables 8 and 9 below illustrate some results for different methods of the present invention. These results present the likelihood of a tank not failing or not leaking. We assume that a probability of 95% or 99% is generally acceptable to justify extending the time interval between inspections. The 99% probabilities are designated in red font and the 95% probabilities are designate in blue font. The 90% probabilities are deemed questionable and are highlighted in yellow. The 90% probabilities designate the maximum extension time that might be considered. More measurement data, such as spatial floor thickness data, would be required to justify an extension. Table 8 is for low corrosion rates, and Table 9 is for high corrosion rates. One can see that the time between inspections can be longer for tanks with low corrosion vice tanks with high corrosion rates.

(35) TABLE-US-00008 TABLE 8 Illustration of the Number of Years that an Internal Inspection can be Extended for Methods where All of the Sensors Indicate Low Corrosion and More than Adequate Floor Thickness at the End of the Inspection Interval Extension Low CR Probability of Extension Time Interval - Years Methods Number of Decision Low Corrosion Activity with More than Adequate Thickness for Each Sensor Sensors/Tests 1 2 3 4 5 in Years Leak Detection Pass* 1 95.0% 70.0% 60.0% 50.0% 50.0% 1 Leak Detection Pass & Local UT Floor Thickness 2 99.0% 95.0% 90.0% 70.0% 60.0% 2 to 3 Leak Detection Pass & Previous Internal Floor Thickness Inspection 2 99.0% 95.0% 90.0% 70.0% 60.0% 2 to 3 Leak Detection Pass & AE Corrosion Activity 2 99.0% 95.0% 90.0% 80.0% 70.0% 2 to 3 Leak Detection Pass & Local UT & Previous Internal Floor Thickness 3 99.0% 99.0% 99.0% 95.0% 90.0% 4 to 5 Inspections Leak Detection Pass & Local UT & AE Corrosion Activity 3 99.0% 99.0% 95.0% 90.0% 90.0% 3 to 4 Leak Detection Pass & Local UT & Previous Internal & AE Corrosion 4 99.0% 99.0% 99.0% 99.0% 99.0% 5 Activity *Assumes some risk/probabilitic Information about the tanks, tank history, and environment exist

(36) TABLE-US-00009 TABLE 9 Illustration of the Number of Years that an Internal Inspection can be Extended for Methods where All of the Sensors Indicate High Corrosion and Minimum Floor Thickness at the End of the Inspection Interval Extension High CR Probability of Extension Time Interval - Years Methods Number of Decision High Corrosion Activity that has Minimum Thickness for Each Sensor Sensors/Tests 1 2 3 4 5 in Years Leak Detection Pass* 1 95.0% 70.0% 60.0% 50.0% 50.0% 1 Leak Detection Pass & Local UT Floor Thickness 2 99.0% 90.0% 70.0% 60.0% 50.0% 1 to 2 Leak Detection Pass & Previous Internal Floor Thickness Inspection 2 99.0% 90.0% 80.0% 80.0% 70.0% 1 to 2 Leak Detection Pass & AE Corrosion Activity 2 95.0% 90.0% 80.0% 70.0% 60.0% 1 to 2 Leak Detection Pass & Local UT & Previous Internal Floor Thickness 3 99.0% 95.0% 90.0% 70.0% 60.0% 2 to 3 Inspections Leak Detection Pass & Local UT & AE Corrosion Activity 3 99.0% 90.0% 70.0% 60.0% 50.0% 1 to 2 Leak Detection Pass & Local UT & Previous Internal & AE 4 99.0% 95.0% 90.0% 80.0% 70.0% 2 to 3 Corrosion Activity *Assumes some risk/probabilitic Information about the tanks, tank history, and environment exist

(37) Powerful statements can be made depending on the type and the results of the Leak Detection and the Thickness Measurements. As described above, the study of the use of AE for determining the corrosion activity across the tank floor has generated some interesting statistics about the integrity status of the tank. The studies suggest that about ? of the tanks studied are in really good shape and do not need maintenance or repair. Stated another way 2 out of 3 tanks are in good shape. Thus, this type of information can be taken into account when establishing the probabilities in Tables 8 and 9 and is the reason the probabilities did not drop below 50%.

(38) A risk-based inspection needs to estimate both the likelihood of a failure and the consequence of the failure. We have made an estimate of the likelihood of that the tank will not leak and that the thickness of the tank floor will maintain a certain minimum thickness (0.1 in. or 0.05 in.) over the Extension Time Interval given that a certain suite of sensor measurement systems were used to generate the data as input to the decision making models and given that certain results were obtained with this sensor suite. If this assessment is inaccurate, then the tank may leak and/or the floor may corrode more than desired. The consequence of an inaccurate decision is the cost of characterizing and remediating the leak, the cost of repairing the tank floor, and the cost of lost operations while the tank is out of service. This latter can be the most significant cost and in a small facility where only 1 or 2 tanks can be used to store a specific type of product, the cost of lost operations can be even more significant. In addition to actual cost, there is a public image issue and potential health hazards. While there is a consequence to having an incident during the Extension Time Interval, there is also a cost to prematurely scheduling an internal inspection where none is required. There is no need to remove a tank from service for maintenance and/or repair when it is not needed. There is no need to lose operational services during this period. In fact, this often leads to more problems because an inspection may not be performed on a tank that really needs one because the decision making process is lacking information. Thus, there are multiple consequences, one for inspecting a tank when it is not really required, another for not inspecting a tank when it would benefit from the inspection, and final one for extending the time between inspections too long, allowing the possibility of an incident to occur. The former is not usually considered and should be, because it is a real expenditure of funds, funds that could be better used on tanks that could benefit more. The proposed method of the present invention helps prioritize and manage tank maintenance and repair operations. It allows the best use of available funds to maintain the tanks in a facility in the best operational shape.

(39) The cost of performing an inspection can be estimated reasonably well. This is also true of the cost of lost operations. The cost of characterizing and remediating a leak is not as easy to estimate and is dependent on the size of the leak and the environmental and health damage resulting from the leak; the cost of lost operations is then a direct function of how long this takes to characterize and remediate the leak. The other costs (e.g., dealing with the public) are equally uncertain and depend up the severity of the incident. The probability of a large leak or a structural failure is relatively small and should be taken into account when estimating the consequence of a problem. Thus, if there is a probability of 3% of the tanks leaking in a facility and the estimated cost of to correct an incident is $3 M, the actual consequence is 3% of $3 M, or $90,000. In general, the cost saving of each inspection dwarfs this consequence cost (e.g., $300,000). While the cost of an incident can be an order of magnitude larger than an inspection if an incident occurs, the probability is low and for facilities with secondary containment, the consequences and the costs are even lower. Estimating the probability of a leak is difficult, and if it is unrealistically large or not taken into account at all (e.g., assuming a probability of a leak of 100%), then it can seriously bias the inspection process and increase the overall costs and increase the chance of an incident. Regardless, it is clear from any reasonable estimate that the consequences of not prioritizing and managing optimally will outweigh the consequence of a leak.

(40) In its simplest application, we can assume the consequences apply equally for all tanks and all extension time intervals. This is probably a reasonable approach if the sensor suite used in the assessment is adequate and includes a passing leak detection test with a reliable method, an in-tank measurement of floor thickness and corrosion rate, and information about the spatial characteristics of the tank floor. If not, one can increase the probability of a leak as a function of the Extension Time Interval, i.e., the longer Extension Time, the higher the probability of a leak. Other things may increase the probability of a leak. For example, the probability may also be higher for tanks with a high rate of corrosion and the floor thickness forecast. In general, if the sensor suite is adequate and the minimum acceptable floor thickness of 0.1 in. (or 0.05 in. for secondarily contained tanks), then the probability of a leak is about the same for all tanks.

(41) Table 10 illustrates the decision making process. If the probability of successfully extending the time interval 5 years between inspections is 95%, the present value of the cost savings of a $300,000 internal inspection is $366,314. If the probability of a leak is 3% for a method with a 99% probability of success, and the probability increases as the probability of success decreases, we can compare the cost savings to the cost. If the cost consequence of a leak exceeds the cost savings, then the method should not be used to extend the time interval. This model increases the probability of a leak for all method probabilities less than 95% by 1.25. Thus, the probability of a leak for a method with a 50% confidence level in the method, the probability of a leak to use in the computation is 1.25 times 6% (1.25*3%/(100%?50%)=7.5%).

(42) In general, the decision about extension is best made assuming a confidence level of 99% or 95%, and it is assumed that the consequence for using a lesser method to base the extension period is too low to accept.

(43) TABLE-US-00010 TABLE 13 Summary of Confidence Levels on Different Methods and the Recommended Extension Times Overall Confidence of Extension Time Integrity Assessment Interval (Years) 0 0 1 0 2 1 3 2 4 2 5 2 6 3 7 3 8 4 9 5 10 5

(44) Tables 11 and 12 summarize a more comprehensive list of various types of Methods and the various types of types of Test Results to illustrate the methods summarized in Table 6 and Table 7, respectively. All of the methods assume that they have Passed a Leak Detection Test. Furthermore, all of the preferred methods have a high probability that the floor thickness will be greater than 0.1 in., or some acceptable minimum floor thickness, and that the corrosion rate is low to moderate, but not high, because of one or more in-tank floor measurements. The Extension Time Interval, described above in terms of Bayesian statistics is selected on the basis of a Confidence Interval that the method will achieve a 95% or 99% probability of not leaking or structurally failing during the Extension Time Interval. In general, the probability is 99%, except where two or more levels of confidence are expressed and the lower probability is assigned. Table 13 summarizes the Confidence Levels estimated for each method and the Extension Time Interval in years.

(45) The Confidence Intervals were assessed in terms of Low, Moderate, and High rates of corrosion rates for the local UT thickness measurements, the previous Out-of-Service Floor Thickness Measurements, and the AE corrosion activity, whether or not the minimum thickness of the tank floor will be exceeded before the Extension Time Interval as assessed by the UT local measurements and the previous Out-of-Service floor inspection measurements, whether or not the UT measurements are correlated and are consistent with these three floor thickness and/or corrosion measurements, whether or not the UT local thickness and corrosion rate measurements are smaller/larger than the Out-of-Service floor thickness and corrosion rate measurements, and whether or not the leak detection results of the AE system are consistent with the results of the Leak Detection test.

(46) In general, almost all of the various methods include local in-tank measurements of the floor thickness so that an estimate of the maximum general or uniform corrosion rate and minimum floor thickness can be determined for the whole tank and to use it in estimating the spatial distribution of the corrosion rate and floor thickness if the floor corrodes evenly. The local measurement of floor thickness is very powerful, because it is a direct indication of the floor thickness made at the time in which the extension time interval is made.

(47) As illustrated in Tables 7 and 8 and 11 and 12, the Methods that permit greater than a 1-year extension all include a Leak Detection Test and at least one other in-tank measurement of the tank floor thickness. A 1-year extension is permitted if only a Leak Detection Test is Passed with an EPA-approved test method providing the corrosion activity of the tank is known to be Low. Given the ease and low incremental cost of making one- or more local measurements of the floor thickness with an in-tank UT sensor, it is unlikely that only a Leak Detection Test will be performed. Thus, it is easy to verify the corrosion activity for a 1-year extension and with adequate floor thickness, more than a 1-year extension is possible. The Methods that permit the longest extension times all include measurements that allow a quantitative estimate of the spatial distribution of corrosion potential of the floor. Up to 5 years is possible.

(48) Table 14 sorts the methods in Table 11 so that the methods with the highest Confidence Intervals and the longest Extension Time Intervals are at the top of the table. Table 15 summarizes a composite interpretation of the Extension Methods. The Extension Time Intervals with the longest extension times involves the use of multiple sensor measurements and low to moderate corrosion rates. All the methods illustrated here have required that the floor thickness at the end of the Extension Time Interval meet the 0.1 in. or 0.05 in. minimum thickness. This does not need to be the case, but it is for all of the illustrated methods because it gives a high level of confidence. It is important to note that unless the tank is taken out-of-service and a full inspection like the ones following API 653, API 12R, or STI SP001, the thickness estimated using the methods of the present invention are all estimates without complete information of the actual spatial distribution of floor thickness.

(49) The number of methods and the summary of the methods is presented in Table 15. The methods with the longest Extension Time involve the use of a Passing Leak Detection Test and at least 2 other measurements of floor thickness, where one of those measurements is almost always a local floor thickness measurement with a UT sensor (i.e., 2 to 5 years). The longest Extension Times occur for the tanks with the lowest rates of corrosion (and highest floor thickness). While it would be preferred that the local UT measurements of floor thickness be correlated and consistent with and lower than the previous API 653 inspection, the results do not support this premise. However, the results indicate that such correlation and consistency is required when using the AE corrosion activity method, because actual measurements of floor thickness are not made. For each Extension Time Interval, there is generally two levels of confidence. Methods with the highest level of confidence are preferred. The higher level of confidence is generally associated with the lower rates of corrosion.

(50) TABLE-US-00011 TABLE 15 Summary of the Extension Time Interval and Confidence Level for 203 Different Measurement Methods and Test Results UT Local Methods Methods Methods Methods Measure- 4 Sensors 4 Sensors 4 Sensors 4 Sensors Number Leak ment (1 LD + 3 (1 LD + 2 (1 LD + 1 (1 LD + 0 of % of Detection Corrosion Floor) Floor) Floor) Floor) Methods Methods Method Rate 65.0% 35.0% 0.0% 0.0% 20 9.9% PASS Low, >, < Moderate 63.2% 36.8% 0.0% 0.0% 19 9.4% PASS Low, >, < Moderate 77.3% 22.7% 0.0% 0.0% 44 21.7% PASS Low, >, < Moderate 65.2% 26.1% 8.7% 0.0% 69 34.0% PASS Low, >, < Moderate, High 52.6% 42.1% 5.3% 0.0% 61 9.4% PASS Moderate, >, < High 59.4% 21.9% 9.4% 9.4% 32 15.8% PASS Moderate, >, < High 203 Extension API 653 UT Local API 653 Time Tank Correlated UT Min Min Overall Interval Floor with API UT Local AE Thickness > Thickness > Confidence (Years) Thickness 653 AE Correlated Correlated 0.1, 0.05 0.1, 0.05 of UT > OOS1 Corrosion Corrosion Corrosion with AE Leak in, Over in. Over Integrity &/OR Rate Rate Activity Corrosion Detection ETI ETI Assessment AE PASS Low, No, Yes Low, Yes Yes Yes Yes 9, 10 5 Moderate Moderate Low, No, Yes Low, Yes, Some Yes Yes Yes 8 4 Moderate Moderate No Low, No, Yes Low, Yes, Some Yes, Some Yes Yes, Some 6, 7 3 Moderate Moderate No No No Low, No, Yes Low, Yes, Some Yes, Some Yes Yes, Some 3, 4 2 Moderate, Moderate, No No No High High Moderate, No, Yes Moderate, Yes Yes Yes Yes 2, 3 1 High High Moderate, No, Yes High Yes, Some Yes, Some Yes Yes, Some 0, 1 0 High No No No

(51) About 20% (19.3%) of the methods illustrating the present invention would permit an Extension Time Interval of 4 or 5 years, and about 16% (15.8%) would not permit any extension and require an out-of-service inspection. About 55% (55.7%) of the methods would permit a 2- or 3-year extension with 10% (9.4%) allowing only a 1-year extension. Thus, 75% (74.8%) of the methods illustrating the present invention would allow a 2 to 5 year extension in the time interval between out-of-service inspections.

(52) The methods and apparatuses of the present invention can include other measurement sensors and different combinations of such sensors. For example, a long range ultrasonic test (LRUT) might be used on the outside shell of the tank vice a previous out-of-service inspection or an AE corrosion activity measurement. In contrast to these two methods, this type of LRUT measurement only measures the tank floor condition in the outer 1.2 m or so of the tank floor, but this LRUT measurement is a measurement of floor thickness and the current floor thickness, where the other methods are not. Also, this LRUT measurement also measures the floor thickness in the area where the tank floor is likely to corrode the most. The confidence levels and the Extension Time Intervals would then change if this LRUT method were to replace the out-of-service inspection or the AE corrosion method. The preferred method of the present invention is comprised of a compact, in-tank set of measurements.

(53) TABLE-US-00012 TABLE 11 In-Service Tank Inspection Methods for Prioritizing Out-of-Service Inspections Extension API 653 UT Local API 653 Time UT Local Tank Correlated UT Min Min Overall Interval Leak Measure- Floor with UT Local AE Thick- Thick- Confidence (Years) Detec- ment Thickness API 653 AE Correlated Correlated ness > 0.1, ness > 0.1, of UT > OOSI tion Corrosion Corrosion Corrosion Corrosion with AE Leak 0.05 in, 0.05 in, Integrity & OR Method Method Rate Rate Rate Activity Corrosion Detection Over ETI Over ETI Assessment AE PASS Method 0 - Leak Detection Only PASS 2 1 FAIL 0 0 Method 1 - Leak Detection and Previous Out-of-Service Floor Inspection PASS Low Yes 5 2 PASS Low No 0 0 PASS Moderate Yes 4 2 PASS Moderate No 0 0 PASS High Yes 4 2 PASS High No 0 0 Method 2 - Leak Detection, UT Local Floor Thickness, and Previous Out-of-Service Floor Thickness 1 PASS Low Yes 5 2 2 PASS Low No 0 0 3 PASS Moderate Yes 4 2 4 PASS Moderate No 0 0 5 PASS High Yes 3 2 6 PASS High No 0 0 Method 3 - Leak Detection, UT Local Floor Thickness, and Previous Out-of-Service Floor Thickness 1 PASS Low > Low Yes Yes Yes 9 5 2 PASS Low > Low No Yes Yes 8 4 3 PASS Moderate > Low No Yes Yes 8 4 4 PASS Moderate > Moderate Yes Yes Yes 9 5 5 PASS Moderate > Moderate No Yes No 7 3 6 PASS Moderate > High Yes Yes Yes 7 3 7 PASS Moderate > High No Yes No 2 1 8 PASS High > Moderate Yes Yes Yes 5 2 9 PASS High > Moderate No Yes No 2 1 10 PASS High > High Yes Yes Yes 5 2 11 PASS High > High No Yes No 1 0 Method 4 - Leak Detection, UT Local Floor Thickness, and Previous Out-of-Service Floor Thickness 1 PASS Low < Low Yes Yes Yes 10 5 2 PASS Low , < Low No Yes Yes 9 5 3 PASS Moderate < Low No Yes Yes 9 5 4 PASS Moderate < Moderate Yes Yes Yes 10 5 5 PASS Moderate < Moderate No Yes No 8 4 6 PASS Moderate < High Yes Yes Yes 8 4 7 PASS Moderate , < High No Yes No 3 2 8 PASS High < Moderate Yes Yes Yes 6 3 9 PASS High < Moderate No Yes No 3 2 10 PASS High < High Yes Yes Yes 6 3 11 PASS High < High No Yes No 2 1 Method 5 - Leak Detection, UT Local Floor Thickness, and AE Corrosion Activity A PASS Low Low Yes Yes Yes 9 5 B PASS Low Moderate Yes Yes Yes 8 4 C PASS Low High Yes Yes Yes 5 2 D PASS Moderate Low Yes Yes Yes 8 4 E PASS Moderate Moderate Yes Yes Yes 8 4 F PASS Moderate High Yes Yes Yes 5 2 G PASS High Low Yes Yes Yes 7 3 H PASS High Moderate Yes Yes Yes 5 2 I PASS High High Yes Yes Yes 2 1 Method 6 - Leak Detection, UT Local Floor Thickness, and AE Corrosion Activity J PASS Low Low No Yes Yes 7 3 K PASS Low Moderate No Yes Yes 6 3 L PASS Low High No Yes Yes 3 2 M PASS Moderate Low No Yes Yes 6 3 N PASS Moderate Moderate No Yes Yes 6 3 O PASS Moderate High No Yes Yes 3 2 P PASS High Low No Yes Yes 5 2 Q PASS High Moderate No Yes Yes 3 2 R PASS High High No Yes Yes 0 0 Method 5a - Leak Detection, UT Local Floor Thickness, and AE Corrosion Activity A PASS Low Low Yes No Yes 6 3 B PASS Low Moderate Yes No Yes 5 2 C PASS Low High Yes No Yes 2 1 D PASS Moderate Low Yes No Yes 5 2 E PASS Moderate Moderate Yes No Yes 5 2 F PASS Moderate High Yes No Yes 2 1 G PASS High Low Yes No Yes 4 2 H PASS High Moderate Yes No Yes 2 1 I PASS High High Yes No Yes 0 0 Method 6a - Leak Detection, UT Local Floor Thickness, and AE Corrosion Activity J PASS Low Low No No Yes 4 2 K PASS Low Moderate No No Yes 3 2 L PASS Low High No No Yes 0 0 M PASS Moderate Low No No Yes 3 2 N PASS Moderate Moderate No No Yes 3 2 O PASS Moderate High No No Yes 0 0 P PASS High Low No No Yes 2 1 Q PASS High Moderate No No Yes 0 0 R PASS High High No No Yes 0 0 Method 7 - Leak Detection, UT Local Floor Thickness, Previous Out-of-Service Floor Thickness, and AE Corrosion Activity 1 A PASS Low > Low Yes Low Yes Yes Yes Yes 10 5 1 B PASS Low > Low Yes Moderate Yes Yes Yes Yes 9 5 1 C PASS Low > Low Yes High Yes Yes Yes Yes 5 2 2 A PASS Low > Low No Low Yes Yes Yes Yes 9 5 2 B PASS Low > Low No Moderate Yes Yes Yes Yes 8 4 2 C PASS Low > Low No High Yes Yes Yes Yes 4 2 3 D PASS Moderate > Low No Low Yes Yes Yes Yes 8 4 3 E PASS Moderate > Low No Moderate Yes Yes Yes Yes 7 3 3 F PASS Moderate > Low No High Yes Yes Yes Yes 3 2 4 D PASS Moderate > Moderate Yes Low Yes Yes Yes Yes 9 5 4 E PASS Moderate > Moderate Yes Moderate Yes Yes Yes Yes 8 4 4 F PASS Moderate > Moderate Yes High Yes Yes Yes Yes 4 2 5 D PASS Moderate > Moderate No Low Yes Yes Yes No 8 4 5 E PASS Moderate > Moderate No Moderate Yes Yes Yes No 7 3 5 F PASS Moderate > Moderate No High Yes Yes Yes No 3 2 6 G PASS Moderate > High Yes Low Yes No Yes Yes 7 3 6 H PASS Moderate > High Yes Moderate Yes No Yes Yes 6 3 6 F PASS Moderate > High Yes High Yes No Yes Yes 2 1 7 G PASS Moderate > High No Low Yes No Yes No 6 3 7 E PASS Moderate > High No Moderate Yes No Yes No 5 2 7 F PASS Moderate > High No High Yes No Yes No 1 0 8 D PASS High > Moderate Yes Low Yes Yes Yes Yes 7 3 8 E PASS High > Moderate Yes Moderate Yes Yes Yes Yes 6 3 8 F PASS High > Moderate Yes High Yes Yes Yes Yes 2 1 9 D PASS High > Moderate No Low Yes No Yes No 6 3 9 E PASS High > Moderate No Moderate Yes No Yes No 5 2 9 F PASS High > Moderate No High Yes No Yes No 1 0 10 G PASS High > High Yes Low Yes Yes Yes Yes 6 3 10 H PASS High > High Yes Moderate Yes Yes Yes Yes 5 2 10 I PASS High > High Yes High Yes Yes Yes Yes 1 0 11 G PASS High > High No Low Yes Yes Yes No 5 2 11 H PASS High > High No Moderate Yes Yes Yes No 4 2 11 I PASS High > High No High Yes Yes Yes No 0 0 Method 8 - Leak Detection, UT Local Floor Thickness, Previous Out-of-Service Floor Thickness, and AE Corrosion Activity 1 J PASS Low > Low Yes Low No Yes Yes Yes 8 4 1 K PASS Low > Low Yes Moderate No Yes Yes Yes 7 3 1 L PASS Low > Low Yes High No Yes Yes Yes 3 2 2 J PASS Low > Low No Low No Yes Yes Yes 7 3 2 K PASS Low > Low No Moderate No Yes Yes Yes 6 3 2 L PASS Low > Low No High No Yes Yes Yes 2 1 3 M PASS Moderate > Low No Low No Yes Yes Yes 6 3 3 N PASS Moderate > Low No Moderate No Yes Yes Yes 5 2 3 O PASS Moderate > Low No High No Yes Yes Yes 1 0 4 M PASS Moderate > Moderate Yes Low No Yes Yes Yes 7 3 4 N PASS Moderate > Moderate Yes Moderate No Yes Yes Yes 6 3 4 O PASS Moderate > Moderate Yes High No Yes Yes Yes 2 1 5 M PASS Moderate > Moderate No Low No Yes Yes No 6 3 5 N PASS Moderate > Moderate No Moderate No Yes Yes No 5 2 5 D PASS Moderate < Moderate No Low Yes Yes Yes No 9 5 5 E PASS Moderate , < Moderate No Moderate Yes Yes Yes No 8 4 5 F PASS Moderate < Moderate No High Yes Yes Yes No 4 2 6 G PASS Moderate < High Yes Low Yes No Yes Yes 8 4 6 H PASS Moderate < High Yes Moderate Yes No Yes Yes 7 3 6 F PASS Moderate , < High Yes High Yes No Yes Yes 3 2 7 G PASS Moderate < High No Low Yes No Yes No 7 3 7 E PASS Moderate , < High No Moderate Yes No Yes No 6 3 7 F PASS Moderate < High No High Yes No Yes No 2 1 8 D PASS High < Moderate Yes Low Yes Yes Yes Yes 8 4 8 E PASS High < Moderate Yes Moderate Yes Yes Yes Yes 7 3 8 F PASS High , < Moderate Yes High Yes Yes Yes Yes 3 2 9 D PASS High < Moderate No Low Yes No Yes No 7 3 9 E PASS High , < Moderate No Moderate Yes No Yes No 6 3 9 F PASS High < Moderate No High Yes No Yes No 2 1 10 G PASS High < High Yes Low Yes Yes Yes Yes 7 3 10 H PASS High < High Yes Moderate Yes Yes Yes Yes 6 3 10 I PASS High , < High Yes High Yes Yes Yes Yes 2 1 11 G PASS High < High No Low Yes Yes Yes No 6 3 11 H PASS High , < High No Moderate Yes Yes Yes No 5 2 11 I PASS High < High No High Yes Yes Yes No 1 0 Method 9 - Leak Detection, UT Local Floor Thickness, Previous Out-of-Service Floor Thickness, and AE Corrosion Activity 1 A PASS Low < Low Yes Low Yes Yes Yes Yes 10 5 1 B PASS Low , < Low Yes Moderate Yes Yes Yes Yes 10 5 1 C PASS Low < Low Yes High Yes Yes Yes Yes 6 3 2 A PASS Low < Low No Low Yes Yes Yes Yes 10 5 2 B PASS Low < Low No Moderate Yes Yes Yes Yes 9 5 2 C PASS Low , < Low No High Yes Yes Yes Yes 5 2 3 D PASS Moderate < Low No Low Yes Yes Yes Yes 9 5 3 E PASS Moderate , < Low No Moderate Yes Yes Yes Yes 8 4 3 F PASS Moderate < Low No High Yes Yes Yes Yes 4 2 4 D PASS Moderate < Moderate Yes Low Yes Yes Yes Yes 10 5 4 E PASS Moderate < Moderate Yes Moderate Yes Yes Yes Yes 9 5 4 F PASS Moderate , < Moderate Yes High Yes Yes Yes Yes 5 2 5 D PASS Moderate < Moderate No Low Yes Yes Yes No 9 5 5 E PASS Moderate ,< Moderate No Moderate Yes Yes Yes No 8 4 5 F PASS Moderate < Moderate No High Yes Yes Yes No 4 2 6 G PASS Moderate < High Yes Low Yes No Yes Yes 8 4 6 H PASS Moderate < High Yes Moderate Yes No Yes Yes 7 3 6 F PASS Moderate , < High Yes High Yes No Yes Yes 3 2 7 G PASS Moderate < High No Low Yes No Yes No 7 3 7 E PASS Moderate , < High No Moderate Yes No Yes No 6 3 7 F PASS Moderate < High No High Yes No Yes No 2 1 8 D PASS High < Moderate Yes Low Yes Yes Yes Yes 8 4 8 E PASS High < Moderate Yes Moderate Yes Yes Yes Yes 7 3 8 F PASS High , < Moderate Yes High Yes Yes Yes Yes 3 2 9 D PASS High < Moderate No Low Yes Ne Yes No 7 3 9 E PASS High , < Moderate No Moderate Yes No Yes No 6 3 9 F PASS High < Moderate No High Yes No Yes No 2 1 10 G PASS High < High Yes Low Yes Yes Yes Yes 7 3 10 H PASS High < High Yes Moderate Yes Yes Yes Yes 6 3 10 I PASS High , < High Yes High Yes Yes Yes Yes 2 1 11 G PASS High < High No Low Yes Yes Yes No 6 3 11 H PASS High , < High No Moderate Yes Yes Yes No 5 2 11 I PASS High < High No High Yes Yes Yes No 1 0 Method 10 - Leak Detection, UT Local Floor Thickness, Previous Out-of-Service Floor Thickness, and AE Corrosion Activity 1 J PASS Low < Low Yes Low No Yes Yes Yes 9 5 1 K PASS Low , < Low Yes Moderate No Yes Yes Yes 8 4 1 L PASS Low < Low Yes High No Yes Yes Yes 4 2 2 J PASS Low < Low No Low No Yes Yes Yes 8 4 2 K PASS Low < Low No Moderate No Yes Yes Yes 7 3 2 L PASS Low , < Low No High No Yes Yes Yes 3 2 3 M PASS Moderate < Low No Low No Yes Yes Yes 7 3 3 N PASS Moderate , < Low No Moderate No Yes Yes Yes 6 3 3 O PASS Moderate < Low No High No Yes Yes Yes 2 1 4 M PASS Moderate < Moderate Yes Low No Yes Yes Yes 8 4 4 N PASS Moderate < Moderate Yes Moderate No Yes Yes Yes 7 3 4 O PASS Moderate , < Moderate Yes High No Yes Yes Yes 3 2 5 M PASS Moderate < Moderate No Low No Yes Yes No 7 3 5 N PASS Moderate , < Moderate No Moderate No Yes Yes No 6 3 5 O PASS Moderate < Moderate No High No Yes Yes No 2 1 6 P PASS Moderate < High Yes Low No No Yes Yes 6 3 6 Q PASS Moderate < High Yes Moderate No No Yes Yes 5 2 6 R PASS Moderate , < High Yes High No No Yes Yes 1 0 7 P PASS Moderate < High No Low No No Yes No 5 2 7 Q PASS Moderate , < High No Moderate No No Yes No 4 2 7 R PASS Moderate < High No High No No Yes No 1 0 8 M PASS High < Moderate Yes Low No Yes Yes Yes 6 3 8 N PASS High < Moderate Yes Moderate No Yes Yes Yes 5 2 8 O PASS High , < Moderate Yes High No Yes Yes Yes 1 0 9 M PASS High < Moderate No Low No No Yes No 5 2 9 N PASS High , < Moderate No Moderate No No Yes No 4 2 9 O PASS High < Moderate No High No No Yes No 1 0 10 P PASS High < High Yes Low No Yes Yes Yes 5 2 10 Q PASS High < High Yes Moderate No Yes Yes Yes 4 2 10 R PASS High , < High Yes High No Yes Yes Yes 1 0 11 P PASS High < High No Low No Yes Yes No 4 2 11 Q PASS High , < High No Moderate No Yes Yes No 3 2 11 R PASS High < High No High No Yes Yes No 1 0

(54) TABLE-US-00013 TABLE 12 In-Service Tank Inspection Methods for Prioritizing Out-of-Service Inspections Extension Extension Extension Extension Time Time Time Time Interval Interval Interval Interval (Years) 2 (Years) 2 (Years) 3 (Years) 4 UT > OOSI UT > OOSI UT < OOSI UT < OOSI & AE Leak & AE Leak & AE PASS & AE Leak Method 7 Method 8 Method 9 Method 10 5 4 5 5 5 3 5 4 2 2 3 2 5 3 5 4 4 3 5 3 2 1 2 2 4 3 5 3 3 2 4 3 2 0 2 1 5 3 5 4 4 3 5 3 2 1 2 2 4 3 5 3 3 2 4 3 2 0 2 1 3 2 4 3 3 2 3 2 1 0 2 0 3 2 3 2 2 2 3 2 0 0 1 0 3 2 4 3 3 2 3 2 1 0 2 0 3 2 3 2 2 2 3 2 0 0 1 0 3 2 3 2 2 2 3 2 0 0 1 0 2 2 3 2 2 1 2 2 0 0 0 0 Number 33 33 33 33 Sum 85 56 103 69 Mean 2.576 1.697 3.121 2.091 Median 3.000 2.000 3.000 2.000 StDev 1.458 1.159 1.409 1.308 Min 0.000 0.000 0.000 0.000 Max 5.000 4.000 5.000 5.000

(55) TABLE-US-00014 TABLE 14 In-Service Tank Inspection Methods for Prioritizing Out-of-Service Inspections Extension Time UT Local UT Local UT Min API 653 Min Overall Interval (Years) Leak Measurement API 653 Tank Correlated with AE UT Local AE Correlated Thickness > 0.1, Thickness > 0.1, Confidence of UT > OOSI Detection Corrosion Floor Thickness Api 653 Corrosion Corrosion Correlated with Leak 0.05 in. 0.05 in. Integrity &/OR Method 1 Method Method Rate Corrosion Rate Rate Activity AE Corrosion Detection Over ETI Over ETI Assessment AE PASS Method 4 31 1 PASS Low < Low Yes Yes Yes 10 5 Method 7 92 1A PASS Low > Low Yes Low Yes Yes Yes Yes 10 5 Method 9 180 1A PASS Low < Low Yes Low Yes Yes Yes Yes 10 5 Method 9 181 1B PASS Low , < Low Yes Moderate Yes Yes Yes Yes 10 5 Method 9 184 2A PASS Low < Low No Low Yes Yes Yes Yes 10 5 Method 4 34 4 PASS Moderate < Moderate Yes Yes 10 5 Method 9 192 4D PASS Moderate < Moderate Yes Low Yes Yes Yes Yes 10 5 Method 3 19 1 PASS Low > Low Yes Yes Yes 9 5 Method 4 32 2 PASS Low , < Low No Yes Yes 9 5 Method 7 93 1B PASS Low > Low Yes Moderate Yes Yes Yes Yes 9 5 Method 7 96 2A PASS Low > Low No Low Yes Yes Yes Yes 9 5 Method 9 185 2B PASS Low < Low No Moderate Yes Yes Yes Yes 9 5 Method 10 224 1J PASS Low < Low Yes Low No Yes Yes Yes 9 5 Method 5 43 A PASS Low Low Yes Yes Yes 9 5 Method 4 33 3 PASS Moderate < Low No Yes Yes 9 5 Method 9 188 3D PASS Moderate < Low No Low Yes Yes Yes Yes 9 5 Method 3 22 4 PASS Moderate > Moderate Yes Yes Yes 9 5 Method 7 104 4D PASS Moderate > Moderate Yes Low Yes Yes Yes Yes 9 5 Methad 9 193 4E PASS Moderate < Moderate Yes Moderate Yes Yes Yes Yes 9 5 Method 9 196 5D PASS Moderate < Moderate No Low Yes Yes Yes No 9 5 Method 3 20 2 PASS Low > Low No Yes Yes 8 4 Method 7 97 2B PASS Low > Low No Moderate Yes Yes Yes Yes 8 4 Method 8 136 1J PASS Low > Low Yes Low No Yes Yes Yes 8 4 Method 10 225 1K PASS Low , < Low Yes Moderate No Yes Yes Yes 8 4 Method 10 228 2J PASS Low < Low No Low No Yes Yes Yes 8 4 Method 5 44 B PASS Low Moderate Yes Yes Yes 8 4 Methad 3 21 3 PASS Moderate > Low No Yes Yes 8 4 Method 7 100 3D PASS Mederate > Low No Low Yes Yes Yes Yes 8 4 Method 9 189 3E PASS Moderate , < Low No Moderate Yes Yes Yes Yes 8 4 Method 4 35 5 PASS Moderate < Moderate No Yes No 8 4 Method 7 105 4E PASS Moderate > Moderate Yes Moderate Yes Yes Yes Yes 8 4 Method 7 108 5D PASS Moderate > Moderate No Low Yes Yes Yes No 8 4 Method 9 197 5E PASS Moderate , < Moderate No Moderate Yes Yes Yes No 8 4 Method 10 236 4M PASS Moderate < Moderate Yes Low No Yes Yes Yes 8 4 Method 4 36 6 PASS Moderate < High Yes Yes Yes 8 4 Method 9 200 6G PASS Moderate < High Yes Low Yes No Yes Yes 8 4 Method 5 47 D PASS Moderate Low Yes Yes Yes 8 4 Method 5 48 E PASS Moderate Moderate Yes Yes Yes 8 4 Method 9 208 8D PASS High < Moderate Yes Low Yes Yes Yes Yes 8 4 Method 8 137 1K PASS Low > Low Yes Moderate No Yes Yes Yes 7 3 Method 8 140 2J PASS Low > Low No Low No Yes Yes Yes 7 3 Method 10 229 2K PASS Low < Low No Moderate No Yes Yes Yes 7 3 Method 6 55 J PASS Low Low No Yes Yes 7 3 Method 7 101 3E PASS Moderate > Low No Moderate Yes Yes Yes Yes 7 3 Method 10 232 3M PASS Moderate < Low No Low No Yes Yes Yes 7 3 Method 3 23 5 PASS Moderate > Moderate No Yes No 7 3 Method 7 109 5E PASS Moderate > Moderate No Moderate Yes Yes Yes No 7 3 Method 8 148 4M PASS Moderate > Moderate Yes Low No Yes Yes Yes 7 3 Method 10 237 4N PASS Moderate < Moderate Yes Moderate No Yes Yes Yes 7 3 Method 10 240 5M PASS Moderate < Moderate No Low No Yes Yes No 7 3 Method 3 24 6 PASS Moderate > High Yes Yes Yes 7 3 Method 7 112 6G PASS Moderate > High Yes Low Yes No Yes Yes 7 3 Method 9 201 6H PASS Moderate < High Yes Moderate Yes No Yes Yes 7 3 Method 9 204 7G PASS Moderate < High No Low Yes No Yes No 7 3 Method 7 120 8D PASS High > Moderate Yes Low Yes Yes Yes Yes 7 3 Method 9 209 8E PASS High < Moderate Yes Moderate Yes Yes Yes Yes 7 3 Method 9 212 9D PASS High < Moderate No Low Yes No Yes No 7 3 Method 9 216 10G PASS High < High Yes Low Yes Yes Yes Yes 7 3 Method 5 51 G PASS High Low Yes Yes Yes 7 3 Method 8 141 2K PASS Low > Low No Moderate No Yes Yes Yes 6 3 Method 9 182 1C PASS Low < Low Yes High Yes Yes Yes Yes 6 3 Method 6 56 K PASS Low Moderate No Yes Yes 6 3 Method 5a 67 A PASS Low Low Yes No Yes 6 3 Method 8 144 3M PASS Moderate > Low No Low No Yes Yes Yes 6 3 Method 10 233 3N PASS Moderate , < Low No Moderate No Yes Yes Yes 6 3 Method 8 149 4N PASS Moderate > Moderate Yes Moderate No Yes Yes Yes 6 3 Method 8 152 5M PASS Moderate > Moderate No Low No Yes Yes No 6 3 Method 10 241 5N PASS Moderate , < Moderate No Moderate No Yes Yes No 6 3 Method 7 113 6H PASS Moderate > High Yes Moderate Yes No Yes Yes 6 3 Method 7 116 7G PASS Moderate > High No Low Yes No Yes No 6 3 Method 9 205 7E PASS Moderate , < High No Moderate Yes No Yes No 6 3 Method 10 244 6P PASS Moderate < High Yes Low No No Yes Yes 6 3 Method 6 59 M PASS Moderate Low No Yes Yes 6 3 Method 6 60 N PASS Moderate Moderate No Yes Yes 6 3 Method 4 38 8 PASS High < Moderate Yes Yes Yes 6 3 Method 7 121 8E PASS High > Moderate Yes Moderate Yes Yes Yes Yes 6 3 Method 7 124 9D PASS High > Moderate No Low Yes No Yes No 6 3 Method 9 213 9E PASS High , < Moderate No Moderate Yes No Yes No 6 3 Method 10 253 8M PASS High < Moderate Yes Low No Yes Yes Yes 6 3 Method 4 40 10 PASS High < High Yes Yes Yes 6 3 Method 7 128 10G PASS High > High Yes Low Yes Yes Yes Yes 6 3 Method 9 217 10H PASS High < High Yes Moderate Yes Yes Yes Yes 6 3 Method 9 220 11G PASS High < High No Low Yes Yes Yes No 6 3 94 1C PASS Low > Low Yes High Yes Yes Yes Yes 5 2 Method 9 186 2C PASS Low , < Low No High Yes Yes Yes Yes 5 2 Method 1 5 PASS Low Yes 5 2 Method 5 45 C PASS Low High Yes Yes Yes 5 2 Method 5a 68 B PASS Low Moderate Yes No Yes 5 2 Method 8 145 3N PASS Moderate > Low No Moderate No Yes Yes Yes 5 2 Method 8 153 5N PASS Moderate > Moderate No Moderate No Yes Yes No 5 2 Method 9 194 4F PASS Moderate , < Moderate Yes High Yes Yes Yes Yes 5 2 Method 7 117 7E PASS Moderate > High No Moderate Yes No Yes No 5 2 Method 8 156 6P PASS Moderate > High Yes Low No No Yes Yes 5 2 Method 10 245 6Q PASS Moderate < High Yes Moderate No No Yes Yes 5 2 Method 10 248 7P PASS Moderate < High No Low No No Yes No 5 2 Method 5 49 F PASS Moderate High Yes Yes Yes 5 2 Method 5a 71 D PASS Moderate Low Yes No Yes 5 2 Method 5a 72 E PASS Moderate Moderate Yes No Yes 5 2 Method 3 26 8 PASS High > Moderate Yes Yes Yes 5 2 Method 7 125 9E PASS High > Moderate No Moderate Yes No Yes No 5 2 Method 8 164 8M PASS High > Moderate Yes Low No Yes Yes Yes 5 2 Method 10 253 8N PASS High < Moderate Yes Moderate No Yes Yes Yes 5 2 Method 10 256 9M PASS High < Moderate No Low No No Yes No 5 2 Method 3 28 10 PASS High > High Yes Yes Yes 5 2 Method 7 129 10H PASS High >> High Yes Moderate Yes Yes Yes Yes 5 2 Method 7 132 11G PASS High > High No Low Yes Yes Yes No 5 2 Method 9 221 11H PASS High , < High No Moderate Yes Yes Yes No 5 2 Method 10 260 10P PASS High < High Yes Low No Yes Yes Yes 5 2 Method 5 52 H PASS High Moderate Yes Yes Yes 5 2 Method 6 63 P PASS High Low No Yes Yes 5 2 Method 2 12 1 PASS Low Yes 5 2 Method 7 98 2C PASS Low > Low No High Yes Yes Yes Yes 4 2 Method 10 226 1L PASS Low < Low Yes High No Yes Yes Yes 4 2 Method 6a 79 J PASS Low Low No No Yes 4 2 Method 9 190 3F PASS Moderate < Low No High Yes Yes Yes Yes 4 2 Method 7 106 4F PASS Moderate > Moderate Yes High Yes Yes Yes Yes 4 2 Method 9 198 5F PASS Moderate < Moderate No High Yes Yes Yes No 4 2 Method 8 157 6O PASS Moderate > High Yes Moderate No No Yes Yes 4 2 Method 8 160 7P PASS Moderate > High No Low No No Yes No 4 2 Method 10 249 7O PASS Moderate , < High No Moderate No No Yes No 4 2 Method 1 7 PASS Moderate Yes 4 2 Method 8 165 8N PASS High > Moderate Yes Moderate No Yes Yes Yes 4 2 Method 8 168 9M PASS High > Moderate No Low No No Yes No 4 2 Method 10 257 9N PASS High , < Moderate No Moderate No No Yes No 4 2 Method 7 133 11H PASS High > High No Moderate Yes Yes Yes No 4 2 Method 8 172 10P PASS High > High Yes Low No Yes Yes Yes 4 2 Method 10 261 10O PASS High < High Yes Moderate No Yes Yes Yes 4 2 Method 10 264 11P PASS High < High No Low No Yes Yes No 4 2 Method 1 9 PASS High Yes 4 2 Method 5a 75 G PASS High Low Yes No Yes 4 2 Method 2 14 3 PASS Moderate Yes 4 2 Method 8 138 1L PASS Low > Low Yes High No Yes Yes Yes 3 2 Method 10 230 2L PASS Low , < Low No High No Yes Yes Yes 3 2 Method 6 57 L PASS Low High No Yes Yes 3 2 Method 6a 80 K PASS Low Moderate No No Yes 3 2 Method 7 102 3F PASS Moderate > Low No High Yes Yes Yes You 3 2 Method 7 110 5F PASS Moderate > Moderate No High Yes Yes Yes No 3 2 Methed 10 238 4O PASS Moderate , < Moderate Yes High No Yes Yes Yes 3 2 Method 4 37 7 PASS Moderate , < High No Yes No 3 2 Method 8 161 7O PASS Moderate > High No Moderate No No Yes No 3 2 Method 9 202 6F PASS Moderate , < High Yes High Yes No Yes Yes 3 2 Method 6 61 O PASS Moderate High No Yes Yes 3 2 Method 6a 83 M PASS Moderate Low No No Yes 3 2 Method 6a 84 N PASS Moderate Moderate No No Yes 3 2 Method 4 39 9 PASS High < Moderate No Yes No 3 2 Method 8 169 9N PASS High > Moderate No Moderate No No Yes No 3 2 Method 9 210 8F PASS High , < Moderate Yes High Yes Yes Yes Yes 3 2 Method 8 173 10O PASS High > High Yes Moderate No Yes Yes Yes 3 2 Method 8 176 11P PASS High > High No Low No Yes Yes No 3 2 Method 10 265 11O PASS High , < High No Moderate No Yes Yes No 3 2 Method 6 64 O PASS High Moderate No Yes Yes 3 2 Method 2 16 5 PASS High Yes 3 2 Method 8 142 2L PASS Low > Low No High No Yes Yes Yes 2 1 Method 5a 69 C PASS Low High Yes No Yes 2 1 Method 10 234 3O PASS Moderate < Low No High No Yes Yes Yes 2 1 Method 8 150 4O PASS Moderate > Moderate Yes High No Yes Yes Yes 2 1 Method 10 242 5O PASS Moderate < Moderate No High No Yes Yes No 2 1 Method 3 25 7 PASS Moderate > High No Yes No 2 1 Method 7 114 6F PASS Moderate > High Yes High Yes No Yes Yes 2 1 Method 9 206 7F PASS Moderate < High No High Yes No Yes No 2 1 Method 5a 73 F PASS Moderate High Yes No Yes 2 1 Method 3 27 9 PASS High > Moderate No Yes No 2 1 Method 7 122 8F PASS High > Moderate Yes High Yes Yes Yes Yes 2 1 Method 9 214 9F PASS High < Moderate No High Yes No Yes No 2 1 Method 4 41 11 PASS High < High No Yes No 2 1 Method 8 177 11O PASS High > High No Moderate No Yes Yes No 2 1 Method 9 218 10I PASS High , < High Yes High Yes Yes Yes Yes 2 1 Method 5 53 1 PASS High High Yes Yes Yes 2 1 Method 5a 76 H PASS Moderate Yes No Yes 2 1 Method 6a $7 P PASS High Low No No Yes 2 1 Method 0 2 PASS High 2 1 Method 8 146 3O PASS Moderate > Low No High No Yes Yes Yes 1 0 Method 8 154 5O PASS Moderate > Moderate No High No Yes Yes No 1 0 Method 7 118 7F PASS Moderate > High No High Yes No Yes No 1 0 Method 10 246 6R PASS Moderate , < High Yes High No No Yes Yes 1 0 Method 10 250 7R PASS Moderate < High No High No No Yes No 1 0 Method 7 126 9F PASS High > Moderate No High Yes No Yes No 1 0 Method 10 254 8O PASS High 5 Moderate Yes High No Yes Yes Yes 1 0 Method 10 258 9O PASS High < Moderate No High No No Yes No 1 0 Method 3 29 11 PASS High > High No Yes No 1 0 Method 7 130 10I PASS High > High Yes High Yes Yes Yes Yes 1 0 Method 9 222 11I PASS High < High No High Yes Yes Yes No 1 0 Method 10 262 10R PASS High , < High Yes High No Yes Yes Yes 1 0 Method 10 266 11R PASS High < High No High No Yes Yes No 1 0 Method 1 6 PASS Low No 0 0 Method 6a 81 L PASS Low High No No Yes 0 0 Method 8 158 6R PASS Moderate > High Yes High No No Yes Yes 0 0 Method 8 162 7R PASS Moderate > High No High No No Yes No 0 0 Method 1 8 PASS Moderate No 0 0 Method 6a 85 O PASS Moderate High No No Yes 0 0 Method 8 166 8O PASS High > Moderate Yes High No Yes Yes Yes 0 0 Method 8 170 9O PASS High > Moderate No High No No Yes No 0 0 Method 7 134 11I PASS High > High No High Yes Yes Yes No 0 0 Method 8 174 10R PASS High > High Yes High No Yes Yes Yes 0 0

(56) While certain representative embodiments and details have been shown for purposes of illustrating the invention, it will be apparent to those skilled in the art that various changes in the methods and apparatus disclosed herein may be made without departing from the scope of the invention which is defined in the appended claims.