The ultrasonic testing (UT) method continues to broaden in its effectiveness and capabilities for nondestructive evaluation (NDE). Much of this expansion can be attributed to advancements in specific techniques of the method. The utilization of electromagnetic acoustic transducers (EMATs) in dedicated ultrasonic systems has provided McDermott Technology, Inc. (MTI), formerly Babcock & Wilcox, with significant advantages over conventional ultrasonics. In recent years, through significant R&D, MTI has been instrumental in bringing about considerable advancements in the maturing EMAT technology. Progress in electronic design, magnet configurations, and sensor concepts has greatly improved system capabilities while reducing cost and equipment size. These improvements, coupled with the inherent advantages of utilizing the non-contact EMAT technique, have combined to make this technology a viable option for many commercial system inspection applications. MTI has recently completed the development and commercialization of an EMAT-based UT scanner for boiler tube thickness measurements. MTI is currently developing an automated EMAT scanner, based on phased array technology, for complete volumetric inspection of circumferential girth welds associated with pipelines (intended primarily for offshore applications). Additional benefits of phased array technology for providing materials characterization are currently being researched.

Ultrasonic propagation in hollow cylinders is dispersive; velocities, displacements, stresses, and, more importantly, the average power flow are all functions of frequency. The average power flow of a wave mode is directly related to its transmissibility, and the displacement/stress distribution of a wave mode is related to its capability of defect detection and characterization. Mode selection and frequency selection, therefore, are both important issues for long-range ultrasonic pipeline inspection. Circumferential crack detection and characterization capabilities of the lowest and the second lowest longitudinal modes [L(0,1) and L(0,2)] and the lowest flexural mode [F(1,1)] are investigated analytically based on average power flow and axial displacement/stress distributions. It is found that the L(0,1) mode has strong power flow only in the low kHz region, and the L(0,2) in the lower-middle kHz region. The F(1,1) mode, however, is found to have strong power flow in a broad frequency range, starting from the low kHz region, and is therefore a preferred wave mode for long-range ultrasonic pipeline inspection.

The feasibility of characterizing a defect in pipe from the defect signal detected by using the magnetostrictive sensor (MsS) technique, which utilizes longitudinal guided waves for long-range inspection of pipe, was investigated. Signals from notches of various cross-sectional areas showed that the reflection coefficient of the wave from these planar defects is insensitive to the wave frequency and increases monotonically with the increasing cross-sectional area of the defect. Signals from simulated corrosion pits, on the other hand, showed that the reflection coefficient from these volumetric defects is dependent on both the cross-sectional area and the axial extent of the defect as well as on the wave frequency. The results indicated that it is feasible to differentiate planar from volumetric defects and to determine the defect size -- namely, its cross-sectional area and axial extent if it is volumetric.

This paper summarizes the findings of a cooperative effort between NOVA Gas Transmission Ltd. (NGTL), the Italian Natural Gas Transmission Company (SNAM), and Arista International, Inc., to determine whether current remote sensing technologies can be utilized to monitor small-scale ground movements over vast geographical areas. This topic is of interest due to the potential for small ground movements to cause strain accumulation in buried pipeline facilities. Ground movements are difficult to monitor continuously, but their cumulative effect over time can have a significant impact on the safety of buried pipelines. Interferometric synthetic aperture radar (InSAR or SARI) is identified as the most promising technique of those considered. InSAR analysis involves combining multiple images from consecutive passes of a radar imaging platform. The resulting composite image can detect changes as small as 2.5 to 5.0 centimeters (based on current analysis methods and radar satellite data of 5 centimeter wavelength). Research currently in progress shows potential for measuring ground movements as small as a few millimeters. Data needed for InSAR analysis is currently commercially available from four satellites, and additional satellites are planned for launch in the near future. A major conclusion of the present study is that InSAR technology is potentially useful for pipeline integrity monitoring. A pilot project is planned to test operational issues.

This paper presents a comparative analysis of three different eddy current testing methods for tube inspection: (1) conventional one side eddy current testing, (2) through- transmission eddy current testing, and (3) remote field eddy current testing. The author also studied the results from different arrangements of exciter coil and receiver coil of the eddy current testing method for tube inspection. The author concludes that the remote field eddy current testing is a through-transmission eddy current testing with exciter coil and receiver coil in the same side of a tube.

Computerized infrared thermographic pipeline inspection is now a refined and accurate process having been thoroughly proven to be an accurate, cost effective, and efficient technology for pipeline rehabilitation programs, during a 10 year development and testing process. The process has been used to test pipelines in chemical plants, water supply systems, steam lines, natural gas pipelines and sewer systems. Its non- contact, non-destructive ability to inspect large areas, from above ground, with 100% coverage and to locate subsurface leaks as well as the additional capability to locate voids and erosion areas surrounding pipelines, make its testing capabilities unique and highly desirable. This paper details the development of computerized infrared thermographic pipeline testing along with case histories illustrating its implementation problems and successes during various rehabilitation programs involving pipelines carrying water, gas, petroleum, and sewage.

Damages of pipes can be inspected and graded by TV technology available on the market. Remotely controlled vehicles carry a TV-camera through pipes. Thus, depending on the experience and the capability of the operator, diagnosis failures can not be avoided. The classification of damages requires the knowledge of the exact geometrical dimensions of the damages such as width and depth of cracks, fractures and defect connections. Within the framework of a joint R&D project a sensor based pipe inspection system named RODIAS has been developed with two partners from industry and research institute. It consists of a remotely controlled mobile robot which carries intelligent sensors for on-line sewerage inspection purpose. The sensor is based on a 3D-optical sensor and a laser distance sensor. The laser distance sensor is integrated in the optical system of the camera and can measure the distance between camera and object. The angle of view can be determined from the position of the pan and tilt unit. With coordinate transformations it is possible to calculate the spatial coordinates for every point of the video image. So the geometry of an object can be described exactly. The company Optimess has developed TriScan32, a special software for pipe condition classification. The user can start complex measurements of profiles, pipe displacements or crack widths simply by pressing a push-button. The measuring results are stored together with other data like verbal damage descriptions and digitized images in a data base.

One of the biggest inspection challenges facing many of the process industries; namely the petrochemical, refining, fossil power, and pulp and paper industries is: How to effectively examine their insulated piping? While there are a number of failure mechanisms involved in various process piping systems, piping degradation through corrosion and erosion are by far the most prevalent. This degradation can be in the form of external corrosion under insulation, internal corrosion through a variety of mechanisms, and internal erosion caused by the flow of the product through the pipe. Refineries, chemical plants and electrical power plants have MANY thousands of miles of pipe that are insulated to prevent heat loss or heat absorption. This insulation is often made up of several materials, with calcium based material being the most dense. The insulating material is usually wrapped with an aluminum or stainless steel outer wrap. Verification of wall thickness of these pipes can be accomplished by removing the insulation and doing an ultrasound inspection or by taking x- rays at a tangent to the edge of the pipe through the insulation. Both of these processes are slow and expensive. The time required to obtain data is measured in hours per meter. The ultrasound method requires that the insulation be plugged after the inspection. The surface needs to be cleaned or the resulting data will not be accurate. The tangent x-ray only shows two thicknesses and requires that the area be roped off because of radiation safety.

Eliminate any doubt that the vessel condition is suitable for continued operation through a planned inspection program that can mitigate or avoid failure of a pressure vessel due to corrosion or erosion. Proper inspection and documentation help you in identifying the problem and confirming the actual thickness leading to properly correcting deficiencies. Proper inspection is the antidote for any inspection program. Vessel life can be extended, risk can be minimized and unscheduled downtime can be prevented by implementing and managing your inspection program. A successful program includes maintaining accurate records, conducting inspections in regular intervals, and taking proper action on deficiencies. Therefore, you will know what you have and the condition of your equipment. Pressure vessel inspections can be classified into two general categories: surface inspection and volumetric inspection. Surface techniques for vessels include two of the commonest types: dye-penetrant and magnetic particle testing. Board qualified inspectors are required to perform these two tests. Volumetric techniques for vessels include three common types: ultrasonic testing, eddy current testing, and radiography. At Abbott the use of advanced NDE (non destructive examination) techniques, ultrasonic b-scan, has provided us with the proper tools to obtain the above objectives. We have been applying ultrasonic b-scan utilizing a pulse echo pitch catch technique to provide us with essential data on each of our pressure vessels. This reduces equipment downtime because the nondestructive examination usually takes place while our vessels are in service. As inspections take place we are able to view a real time image of the defective discontinuities on a video monitor. This ultrasonic b-scan technique is allowing us to perform fast accurate examinations covering up to 96% of the surface area of each pressure vessel.

An electrochemical impedance spectroscopy (EIS)-based in-situ corrosion sensor has been adapted and evaluated for use with steel heat exchanger tubes in boilers, coated buried steel pipes, and painted steel structures. An excellent correlation was obtained between the algorithm of the ratio of the breakpoint frequencies, as measured by the sensor, and corrosion rate for the boiler tubes. Use of this sensor and appropriate electronics would allow the corrosion of the boiler tubes to be monitored in real time and the inhibitor concentration automatically controlled to prevent excessive corrosion. The EIS sensor is also sensitive to the quality of coating of a buried steel pipe with and without the application of cathodic protection. Similar results were obtained from a sensor attached to the pipe and from a separate electrode driven into the soil. A hand-held version of the EIS in-situ sensor is suitable for inspecting painted metal structures, such as storage tanks and locks and dams, under ambient, service conditions. An excellent correlation was obtained between the sensor measurements, and the amount of corrosion on test panels immersed for up to 28 years.

The top, wall and floor of a large aboveground storage tank (LAST) are all subject to corrosion. Of these, the floor is often the most critical part because access is limited to periods when the tank is taken out of service. Tank floor corrosion can be either top or bottom side. Bottom side corrosion and top side corrosion under a coating are the most difficult to quantify rapidly and economically. An instrument based upon magnetic flux leakage (MFL) has been developed that permits the rapid, quantitative evaluation of tank floor corrosion in the presence of a coating up to 3 mm thick. This instrument produces a map of the magnetic field distribution (normal component) in a fixed reference plane about 1 mm above the steel or coating surface. Under a variety of practical circumstances, this magnetic field map is highly reproducible. The resulting 'image' of corrosion can usually be interpreted in terms of pit depth with an accuracy of better than plus or minus 10% of the nominal plate thickness. This in normally adequate for any pitting less than 50% of the nominal plate thickness in depth. For deeper pits and in order to assess for general thinning, it is normally desirable to use a standard ultrasonic thickness gauge in order to have better measurement accuracy. Inspections performed with this instrument provide the tank owner with a permanent quantitative, reproducible paper and digital record of the tank floor corrosion that can be compared with subsequent inspection and repair records.

Our water resources infrastructure is susceptible to aging degradation just like the rest of this country's infrastructure. A critical component of the water supply system is the flood gate that controls the outflow from dams. Long steel rods called tendons attach these radial gates to the concrete in the dam. The tendons are typically forty feet long and over one inch in diameter. Moisture may seep into the grout around the tendons and cause corrosion. Lawrence Livermore National Laboratory is working with the California Department of Water Resources to develop advanced ultrasonic techniques for nondestructively inspecting their tendons. A unique transducer was designed and fabricated to interrogate the entire tendon. A robust, portable unit was assembled that included a computer controlled data acquisition system and specialized data processing software to analyze the ultrasonic signals. This system was tested on laboratory specimens and is presently being fielded at two dam sites.

Tube failures in aging steam plant surface condensers, feedwater heaters, and oil coolers are a significant reliability problem for the electric power industry. Tube failures can also result in an increase in replacement power costs. In addition, condenser leaks from failed tubes have potentially harmful effects on major components such as steam generators and turbines. To reduce the number of tube failures and consequent leakage, periodic maintenance programs have used the nondestructive evaluation (NDE) method of eddy current testing (ET) to inspect the condition of the tubes from the water side. This NDE method can identify tubes that have experienced major degradation and should be plugged to prevent in-service failure. Variability of inspection results and difficulty in inspecting some types of tubing (Monel, carbon steel) have caused many utility sites to question the value of inspection of heat transfer tubing from the water side. Recognizing these problems, advanced ET systems have been developed that use multi-frequency, remote field, and digital data processing techniques to inspect a variety of tubing materials and produce on-site, computer generated inspection reports. These results have been used to determine tube plugging, replacement, and inspection intervals.

Many cities in the northeastern U.S. transport electrical power from place to place via underground cables, which utilize voltages from 68 kv to 348 kv. These cables are placed in seamless steel pipe to protect the conductors. These buried pipe-type-cables (PTCs) are carefully designed and constantly pressurized with transformer oil to prevent any possible contamination. A protective coating placed on the outside diameter of the pipe during manufacture protects the steel pipe from the soil environment. Notwithstanding the protection mechanisms available, the pipes remain vulnerable to electrochemical corrosion processes. If undetected, corrosion can cause the pipes to leak transformer oil into the environment. These leaks can assume serious proportions due to the constant pressure on the inside of the pipe. A need exists for a detection system that can dynamically monitor the corrosive potential on the length of the pipe and dynamically adjust cathodic protection to counter local and global changes in the cathodic environment surrounding the pipes. The northeastern United States contains approximately 1000 miles of this pipe. This milage is critical to the transportation and distribution of power. So critical, that each of the pipe runs has a redundant double running parallel to it. Invocon, Inc. proposed and tested a technically unique and cost effective solution to detect critical corrosion potential and to communicate that information to a central data collection and analysis location. Invocon's solution utilizes the steel of the casing pipe as a communication medium. Each data gathering station on the pipe can act as a relay for information gathered elsewhere on the pipe. These stations must have 'smart' network configuration algorithms that constantly test various communication paths and determine the best and most power efficient route through which information should flow. Each network station also performs data acquisition and analysis tasks that ultimately determine the corrosion risk in a local area. The system has virtually no installation costs and can operate on battery power for at least two years.

Distributed fiber optic sensors for use in the prevention of catastrophic corrosion failure when embedded in key structures such as high pressure gas and hazardous fluid pipeline delivery systems, potable water distribution piping, steel reinforced concrete structures, and steel and aluminum access structures are reported here. Its principle of operation is based on the intrinsic optical properties of a distributed fiber optic corrosion sensor (DIFOCS) whose entire length is sensitive to corrosion progression indicators, such as moisture and pH. The sensors can be used to locate precisely with a 10-cm spatial resolution where the moisture infiltration or corrosions damage has occurred. A low-cost, light weight, optoelectronics package can be used to provide timely warnings of corrosion induced moisture and pH changes into these 'smart' structures, significantly reducing the cost and complexity of periodic inspections. Optical transmission through the fibers can be monitored either periodically or continuously to determine the extent of corrosion.

The aging hollow forged steel rotors of steam turbine and generator units typical to utility power plants are a major area of concern for the future safety and integrity of the overall power plant. These components are also critical in determining future inspection intervals for the turbine unit and its remaining life. Over the past five years a number of lifetime extension projects have been conducted using an integrated nondestructive evaluation (NDE), materials and fracture mechanics approach to determining inspection intervals and remaining life. These projects have resulted in extending inspection intervals, predicting remaining life, and restoring original equipment manufacturer (OEM) retired rotors to operation. Key aspects of the integrated program will be covered using the results of a recently completed project.

For a company to maintain its competitive edge in today's global market every opportunity to gain an advantage must be exploited. Many companies are strategically focusing on improved utilization of existing equipment as well as regulatory compliance. Abbott Laboratories is no exception. Pharmaceutical companies such as Abbott Laboratories realize that reliability and availability of their production equipment is critical to be successful and competitive. Abbott Laboratories, like many of our competitors, is working to improve safety, minimize downtime and maximize the productivity and efficiency of key production equipment such as the pressure vessels utilized in our processes. The correct strategy in obtaining these objectives is to perform meaningful inspection with prioritization based on hazard analysis and risk. The inspection data gathered in Abbott Laboratories pressure vessel program allows informed decisions leading to improved process control. The results of the program are reduced risks to the corporation and employees when operating pressure retaining equipment. Accurate and meaningful inspection methods become the cornerstone of a program allowing proper preventative maintenance actions to occur. Successful preventative/predictive maintenance programs must utilize meaningful nondestructive evaluation techniques and inspection methods. Nondestructive examination methods require accurate useful tools that allow rapid inspection for the entire pressure vessel. Results from the examination must allow the owner to prove compliance of all applicable regulatory laws and codes. At Abbott Laboratories the use of advanced NDE techniques, primarily B-scan ultrasonics, has provided us with the proper tools allowing us to obtain our objectives. Abbott Laboratories uses B-scan ultrasonics utilizing a pulse echo pitch catch technique to provide essential data on our pressure vessels. Equipment downtime is reduced because the nondestructive examination usually takes place while our vessels are in service. As the inspection takes place we are able to view a real time image of detected discontinuities on a video monitor. The B-scan ultrasonic technique is allowing us to perform fast accurate examinations covering up to 95% of the surface area of each pressure vessel. Receiving data on 95% of a pressure vessel provides us with a lot of useful information. We use this data to determine the condition of each pressure vessel. Once the condition is known the vessels are classed by risk. The risk level is then managed by making decisions related to repair, operating parameters, accepting and monitoring or replacement of the equipment. Inspection schedules are set at maximum intervals and reinspection is minimized for the vessels that are not at risk. The remaining life of each pressure vessel is determined, mechanical integrity is proven and regulatory requirements are met. Abbott Laboratories is taking this proactive approach because we understand that our process equipment is a critical element for successful operation. A run to failure practice would never allow Abbott Laboratories to achieve the corporation's objective of being the world's leading health care company. Nondestructive state of the art technology and the understanding of its capabilities and limitations are key components of a proactive program for life extension of pressure vessels. 26

A probabilistic model has been developed for predicting the reliability of structures based on fracture mechanics and the results of nondestructive examination (NDE). The distinctive feature of this model is the way in which inspection results and the probability of detection (POD) curve are used to calculate a probability density function (PDF) for the number of flaws and the distribution of those flaws among the various size ranges. In combination with a probabilistic fracture mechanics model, this density function is used to estimate the probability of failure (POF) of a structure in which flaws have been detected by NDE. The model is useful for parametric studies of inspection techniques and material characteristics.

Alkali-aggregate reaction (AAR) has affected the concrete in drilled shafts (cast in place piles) beneath electricity transmission towers along a 42-mile (67 km) section of transmission line in Southern California. In order to prioritize the maintenance program for these shafts, a nondestructive test methodology was sought to quantify the severity of the AAR with depth in each shaft. Shaft diameters of 19, 30, 36, 42, and 54 inches (475, 760, 910, 1067 and 1660 mm) were present, with shaft lengths between 10 and 30 feet (3 and 6 m). Over the last thirty years, impulse-response (I-R) testing has been successfully used to evaluate the integrity of drilled shafts, and computer simulation programs have also been developed for matching I-R test responses with theoretical shaft shapes and concrete quality. A program to test as many shafts as could be accessed in the difficult, mountainous terrain along this transmission line included mobilization of equipment and testing personnel by helicopter. Two hundred ten shafts were tested along the line in five days. Matching of test response mobility-frequency plots in computer simulation was achieved by varying the simulated concrete modulus and density, as well as the shaft cross section area. Up to three grades of concrete quality were identified in each shaft, representing the decreasing degree of AAR with depth. The tested shafts were then rated for increasing AAR severity, in order to select shafts for repair or replacement.

Pre-stressed concrete water pipelines are commonly helically wrapped with highly stressed wire. Although passivated by use of high pH concrete coating, these wires can corrode and break, ultimately resulting in catastrophic failure of the pipe. The failure of these wires releases stored acoustic energy into the walls of the pipes, and into their contents. Continuous acoustic monitoring of the water column in the pipe using various methods can reveal the condition and rate of deterioration of the pipe. This paper discuses the evidence that the method is workable, and suggests a three-stage approach to efficiently examine long pipelines with no interruption in service.

Steel reinforced concrete is the most widely used construction material in the world. The economic costs of repair or replacement of environmentally damaged concrete structures is astronomical. For example, half of the concrete bridges in the Federal Department of Transportation highway system are in need of major repairs. Microbially influenced degradation of concrete (MID) is one of the recognized degradative processes known to adversely affect concrete integrity. It is not possible to assign a specific percent of effect to any of these processes. However, MID has been shown to be as aggressive as any of the physical/chemical phenomena. In addition, the possibility exists that there is a synergism which results in cumulative effects from all the processes. Three groups of bacteria are known to promote MID. Of these, sulfur-oxidizing bacteria (SOB) are the most aggressive. Much is known about the nutritional needs of these bacteria. However, there has not been a biological linkage established between the presence of environmental, polluting sulfur sources and the degradation of concrete structures. It has been shown that the environmental pollutants sulfur dioxide and sulfite can be utilized by active SOB for the biological production of sulfuric acid. Therefore, it is not a reach of reality to assume that SOB exposed to these pollutants could have a major impact on the degradation of concrete structures. But, until the environment sulfur loop is closed it will not be possible to calculate how important SOB activity is in initiating and promoting damage.

A leak survey of a major metropolitan area aqueduct was carried out using a combination of infrared thermography, ground penetrating radar (GPR), and ultrasonic techniques. The objective of the infrared survey was to investigate the entire length of the aqueduct in order to reveal possible leak conditions which would not be observable by other means. The objective of the GPR survey was to focus attention more locally on key areas such as known leak locations, proposed test pit locations, and areas which were identified from the infrared survey. The ultrasonic tests were carried out on the concrete wall of the aqueduct when it was exposed for detailed evaluation. The infrared survey was carried out from a helicopter, and covered the entire 16 mile length of the aqueduct. The GPR survey was carried longitudinally on 20665 linear feet of the aqueduct (26% of the total near surface length), and transversely at 89 different stations. The ultrasonic tests were carried out in 8 excavated test pits. The analysis of the infrared and GPR survey results revealed that: (1) of the 25 documented leaks surveyed, 13 were confirmed, 9 show no evidence of leakage, and 3 could not be evaluated; (2) 35 additional sites have indications of possible leakage; (3) the soil cover in one area far exceeds the anticipated design conditions; (4) the soil conductivity is high (i.e., corrosion is likely) in 9 areas, 6 of which surround or are close to documented leak sites; and (5) there is a major leakage channel along the side of the pipe caused by one of the leaks. The results of the ultrasonic testing revealed occasional delamination between the structural wall of the aqueduct and the inner steel lining.

Not Available

Detecting corrosion in insulated piping is a major industry problem and the consequences of not detecting corrosion can be costly. Digital radiography allows the user to examine insulated piping for internal and external corrosion defects while the piping remains in service. This technique minimizes the need for scaffolding, eliminates the need for insulation removal, and provides industry with a cost-effective means of examining its insulated piping systems.