ASNT

(2) to avoid failures, prevent accidents, and save human life (Figures 1 and 2); (3) to make a profit for the user; (4) to ensure customer satisfaction and maintain the manufacturer’s reputation; (5) to aid in better product design; (6) to control manufac- turing processes; (7) to lower manufacturing costs; (8) to maintain uniform quality levels; and (9) to ensure operational readiness. These reasons for widespread profitable use of nondestructive testing are sufficient in themselves, but parallel developments have contributed to its growth and acceptance. Increased Engineering Demand In the interest of greater performance and reduced cost, the design engineer seeks to reduce weight. Designing with lightweight metal alloys (aluminum or magnesium alloys for steel or iron); polymer composites, or ceramics are examples. Such lighter weight components are not necessarily of the same size or design as those they replace. These changes may subject parts to increased stress levels. The stress to be supported is seldom static. It often f luctuates and reverses at low or high frequencies. Frequency of stress reversals increases with the speeds of operation, risking fatigue damage. Because nondestructive testing can reveal, characterize, and quantify anomalies on the surface and throughout the component’s volume, it is a major tool to ensure raw materials and fabricated components meet design expectation for quality,

reliability, and service. Nondestructive testing can provide data to let engineers reduce safety factors and cost. Due to the success of nondestructive testing in fabrication, operation engineers use nondestructive testing to locate and describe service discontinuities and monitor their growth. Today’s nondestructive testing technologies ensure structural integrity of operating components that allow continued service of critical components. Extended component life reduces operational costs while ensuring continued safe operation. For this and other reasons, national codes and standards have also adopted nondestruc- tive testing in in-service requirements. The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, for example, has an entire section dedicated to in-service inspection of critical components. That section uses nondestructive testing as its primary tool. ASME Section V ( Nondestructive Examination ) provides the “how to” requirements for the performance of various nondestructive testing methods. Other sections of the Boiler and Pressure Vessel Code also identify specific requirements when nondestructive test methods are to be used. Engineers also use nondestructive testing for plant life extension. Most designs project an expected life of operation. For example, nuclear reactors at energy generation stations in the United States were designed originally for a service life of 40 years. After their designed service life, the reactor would be shut down and decommissioned. However, because of the critical need for energy, the lead time for the construction of new power plants, and the cost of construction, plant owners have commissioned studies, including nondestructive testing, to determine if plant operations can safely continue beyond 40 years. Once complete, the plant owner will submit a formal request to the appropri- ate regulatory authority (in this example, the US Nuclear Regulatory Commission) using the study as a basis for continued service. As technology improves and as service requirements increase, structures and equipment are subjected to greater variations and to wider extremes of all kinds of stress, creating a demand

Figure 1 View of Aloha Airlines Flight 243 pressure cabin skin departure looking aft on left-hand side of fuselage (FAA training), 1988.

CHAPTER 1

4

Part 1