Inspection Techniques

Fokker Bond Tester. An ultrasonic inspection technique commonly used for aircraft structures is based on ultrasonic spectroscopy [2]. Commercially available instruments (bond testers) used for this test operate on the principle of mechanical resonance in a multi-layer structure. A piezoelectric probe shown in Figure 3b, excited by a variable frequency sine signal is placed on the surface of the inspected structure. A frequency spectrum in the range of some tens of kHz to several MHz is acquired by the instrument, see Figure 3a. 

T R Schmidt. History of the Remote-Field Eddy Current Inspection Technique. Materials Evaluation Jan 1989... 

It is particularly in the serial inspection of castings, that radioscopy constitutes state-of-the-art when applied in conjunction with systems for image intensification, digital image processing and automatic image evaluation. For the examination of welds, however, standardization is still non-existent, thus rendering more difficult the application of this inspection technique.As a consequence the approval procedures of the respective supervisory or certification boards are often complicated and of necessity set up for each individual case. 

However, in various industrial sectors the application of the radioscopic inspection technique is aggravated by a lack of the respective standards, contrary to radiography. This leads to complicated approval bureaucracy by the respective supervisory or certificatiomn authorities. 

Therefore, the establishment of the Non-Destructive Inspection technique to understand the presence of the defect on the bonding interface by the ultrasonic wave etc. accurately is demanded. And, the reliability of the product improves further by feeding back accurate ultrasonic wave information obtained here to the manufacturing process. 

The Development of Acceptance Criteria for the TOFD Inspection Technique. Draft final report of a Dutch KINT project (draft, document number T098-54, Rev. 0, January 1998)... 

A D—T fusion reactor is expected to have a tritium inventory of a few kilograms. Tritium is a relatively short-Hved (12.36 year half-life) and benign (beta emitter) radioactive material, and represents a radiological ha2ard many orders of magnitude less than does the fuel inventory in a fission reactor. Clearly, however, fusion reactors must be designed to preclude the accidental release of tritium or any other volatile radioactive material. There is no need to have fissile materials present in a fusion reactor, and relatively simple inspection techniques should suffice to prevent any clandestine breeding of fissile materials, eg, for potential weapons diversion. 

Defects such as hot tears or laps, quench cracks, localized overheating during stress rehef, and corrosion may occur during the tubemaking process (154). Magnetic particle, ultrasonic, and visual inspection techniques are used to ensure that relatively few tubes enter service with significant defects. 

The most effective specification is that which accomplishes the desired result with the fewest requirements. Properties and performance should be emphasized rather than how the objectives ate to be achieved. Excessive demonstration of emdition on the part of the writer or failure to recognize the usually considerable processing expertise held by the vendor results in a lengthy and overly detailed document that generally is counterproductive. Redundancy may lead to technical inconsistency. A requirement that cannot be assessed by a prescribed test method or quantitative inspection technique never should be included in the specifications. Wherever possible, tests should be easy to perform and highly correctable with service performance. Tests that indicate service life are especially useful. Standard test references, eg, ASTM methods, ate the most desirable, and those that ate needed should be selected carefully and the numbers of such references should be minimized. To eliminate unnecessary review activity by the would-be complier, the description of a standard test should not be paraphrased or condensed unless the original test is referenced. 

The color development of photochromic compounds can also be utili2ed as a diagnostic tool. The temperature dependence of the fa ding of 6-nitroindolinospiropyran served as the basis for a nondestmctive inspection technique for honeycomb aerospace stmctures (43). One surface of the stmcture to be exarnined was covered with a paint containing the photochromic compound and activated to a violet color with ultraviolet light. The other side of the stmcture was then heated. The transfer of heat through the honeycomb stmcture caused bleaching of the temperature-dependent photochromic compound. Defects in the honeycomb where heat transfer was inhibited could be detected as darker areas. 

Visual inspection techniques are stressed as the most important tools used to study failures. This text is not a substitute for rigorous failure analysis conducted by experts, but it will help the reader identify and eliminate many cooling water system problems. Still, on occasion, the experienced, skilled, failure analyst using sophisticated analytical techniques and specialized equipment may be required to solve complex or unusual problems. Common sense, appropriate experience, and systematic investigation are, however, often superior to the more elaborate, but less effective, techniques used by some. 

There are numerous other inspection techniques that have been developed in the last couple of decades such as holographic interferometry, acoustical holography, acoustic emission, thermal emission scanning, etc. They all have been developed to address shortcomings of more popular inspection techniques but for the most part remain niche techniques. 

This process of conversion from a metals production environment to a composite materials production environment is much more involved than just laminate layup and curing. Issues of inspection arise to make certain that the composite product is put together properly. Some of those inspection techniques are much more complicated than they were for a metallic structure. Truly, the picture is not totally rosy for composite materials. It would be quite unrealistic to say (1) there are no problems and (2) composite materials are absolutely the best way to go. 

Inspection techniques are available for specific coating and lining systems. Proper bonding to substrate is necessary to avoid blistering and disbonding in case of a vacuum being created in the vessel. 

An overall assessment as to the reliability of inspection techniques (NOT), including ultrasonics, is given by Silk". ... 

Eddy currents The examination of non-ferrous tubing using external coils is a well-tried and successful inspection technique, owing mainly to the pioneering work of Forster in Germany. The adoption of this method for in-situ inspection of condenser tubes, by mounting eddy-current coils in probes (or bobbins) that can be inserted in condenser tubes, was a logical development of the technique. Suitable apparatus was developed in the immediate post-war period more or less independently by several oil and chemical companies. The principle of operation has been described in the literature... 

Dilcer Jr., Samuel B. Dromgoole, Jim C. Waterside Inspecting Techniques for Industrial Boilers. Ultrapure Water, Tall Oaks Publishing, Inc., USA, November 1998. 

Molnar, T. L. Boiler System Equipment Inspection Techniques. Mogul Applications Discussion Document. Mogul Corporation (Dexter), USA, 1982. 

The Pharmaceutical Inspection Cooperation Scheme (PICS) was established in 1995. It brings together regulatory authorities from different countries, for the purpose of developing harmonised GMP requirements and inspection techniques, with the goal... 

The relationship between the main subsystems and other minor systems is illustrated schematically in Figure 12.4. This places management at the core of the quality system, with the other systems arranged as major and minor satellites that revolve around it. This perspective provides the basis for the Quality System Inspection Technique (QSIT), which the FDA uses for auditing medical device facilities. This is based on a top-down approach, which starts with management controls and then looks at three other key subsystems of Design Controls, Corrective and Preventative Actions (CAPA) and Production and Process Controls. The belief is that by focussing on just these four subsystems, you will actually touch on all the other subsystems and obtain a sufficiently satisfactory overview of the state of compliance of the facility. 

GP 11] ]R 19] Using the above visual inspection technique, the minimum residence time can be estimated. Flow was increased and so the residence time decreased, until the whole reactor was glowing. This corresponds to a residence time as low as approximately 50 ps (0.1 slpm hydrogen, 0.14 slpm oxygen, 0.45 slpm nitrogen) [9]. 

The QA SOP manual should describe QAU audit and inspection techniques with attached inspection checkhsts, if used. Statistically based methods for random selection of phases of studies for inspection and for random selection of data points during final report audits should be described and justified. Any designation of study phases as critical or noncritical used to estabhsh the frequency of study inspec-... 

When needed to achieve the required standard of quality, quality control, inspection techniques, and instrumentation are updated. As needed to achieve the required quality, any controls, processes, inspection equipment, fixtures, total production resources, and skills are identified and acquired. 

The new medical device regulations were codified in 1996, significantly altering the way in which medical device manufacturers were inspected by the FDA. The quality systems inspection technique (QSIT) was launched as part of the new strategy for inspecting the device industry. This inspection technique allowed FDA to move closer to global harmonization guidelines... 

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