Metal objects

But, with the use of digitization, 2D quantitative measurements are allowed for industrial radiography. These can be done by powerful tools, like estimation of defect extension, automatic segmentation, recognition of individual defects and image analysis (figure 7). For validation, results can be compared with destractive examination of metallic objects. 

Deteriora.tlon. Apart from physical damage that can result from carelessness, abuse, and vandaUsm, the main problem with metal objects Hes in thek vulnerabihty to corrosion (see Corrosion and corrosion control) (127,128). The degree of corrosion depends on the nature and age of the object. Corrosion can range from a light tarnish, which may be aesthetically disfiguring on a poHshed silver or brass artifact, to total mineralization, a condition not uncommon for archaeological material. 

Conserva.tlon, Because the most common conservation problem with metal objects occurs when corrosion processes form a threat to the safety of the object or disfigure its appearance to an unacceptable degree (130,131), many conservation treatments are intended to stabilize the corrosion processes and to remove aesthetically displeasing corrosion cmsts. The latter requkes a great deal of thought and discussion as to when a corrosion layer ceases to be a deskable patina and becomes unacceptable. 

Vapors emitted from the materials of closed storage and exhibit cases have been a frequent source of pollution problems. Oak wood, which in the past was often used for the constmction of such cases, emits a significant amount of organic acid vapors, including formic and acetic acids, which have caused corrosion of metal objects, as well as shell and mineral specimens in natural history collections. Plywood and particle board, especially those with a urea—formaldehyde adhesive, similarly often emit appreciable amounts of corrosive vapors. Sealing of these materials has proven to be not sufficiently rehable to prevent the problem, and generally thek use for these purposes is not considered acceptable practice. 

Nonplanar metal objects can be clad, eg, the inside of a cylindrical nozzle can be clad with a corrosion-resistant liner. 

Textiles. Microwave drying of textiles is under investigation, in addition to the possible uses for curing of impregnated and dyed fabrics (182). A microwave clothes dryer for consumer or commercial apphcation is also under discussion (183). Considerable developmental work and media pubhcity have occurred. Problems remain, however, particularly relating to arcing and resonant heating of metal objects that may be present in a load of clothes. These problems may be alleviated by operation at 915 rather than 2450 MHz (184). 

Eye and Skin Contact. Some nickel salts and aqueous solutions of these salts, eg, the sulfate and chloride, may cause a primary irritant reaction of the eye and skin. The most common effect of dermal exposure to nickel is allergic contact dermatitis. Nickel dermatitis may occur in sensitized individuals following close and prolonged contact with nickel-containing solutions or metallic objects such as jewelry, particularly pierced earrings. It is estimated that 8—15% of the female human population and 0.2—2% of the male human population is nickel-sensitized (125). 

Description A tray or compartment diyer is an enclosed, insulated housing in which solids are placed upon tiers of trays in the case of particulate solids or stacked in piles or upon shelves in the case of large objects. Heat transfer may be direct from gas to sohds by circulation of large volumes of hot gas or indirect by use of heated shelves, radiator coils, or refractoiy walls inside the housing. In indirec t-heat units, excepting vacuum-shelf equipment, circulation of a small quantity of gas is usually necessary to sweep moisture vapor from the compartment and prevent gas saturation and condensation. Compartment units are employed for the heating and diying of lumber, ceramics, sheet materi s (supported on poles), painted and metal objects, and all forms of particulate solids. 

Heat Treatment Heat treatment can be divided into two types, treatment of fluidizable solids and treatment of large, usually metallic objects in a fluid bed. The former is generally accomplished in nmlti-compartment units to conserve heat (Fig. 17-27). The heat treatment of large metallic objects is accomplished in long, narrow heated beds. 

In die production of metallic objects for technological applications, an important way to produce drese is via die compacting of metal powders. One... 

Soil resistivity measurements can be affected by uncoated metal objects in the soil. Values that are too low are occasionally obtained in built-up urban areas and in streets. Measurements parallel to a well-coated pipeline or to plastic-coated cables give no noticeable differences. With measurements in towns it is recommended, if... 

PTFE is used for lining chutes and coating other metal objects where low coefficients of friction or non-adhesive characteristics are required. Because of its excellent flexing resistance, inner linings made from dispersion polymer are used in flexible steam hose. A variety of mouldings are used in aircraft and missiles and also in other applications where use at elevated temperatures is required. 

Because of its high volume cost PTFE is not generally used to produce large objects. In many cases, however, it is possible to coat a metal object with a layer of PTFE and hence meet the particular requirement. 

In order to develop measures for removal of debris from the waste matrix, the general types of debris anticipated need to be identified. A composite list, based on debris found at 29 Superfund sites, was developed. The list includes cloth, glass, ferrous materials, nonferrous materials, metal objects, construction debris, electrical devices, wood existing in a number of different forms, rubber, plastic, paper, etc., as presented in Table 11. Similar types of debris would be expected at RCRA sites. 

Debris with particularly good absorbent qualities such as wood, some paper products, paper, cloth materials, etc., are go candidates for shredding so that they can be included in the remediation process. Materials that are not porous and are not adsorbent are glass, plastic, metal objects, some types of construction debris, tanks, etc., are good candidates for manual or magnetic separation. 

A glass distillation column cracked, and water was sprayed onto the crack. A spark was seen to Jump from the metal cladding on the insulation. which was not grounded, to the end of the water line. Although no ignition occurred in this case, the incident shows the need to ground all metal objects and equipment. They may act as collectors for charges from steam leaks or steam or water Jets. 

The substation and its environment should not be connected to metal objects such that the voltages arising within the substation under fault conditions can be transferred to a point remote from the substation. 

Surfactants are probably the materials which most affect the performance of alkali cleaners. Surfactants are complex chemicals which modify the solubility of various materials in, and their surface affinity for, oil and water. The diverse composite which makes up the surface of a metal object must be fully wetted out if the cleaner is to perform properly. Surfactants lower the surface tension to allow wetting out to occur. Oils and greases must either be dissolved off the surface or lifted from it surfactants assist in both areas. 

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