Gunned refractories

Gunning refractories have course and fine refractory grains and bonding agents, suitable for installation with a gunning machine. 

Case 4 Physical Wear, Some Atmospheres, Liquid Slag or Scale, Leaking Cooling Water These also can be bad for refractories. After installation of castable, rammed, and gunned refractories, a long, slow dryout period is necessary to prevent spalling or explosions from steam formation within the refractories. 

ISO 20182 2005 Refractory test-piece preparation - gunning refractory panels by pneumatic-nozzle mixing-type guns... 

Banerjee S, Harbin H, Reno E. Spray-gunning refractories. Proc. UNITECR 97,... 

Table 16 Properties of Insulating and Plastic Gunning Refractories...

Refractories may be preformed, ie, shaped, or formed and installed on-site, ie, specialties. Iimovations in placement and vessel constmction has led to a greater emphasis on specialty refractory products. Castables, gunning mixes, and plastic and ramming mixes are used either for repair or for complete new constmction of what is known as monolithic linings. The tendency to use monolithics instead of constmctions using shaped products has been steadily increasing. As of the mid-1990s, monolithic installations are as common as conventional shaped product constmction. 

Specialty Refractories. Bulk refractory products include gunning, ramming, or plastic mixes, granular materials, and hydrauhc setting castables and mortars. These products are generally made from the same raw materials as their brick counterparts. 

Another type of ion gun produces positive ions from a liquid metal (almost always gallium) in the manner shown schematically in Fig. 3.2 [3.7]. A fine needle (f tip radius 5 pm) of refractory metal passes through a capillary tube (d) into a reservoir of liquid metal (e). The liquid is drawn up through the tube over the needle tip by capil-... 

Other common refractory forms include setter tile and kiln furniture, fusion-cast shapes, cast and hand-molded refractories, insulating refractories. castables and gunning mixes, plastic refractories and ramming mixes, mortars, composite refractories, and refractory coatings,... 

Nonmetallic castable refractories, reinforced with hexagonal steel mesh, are particularly good, since they resist both corrosion and erosion. Conventional refractories are susceptible to deterioration by water sprays, but this difficulty can be overcome by shielding from water impingement or by use of special cements. For best results, the refractory is installed flush with the surface of the steel mesh and is commonly applied with a pneumatic gun to ensure completeness of fill and maximum... 

In contrast to the basic refractory services provided by their predecessors, today s gunited or cast liners are much more dependent upon the ability of the applied material to resist possible chemical attack. Additionally, the fact that the cementitious materials utilized in these applications are somewhat absorptive and brittle causes another type of concern which should also be considered when they are specified for "wet" chimneys. (Figure 48-8 illustrates a gunned lining placed over a membrane as a lining of a concrete shell. This same design may be followed in application to a steel liner.)... 

Evaporation without contamination has today been solved by modem means such as new types of non-reactive boat material and inserts or electron beam guns for refractory metals most difficult to evaporate because of high evaporation temperatures. Condensation, problematic in a few cases, such as Zn, Cd, Ga, Sn, Sb, can be influenced by nucleation and the selection of evaporation speed (generally high) and substrate temperature (generally low). Reactions with the residual gas during condensation which cause undefined film products, difficult to reproduce, can be reduced by decreasing the residual gas pressure and the unwanted gas components, and by correct choice of substrate temperature and evaporation speed [292, 293]. 

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