Green sand system

The water used for a green sand system should be clean and it should be consistent. It should have a pH that is neutral to alkaline, not acidic, because acids prevent bentonite from swelling. In... 

The dimensional capabiUties and tolerances of chemically bound systems are better than those of green sand. The cost for produciag components with these methods is 1.5 to 2 times higher than the cost of produciag green sand. 

The reclamation of clay-bonded molding sand (green sand) has been practiced in Japan for the past 20 years and is currently being adopted in the United States (ASM 1988). Wet reclamation systems were employed in the 1950 s for handling clay-bonded system sands, but they are no longer utilized. 

When working with the green sand method, a simple system of vents can be created by lancing the completed mold/ pattern several times w/a piece of sharpened welding rod,Do this just prior to pouring the metal. 

In addition to green sand molds, chemically bonded sand cast systems are also used. These systems involve the use of one or more organic binders in conjunction with catalysts and different hardening/setting procedures. Foimdry sand makes up about 97% of this mixture. Chemically bonded systems are most often used for cores (used to produce cavities that are not practical to produce by normal molding operations) and for molds for nonferrous castings. 

Table 4.24 shows operational emission values for benzene, toluene, xylene and phenol, as measured in one aluminium green sand foundry. Measurements were performed both at the shake-out grate and in the exhaust-air stack. Data are given for the traditional cold-box system and for one using vegetable-oil based solvents. A clear reduction in BTX and C-emissions is observed (25 - 50 % of stack emissions). 

The exhaust air from the green sand preparation is saturated with water. Therefore, wet systems (often of the low pressure type) seem to be most suitable for exhaust capture. However, the wet system is widely being replaced by dry dust abatement. The latter has the advantage that part of the dust may be recirculated and that no waste water stream is generated. Additionally, the wet systems are prone to internal eorrosion and the build-up of dust and oxidation products. The wet separation of exhausted air impurities can result in problems for the waste water cleaning. Dust contains bentonite which is difficult to dispose of due to its anti-sedimentable effects. [225, TWG, 2003]... 

An overall reclamation ratio of 92 %, as given above, is a normal value for mixed green sand -chemically bonded sand systems. Regeneration ratios of up to 98 % have been reported. The actual ratio depends on the volume and chemical composition of the used cores. For fiiran cold setting monosands, values around 78 % are reported. 

For a green sand monosystem, regeneration ratios of 98 % may be achieved. Systems with a high degree of incompatible cores, may achieve a regeneration ratio of 90 - 94 %. 

Silicosis is the classic example of pneumoceniosis. The lung s protective system tries to remove the silica particles by phagocytizing or engulfing them. The silica destroys the phagocytes, and other phagocytes form layer-nodules, which usually are detected by X-rays. Foundry workers exposed to silica experienced relief when green olivine, nonsilica sands were used. 

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