Grinding pits

Final polish on Texmet or equivalent with 0.3-pm alumina (or 0.25-pm diamond, or a mixture of the two) for roughly four minutes. Examine the section microscopically and repolishif grinding pits are observed. 

Photograph 8-1 Grinding pits remaining on hastily polished surface of clinker appear somewhat like dark alkali sulfate. (S A6717)... 

Grinder Variables. The quaUty of pulp depends on wood species, moisture content, and grinder variables such as peripheral stone speed, grit size and number per unit area, and pattern on the stone surface. Process variables that affect pulp quaUty include grinding pressure pit consistency, ie, consistency in the space immediately below the grinder (2—6%) and temperature (40—80°C). The combination of moisture and raised temperature tends to soften the lignin. 

FIG. 20-43 Single -stage closed-circuit wet-grinding system, [Tomy, Pit Quarry Tehixiaiy-March 1.9,59),]... 

FIG. 20-45 Closed -circuit wet grinding with liquid-solid cyclone. [Tonty, Pit Quarry (Fehtuaty-March L95.9).]... 

FIG. 20-58 Combined drying-grinding system using ball-mill and hot Idln exhaust gases. To convert inches to centimeters, multiply by 2.54 to convert feet to centimeters, multiply by 30.5 = ( F - 32) X 5/9. [Tonty, Pit Quarry (Fehtuaty-... 

Mechanical surface preparation shall be performed by wire brushing, grinding, buffing, and polishing when required, to remove harmful defects such as fissures, pits, gouges, folds, laps, or oxides. 

After the fabrication of the tank, the metal surface should be inspected for any pittings or projection and the same is to be leveled out by grinding. 

Discrepancies between reactive and adsorption surface area may also be related to the presence of deep etch pits or pore outcrops which can constitute transport-limited micro-environments for dissolution (Jeschke and Dreybrodt, 2002). Much of the BET surface area for some alkali feldspars used for dissolution in the laboratory has been attributed to grinding-induced microporosity (Hodson et al, 1999), and such pore outcrops are candidates for transport limitation. If such induced surfaces react dilferently than surfaces of weathered samples, then the BET surface area may be an inappropriate parameter to use for extrapolating interface-limited kinetics from laboratory to field (Lee et al, 1998 Brantley and Mellott, 2000 Jeschke and Dreybrodt, 2002) and consideration may need to be given to length and extent of grinding for laboratory samples (Hodson, 1999). It may be more appropriate to use geometric rather than BET surface area to extrapolate kinetics for samples where etch pits or pore outcrops are important contributors to BET surface area (Gautier et al, 2001 Jeschke and Dreybrodt, 2002 Mellott et al, 2002). 

Surface Preparation The steel surfaces to receive the membrane lining must be smooth, free from pits, millscale, weld splatter, and lap welds. Corners must be rounded to an internal and external radius of % inch minimum. The surface must be sandblasted just before application of the membrane on interior surfaces and a paint system on exterior surfaces. Sandblasting should be in accordance with specifications supplied by the manufacturers of the membrane and protective coating system. This may require welding inside corners and then grinding to the proper radius. 

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