Screen loading density

Figure 6. Effect of percent total volatiles on the screen loading density of casting powder...

Figure 8. Effect of tumbling time on screen loading density...

One basic assumption was that compartments with a low fire load density do not impact the overall Fire PSA result. Such compartments were screened out before starting the analysis. The fire induced core damage frequencies of all remaining compartments were determined in a first step with simplified and conservative assumptions. In the following step, only those compartments were analyzed in detail, for which in case of fire a significant contribution to the fire induced core damage frequency of the entire plant is expected. 

The mats are moved along the line to the press loader. When the loader is filled and the press opens to remove the load of freshly pressed boards, the loader pushes the new boards into the unloader and deposits the load of mats on the press platens. The press closes as quickly as possible to the desired panel thickness. More pressure, as much as 4.8—6.9 MPa (700—1000 psi) is required to press high density dry-process hardboard, because the dry fiber exhibits much more resistance to compression and densification than wet fiber. Press temperatures are also higher, in the range of 220—246°C. No screens are used in the dry-process, but the moisture in the mats requires a breathe cycle during pressing to avoid blowing the boards apart at the end of the cycle. Because no screens are used, the products are called smooth-two-sides (S-2-S), in contrast to the wet-process boards, which have a screen pattern embossed into the back side and are known as smooth-one-side (S-l-S). 

In a typical process the finely divided dry crystals are compacted under heat and pressure in a roU press into briquettes having a density of 1.550 to 1.590. The briquettes are passed to a rotary screen where the fins, thin layers of material attached to the periphery of the briquette centerline, are removed and reprocessed. The finished briquettes pass into large storage bins from where they are loaded into rail-hopper cars or shipping bins or packaged into dmms and other shipping containers. 

The cold pressing is carried out in hardened steel dies. The carbide powder is first mixed with 0.5-5% of binder lubricants, such as paraffin, camphor, Carbowax, cetyl alcohol, or beeswax dissolved in nonaqueous inert solvents such as benzene, isopropyl alcohol, or methyl alcohol. The bonded carbide powder is granulated by forcing through a screen and then loaded into the dies. The density of the cold-pressed pellets may be as high as 80% of theoretical, and the sintered pellets may be densified to 90% of theoretical. The optimum sintering condition is 1800°C for 4 h. 

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