Final line sizing

The final line size of single phase flow, two phase flow, gravity flow, and sluny flow should be ba.sed on hydraulic loop pressure proflle calculation using actual line length and pipe fittings shown in the piping isometric drawings. 

---

The final line size should be such as to give an economical balance between pressure drop and reasonable velocity. 

Values listed are guides, and final line sizes and flow velocities must be determined by appropriate calculations to suit circumstances. Vacuum lines are not included in the table, but usually tolerate higher velocities. High vacuum conditions require careful pressure drop evaluation. 

The procedure recommended by Reference [18] is based on the conventional gas flow equations, writh some slight modifications. The importance in final line size determination is to determine w hat is a reasonable pressure loss at the absolute pressure required and the corresponding pipe size to balance these. In some cases a trial/error approach is necessary. 

U.S. Pat. No. 3,668,088 to Her describes the preparation by electrodialysis at high temperature of aqueous sodium or potassium silicate, of dilute silica sols of large particle size and very dilute sols of small particle size larger than 10 nm which can be concentrated by evaporation. The patent recites that at lower temperatures only extremely small particles of colloidal silica are obtained and the sols can therefore not be concentrated without gelling (Column 2, lines 27-29). Again in this case, the number of nuclei was not kept constant during the heatup period so that in aU examples the final particle size is larger than 10 nm. 

In suspension polymerization the vinyl chloride monomer is dispersed in water using a protective colloid or a surfactant to control the final particle size (usually between 130 and 165 xm) and a monomer-soluble initiator (usually an azo compounds or a peroxide) is used. Gelatin, soaps, glycols, and pentaerythritol or their mixtures can be used as dispersing agents in the reaction mixture. The polymerization is usually carried out in a glass-lined reactor with controlled agitation, at a... 

Phase 6 Line optimization Merchandising team will review the final line against orders, drop styles with inadequate orders, and replace with new styles, colors, and sizes to optimize the line for profitability. If changes are made, the model will direct to previous phases as appropriate. This phase will continue while production is in progress. 

The dope solids for air-gap spinning are higher than for wet spinning, the intent being to achieve quick gelation on extrusion. The spinnerette is positioned a short distance above the bath, which is a solvent/nonsolvent mixture, typically at low temperature. The fiber is spim vertically into the bath, and then rerouted out via a tube or pulley as shown in Figure 12. Spinnerettes may be less then 1000 holes for a textile product or as many as 4000 for a carbon fiber precursor. The remainder of the process resembles the wet-spinning process, except that there are many small bundles that must be kept separate and the final product is taken up on bobbins. Final line speeds may be up to 500 m/min, but because of the small bundle size, machine productivity may be only 5 ton/day. 

The pressures in industry are to introduce on-line size analysis systems, preferably methods that can operate without pre-dilution since this may modify the suspension. The drive is always to finer and finer powders hence sub- lm, on-line size analysis of concentrated suspensions would be ideal. Failing this, rapid off-line analyses of concentrated suspensions would be acceptable. Accuracy is not always important detecting changes which may affect powder handling or final product may be all that is necessary. 

To help us understand the effect of chemical potential difference and interfacial tension on final particle size and processing times, a graph was constructed (see Figure 12). The construction of contour lines attributable to constant particle diameter and constant processing times, respectively, were facilitated by the introduction of two dimensionless parameters ... 

Friction tor Use 0.015 for friction factor for first optimum line size calculation. Once the preliminary ptimujn tine size is estimated, Eq. (7) is used to calculate the actual friction factor, and the final optimum line size will be caiculated. 

---