Valve Resistance

NOTE Outline drawings for flanged valves shown VS-in raised face machined onto flange, as for 400-lb cast-steel valves 150- and 300-lb cast-steel valves and 2.50-lb cast-iron valves have i/ifi-in raised faces 125-lb cast-iron and 150-lb corrosion-resistant valves covered by MSS-SP-42 have no raised faces. 

For higher resistance valves, such as globes and angles, the losses are less than sudden enlargements or contractions situations. For these reduced seat valves the resistance coefficient EL, can be calculated as [3] ... 

Vapor load near the column top was three times lower than near tire column bottom, causing turndown problems. Successful resolution was achieved by different modifications to top 40% of trays. Modifications included (a) blanking half the valves, (b) using leak-resistant valve units, each containing a lijditwei t plate located below the normal disk (c) retraying with bubble-cap trays. 

A dramatic increase in efficiency resulted from retraying ccduirm with leak-resistant valve units, each containing a lightweight plate located below the normal disk. 

Leakage though valves reduces drug delivery. Leakage is more coimnon through low-resistance valves. 

NebuChamber is a 250-mL metal spacer with high-resistance valves and no dead space between the valves. 

Babyhaler is a 350-mL plastic spacer with low-resistance valves and a 40-mL dead space between inlet and outlet valves. 

The following nonlinear resistive valve relations are used. These not necessarily follow the basic relations of linear bond graph elements but their own ... 

CO2 by weight was then injected into the polymer melt. Phase separation was prevented by setting the average die pressure between 3000 and 4000 psi, using the resistance valve (Fig. 1). The adequacy of this die pressure was confirmed by the solubihty measurement of CO2 in PS685D (Table 2) [17]. Also, the measured pressme profile was fotmd to be as linear, like that of the pure PS. 

---