Page 420 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

Ejectors and Mechanical Vacuum Systems 387

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0 2 3 4 5
Factor - f
Total volume to be extracted Volume of vessel x f
(f at the working vacuum from the above chart)
Evacuating time = Total volume to be extracted
Capacity of the vacuum pump at the working vacuum
Exampie: Vessel size 200 ft3
Working vacuum = 60mm Hg. abs.
Evacuating time = 3 minutes
Total volume to be extracted = 200 x f = 200 x 2.5 = 500 ft3
Capacity to be extracted = 500 = 167 CFM at 60mm Hg. abs;
3
Pump selection = V5212 (from chart p.6) at 1750 rpm.
Figure 6-38. Chart for liquid ring vacuum pump to estimate the total volume to be displaced to evacuate a closed vessel to a predetermined
vacuum. By permission, Graham Manufacturing Co., Inc.