134 ◾  Index
U
Ultimate gain tuning of control
loops, 82–84
Ultimate peak-to-peak time period
(UTP), 82

Ultimate proportional gain (UG),
82

Undershoot, 85

V

Vacuum towers, 29

Vapor concentration response, D/F
changes and, 27

Vapor flow rate, 42–43
Vapor pressures, rule of thumb for
calculating, 14

Vapor side draw, 41

Vapor traffic, 45–46
Vapor-liquid relative volatility,
single stage, 13–16
Variability

quality measurement and, 58

reduction of to improve quality,
63–65

Volatility, 46

W
Weight fraction concentration,
24–25
Z
Ziegler–Nichols closed-loop tuning
method, 82–84
rules of thumb for, 107–110