chapter 12 hydraulic transient design for pipeline systems

HYDRAULIC TRANSIENT DESIGN FOR PIPELINE SYSTEMS
a.) Gate valve
(circular gate)
c.) Needle valve
e.) Butterfly valve
Hydraulic Transient Design for Pipeline Systems 12.5
b.) Globe valve
d.) Gate valve
(square gate)
f.) Ball valve
FIGURE 12.2 Cross sections of selected control valves: (From Wood and Jones, 1973).
12.3.2 Definition of Geometric Characteristics of Valves
The valve geometry, expressed in terms of cross-sectional area at any opening, sharpness
of edges, type of passage, and valve shape, has a considerable influence on the eventual
hydraulic characteristics. To understand the hydraulic characteristics of valves it is useful,
however, to express the projected area of the valve in terms of geometric quantities. With
reference to Fig. 12.2 the ratio of the projected open area of the valve A v to the full open
valve A vo can be related to the valve opening, either a linear measure for a gate valve, or
an angular one for rotary valves such as ball, cone, plug, and butterfly types. It should be
noted that this geometric feature of the valve clearly has a bearing on the valve hydraulic
performance, but should not be used directly for prediction of hydraulic performance—
either steady state or transient. The actual hydraulic performance to be used in transient
calculations should originate from experiment.
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