- Title : Proses Industrial Instrument & Control Handbook [ pdf ] by Gregory K. McMillan and Douglas M. Considine
- Publish : McGRAW-HILL
- Type Document : pdf
- Release : December 1999
- Total Page : 11 Chapter
- Size : 11.30 Mb
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Decrypted Contents
General Categories of Control Valves
Control valve here means any power-operated valve, whether used for throttling or on–off control. Varieties from which to select, as listed in Table 1, include sliding stem valves and rotary valves. Typical sliding-stem valves are straight-pattern valves (sometimes called globe valves) and anglepattern valves. Rotary valves include ball and butterfly valves. Other varieties such as motorized gate valves, louvers, pinch valves, plug valves, and self-operated regulators are not considered here. These major types, sliding-stem and rotary, are further divided into ten subcategories according to relative performance and cost. Despite variations found within each category—such as cage guiding and stem buiding—all valves within a given subcategory can be considered very much alike in the early stages of the valve selection process. Selecting a valve involves narrowing your selection to one of these subcategories and then comparing specific valves in that group (Table 2).
Control valve here means any power-operated valve, whether used for throttling or on–off control. Varieties from which to select, as listed in Table 1, include sliding stem valves and rotary valves. Typical sliding-stem valves are straight-pattern valves (sometimes called globe valves) and anglepattern valves. Rotary valves include ball and butterfly valves. Other varieties such as motorized gate valves, louvers, pinch valves, plug valves, and self-operated regulators are not considered here. These major types, sliding-stem and rotary, are further divided into ten subcategories according to relative performance and cost. Despite variations found within each category—such as cage guiding and stem buiding—all valves within a given subcategory can be considered very much alike in the early stages of the valve selection process. Selecting a valve involves narrowing your selection to one of these subcategories and then comparing specific valves in that group (Table 2).
Designations NPS and DN are used in Table 1 and throughout this section. NPS is a designation for nominal pipe size. It comprises the letters NPS followed by a dimensionless number, which is indirectly related to the physical size, in inches, of the end connections. DN is an international designation for nominal diameter. It comprises the letters DN followed by a dimensionless whole number, which is indirectly related to the physical size, in millimeters, of the end connections.
Sliding-Stem Valves
The most versatile of the control valves are the sliding-stem valves. Straight-pattern, angle-pattern, and three-way valves can be purchased in sizes ranging from NPS 1/2 to NPS 20 or from DN 15.
The most versatile of the control valves are the sliding-stem valves. Straight-pattern, angle-pattern, and three-way valves can be purchased in sizes ranging from NPS 1/2 to NPS 20 or from DN 15.
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