A globe valve is a linear motion valve designed for precise flow regulation and reliable shut-off, characterized by its spherical body cavity and movable disc/plug mechanism. Key components include:
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Body: Typically Z-pattern (standard), Y-pattern (low-resistance), or angle-pattern (direction change)
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Bonnet: Bolted/screwed to the body, housing stem assembly
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Disc & Seat: Conical/parabolic disc mates with stationary seat ring for sealing
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Stem: Threaded design converts handwheel rotation into linear disc movement
2. Operational Mechanism
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Flow Control Principle:
Disc position modulates flow by varying the annular space between disc and seat (V-notch discs enable finer control). -
Pressure-Temperature Relationship:
ASTM A217 grades (e.g., WC6/WC9) determine maximum working pressures (Class 150–2500 per ASME B16.34).
3. Technical Specifications (Comparative Table)
|
Parameter |
Standard Globe Valve |
High-Performance Variant |
|---|---|---|
|
Flow Coefficient (Cv) |
5–200 |
10–500 (cage-guided) |
|
Leakage Class |
ANSI Class IV |
Class V (metal-seated) |
|
Actuation Torque |
20–800 Nm |
50–2000 Nm (piston-actuated) |
4. Industrial Deployment
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Power Generation: Main steam isolation (ASTM A182 F91/F92 bodies)
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Oil & Gas: Choke valves for wellhead pressure control (API 6A compliant)
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Cryogenics: Extended bonnet designs for LNG applications (-196°C)
5. Evolution & Innovation
Modern designs integrate:
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Smart Positioners: IEC 61508-certified partial stroke testing
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Erosion-Resistant Coatings: Stellite 6 overlay on seat/disc surfaces
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3D-Printed Components: Reduced lead times for customized geometries
6. Standards Compliance
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Dimensional: ASME B16.10 (face-to-face dimensions)
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Testing: API 598 (pressure/seat leakage tests)
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Material: NACE MR0175 for sour service environments