I. Non-Rising Stem (NRS) Gate Valves
Structural feature: The stem remains inside the valve body, with vertical movement achieved through internal transmission mechanisms. The stem is never externally exposed during operation.
Advantages:
Superior sealing: The enclosed stem design minimizes leakage risks, making NRS valves ideal for critical sealing applications.
Environmental resistance: Protected from corrosive gases/dust, extending service life.
Aesthetic appeal: Streamlined appearance suits visually sensitive installations.
Disadvantages:
Complex maintenance: Stem access requires full valve disassembly, increasing downtime.
Higher costs: Intricate structure elevates manufacturing/maintenance expenses.
II. Rising Stem (RS) Gate Valves
Structural feature: The stem extends externally and is directly driven by handwheels or actuators for linear motion.
Advantages:
Ease of maintenance: Exposed stem allows direct access for repairs/parts replacement.
Simplified design: Lower manufacturing/installation costs; adaptable to diverse actuators.
Visual feedback: Operators can instantly verify valve status via stem position.
Disadvantages:
Sealing vulnerability: External exposure increases risk of seal degradation from corrosion/contaminants.
Environmental sensitivity: Requires frequent inspection in harsh conditions (e.g., offshore/marine).
