Nrs (non Rising Stem) Valve

Overview

NRS (Non Rising Stem) valves are gate valves in which the stem rotates to open or close the valve without moving vertically. Unlike OS&Y (Outside Stem and Yoke) valves, the stem position of an NRS valve does not indicate whether the valve is open or closed.

Operating Principle (As Provided)

In an NRS valve, the stem turns inside the valve body to operate the gate while remaining at a fixed height. This design makes the valve compact and suitable for installations where vertical space is limited or where the valve must be installed underground.

Use in Fire Protection Systems (As Provided)

NRS gate valves are commonly used as cut-off and zone control valves in fire protection systems. They are developed as an alternative to supervisory switched butterfly valves and OS&Y rising stem valves, particularly in underground installations.

Underground Installation & Visibility (As Provided)

These valves are typically buried underground to protect them from freezing conditions. Since the stem does not rise, NRS valves are usually equipped with post indicators instead of handwheels. Post indicators allow operators to remotely open or close the valve and visually confirm the valve position.

Advantages & Disadvantages (As Provided)

• Advantages: Compact size, suitable for underground use, and easy maintenance.
• Disadvantages: Larger than some fire protection valves and generally less economical compared to certain alternatives.

Connection Type (As Provided)

• Flanged connection

Technical Specifications (As Provided)

• Working Pressure: 200 psi – 300 psi
• Maximum Working Temperature: 0.6°C – 52°C
• Available Dimensions: 2½” – 16”

Material Features (As Provided)

• Body: ASTM A536 Nodular Cast Iron
• Cover: ASTM A536 Nodular Cast Iron
• Spindle: ASTM AISI 420 Stainless Steel
• Slide: EPDM covered nodular cast iron
• Gasket: EPDM
• O-Ring: EPDM

Application Areas (As Provided)

NRS valves are widely used in fire protection systems installed underground, particularly in areas not affected by freezing. They are ideal for zone isolation and main line control in fire water distribution networks.

Approvals & Certifications (As Provided)

• UL Listed
• ULc Listed
• FM Approved

Operational Benefits

• Reliable shut-off and zone control
• Suitable for underground fire protection systems
• Durable materials for long service life
• Compatible with post indicator supervision
• Compliance with international fire protection standards