Zero Velocity Valve

Effective Surge Protection for Pumping Pipelines

Zero Velocity Valve is a surge protection device used in cross-country water supply and irrigation pipelines. It consists of a spring-loaded closing disc enclosed in an outer shell, designed to stop reverse flow in case of pump failure.

Working Principle

• A well-designed dome is located behind the disc to streamline flow during normal operation
• The disc is mounted on a central shaft and supported by guide rods
• Springs are designed such that the valve remains fully open at ~25% of design velocity
• During pump shutdown, the disc starts closing with reduction in velocity
• The valve fully closes when velocity approaches zero

Thus, the upstream water column is arrested at zero velocity before any reverse flow is established, preventing water hammer.

Bypass & Pressure Control

• Valve is provided with one or multiple bypass arrangements
• Maintains pressure balance across the disc
• Prevents vacuum formation on downstream side
• Bypass area is generally not less than 10% of nominal bore area

Design & Construction Features

• Outer shell with internally fixed dome creating a streamlined annular passage
• Spring-loaded central closing disc with guide support
• Available in barrel type or flanged end connections
• Designed for automatic operation without external power

Objectives of Zero Velocity Valve

• To arrest forward moving water column at zero velocity
• To prevent reverse flow in pipeline during pump failure
• To eliminate water hammer effect
• To maintain pressure balance across the valve
• To avoid vacuum formation in downstream pipeline

Key Advantages

• Controlled closing characteristics
• Low head loss due to streamlined design
• No external power or control system required
• Reliable and fully mechanical operation