What is a Stop Valve?

Stop valves, also known as isolation valves or shut-off valves, are designed to completely stop the flow of fluid through a pipeline. These valves provide a tight seal when closed and are typically used for maintenance, emergency shutdowns, or to isolate sections of a piping system.

Primary Function

Stop valves are used to completely shut off fluid flow in a pipeline. They are operated either fully open or fully closed and are not designed for flow regulation or throttling purposes.

Working Principle

The operation of stop valves involves:

• Linear motion of a closure element (disc, plug, or ball)
• Manual or automated operation via handwheel, lever, or actuator
• Positive sealing when in closed position
• Full bore opening when in open position

Key Components

• Valve body
• Closure element (disc, plug, or ball)
• Stem and stem nut
• Handwheel or actuator
• Seating surfaces
• Packing gland

Types of Stop Valves

Gate Valves

Use a wedge-shaped gate that moves perpendicular to flow

Globe Valves

Feature a plug-type disc that moves parallel to flow

Ball Valves

Utilize a rotating ball with a bore through it

Plug Valves

Employ a cylindrical or tapered plug with a passage

Common Applications

• Main water supply lines
• Steam systems
• Process piping isolation
• Emergency shutdown systems
• Equipment isolation for maintenance
• Fuel line shutoff

Materials of Construction

• Bronze and brass for general service
• Cast iron for water applications
• Stainless steel for corrosive services
• Forged steel for high-pressure applications
• PVC and CPVC for chemical services

Selection Considerations

• Pressure rating requirements
• Temperature limitations
• Fluid compatibility
• Operation frequency
• Space constraints
• Leakage requirements

Installation Guidelines

• Install in accessible locations
• Ensure proper orientation
• Follow manufacturer's torque specifications
• Use appropriate gaskets and seals
• Consider flow direction requirements

Maintenance Requirements

• Regular operation to prevent seizing
• Stem lubrication when required
• Packing gland adjustment
• Seat and disc inspection
• Leak testing