Ball Valves Explained

Introduction to Ball Valves

Ball valves are a type of quarter-turn valve which use a hollow, pivoting, and perforated ball to control flow through it. They are prized for their durability, excellent shutoff capabilities, and ease of operation, making them one of the most common valve types in a wide range of industrial, commercial, and residential applications. This infographic explores the fundamentals of ball valves, from their working principle to selection criteria.

Working Principle: Simple & Effective

The operation of a ball valve is straightforward:

Quarter-Turn Operation: A 90-degree turn of the handle or actuator rotates the ball.
Port Alignment:
- When the ball’s hole (port) is in line with the flow, the valve is OPEN, allowing fluid to pass.
- When the ball is rotated 90 degrees so the hole is perpendicular to the flow path, the valve is CLOSED, blocking the flow.
Sealing: Soft seats (e.g., PTFE, PEEK) or metal seats press against the ball to create a tight seal in the closed position.

This quick action makes them ideal for on/off applications, though some specialized ball valves (V-port) can be used for throttling.

OPEN

CLOSED

Key Components of a Ball Valve

Valve Body

The main pressure-containing structure that houses all internal parts and connects to the pipeline.

Ball

A spherical closure element with a bore (port) through its center. Rotates to control flow.

Stem

Connects the actuator/handle to the ball, transmitting the rotational force to open or close the valve.

Seats

Rings that create a seal between the ball and the valve body. Made from resilient materials (soft seats) or metal (metal seats).

Stem Packing

Seals around the stem to prevent leakage to the atmosphere. Usually made of materials like PTFE or graphite.

Actuator/Handle

The mechanism used to operate the valve, e.g., a manual lever, gear operator, or a pneumatic/electric actuator.

Main Types of Ball Valves

Based on Port (Bore) Size:

Full Port (Full Bore): Bore diameter is the same as the connecting pipe’s inner diameter. Offers minimal flow restriction.

Reduced Port (Reduced Bore): Bore diameter is smaller than the pipe’s ID (typically one pipe size smaller). More economical, higher flow restriction.

V-Port: Ball has a V-shaped port. Allows for more precise flow control (throttling) characteristics.

Based on Body Construction:

One-Piece: Body is a single cast or forged piece. Ends are typically threaded or socket weld. Difficult to repair.

Two-Piece: Body consists of two pieces joined by threads or bolts. Allows for some maintenance.

Three-Piece: Body has three pieces (center body and two end caps) held by bolts. Allows for easy in-line maintenance and seat/seal replacement.

Top Entry: Ball and seats can be accessed from the top of the valve body without removing the valve from the pipeline. Ideal for welded-in valves.

Welded Body: Fully welded construction for critical applications to eliminate potential leak paths. Not repairable in-line.

Based on Ball Design:

Floating Ball: Ball is held in place by the compression of two elastomeric seats. The upstream pressure pushes the ball against the downstream seat for sealing. Common for smaller sizes and lower pressures.

Trunnion Mounted Ball: Ball is supported by a trunnion (short shaft extensions) at the top and bottom. Seats are spring-loaded and push against the ball. Used for larger sizes and higher pressures, as it reduces operating torque.

Actuation Methods

Ball valves can be operated in various ways:

🖐️

Manual (Lever/Gear)

Simple lever for smaller valves, gear operator for larger valves to reduce operating effort.

💨

Pneumatic

Uses compressed air to drive an actuator (piston or diaphragm type). Fast acting.

⚡

Electric

Uses an electric motor and gearbox. Good for remote control and precise positioning.

💧

Hydraulic

Uses hydraulic fluid pressure. Provides high torque for very large or high-pressure valves.

Common Actuation Methods Usage (Illustrative)

Advantages & Disadvantages

Advantages

Quick quarter-turn on-off operation.
Tight sealing with low torque.
Compact and lightweight compared to other valve types.
Cost-effective and low maintenance.
Wide range of materials for diverse applications.
Good durability and long service life.
Can handle slurries and liquids with solids (depending on design).

Disadvantages

Poor throttling characteristics for standard port valves (V-port improves this).
Susceptible to cavitation in some high-velocity liquid applications.
Soft seats can be damaged by abrasive particles or high temperatures.
Not ideal for highly viscous fluids that can clog the ball cavity.
Rapid closing can cause water hammer in liquid lines.

Common Materials of Construction

Valve Body

Brass, Bronze
Carbon Steel (e.g., ASTM A216 WCB, A105)
Stainless Steel (e.g., ASTM A351 CF8M/316, CF8/304)
Alloy Steels (e.g., Chrome Moly)
Plastics (PVC, CPVC, PP, PVDF)

Ball

Stainless Steel (most common)
Chrome-plated Carbon Steel
Alloy 20, Hastelloy, Monel
Ceramic
Plastics (for plastic valves)

Seats

PTFE (Teflon®) – common, wide chemical resistance
Reinforced PTFE (RPTFE) – for higher pressures/temperatures
PEEK – for high temperature/pressure, abrasive service
Delrin®, Nylon
Metal (e.g., Stellite overlay) – for severe service

Typical Applications

Ball valves are used extensively across numerous industries:

Oil & Gas (Upstream, Midstream, Downstream) Chemical & Petrochemical Processing Water & Wastewater Treatment Power Generation Food & Beverage Industry Pharmaceutical Manufacturing Pulp & Paper Residential & Commercial Plumbing HVAC Systems

Key Selection Considerations

Fluid Properties: Type of fluid (liquid, gas, slurry), corrosiveness, viscosity, presence of solids.
Pressure & Temperature: Operating and design conditions. Determines material and pressure class.
Flow Rate & Cv: Required flow capacity and acceptable pressure drop.
Shutoff Class: Required tightness of seal (e.g., ANSI/FCI 70-2 Class VI for bubble-tight).
End Connections: Threaded, socket weld, butt weld, flanged.
Materials of Construction: Compatibility with fluid and environment.
Actuation Method: Manual or automated, speed of operation.
Industry Standards & Certifications: API, ASME, ISO, NACE requirements.
Maintenance Requirements: Ease of repair, availability of spare parts.
Cost: Initial purchase cost vs. total cost of ownership.

The Versatile Flow Controller

Ball valves are a remarkably versatile and reliable solution for flow control in a multitude of applications. Their simple yet effective design, combined with a wide array of types, materials, and actuation methods, ensures their continued prominence in piping systems globally. Understanding their characteristics and proper selection is key to ensuring efficient and safe system operation.