Ball Valves

A ball valve is a quarter-turn valve that controls flow by means of a rotary ball having a bore through it. The ball is rotated 90 degrees (a quarter turn) by a handle or actuator to either allow flow (when the bore is aligned with the pipe) or stop flow (when the bore is perpendicular to the pipe). Ball valves are widely used for shut-off applications because they offer quick, reliable shut-off even after long periods of disuse, and they are generally very durable and can maintain their sealing integrity.

Types of Ball Valves

By Body Construction:

One-Piece Ball Valve: Simplest and cheapest, body is cast or forged as a single piece. Cannot be disassembled for maintenance. For low-demand applications.

Two-Piece Ball Valve: Consists of two pieces (main body and an end connector). Can be disassembled for cleaning or service, but usually requires removal from the pipeline.

Three-Piece Ball Valve: Consists of three pieces (main body and two end caps). Allows the central body section (containing the ball and seats) to be removed for maintenance without disassembling the entire pipeline. Ideal for applications requiring frequent service.

Split Body Ball Valve: The main body is split into two or more parts, allowing easy access to internal components.

Top Entry Ball Valve: Allows internal components to be removed from the top without removing the valve from the line.

Welded Body Ball Valve: Body parts are welded together, making it impossible to disassemble but suitable for high-pressure or critical applications where leakage must be absolutely avoided.

By Bore Type:

Full Port (Full Bore) Ball Valve: The bore through the ball is the same size as the pipeline's internal diameter, allowing unrestricted flow and minimal pressure drop. Ideal for pigging (cleaning pipeline with sphere).

Reduced Port (Reduced Bore) Ball Valve: The bore through the ball is smaller than the pipeline's internal diameter, resulting in a slight pressure drop. More compact and cost-effective.

V-Port Ball Valve: Has a "V" shaped opening in the ball, allowing for more precise throttling and flow control.

Multi-Port Ball Valve (3-Way, 4-Way): Has multiple ports (L-port or T-port configurations) to divert or mix flow paths.

By Operating Mechanism:

Manually Operated Ball Valves: Operated by a lever or handwheel.

Actuated Ball Valves: Operated by pneumatic, electric, or hydraulic actuators for remote control or automation.

Floating Ball Valve: The ball is held in place by the compression of the two seats, allowing it to "float" slightly and press against the downstream seat for a tight seal.

Trunnion Mounted Ball Valve: For larger sizes and high pressures, the ball is supported by trunnions (shafts) at the top and bottom, reducing torque requirements and seat wear.

Applications in Various Industries:

Oil & Gas Industry: Upstream, midstream, and downstream applications for flow control, shut-off, and isolation in pipelines, refineries, and petrochemical plants. Requires high-pressure, high-temperature, and corrosion-resistant designs.

Chemical & Pharmaceutical Industries: Handling corrosive chemicals, slurries, and high-purity fluids. Stainless steel or plastic valves are common.

Water & Wastewater Treatment: Controlling water flow in municipal water supply, sewage systems, and treatment plants. Brass, bronze, or PVC valves.

HVAC Systems: Shut-off valves in heating, ventilation, and air conditioning systems.

Food & Beverage Industry: Sanitary ball valves (often polished stainless steel) for hygienic applications, preventing contamination.

Manufacturing: General industrial flow control in various processes.

Technology:

Seat Materials: Advanced polymers (PTFE, PEEK, Delrin) or metal seats for specific temperature, pressure, and chemical compatibility.

Fire-Safe Design: For hazardous applications, designed to prevent external leakage even if soft seats are destroyed by fire.

Blow-out Proof Stem: Design feature where the stem is inserted from the inside of the valve, preventing it from being expelled under pressure.

Antistatic Devices: To prevent static electricity buildup in flammable fluid applications.

Live-Loaded Stem Packing: Springs apply constant compression to stem packing for a tighter, longer-lasting seal.

NACE Compliance: For corrosive service (oil and gas) to resist sulfide stress cracking.

Material Selection Considerations:

Body Materials:

• Brass: Good for general purpose water, air, non-corrosive liquids; durable and economical. Not suitable for high temperatures or aggressive chemicals.
• Carbon Steel (WCB, LCB): For higher pressure and temperature applications than brass, good strength, but susceptible to corrosion in some environments unless coated.
• Stainless Steel (304, 316, 316L): Excellent corrosion resistance, hygienic properties, suitable for food, pharmaceutical, chemical, and marine applications. 316L for superior corrosion resistance against chlorides.
• Ductile Iron: More economical than steel for some applications, good strength.
• PVC (Polyvinyl Chloride), CPVC, PP (Polypropylene), PVDF: For corrosive chemicals, water, and low-temperature applications where metal is not suitable. Offers good chemical resistance but lower pressure/temperature ratings.

• Ball: Same material as the body or sometimes plated (e.g., chrome-plated brass or steel) for surface hardness and corrosion resistance.
• Stem: Stainless steel for corrosion resistance and strength.
• Seats: PTFE (Teflon) is very common due to excellent chemical resistance and low friction. Other polymers like RPTFE (reinforced PTFE), Delrin (acetal), Nylon, PEEK for higher temperatures/pressures. Metal seats for very high temperatures or abrasive slurries.
• Seals & Gaskets: PTFE, Graphite, Viton, EPDM, Buna-N (NBR), selected based on fluid, temperature, and pressure.