Шаровой кран: 7 типов, материалы и руководство по выбору

Quick answer: A ball valve is a quarter-turn valve that uses a drilled spherical closure member to start or stop flow. Industrial ball valve selection depends on pressure, temperature, medium, bore size, body construction, seat material, shutoff requirement, actuation and the applicable project standard.Ball valves are widely used in oil and gas, chemical processing, water treatment, power generation, LNG, marine and general industrial systems. Their compact operation and clear open-or-closed position make them practical for isolation, but one design cannot cover every service. High pressure gas, abrasive slurry, cryogenic liquid and corrosive chemicals require different valve structures and materials.

How Does a Ball Valve Work?

The valve contains a ball with a bore through its center. When the bore aligns with the pipeline, fluid passes through. Turning the stem by 90 degrees moves the solid side of the ball across the flow path and closes the valve.

Soft seats can provide tight shutoff in compatible services. Metal-seated designs are considered where temperature, abrasion or operating conditions exceed the limits of polymer seats. Ball valves are primarily used for on-off isolation. Throttling requires a design such as a V-port or segmented ball valve that is engineered for control duty.

7 Common Ball Valve Types

Ball valve type	How it is built	Типичные области применения	Main selection point
Floating ball valve	The ball is supported by the seats and moves slightly under pressure.	Small and medium sizes for general isolation	Seat load and operating torque increase with size and pressure.
Trunnion-mounted ball valve	Upper and lower supports hold the ball while the seats move toward it.	Large diameter, high pressure and pipeline service	Seat design, cavity relief, injection fittings and double-block requirements
Top-entry ball valve	Internal components can be accessed through the upper body opening.	Systems where in-line maintenance is important	Maintenance clearance, body sealing and approved service procedure
Side-entry ball valve	The body is assembled from two or three sections along the pipeline axis.	Oil, gas, petrochemical and pipeline isolation	Body-joint construction, bolting and maintenance plan
Three-piece ball valve	A center body section is clamped between two end pieces.	Process lines requiring convenient cleaning or seat replacement	End connection, body bolting and assembly control
V-port or segmented ball valve	A shaped opening provides a defined relationship between travel and flow.	Modulating flow control	Cv or Kv, characteristic, pressure drop, cavitation and actuator accuracy
Multi-port ball valve	An L-port, T-port or other drilled ball connects three or more flow paths.	Flow diversion, mixing and process routing	Port pattern and every permitted handle or actuator position

Floating vs. Trunnion Ball Valve

A floating ball valve uses line pressure to push the ball toward the downstream seat. This arrangement is compact and widely used in smaller sizes. As size and differential pressure increase, seat load and required torque can rise.

A trunnion-mounted ball valve supports the ball mechanically and commonly uses spring-loaded or pressure-assisted seats. This arrangement is often selected for larger sizes and higher pressure pipeline duties. The final decision should consider size, class, pressure direction, shutoff requirement, cavity pressure relief and actuator torque.

Full-Port vs. Reduced-Port Ball Valve

Bore option	Flow passage	Typical reason to select	Check before ordering
Full port	Bore is close to the connected pipe inside diameter.	Lower restriction, pigging or reduced solids accumulation	Actual bore, pig size and end-connection dimensions
Reduced port	Bore is smaller than the connected pipe.	More compact construction where pressure loss is acceptable	Velocity, pressure drop, noise and cleaning requirements

The term “full port” should be verified against the specified standard and manufacturer drawing. A nominal label alone does not confirm that a cleaning pig or inspection tool can pass through the valve.

How Should Ball Valve Materials Be Selected?

Material selection starts with the fluid composition, concentration, contaminants, temperature and pressure. Carbon steel is common in hydrocarbon and general industrial service. Stainless steel may be used for water, chemicals and corrosive environments. Duplex and super duplex stainless steels are considered for chloride-rich media, while nickel alloys, Monel and titanium are used only after compatibility and project requirements are reviewed.

Every wetted component matters. The body may be compatible while the ball, stem, seat, seals, packing or fasteners are not. Sour gas service can also require material hardness control and compliance with the specified NACE or ISO sour-service document.

Soft-Seated or Metal-Seated Ball Valve?

PTFE, reinforced PTFE, PEEK and other polymer seats can provide low torque and tight shutoff within their approved pressure, temperature and chemical limits. The exact limit depends on the compound, filler and valve construction.

Metal-seated ball valves are considered for higher temperatures, abrasive particles, erosive flow or services where soft seats would be damaged. Hardfacing, coating thickness, ball finish, seat contact and leakage acceptance must be stated in the datasheet. “Metal seated” does not automatically mean zero leakage.

7 Ball Valve Selection Checks

Define the medium. State the chemical composition, phase, solids, water content, corrosive components and cleaning media.
Provide design conditions. Include design and operating pressure, temperature, differential pressure and credible upset conditions.
Select the valve function. Distinguish isolation, emergency shutdown, control, diversion, pigging and double-block requirements.
Confirm bore and ends. Specify full or reduced bore, flange facing, weld ends, threaded ends and face-to-face dimensions.
Set leakage requirements. Identify the applicable seat-test direction, test medium, acceptance criteria and shutoff differential pressure.
Review safety features. State fire-safe, antistatic, blowout-resistant stem, cavity-relief and fugitive-emission requirements where applicable.
Size the actuator. Provide maximum differential pressure, required operating time, power supply, fail position, controls and environmental conditions.

Which Standards Apply to Industrial Ball Valves?

The applicable standard depends on the industry and valve construction. Спецификация API 6D addresses pipeline and piping valves. API 608 covers metal ball valves for petroleum, petrochemical and industrial applications. ISO 17292 covers metal ball valves for petroleum, petrochemical, natural gas and related industries.

ASME B16.34 covers pressure-temperature ratings, materials, testing, marking and other requirements for flanged, threaded and welding-end valves. Projects may also specify separate standards for face-to-face dimensions, flanges, fire testing, emissions, inspection and sour service. List every required edition in the purchase specification.

What Information Should a Ball Valve RFQ Include?

RFQ item	Information required
Service	Medium, composition, solids, pressure and temperature
Valve design	Floating or trunnion, entry type, bore, body construction and flow direction
Size and rating	DN or NPS, PN or ASME Class and pressure-temperature basis
Материалы	Body, ball, stem, seat, seals, packing, bolting and coating
Связи	RF, RTJ, butt weld, socket weld or threaded ends
Эксплуатация	Lever, gearbox, pneumatic, electric or hydraulic actuator
Compliance	Design, testing, fire-safe, emissions, sour-service and documentation requirements

Common Ball Valve Selection Mistakes

Selecting a valve from size and pressure class alone
Using a standard soft seat above its approved temperature range
Assuming every full-port valve is piggable
Using an ordinary on-off ball valve for continuous throttling
Ignoring trapped cavity pressure and thermal expansion
Specifying “zero leakage” without a test standard or acceptance criterion
Sizing the actuator from normal pressure instead of the maximum operating differential

Часто задаваемые вопросы

What is the main advantage of a ball valve?

A ball valve provides quarter-turn operation, a clear position indication and reliable isolation when its design and materials match the service.

Can a ball valve control flow?

A standard ball valve is mainly intended for isolation. A V-port or segmented ball valve can be engineered for flow control using the required Cv or Kv, characteristic and actuator package.

Which is better, a floating or trunnion ball valve?

Neither design is universally better. Floating designs are common in smaller sizes, while trunnion-mounted valves are often selected for larger sizes and higher differential pressure. Project conditions decide the choice.

Can a ball valve be used for steam?

It can be used only when the valve pressure-temperature rating, seat, seals, packing and body materials are approved for the steam conditions. Do not rely on pressure class alone.

What causes a ball valve to leak?

Possible causes include seat wear, debris, chemical attack, temperature damage, ball-surface damage, incorrect assembly and operation outside the rated conditions.

Discuss Your Ball Valve Requirements

WDL Valve supplies industrial ball valves in carbon steel, stainless steel, duplex stainless steel and selected special alloys. Explore the WDL ball valve range, the дуплексный шаровой кран, the top-entry cryogenic ball valve guide и side-entry cryogenic ball valve guide.

For technical review, send the medium, size, pressure class, temperature, materials, connections, shutoff requirement and actuation details through the WDL Valve contact page.

Автор: Wong WP, Sales Manager, Xiamen WDL Valve Co., Ltd.