Segmented Ball Valves

What Is a Segmented Ball Valve?

A segmented ball valve is a control valve type that brings together globe-valve robustness and rotary-valve efficiency. Instead of a full sphere, the valve contains only the ball segment that forms the sealing surface. A contoured V-notch on the leading edge of the segment opens the flow area gradually as the ball rotates and produces a modified equal percentage characteristic.

As the ball turns, the shearing movement between the V-notch and the ball seal cuts fibers and solids in the fluid and prevents the valve from clogging. The seal also wipes the ball surface continuously, so scale and sludge cannot build up. For this reason segmented ball valves are used not only with clean gases and liquids but also with steam and fibrous slurries.

A one-piece body eliminates the leak paths associated with gaskets in two-piece bolted bodies and improves pressure boundary integrity. The seal assembly can be replaced at the valve inlet without removing the actuator or taking the ball out of the body. The same valve family can be combined with many rotary actuators and manual operators for both throttling and automated on-off service, which allows standardization on one valve type across different control points.

How Does a V-Notch Ball Control Flow?

The valve is operated by a rotary actuator connected through a splined shaft, and the ball rotates up to 90 degrees. In standard installations the flow approaches the convex side of the ball.

1.      Actuator motion: A diaphragm or piston rotary actuator turns the ball through the splined shaft. The actuator can be field-reversed between push-down-to-close and push-down-to-open.

2.      Opening the V-notch: As the ball turns, the V-notch passes the seal line and the flow area opens gradually from small to large; this geometry gives the modified equal percentage characteristic.

3.      Shearing and wiping: The shearing motion between notch and seal cuts fibers and solids; because the seal wipes the ball surface, deposits do not form.

4.      Shutoff: In the closed position the seal rests on the ball surface. Depending on the seal type, shutoff ranges from Class VI to the flow ring configuration.

Seal options

Composition seals provide Class VI shutoff in forward flow. A flat metal seal offers Class IV in forward flow on 3–12 in valves. The heavy-duty metal seal suits bidirectional flow and gives Class IV shutoff, while reverse flow is limited to a pressure drop of 6.9 bar. The high-temperature heavy-duty seal provides Class III. The flow ring configuration is for bidirectional services where no seal is needed and leakage in the order of 5% of full-open capacity is acceptable.

Severe service trims

A rotary attenuator reduces cavitation and noise effects in both liquid and gas service. An anti-cavitation trim is used on 4–20 in valves in liquids with severe cavitation, and a Kc of 1.0 can be reached at extreme service conditions. For gas and steam, a noise-attenuating trim gives up to 20 dBA of acoustical attenuation depending on service conditions; this trim is not suitable for liquid service.

Key Features

·         Non-clogging shearing action: The shearing effect between V-notch and seal gives smooth operation with fibrous and solids-laden fluids.

·         High straight-through capacity: An unrestricted flow path offers high capacity in gas, steam, liquid and slurry services.

·         One-piece body: No leak paths from bolted body gaskets; better pressure boundary integrity.

·         Easy maintenance: The seal assembly is changed at the valve inlet without removing the actuator or the ball; no special tools are required.

·         Common trim: Trim components are shared between flanged and flangeless series, reducing spare parts inventory.

·         Low-flow option: Small-notch ball on 1 in valves for precise control of very low flows; stainless, cobalt alloy and ceramic ball options.

·         Low emissions: Live-loaded packing systems are designed to keep emissions below the 100 ppm limit.

·         Easy installation: Flanged bodies leave no exposed line flange bolting, reducing alignment and installation time.

Technical Specifications

The table summarizes the configuration range of the segmented ball control valve family.

Maximum shutoff pressure and allowable pressure drop vary with seal type and material; confirm per project.

Key Advantages

·         Reliable with difficult fluids: Non-clogging control of fibrous and solids-laden fluids.

·         High capacity: Higher flow capacity and a more compact design than a globe valve of the same line size.

·         Wide seal portfolio: From Class VI composition seals to metal seals operating up to 427 °C.

·         Low maintenance: The wiping action prevents deposits and seal replacement is quick.

·         Adaptable to severe service: Cavitation and noise trims can be added without losing rotary-valve efficiency.

Applications

Segmented ball control valves are used in process industries for throttling or on-off service with very different fluids.

Fibrous slurry services

Non-clogging control of fibrous and solids-laden slurries thanks to the shearing action and straight flow path.

Steam and gas

Steam and gas control lines; with noise-attenuating trim at noise-critical points.

Liquid process lines

General liquid control; with anti-cavitation trim on lines with severe cavitation risk.

Sour service

Sour liquid and gas applications with materials meeting NACE MR0175 and MR0103 requirements.

Segmented Ball Valve Selection Criteria

The performance of a segmented ball valve depends largely on seal and trim selection.

Fluid and seal

·         Composition or metal seal according to process temperature

·         Required shutoff class

·         Need for reverse flow and bidirectional shutoff

·         Abrasive particle content

Body and connection

·         Pressure class (CL150 / CL300 / CL600) and flange standard

·         Flanged or flangeless body

·         Face-to-face dimension (ISA or ASME short)

·         Body material and sour service

Control and trim

·         Flow range and required rangeability

·         Need for a small-notch at very low flow

·         Cavitation or noise risk

·         Need for wear-resistant coatings

Actuation

·         Actuator mounting and closing direction

·         Fail position

·         Digital valve controller and diagnostics

·         Packing according to emission requirements

Standards and Compliance

Segmented ball control valves are configured in line with the following standards.

Packing emission performance is defined on the basis of the 100 ppm limit.

Rotary Control Valve Selection with TLY Enerji

A segmented ball valve provides a long-lasting solution in many services when matched with the right seal and trim, whereas the wrong seal quickly leads to leakage and loss of performance. During selection TLY Enerji evaluates process temperature, flow direction, solids and fiber content and shutoff expectations together.

At points with cavitation or noise risk, the need for severe service trims is analyzed, and actuator, digital valve controller and packing selection are aligned with project requirements. For existing control points suffering from plugging or wear, alternative configurations are proposed with their technical justification. The temperature and pressure limits of the selected seal, trim and packing combination are clearly stated in the project documentation at quotation stage.

·         Seal and trim selection

·         Cavitation and noise assessment

·         Actuator and controller selection

·         Improvement proposals for existing valves

·         Quotation and technical documentation

Frequently Asked Questions

Why does a segmented ball valve not clog?

As the ball rotates, a shearing movement occurs between the V-notch and the seal. This movement cuts fibers and solids in the fluid and prevents them from accumulating in the valve. The seal also wipes the ball surface continuously, so no scale or sludge layer forms. The straight-through flow path reduces dead zones where solids could collect.

Which shutoff class does a segmented ball valve provide?

The shutoff class depends on the seal type. Composition seals give Class VI in forward flow, a flat metal seal Class IV, the heavy-duty metal seal Class IV in bidirectional flow, and the high-temperature heavy-duty seal Class III. The flow ring configuration is not intended for tight shutoff.

Can a segmented ball valve be used in reverse flow?

In standard installations the flow approaches the convex side of the ball. For services with flow in both directions, the heavy-duty metal seal or the flow ring configuration is used. With the heavy-duty metal seal, reverse flow is limited to a pressure drop of 6.9 bar.

What is a small-notch?

A small-notch is a ball with a small notch used on 1 in valves for precise control of very low flows. Chrome-plated stainless steel, solid cobalt alloy and ceramic ball options are available. The ceramic design is limited to 93 °C, while the other materials follow the limits of the standard construction.

Can segmented valves be used on lines with cavitation or high noise?

Yes. In liquid service a rotary attenuator or, for severe cavitation, an anti-cavitation trim can be added; in gas and steam service a noise-attenuating trim can be used. The anti-cavitation trim is offered on 4–20 in valves and the noise trim on 4–12 in valves. The noise trim must not be used in liquid service.

How do I choose between a flanged and a flangeless body?

Flanged bodies leave no exposed line flange bolts, making installation and alignment easier. Flangeless bodies are clamped between line flanges and are more compact; the CL600 series is available flangeless in all sizes and flanged in 2–8 in. Pressure class, piping standard and maintenance access should guide the choice.