What Is a Full-Bore Ball Control Valve?
A full-bore ball control valve has a ball bore close to the pipe inside diameter and opens or closes with a quarter turn (90 degrees). Unlike conventional on-off ball valves, it is designed for control: splined ball-to-shaft and shaft-to-actuator connections, double power-end bushings and trunnion guiding reduce lost motion and improve dynamic control performance.
The valve family has three configurations. The drilled attenuator version for gas service reduces aerodynamic noise and pipeline vibration. The attenuator version for liquid service limits cavitation and the associated noise. The unattenuated full-bore version offers almost no restriction to flow in automated bypass, batch, monitor and emergency shutoff services.
The attenuator does not belong to the sealing assembly: the seal wipes the ball surface rather than the attenuator. This design extends seal life and gives reliable shutoff even in attenuated versions. Because body, ball, shaft and bearings are shared by the three configurations, spare parts management is simpler and the same valve platform can serve different duties.
Working Principle and Attenuator Design
The valve operates as the actuator rotates the ball by up to 90 degrees. The ball position determines the flow area and therefore the flow rate.
1. Rotary motion: The actuator turns the ball through the splined shaft. Splined connections and trunnion guiding transfer even small position changes to the ball without play.
2. Changing flow area: As the ball rotates, the opening between inlet and ball bore changes. The characteristic is modified equal percentage without attenuator, and modified linear or modified equal percentage with attenuators.
3. Energy dissipation: In attenuated versions the flow is split through many holes in the ball. Distributing the pressure drop in a controlled way reduces noise in gas and cavitation effects in liquid.
4. Shutoff: In the closed position a pressure-assisted, self-adjusting seal is pressed against the ball. The seal is held in a stainless steel carrier and shuts off at full rated pressure drop.
Three configurations
The gas attenuator version can achieve up to 20 dBA of acoustical attenuation in a single stage, and a two-stage option exists. The liquid attenuator version is offered with one, two or three stages, and a Kc of 1.0 can be reached depending on service conditions. The attenuator can be active across the full ball rotation, or a characterized attenuator can be matched to the service.
Seal arrangement and flow direction
Standard flow direction is forward, with the seal upstream. Single-seal designs are used only for one-directional flow and shutoff. With dual seals, the gas and unattenuated versions can be used for flow in both directions; bidirectional shutoff and double block-and-bleed duty require the dual-seal design. The liquid attenuator version should be used in one flow direction for effective cavitation protection.
Key Features
· Integral drilled attenuator: An attenuator built into the ball controls noise and vibration in high pressure drop liquids and gases.
· Splined connections: Splined ball-to-shaft and shaft-to-actuator connections with double power-end bushings reduce lost motion.
· Heavy-duty trunnions: Ball trunnions are designed for long service life and reduced maintenance time.
· Pressure-assisted seal: A self-adjusting seal held in a stainless carrier; Class IV standard, Class VI optional shutoff.
· Easy seal replacement: The ball seal can be exchanged without removing the actuator.
· Shared components: Body, ball, shaft and bearings are common to all three configurations.
· Low-emission packing option: In addition to standard PTFE packing, a live-loaded packing system with improved sealing and guiding is available.
· Low profile: A compact design makes piping easier.
Technical Specifications
Values show the standard configuration range of the valve family.
Parameter | Technical data |
Valve type | Full-bore, trunnion-guided ball control valve; up to 90 degrees rotation |
Configurations | Drilled attenuator for gas, drilled attenuator for liquid, unattenuated full bore |
Sizes | 6, 8, 10, 12, 16, 20 and 24 in nominal sizes (NPS) |
Connection | CL150, CL300 or CL600 raised-face flanges compatible with ASME B16.5; optional CL900 and RTJ flanges |
Pressure-temperature | Consistent with CL150, CL300 or CL600 ratings per ASME B16.34 |
Max. shutoff pressure drop (38 °C) | CL150: 20 bar (285 psi); CL300: 51 bar (740 psi); CL600: 103 bar (1480 psi) |
Flow characteristic | Modified linear with high-density attenuator; modified equal percentage with characterized attenuator or without attenuator |
Leakage class | Class IV, optional Class VI per ANSI/FCI 70-2 / IEC 60534-4 (single and dual seal) |
Seal material / temperature | Standard POM: -29 to 82 °C; optional PTFE/PEEK: -73 to 260 °C |
O-ring | Standard nitrile: -45 to 100 °C; up to 232 °C evaluated per project |
Noise attenuation (gas) | Up to 20 dBA in a single stage; two-stage option |
Cavitation (liquid) | One-, two- or three-stage attenuator; Kc of 1.0 depending on service |
Standard materials | LF2 carbon steel body; WCC or low-temperature carbon steel ball; 17-4 stainless attenuator and shaft |
Packing | PTFE (standard); live-loaded low-emission packing (optional) |
Sour service | Optional materials compliant with NACE MR0175-2002 |
Pressure and temperature limits and applicable standard limits must not be exceeded; values are confirmed per project.
Key Advantages
· Low pressure loss: An almost unobstructed flow path when fully open benefits pipeline and pump energy.
· Noise and cavitation control: Gas- or liquid-specific attenuator options on the same body.
· Control and shutoff combined: Control performance together with shutoff up to Class VI and double block-and-bleed capability.
· Long seal life: The seal wipes the ball, not the attenuator; the pressure-assisted design maintains tightness over time.
· Lower maintenance cost: Shared parts, seal replacement without actuator removal and heavy-duty trunnions.
Applications
Full-bore ball control valves are used where high capacity and control capability are both required.
Gas services
Control points on high pressure drop gas lines where noise and pipeline vibration must be reduced.
Pump bypass and pipeline take-off
Limiting cavitation at pump bypass and pipeline take-off points with the liquid attenuator version.
Bypass, batch and monitor services
Automated control with the low flow resistance of the unattenuated full-bore version.
Emergency shutoff
Fast, tight shutoff with a full-bore ball valve in automated emergency shutoff service.
Selection Criteria
The right configuration depends on fluid phase, pressure drop and shutoff requirement.
Fluid and pressure drop
· Gas or liquid; noise or cavitation risk
· Normal and maximum pressure drop
· Number of attenuator stages required
Sealing and direction
· One- or two-directional flow and shutoff
· Double block-and-bleed requirement
· Required leakage class (IV or VI)
Mechanics and materials
· Pressure class and flange type
· Seal and O-ring material for process temperature
· Sour service requirement
· Actuator mounting side (right/left) and emission requirements
Standards and Leakage Classes
Full-bore ball control valves are configured in line with the following standards.
Standard / approval | Scope and description |
ASME B16.34 | Pressure-temperature classes (CL150, CL300, CL600). |
ASME B16.5 | Compatibility of raised-face flange connections. |
ANSI/FCI 70-2 / IEC 60534-4 | Shutoff leakage classification: Class IV, optional Class VI. |
NACE MR0175-2002 | Optional materials for sour service and sour crude applications. |
Availability of options must be confirmed for size and pressure class.
The TLY Enerji Solution Approach
Selecting a control valve for large lines means balancing capacity against control accuracy. For full-bore ball control valve requests, TLY Enerji first establishes the noise and cavitation profile of the service, then determines attenuator type and number of stages, seal arrangement and pressure class.
In pump bypass, pipeline take-off or emergency shutoff services, compatibility with the control system and safety logic is addressed as well. Actuator sizing, mounting side, packing choice and spare parts strategy are clarified at quotation stage, and commissioning and site support are included in the project plan. Where existing lines suffer from noise or vibration, the technical feasibility of switching to an attenuated design is reported separately.
· Noise and cavitation assessment
· Attenuator and seal arrangement selection
· Actuator sizing
· Spare parts planning
· Commissioning coordination
Frequently Asked Questions
How does a full-bore ball control valve differ from an on-off ball valve?
On-off ball valves are usually designed to operate fully open or fully closed. In a full-bore ball control valve, splined shaft connections, double power-end bushings and trunnion guiding reduce lost motion, so accurate and repeatable control is possible in intermediate positions. Attenuator options also limit noise and cavitation during throttling.
What is an attenuator and what does it do?
An attenuator is a drilled structure integrated into the ball. It divides the flow into many small passages and distributes the pressure drop in a controlled way. In gas service it can reduce aerodynamic noise by up to 20 dBA in a single stage; in liquid service it limits cavitation and the resulting vibration. Two- or three-stage attenuators can be used where needed.
When is a dual-seal design required?
Single-seal designs are suitable only for one-directional flow and shutoff. If bidirectional shutoff or double block-and-bleed is required, the dual-seal design must be selected. The gas attenuator and unattenuated versions can handle flow in both directions with dual seals, while the liquid attenuator version should run in one direction for cavitation protection.
Which leakage classes are available?
Single- and dual-seal composition seal constructions provide Class IV as standard and Class VI as an option according to ANSI/FCI 70-2 / IEC 60534-4. The shutoff class should be evaluated together with seal material, process temperature and shutoff pressure drop.
What is the maximum shutoff pressure drop?
At 38 °C the maximum allowable shutoff pressure drop for single- and dual-seal designs is 20 bar for CL150, 51 bar for CL300 and 103 bar for CL600. These values may be further limited by the body pressure-temperature rating, and body and seal material limits must be considered at higher temperatures.
How is the seal material selected?
The standard POM seal can be used from -29 to 82 °C. For a wider temperature range, a PTFE/PEEK seal works from -73 to 260 °C. Standard nitrile O-rings suit -45 to 100 °C; higher temperatures require a project-specific evaluation.