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Views: 0 Author: Site Editor Publish Time: 2026-09-07 Origin: Site
Choosing between a floating ball valve and a trunnion ball valve affects sealing, operating torque, actuator size, service life, and project cost. Although both use a rotating ball for quarter-turn isolation, their internal support arrangements differ. In a floating ball valve, the ball is held by the seats and can move toward the downstream seat under pressure. In a trunnion-mounted ball valve, fixed supports carry much of the ball load and help reduce operating torque. This guide explains floating ball valve vs trunnion ball valve differences, advantages, limitations, applications, installation, maintenance, and selection factors for industrial piping systems.
Table of Contents
A floating ball valve uses line pressure to push the unsupported ball against the downstream seat.
A trunnion ball valve uses fixed supports to carry the ball load and reduce operating torque.
Floating designs are often practical for small- and medium-size lines and simpler isolation duties.
Trunnion designs are commonly selected for larger sizes, higher pressures, frequent actuation, and demanding pipeline service.
The floating design can provide strong pressure-assisted sealing, but seat loading and torque may increase as size and pressure rise.
The trunnion design normally offers more predictable torque, but its additional components can increase initial complexity and maintenance considerations.
Neither design is automatically better; the correct choice depends on pressure, temperature, media, line size, shutoff, operating cycles, and project standards.
A floating ball valve is a quarter-turn isolation valve in which the ball is held between two seats but is not supported by a lower trunnion. The stem connects to the top of the ball and transfers the actuator’s rotational movement. The ball can move slightly within the body, especially in the direction of the downstream seat.
When the valve is closed and pressure is applied from the upstream side, the pressure difference pushes the ball toward the downstream seat. This pressure-assisted movement increases contact between the ball and seat and helps create a tight shutoff. The higher the differential pressure, within the valve’s design limits, the greater the seating force may become.
This arrangement has a relatively direct internal structure. It can provide effective sealing with fewer support components, which is one reason a floating ball valve is widely used in small- and medium-diameter process lines, utility systems, gas service, and general industrial isolation.
However, the same pressure-assisted action that helps sealing also increases friction between the ball and seats. As valve size, pressure, or differential pressure rises, the force needed to rotate the ball can increase significantly. For this reason, floating designs require careful torque analysis before manual or actuated operation is specified.
Didtek’s floating ball valve product is a metal-to-metal design with an extended stem. The listed product is a 2-inch, 150LB valve with a CF8 body, F304 with Ni55 metal seating, a temperature range of -26°C to 420°C, ISO 17292 design, and API 6FA fire safety. These details show that a floating ball valve is not limited to light-duty, low-temperature service; the actual capability depends on its materials, seat construction, pressure class, and design qualification.
A trunnion ball valve uses a fixed ball supported by a lower trunnion, upper stem, or other bearing arrangement. The ball is not free to move significantly toward the downstream seat. Instead, the trunnions carry much of the ball’s weight and the forces generated by pressure and operation.
Because the ball is supported, the seats do not need to carry the full mechanical load of the ball. Spring-loaded or pressure-energized seats move toward the ball to maintain contact and sealing. The resulting design generally requires less torque than a floating ball valve of a similar size and pressure rating.
Lower operating torque is particularly valuable for large valves and automated systems. It can allow the use of a smaller actuator, reduce the energy required for each operating cycle, and make emergency isolation or remote operation easier to manage. Trunnion ball valves are therefore common in oil and gas pipelines, gas processing, petrochemical plants, LNG systems, power facilities, and other critical industrial services.
The trunnion ball valve category includes different body, seat, bore, pressure, and actuation configurations. A trunnion-mounted design can be supplied as a side-entry or top-entry valve, with soft or metal seats, and with manual, electric, pneumatic, or hydraulic operation.
The presence of trunnions does not by itself determine the valve’s complete performance. Buyers still need to review the body material, seat material, bore, pressure-temperature rating, stem construction, cavity relief, fire-safe design, end connections, and applicable standards.
Both valve types use the same basic quarter-turn principle. A ball with a through-bore rotates inside the valve body. When the bore is aligned with the pipeline, the valve is open. When the ball turns 90 degrees, the solid side of the ball blocks the flow path.
The major difference is how the ball is supported and how the seats create shutoff.
In a floating design, the stem rotates the ball while the ball is held between the upstream and downstream seats. When the valve is closed, the upstream pressure acts on the ball and moves it toward the downstream seat. This creates a pressure-assisted seal.
At low or moderate differential pressure, the seats and their preload provide much of the initial sealing force. As differential pressure increases, the ball may press more firmly against the downstream seat. This can be effective for shutoff, but it also increases friction and operating torque.
In a trunnion design, the ball rotates around a fixed axis supported by trunnions or bearing surfaces. The seats are pushed toward the ball by springs, line pressure, or a combination of both. Since the ball is supported, pressure forces are distributed through the trunnion structure rather than transferred entirely to the seats and stem.
This arrangement reduces the torque required to rotate the ball, particularly in larger valves. It can also reduce seat loading during operation. The seats must still be designed to provide the required shutoff under both high and low pressure conditions.
Both floating and trunnion ball valves can be designed with:
Full or reduced bore
Soft or metal seats
Two-way or multi-way flow paths
Side-entry, top-entry, or fully welded bodies
Manual or actuated operation
Fire-safe, anti-static, and blowout-proof stem features
Double block and bleed or cavity pressure relief functions, when specified
The internal support design is only one part of the complete valve specification. Two valves with different support arrangements may both be suitable for the same medium, but one may be more appropriate for the required size, pressure, operating cycle, or maintenance strategy.
The following table summarizes the main differences in a floating ball valve vs trunnion ball valve comparison.
Comparison Factor | Floating Ball Valve | Trunnion Ball Valve |
|---|---|---|
Ball support | Ball is held by the stem and seats | Ball is supported by fixed trunnions or bearings |
Sealing action | Line pressure pushes the ball toward the downstream seat | Spring- and pressure-energized seats move toward a supported ball |
Operating torque | Can increase substantially with size and pressure | Usually lower and more predictable for larger valves |
Typical size range | Often selected for small- and medium-size lines | Commonly selected for medium- and large-size lines |
Actuator requirement | May require a larger actuator as pressure rises | Often permits lower actuator torque requirements |
Construction | Relatively simple internal arrangement | More support and bearing components |
Seat loading during operation | Can be higher because the ball moves against the seat | Often lower because the ball is fixed |
Pressure-assisted shutoff | Strong downstream seat loading | Depends on seat energizing and pressure direction |
Maintenance access | Often simple, depending on body construction | May include more components but can support specialized access designs |
Typical applications | General process isolation, gas, water, oil, and moderate-size lines | Pipelines, oil and gas, LNG, petrochemical, high-pressure and large-size service |
A floating valve is not automatically unsuitable for high pressure, and a trunnion valve is not automatically required for every large line. The correct choice depends on the manufacturer’s design limits and the operating torque calculation.
As size and pressure increase, the ball in a floating design creates greater seat contact force. The resulting torque may require a larger actuator and stronger stem and seat components. A trunnion design carries much of the ball load through its supports, which can make it more practical for larger nominal sizes and higher pressure classes.
For example, Didtek’s listed metal-seated trunnion product is a 2-inch, full-bore, 150LB valve with a WCB body and a stated size range from 2 to 48 inches across the design range. Its listed pressure classes extend from ASME Class 150 to 1500, with a stated temperature range of -29°C to 425°C. These are product-specific details, not universal limits for every trunnion ball valve, but they illustrate how a trunnion platform may be configured for a broad industrial range.
Torque is one of the most important engineering differences. A floating ball valve must overcome the friction caused by the ball pressing against the downstream seat. The torque can vary with differential pressure, seat material, temperature, media, and operating frequency.
A trunnion ball valve normally has lower friction-related torque because the supported ball does not have to move against the seats in the same way. This can simplify actuator selection, especially when the valve must be operated remotely or repeatedly.
The actuator should never be selected from valve size alone. The supplier should provide or confirm breakaway torque, running torque, ending torque, minimum operating torque, maximum differential pressure, and the relevant safety factor. Low-temperature, high-temperature, dry-gas, metal-seat, and contaminated-media conditions may change the torque requirement.
Both designs can provide effective isolation when correctly specified. A floating design uses the movement of the ball to increase downstream contact. A trunnion design relies on seat energizing and accurate alignment around a supported ball.
Soft seats may deliver tight shutoff for compatible fluids and temperatures, while metal seats may be selected for high-temperature, abrasive, or severe service. A trunnion-mounted metal-seated valve can be useful where the valve must tolerate wear and repeated operation under demanding conditions. A floating metal-seated valve can also perform effectively when its materials and torque limits are properly matched to the application.
Shutoff performance depends on more than the ball support arrangement. It is affected by seat geometry, surface finish, material compatibility, pressure direction, temperature, contamination, manufacturing tolerances, and testing.
The simpler internal arrangement of a floating valve can make it attractive when initial construction and basic maintenance are priorities. However, repeated seat loading may affect wear if the valve operates frequently or handles abrasive media.
A trunnion valve contains additional support components, bearings, springs, and seat mechanisms. This can increase the number of parts to inspect, but the lower operating torque and controlled ball movement may support a longer service life in larger or more frequently operated systems.
Lifecycle cost should include the valve, actuator, installation, spare parts, inspection, shutdown access, energy use, and expected operating cycles. A valve with a higher purchase price may be more economical if it reduces actuator size, maintenance frequency, or unplanned downtime.
A floating ball valve may be preferred for the following reasons:
Simple and compact internal structure
Effective pressure-assisted shutoff
Often economical for small- and medium-size applications
Fewer support components than a trunnion design
Suitable for manual quarter-turn operation
Available with soft or metal seats for different services
Can be configured for high-temperature or insulated applications when properly designed
The listed Didtek metal-to-metal floating model demonstrates how an extended-stem configuration can be used for high-temperature, abrasive, and insulation-related requirements. The actual product specification should be checked before applying the valve to a particular system.
Potential limitations include:
Operating torque can increase with size and differential pressure
Greater seat friction may affect frequent cycling
Larger actuators may be required in demanding services
Seat wear can become a concern with abrasive or contaminated media
The ball’s movement can increase seat loading during operation
Very large or high-pressure applications may be more efficiently served by a trunnion design
A trunnion ball valve can offer several advantages:
Lower operating torque for many large or high-pressure applications
More stable ball positioning during operation
Reduced mechanical load on the stem and seats
Good compatibility with electric, pneumatic, and hydraulic actuators
Suitable for pipeline isolation and frequent remote operation
Flexible configurations for full bore, reduced bore, metal seats, and double block and bleed
Practical for demanding oil, gas, LNG, petrochemical, and power applications
The WCB metal-seated trunnion ball valve product lists full-bore construction, metal seating, low-torque operation, block and bleed, self-cavity pressure relief, fire-safe design, blowout-proof stem construction, and anti-static design. These functions are useful examples of what buyers may evaluate in a critical industrial valve, but the required features must be confirmed for each project.
Potential limitations include:
More complex construction than a basic floating design
Higher initial purchase cost in some size and pressure ranges
More internal components to inspect or replace
Greater body weight in some configurations
Requires accurate actuator sizing and maintenance planning
May be unnecessary for low-pressure, infrequently operated, small-diameter lines
The purpose of this comparison is not to label one design as universally superior. The right selection is the one that provides the required shutoff, torque, pressure rating, service life, and maintenance access at an acceptable lifecycle cost.
Pressure, line size, and torque are closely related. Treating them as separate purchasing decisions can lead to an incorrectly specified valve or actuator.
The pressure acting across a closed valve affects seat loading and operating torque. A floating ball valve may experience greater torque as the differential pressure pushes the ball more firmly against the downstream seat. A trunnion valve may maintain lower torque because the ball is supported, but its seat springs and pressure-assisted design still need to overcome sealing and friction forces.
The supplier should review both normal and maximum differential pressure. The actuator may need to operate the valve after a long period without movement, when deposits or seat friction have increased.
Full-bore valves have a flow passage close to the connected pipe diameter. They are often selected when low pressure loss, product recovery, or pipeline pigging is important. Reduced-bore valves have a smaller passage and may reduce weight, cost, or overall size, but they can increase velocity and pressure loss.
A trunnion or floating design can be supplied in either full or reduced bore, depending on the product family. Bore selection should be based on process calculations and pipeline cleaning requirements rather than on the support design alone.
The valve’s pressure rating must be checked together with its temperature range. Allowable pressure may decrease as temperature increases, and seat materials may impose a lower practical limit than the metal body.
Relevant questions include:
What are the normal and maximum operating pressures?
What is the maximum differential pressure during opening and closing?
What are the minimum, normal, and maximum temperatures?
Is the medium clean, abrasive, corrosive, toxic, flammable, or cryogenic?
Is the valve soft-seated or metal-seated?
Are thermal cycles, fire exposure, or rapid depressurization expected?
Is the valve installed above ground, underground, offshore, or inside a skid?
Floating designs can require higher breakaway torque than expected, particularly with metal seats, high differential pressure, or low-temperature service. Trunnion designs usually offer a more predictable torque profile, but the actuator still must be sized for the complete operating envelope.
Actuator selection should consider fail-open or fail-closed requirements, air or hydraulic supply pressure, electrical power, emergency shutdown time, environmental protection, manual override, position feedback, and partial-stroke testing where applicable.
Trunnion ball valves are commonly considered for pipeline isolation because they can support large sizes, high pressure classes, automated operation, and long service intervals. Full-bore configurations may be preferred when pipeline pigging or low pressure loss is important.
Floating ball valves can also serve oil and gas applications, especially in smaller branch lines, equipment connections, utility systems, and moderate-size isolation duties. The decision should reflect the actual pressure, size, media, and operating cycles rather than the industry name alone.
Chemical service requires careful attention to corrosion, material compatibility, fugitive emissions, fire safety, and seat performance. Metal-seated valves may be selected for high temperatures or abrasive media, while soft-seated valves may be suitable for compatible chemicals within their temperature and pressure limits.
For process plants, the purchaser may need to specify anti-static construction, blowout-proof stems, fire-safe testing, cavity relief, special alloy trim, or emissions testing. The required features should be recorded in the valve data sheet.
Low-temperature service can cause metals to contract and some seals to lose flexibility. Both floating and trunnion ball valves can be specially designed for cryogenic applications, but a standard ambient-temperature valve should not be used without confirming its low-temperature suitability.
Important considerations include extended bonnet design, low-temperature body and trim materials, seat performance, thermal contraction, insulation clearance, trapped-liquid relief, and cryogenic testing. A project requiring low-temperature operation should be reviewed through the appropriate industrial ball valve range and the specific cryogenic design documentation.
High-temperature steam, boiler feed, fuel, and auxiliary systems may use metal-seated ball valves when rapid isolation and resistance to wear are required. The body, trim, seat coatings, stem packing, actuator, and fire-safe requirements must be checked together.
The floating product referenced above lists a temperature range of -26°C to 420°C and metal seating, but this does not mean every floating valve can operate at those conditions. Product-specific ratings and the process engineer’s requirements must always control the selection.
Floating ball valves are often practical for water, oil, air, gas, and other compatible fluids in small- and medium-size systems. Trunnion valves may be selected for larger water transmission lines, higher pressure systems, or applications requiring motorized operation and lower torque.
In dirty or abrasive service, seat material and flushing provisions may be more important than whether the valve is floating or trunnion mounted. Metal seats, hardfacing, cavity design, and cleaning procedures should be reviewed with the manufacturer.
Correct installation is essential for both valve designs. A well-designed valve can experience early leakage or torque problems if the pipeline is misaligned, contaminated, overstressed, or incorrectly supported.
Before installation:
Confirm the valve tag, size, pressure class, bore, material, and flow direction requirements.
Inspect the body, end connections, stem, actuator, and protective packaging for damage.
Clean the pipeline and remove welding slag, rust, sand, and other debris.
Check that the pipe is properly aligned and independently supported.
Avoid using the valve to correct pipe misalignment.
Confirm flange, gasket, bolt, and face-to-face dimensions.
Verify actuator orientation, control wiring, air supply, and fail position.
Operate the valve according to the manufacturer’s instructions after installation.
Ball valves should normally be installed in the fully open or fully closed position unless the design is specifically intended for control service. Leaving a standard isolation ball valve partially open can produce turbulence, erosion, and seat damage.
Maintenance of a floating ball valve should include inspection of seat leakage, stem seals, packing, handle or actuator connection, body joints, and external corrosion. If operating torque rises, investigate pressure conditions, contamination, seat damage, deposits, and actuator problems before forcing the valve.
Metal-seated floating valves used in abrasive or high-temperature service may require more frequent inspection of the ball and seat surfaces. The inspection interval should be based on service severity and operating history.
Trunnion valve maintenance may include checking seat leakage, stem seals, bearing areas, springs, cavity pressure relief, emergency sealant injection provisions, actuator operation, and position indication. For critical pipeline valves, functional testing and partial-stroke testing may be included in the asset integrity program.
A trunnion valve’s lower operating torque does not eliminate the need for testing. Springs, seats, bearings, seals, and actuators can still degrade due to corrosion, contamination, thermal cycling, or long periods without operation.
Store both valve types in a clean, dry, protected environment. Keep end protectors installed until the valve is ready for connection, and follow the manufacturer’s instructions for lubrication, orientation, preservation, and actuator commissioning.
Before placing the system into service, verify shell and seat testing, line flushing, actuator calibration, limit switch settings, emergency shutdown logic, and any required documentation. Testing should follow the applicable project and manufacturer procedures.
Use the following selection process when deciding between a floating and trunnion configuration.
Confirm whether the valve is for routine isolation, emergency shutdown, pipeline sectioning, equipment isolation, flow diversion, or a special double block and bleed arrangement. A valve intended for frequent emergency operation may need a different actuator and testing plan from one operated once a year.
Provide the fluid name, pressure, temperature, flow rate, viscosity, solids content, corrosive components, toxicity, and flammability. Include normal, minimum, maximum, and upset conditions.
Consider a floating ball valve when the line is relatively small or moderate in size, the operating frequency is limited, and pressure-assisted sealing is suitable. Consider a trunnion ball valve when the line is larger, pressure is higher, actuation is frequent, or torque must be reduced and controlled.
These are starting points, not fixed rules. The manufacturer should confirm the design through pressure, torque, seat, and lifecycle calculations.
Choose soft or metal seating according to temperature, chemical compatibility, abrasion, fire safety, leakage requirements, and thermal cycling. In severe service, hardfacing or special alloys may be needed to resist erosion and wear.
Specify full or reduced bore, flange standard, butt-welded or threaded ends where applicable, face-to-face dimensions, pressure class, and installation orientation. Full-bore valves may be important for pigging or pressure-loss control.
Confirm manual, electric, pneumatic, or hydraulic operation. Define the required emergency position, shutdown time, fail action, manual override, position feedback, locking device, anti-static design, blowout-proof stem, cavity relief, and fire-safe requirements.
Depending on the project, the specification may reference API 6D, ISO 17292, ASME B16.34, API 607, API 6FA, API 598, NACE MR0175/ISO 15156, or other standards. Each standard addresses a different aspect of design, testing, materials, fire safety, or service suitability. The exact edition and scope should be confirmed before ordering.
Compare the purchase price, actuator size, installation, spare parts, inspection, expected operating cycles, maintenance access, energy consumption, and replacement cost. A trunnion valve may have a higher initial price but provide lifecycle advantages in a large, automated, or frequently operated system. A floating valve may be the more efficient choice for a smaller and less demanding line.
The main difference is ball support. A floating ball valve has a ball held by the stem and seats, allowing it to move toward the downstream seat under pressure. A trunnion ball valve has a ball supported by fixed trunnions or bearings, which reduces movement and usually lowers operating torque.
Neither design is universally better. A trunnion ball valve is often more suitable for larger, higher-pressure, or frequently actuated systems. A floating ball valve may be more economical and practical for smaller or moderate-size isolation duties. The correct choice depends on actual process data and valve sizing.
A floating ball valve may be suitable for small- and medium-diameter pipelines, general process isolation, gas, water, oil, and other compatible fluids. It is especially practical when the pressure and operating torque remain within the design limits and the valve will not be used for continuous throttling.
A trunnion ball valve is often considered for large line sizes, high-pressure service, pipeline isolation, oil and gas facilities, LNG systems, petrochemical plants, and applications requiring frequent or remote actuation. Its supported ball can reduce torque and actuator requirements.
In many comparable applications, a trunnion ball valve has lower operating torque because its fixed supports carry much of the ball load. The actual torque still depends on pressure, seat material, temperature, media, bore, lubrication, and operating conditions.
Yes, a floating ball valve can be designed for high-temperature service when the body, ball, seats, packing, stem, and extended-stem arrangement are suitable. The specific pressure-temperature rating and seat materials must be confirmed from the manufacturer’s data sheet.
They can be suitable when configured with appropriate metal seats, hardfacing, materials, and flushing or cleaning provisions. Abrasive service can damage any valve if the seat, ball, and flow velocity are not properly matched to the medium.
Both can provide tight shutoff when correctly designed and maintained. Floating valves use pressure-assisted ball movement, while trunnion valves use pressure- or spring-energized seats around a supported ball. Leakage performance also depends on seat materials, surface finish, temperature, media, and testing.
Standard floating and trunnion ball valves are primarily isolation valves. Continuous throttling can cause turbulence, vibration, erosion, and seat damage. If flow regulation is required, use a control valve or a ball valve specifically designed and sized for control service.
Provide the medium, line size, pressure class, normal and maximum pressure, temperature range, flow rate, bore requirement, end connection, seat material, body material, actuation method, shutdown time, installation environment, applicable standards, and required inspection or documentation. This information allows the supplier to compare floating and trunnion options accurately.
The floating ball valve vs trunnion ball valve decision is primarily a question of support structure, seat loading, operating torque, size, pressure, and service demands. A floating ball valve relies on pressure-assisted movement of the ball toward the downstream seat and can provide a compact, practical, and economical solution for many small- and medium-size isolation applications. A trunnion ball valve uses fixed supports to stabilize the ball and reduce torque, making it a strong option for larger pipelines, higher pressure classes, automated operation, and demanding industrial service.
The most reliable selection process begins with the medium, pressure, temperature, line size, operating frequency, shutoff requirements, actuator, and applicable standards. Seat and trim materials are equally important, particularly for high-temperature, abrasive, corrosive, fire-risk, or cryogenic applications. Buyers should also compare installation, inspection, spare parts, and lifecycle costs rather than focusing only on the initial valve price.
Didtek provides both floating ball valve and trunnion ball valve configurations for different industrial requirements. By matching the valve design to the actual process conditions, engineers and purchasing teams can select a reliable isolation solution with appropriate sealing performance, actuator compatibility, and service life.
