What are the advantages of trunnion ball valves over floating ball valves?

Trunnion ball valves offer lower operating torque, superior sealing reliability, enhanced safety features, and are ideal for critical service applications. They provide consistent sealing across wide pressure ranges and require smaller, more energy-efficient actuators.

When should I choose a trunnion ball valve?

Choose a trunnion ball valve for high pressures (ASME Class 600+), large valve sizes (NPS 6"+), critical service applications, frequent cycling operations, and when you need to minimize operating torque and actuator costs.

What is a trunnion Ball Valve - general-valve.com

What Is a Trunnion Ball Valve? The Ultimate Guide

Discover the superior engineering and applications of trunnion ball valves in high-pressure industrial environments

Professional trunnion ball valve assembly and cross-section diagram

Industrial Equipment Engineering Guide Technical Analysis

In the world of industrial fluid control, selecting the right valve is critical for safety, efficiency, and reliability. Among the myriad of options, the Trunnion Mounted Ball Valve stands out as a robust solution for high-pressure, large-diameter, and critical service applications. Trunnion mounted ball valves are manufactured in accordance with major industry standards such as ASME, API, and ISO, ensuring quality and reliability. But what exactly is it, and why is it often the superior choice over more common valve types?

This ultimate guide will walk you through everything you need to know. We’ll explore its fundamental working principle, compare it directly to its main alternative, and detail the features, applications, and selection criteria that make it indispensable in demanding industries. Trunnion ball valves are available in an extensive range of designs, materials, and sizes to suit a variety of industrial applications.

Trunnion Ball Valve 101: Definition & Core Working Principle

To understand its value, we must first grasp its unique design. Trunnion ball valves are a specific type of quarter turn valves used for precise flow control.

A Clear Definition of the Trunnion Ball Valve

A trunnion ball valve is a type of quarter-turn valve that uses a solid, rotating ball to start or stop flow. Its defining characteristic is its method of ball support: the ball is supported by two short shafts, called trunnions, at the top and bottom. These trunnions are fixed in the valve body, anchoring the ball in place and allowing it to rotate while absorbing the pressure load from the fluid.

How It Works (Illustrated)

Floating Ball Valve

Picture a standard floating ball valve, where the ball is held in place only by the two downstream and upstream seats, “floating” in the flow. When pressure is applied, the entire ball is pushed against the downstream seat to create a seal.

Trunnion Design

The ball has an integral stem at the top and a pivot (the trunnion) at the bottom. These two points are held by bearings within the valve body. Because the trunnions absorb the force from the line pressure, the ball is not pushed into the downstream seat.

Floating Ball Valve Design

Trunnion Mounted Ball Valve Design

Key Insight: Instead, the seats are spring-loaded and float towards the anchored ball to create a tight, reliable seal on both the upstream and downstream sides. This fundamental design difference is the source of all its advantages.

The Fundamental Difference: Trunnion vs. Floating Design

Detailed comparison between floating ball valve and trunnion ball valve designs

Design Type Sealing Method Ball Position

Floating Ball Valve Line pressure pushes the ball into the downstream seat to seal The ball “floats”

Trunnion Ball Valve Line pressure is absorbed by the trunnions. Spring-loaded seats move towards the fixed ball Ball is anchored by trunnions

This distinction becomes critically important as pressure and valve size increase. The trunnion design is particularly suitable for high pressure applications due to its robust construction and reliable sealing.

Trunnion Ball Valve vs. Floating Ball Valve: An In-Depth Comparison

For engineers and procurement managers, choosing between a trunnion and a floating ball valve is a common decision. The use of trunnion ball valves is often preferred in high-pressure and demanding environments due to their superior performance. Here’s a detailed breakdown to make that choice clear.

Structural Design: Fixed Ball vs. Floating Ball

As explained, the trunnion’s fixed-ball design provides a stable pivot point. The floating ball design relies on the process flow to create a seal. This makes the trunnion design inherently more stable and robust, especially in large-diameter valves where the weight of the ball and the force of the pressure are immense.

For safe handling and installation, 6-inch and larger valves are typically equipped with lifting lugs, making them suitable for bigger, more complex valve applications.

Torque & Actuator Requirements: Why Trunnion Valves Are More Energy-Efficient

This is a major advantage. In a floating valve, high pressure creates significant friction between the ball and the downstream seat. Overcoming this friction requires high operational torque, which in turn necessitates a larger, more expensive, and more power-hungry actuator.

In a trunnion valve, the pressure load is handled by the low-friction trunnion bearings. The only force the actuator needs to overcome is the friction of the spring-loaded seats and the stem seals. This results in significantly lower operating torque, allowing for smaller, more cost-effective, and energy-efficient actuators.

Trunnion ball valves can act through manual, electric, or pneumatic actuators, enabling precise control in fluid handling systems.

Sealing Performance: How They Differ Under High Pressure

The trunnion valve provides a superior and more reliable seal in high-pressure scenarios. Because the seats are spring-loaded, they create a tight primary seal regardless of pressure fluctuations. In contrast, a floating ball valve’s seal quality is dependent on the line pressure; at very low pressures, it may not seal as effectively.

The advanced design of trunnion ball valves enhances valve performance by providing reliable, bubble-tight shutoff even in extreme conditions.

Cost Considerations: Initial Investment vs. Long-Term Operational Costs

Initial Investment (CAPEX)

Trunnion ball valves are generally more expensive than floating ball valves of the same size and material due to their more complex construction.

Long-Term Operational Costs (OPEX)

The tables turn here. The smaller actuator requirement reduces initial cost. The lower torque reduces energy consumption over the valve’s lifetime.

Furthermore, the robust design leads to fewer maintenance interventions and more efficient long-term operation, as the reduced wear and tear on the seats lead to a longer service life and lower maintenance costs.

Decision Chart: When to Choose a Trunnion Ball Valve

Choose a Trunnion Ball Valve if your application involves:

High Pressures (e.g., ASME Class 600 and above)

Large Valve Sizes (e.g., NPS 6″ and larger)

Critical Service where reliable sealing is non-negotiable

The need to minimize operating torque and actuator size/cost

Frequent cycling where seat wear is a concern

Upstream and downstream sealing requirements (Double Block and Bleed)

Exploring the Core Components & Design Features

The superior performance of a trunnion ball valve comes from its specialized components and features. Trunnion mounted ball valves incorporate advanced design features to ensure superior performance in demanding applications.

Key Component Breakdown: Body, Ball, Seats, and Stem

Detailed breakdown of ball valve components and internal parts

Body

Houses all internal parts. Can be a two-piece, three-piece, or fully welded design.

Ball

The core flow-control element, anchored by the trunnions.

Seats

Rings that seal against the ball. They are typically spring-loaded to ensure constant contact.

Stem

Connects the actuator to the ball to facilitate rotation. It is separate from the ball itself.

Seat Design: Self-Relieving Seats (SRS) vs. Double Piston Effect (DPE)

This is a critical design choice.

Self-Relieving Seats (SRS)

In this design, if pressure in the body cavity exceeds the upstream line pressure, the upstream seat is pushed away from the ball, venting the excess pressure back into the upstream line. This is a standard safety feature.

Double Piston Effect (DPE) Seats

Both the upstream and downstream seats can seal against pressure from either direction. This means if the upstream seat fails, the downstream seat will still seal. This design traps pressure in the body cavity and is used for applications requiring double isolation.

Core Safety Features: Anti-Static, Fire-Safe Design, and Anti-Blowout Stem

Anti-Static Device

A spring-loaded pin ensures electrical continuity between the ball, stem, and body, preventing static electricity buildup that could cause a spark—critical in flammable media.

Fire-Safe Design (e.g., API 607)

If a fire occurs and the primary soft seats are destroyed, a secondary metal-to-metal seat provides emergency sealing to prevent external leakage.

Anti-Blowout Stem

The stem is designed with a shoulder that is inserted from inside the valve body, making it impossible for high pressure to push it out of the valve.

Double Block and Bleed (DBB): Achieving True Zero-Leakage Isolation

Many trunnion valves are configured as DBB valves. This means they have two independent seats that seal simultaneously, with a bleed or vent port in the body cavity between them. This allows operators to bleed off pressure from the cavity to verify that both seats are providing a tight seal, offering a proven method for positive isolation during maintenance.

Emergency Sealant Injection System

For the most critical services, trunnion valves can be equipped with sealant injection fittings at the stem and seat areas. If a seat or stem seal is damaged and begins to leak, a special sealant can be injected to provide a temporary, emergency seal until maintenance can be performed.

Key Advantages and Industry Applications

The combination of these features delivers clear benefits across various industries. Trunnion ball valves are widely used in both offshore and onshore oil and gas operations, as well as in cryogenic and high-temperature applications.

Why Choose a Trunnion Valve? 4 Core Advantages

Lower Operating Torque

Reduces actuator size, cost, and energy consumption.

Superior Sealing Reliability

Provides a tight, consistent seal across a wide range of pressures, including both high and low pressures.

Enhanced Safety and Durability

Features like anti-blowout stem, fire-safe design, and reduced seat wear contribute to a safer and longer service life.

Ideal for Critical Service

The DBB capability and robust design make it the standard for applications where leakage is not an option.

Typical Industry Applications (With Case Studies)

Oil & Gas Pipeline Applications

High-Pressure Industrial Applications

Oil & Gas (Upstream, Midstream, & Downstream)

Trunnion valves are the workhorse of pipelines. In long-distance natural gas or crude oil pipelines, their ability to handle high pressure over large diameters with low torque is essential for main line isolation.

Chemical & Petrochemical Processing

In processes involving hazardous or corrosive media, the reliable sealing and safety features (like DBB and fire-safe design) of trunnion valves are paramount for preventing dangerous leaks.

Power Generation

Used in high-pressure steam or cooling water systems where reliable shutoff is needed to isolate equipment for maintenance.

Long-Distance Pipelines

For both liquid and gas transmission, trunnion valves are the default choice for mainline block valves due to their reliability and suitability for actuation.

Trunnion Ball Valve Types and Specifications

When specifying a trunnion valve, you’ll need to consider the following.

Technical specifications and design details of trunnion mounted ball valves

Types by Body Construction: Two-Piece, Three-Piece, and Fully Welded

Two-Piece/Three-Piece

Bolted body construction allows for easier maintenance and repair of internal components.

Fully Welded

Offers maximum structural integrity and eliminates potential leak paths from body flanges. It is lighter than bolted body designs and is preferred for buried pipeline applications.

Types by End Connection: Flanged, Butt-Weld, and Threaded

Flanged (RF, RTJ)

The most common type, allowing for easy installation and removal from a pipeline.

Butt-Weld (BW)

Welded directly into the pipeline, creating a permanent, leak-free connection ideal for high-pressure and high-temperature services.

Threaded (NPT)

Typically used only for smaller-sized valves in lower-pressure applications.

Understanding Key Technical Parameters

Size & Pressure Range

Size Range: Typically from NPS 2″ up to NPS 60″ and beyond

Pressure Class/Rating: From ASME Class 150 up to Class 2500 and API 15000

Materials & Standards

Body Materials: Carbon Steel (A216 WCB), Stainless Steel (A351 CF8M)

Design Standards: API 6D, ASME B16.34, ISO 17292, API 598

How to Properly Select and Maintain Your Trunnion Ball Valve

Making the right choice and ensuring long-term performance requires a systematic approach.

A 5-Step Guide to Selecting the Right Trunnion Valve

1

Define Application Requirements

What is the fluid, pressure, temperature, and required shutoff class?

2

Determine Technical Specifications

What are the required valve size (NPS), pressure class, and design standards (e.g., API 6D)?

3

Select Material Compatibility

Choose body, trim, and seal materials that are compatible with the process fluid and operating conditions.

4

Choose Body and End Connections

Decide between a bolted or welded body and the appropriate end connections (flanged, BW) for your installation.

5

Specify Actuation and Controls

Determine the required operating torque and select an appropriate actuator (pneumatic, electric, hydraulic) and control system.

Installation and Operation Best Practices

Ensure pipelines are properly aligned to avoid stressing the valve body.

Clean the pipeline of debris before installation to prevent damage to the seats.

Operate the valve fully open or fully closed; throttling can cause premature seat wear.

Common Troubleshooting and Routine Maintenance Guide

Regularly Cycle the Valve: For valves that remain in one position for long periods, cycling them periodically can prevent seizure.

Inspect for Leaks: Routinely check the stem packing and body flanges for any signs of external leakage.

Follow Manufacturer’s Guidelines: Adhere to the recommended maintenance schedule, especially for critical service valves with features like sealant injection.

Conclusion: Why Trunnion Valves Are the Premier Choice for High-Pressure and Critical Applications

Professional high-pressure valve applications in industrial settings

The trunnion mounted ball valve is more than just a piece of hardware; it is a feat of engineering designed for the most demanding environments. Its unique trunnion-supported ball design translates directly into lower operating torque, superior sealing performance, and enhanced safety.

While the initial investment may be higher than a floating ball valve, its long-term reliability, lower operational costs, and suitability for critical service make it the undisputed premier choice for high-pressure, large-diameter, and essential isolation applications across the globe.

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Navigating the specifications for a trunnion ball valve can be complex. If you need assistance selecting the perfect valve for your application or require a customized solution, our team of experts is here to help.

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Design Type	Sealing Method	Ball Position
Floating Ball Valve	Line pressure pushes the ball into the downstream seat to seal	The ball “floats”
Trunnion Ball Valve	Line pressure is absorbed by the trunnions. Spring-loaded seats move towards the fixed ball	Ball is anchored by trunnions

Floating Ball Valve

Trunnion Design

Body

Ball

Seats

Stem

Self-Relieving Seats (SRS)

Double Piston Effect (DPE) Seats

Anti-Static Device

Fire-Safe Design (e.g., API 607)

Anti-Blowout Stem

Lower Operating Torque

Superior Sealing Reliability

Enhanced Safety and Durability

Ideal for Critical Service

Oil & Gas (Upstream, Midstream, & Downstream)

Chemical & Petrochemical Processing

Power Generation

Long-Distance Pipelines

Two-Piece/Three-Piece

Fully Welded

Flanged (RF, RTJ)

Butt-Weld (BW)

Threaded (NPT)

Size & Pressure Range

Materials & Standards

Define Application Requirements

Determine Technical Specifications

Select Material Compatibility

Choose Body and End Connections

Specify Actuation and Controls

Get Expert Consultation