1 Introduction

If you work with industrial pipelines—oil & gas, petrochemical, refining, power generation—you’ve probably come across trunnion ball valves more times than you can remember. But there’s one question buyers still ask all the time: “Are trunnion ball valves bidirectional?” It sounds simple, yet the answer carries huge implications for safety, flow control, and long-term reliability. In this guide, you’ll walk through everything you need to know: how the valve works, how bidirectionality really functions, where directional flow matters, and how choosing the right manufacturer (like GOTEB) helps avoid costly installation mistakes.

2 Understanding the Basics: What ls a Trunnion Ball Valve?

Before we go any further, let’s slow down and talk about trunnion meaning.
In engineering, a trunnion is a mechanical support that holds a rotating component in place. Think of it like the hinge of a door—but for a valve.

So, what is a trunnion ball valve?
It’s a trunnion mounted ball valve where the ball is fixed in position by trunnions at the top and bottom, while the seats move to create a tight seal. This design dramatically reduces operating torque and enhances sealing performance in both high-pressure and large-diameter pipelines.

And if you compare it with a floating-ball design, you’ll immediately notice the difference: the ball in a trunnion system doesn’t shift under pressure. The seats do the work.

This detail becomes extremely important when evaluating whether trunnion ball valves are bidirectional.

3 So… Are Trunnion Ball Valves Bidirectional?

Here’s the straight answer you’ve been waiting for:
Yes, most trunnion ball valves are bidirectional — but not all.

The majority of trunnion mounted ball valve designs are engineered to seal both upstream and downstream, meaning they can handle flow in either direction. This is what pipeline engineers mean when they discuss “are ball valves bidirectional” in general.

But, wait—there’s a nuance.
Some trunnion valves include self-relieving seats, which are designed to release upstream overpressure. These are typically unidirectional, and they require correct installation based on a marked flow arrow.

In other words… don’t just assume the valve you’re buying is fully bidirectional. You want to know exactly what design you’re getting.

4 Why Bidirectionality Matters for Buyers

If you’re sourcing valves for a pipeline—especially high-pressure lines—you know installation mistakes are expensive. A bidirectional valve gives you:

• More flexibility during installation

• Fewer risks of flow reversal issues

• Simpler maintenance procedures

• Reduced downtime due to directional failures

• Lower risk of seat damage if flow occasionally reverses

Imagine this common scenario:
You’re installing a 24-inch, Class 600 oil pipeline. Everything looks correct… until the startup team notices that the seat relief is facing the wrong direction. Now your shutdown schedule is blown, and the budget takes a hit. All because the valve wasn’t bidirectional.

That’s why buyers like you deserve clarity, especially when dealing with trunnion ball valve manufacturers across global supply chains.

5 How Trunnion Ball Valve Design Affects Bidirectionality

Let’s dig into the engineering a bit. You don’t need to be a valve designer—you just need to understand what affects the flow direction.

5-1 The Key Trunnion Ball Valve Parts That Define Flow Direction

Here are the components that matter:

• Ball (fixed and supported by trunnions)

• Upper and lower trunnions

• Spring-loaded seats

• Body cavity

• Seat insert materials (PTFE, Nylon, Devlon, PEEK, metal seat, etc.)

• Self-relieving mechanism (only in certain designs)

Some valves are purely double-sealing. Others are single-sealing with cavity relief.

5-2 Two Major seat Types:

Double-Block Double-Isolation (True Bidirectional)

This design uses two independent seating surfaces. Flow direction does not matter.
These are the valves most buyers hope to get.

Self-Relieving Seats (Typically Unidirectional)

These automatically relieve cavity pressure to one side.
If installed backward, the valve will not seal properly on reverse flow.

Below is a simple comparison table you can use when reviewing technical sheets:

As a buyer, knowing which seat design you’re dealing with protects you from installation disasters.

6 How to ldentify Whether Your Trunnion Valve ls Bidirectional

Even without being a valve expert, you can spot clues.
Here’s what you check:

• Look for a flow-direction arrow (arrow means unidirectional).

• Review the datasheet under the section “Seat Type.”

• Ask your manufacturer whether the valve uses single-piston or double-piston seats.

• Check the body cavity relief design.

• Confirm the ball valve open close direction is standard quarter-turn clockwise/CCW.

And remember this insider tip that suppliers rarely tell you:
When a manufacturer uses cheaper seat designs, they often avoid mentioning flow direction completely.

If you’re ever unsure, reputable manufacturers like GOTEB will provide clear documentation and testing data.

7 Case Example: Gas Pipeline Flow Reversal Incident

A mid-sized natural gas operator (let’s call them “Company A”) installed a set of trunnion ball valves assuming they were bidirectional. The supplier lacked clear documentation, and the installation contractor didn’t notice the small directional arrow on the body.

During commissioning, flow was reversed for a pressure-test bypass.
Almost immediately, one valve failed to seal.

Result?

• 16 hours of unplanned shutdown

• Emergency replacement of the valve

• Over $50,000 in losses

The cause?
Unidirectional self-relieving seats installed backward.

Lessons like this are why this topic matters—especially for procurement teams.

8 Why Trunnion Ball Valves Are Often Preferred in Industry

You’re not buying a valve to admire it. You’re buying it because you want a solution that:

• reduces torque

• lasts a long time

• handles high pressures

• maintains sealing performance

• reduces downtime

• supports pipeline safety

Trunnion valves deliver on all of these.

Here’s a quick reference table comparing floating vs trunnion valve selection:

As a procurement professional, you’ll likely find trunnion valves a better long-term investment for high-demand applications.

9 Conclusion

So, are trunnion ball valves bidirectional? In most cases, yes—but only if the design uses double-sealing seats and no internal self-relieving mechanism. As a buyer, you’re responsible for verifying whether your valve is truly bidirectional or a unidirectional ball valve that requires specific installation. Understanding this prevents costly shutdowns, flow failures, and safety risks. If you’re sourcing valve components or complete OEM solutions, GOTEB gives you reliability you can trust. With precision-engineered valve balls and advanced manufacturing capabilities, GOTEB trunnion ball valves deliver the durability, sealing performance, and consistency your projects demand. Ready to upgrade your supply chain? Partner with GOTEB today and experience confidence in every valve.

10 FAQs

1. Is a trunnion mounted ball valve always bidirectional?
Most are, but valves with self-relieving seats are unidirectional. Always check for a flow arrow.

2. What’s the difference between a floating ball valve and a trunnion ball valve?
A floating ball moves with pressure; a trunnion-supported ball stays fixed and offers lower torque.

3. How do I know the ball valve open close direction?
Most trunnion valves follow standard quarter-turn operation: open (parallel), close (perpendicular).

4. Can a bidirectional valve be used in high-pressure gas?
Yes—especially double-piston seat trunnion designs used in pipeline operations.

5. Why choose GOTEB as a supplier?
Because GOTEB provides precision-made valve balls, advanced materials, and consistent quality trusted by global OEMs.