Jun.28.2025
Struggling with valve selection? The wrong choice can lead to leaks, high operating costs, and even dangerous failures. Let's make sure you pick the right one for your system.
Choose a floating ball valve for smaller, low-pressure pipelines. Use a trunnion mounted ball valve for high-pressure services and large-diameter pipes. The trunnion design provides extra mechanical support, ensuring a reliable seal and lower operating torque under heavy loads.
Over my 15 years in this industry, I've seen this question come up countless times. A client like Jacky, designing complex industrial boiler systems, can't afford a mistake here. The choice between a floating and a trunnion ball valve isn't just about price; it's about safety, reliability, and long-term performance. The good news is that the decision is straightforward once you understand the core differences. Let's break down the details so you can choose with confidence and avoid any future headaches.
Confused by valve mechanics? Choosing the wrong design can cause high torque and seat damage. It’s important to understand how each one creates a seal before you decide.
The main difference is how the ball is supported. In a floating valve, the ball is held by the valve seats and floats against the downstream seat to seal. In a trunnion valve, the ball is anchored by a top stem and a bottom trunnion.
Let’s look at this more closely. In a floating ball valve, the ball is literally "floating" between two seats. When the valve is closed, the upstream pressure pushes the ball firmly against the downstream seat. This force creates the seal. This simple design is very effective and cost-efficient for smaller sizes and lower pressures.
A trunnion ball valve works differently. The ball has an extra shaft, or "trunnion," at the bottom and is connected to the stem at the top. These two points anchor the ball in place. It doesn't move with the flow pressure. Instead, the pressure helps push the spring-loaded seats against the stationary ball to create the seal. This mechanical anchoring makes a huge difference. Because the ball is supported, the operating torque is much lower, especially under high pressure.
Here is a simple table to show the differences:
| Feature | Floating Ball Valve | Trunnion Mounted Ball Valve |
|---|---|---|
| Ball Support | Held in place by two seats | Supported by a stem and a bottom trunnion |
| Sealing Action | Upstream pressure pushes the ball into the downstream seat | Pressure helps push spring-loaded seats against the ball |
| Operating Torque | Higher, increases with pressure and size | Lower, much more stable under high pressure |
| Typical Size | Generally up to 10 inches | Typically 2 inches and larger, common for large sizes |
| Common Use | Low to medium pressure applications | High-pressure, critical, and large-diameter services |
Are you worried about valve failure in a high-pressure line? Using a standard floating valve in a demanding application is a risk. Trunnion valves are built for these exact situations.
You should use a trunnion ball valve in high-pressure systems, large-diameter pipelines (usually above 10 inches), and critical process applications. Its design is safer and more reliable for services handling heavy loads, like in the oil and gas or power generation industries.
During my time at Fleyenda, I’ve worked with many engineers on projects where the stakes are high. For someone like Jacky, who manages EPC projects for industrial boilers, choosing the right valve is critical for system integrity. Here are the key situations where I always recommend a trunnion ball valve:
High-Pressure Service: This is the most common reason. In my experience with Chinese factories, valves for Class 600LB, 900LB, and higher are almost always trunnion-mounted. The fixed ball and supported seats handle the immense force without binding, which prevents high torque and potential seal damage.
Large Pipe Sizes: As a rule of thumb, we use trunnion valves for sizes 10 inches and larger. Imagine the force on a 24-inch ball in a high-pressure line. A floating design would require a massive actuator to operate and put extreme stress on the seats. The trunnion design solves this problem completely.
Critical and Automated Services: Trunnion valves often come with a Double Block and Bleed (DBB) feature. This allows you to bleed pressure from between the seats to verify a tight seal, which is essential for safety. Their low and predictable torque also makes them ideal for automated or actuated systems, as you can use a smaller, more cost-effective actuator.
Wait, is a "float valve" the same as a "floating ball valve"? Absolutely not. This very common mix-up can cause major confusion and lead to ordering the completely wrong part.
A ball valve is a shutoff valve that uses a rotating ball to control flow in a pipe. A float valve is a different device entirely; it's a mechanical level controller that automatically opens or closes to fill a tank, like the one in a toilet cistern.
I remember a project manager early in my career who kept asking for a "float valve" for a natural gas pipeline. He thought it was just another name for a floating ball valve. We caught the mistake before it caused a problem, but it shows how important clear terms are.
Let’s be very clear on this:
Here’s a comparison to make it simple:
| Feature | Ball Valve (Floating or Trunnion) | Float Valve |
|---|---|---|
| Purpose | To start or stop flow in a pipe (on/off) | To automatically regulate the liquid level in a tank |
| Operation | Manual (handle) or automated (actuator) | Automatic, controlled by a float and lever mechanism |
| Key Components | Body, ball, stem, seats | Body, lever arm, float, seal |
| Typical Use | Industrial pipelines, process control | Water tanks, toilet cisterns, cooling towers |
Everyone wants the "best" product. But in engineering, the best valve isn't just one type. The best valve is the one that is perfectly suited for your specific job.
There is no single "best" type of ball valve. The right choice depends entirely on your application's pressure, temperature, pipe size, and the fluid being handled. A floating ball valve is best for standard services, while a trunnion valve is best for demanding, high-pressure systems.
I always advise my clients to stop thinking about "best" and start thinking about "right." The "right" valve will operate reliably for years, while the "wrong" one will cause a constant headache. To find the right valve, you just need to answer a few questions about your system.
Here is a simple checklist to guide you:
I often tell engineers like Jacky to describe their application to me first. Tell me the pressure, the fluid, the size. Then, together, we can select the valve that provides safety and peace of mind.
Choosing between floating and trunnion valves is simple. It is about matching the valve's design to your system's demands. Focus on your pressure and size to make the right choice.
