Floating Ball Valves vs. Trunnion Mounted Ball Valves

Ball valves are one of the most widely used types of valves. They are suitable for a wide range of applications, from heavy-duty industrial use to household plumbing. There are two main types of ball valves: floating ball valves and trunnion mounted ball valves. Both types have their own unique features and benefits. But what’s the difference between these two types of valves? Here are the difference between floating ball valves and trunnion mounted ball valves.

What is a Floating Ball Valve?

The ball of the floating ball valve is floating, and the valve seat is fixed. With the effect of the medium pressure, the ball can produce a certain displacement and press tightly on the sealing surface of the outlet end to ensure that the outlet end is sealed.

Floating Ball Valves vs. Trunnion Mounted Ball Valves

Forged steel floating ball valve

How Does a Floating Ball Valve Work ?

A floating ball valve comprises 3 main parts:

1. An actuator lever

2. A stem

3. A floating ball

The actuator lever is the outermost part used to open or shut-off fluid flow. When it is turned within a 90-degree angle, it rotates the stem which turns the ball to an open or closed position.

At the base of the valve, the ball remains unmounted and is only supported by a stationary polymer ring and seats.

When the valve is shut, medium pressure pushes the ball firmly against the seats. This provides a tight seal and stops flow immediately. However, given as the ball is unsupported, high levels of pressure can not be distributed to a base to lessen the force on the ball. A floating ball valve is thus only recommended for low to medium pressure applications with average temperatures. Where necessary, it can also be customized to work in cryogenic applications.

Regarding overflow management and controlling leakages, a quality floating ball valve should have designs with anti-static and anti-blow out stem. This means that when pressure is elevated or during fluid surges, the stem will keep with no leakages. A flexible soft seat is equally essential as it creates sealing around the floating ball to stop media flow.

Pros & Cons of a Floating Ball Valve

Pros:

1. A floating ball provides impenetrable sealing when pushed onto its seats.

2. It responds fast to shutting off or allowing fluid flow.

3. It is very efficient in small scale applications for which other valves would be unsuitable due to size.

Cons:

1. It is limited to small designs to manage torque levels.

2. It operates at high torque.

3. The high pressure experienced by seats and seals during shut off can increase their rate of wear and tear.

What is a Trunnion Mounted Ball Valve?

A trunnion Mounted Ball Valve is a quarter-turn valve. It has a ball supported by both the stem and trunnion, giving it greater strength and a reduced operating torque.

Trunnion Mounted Ball Valve

How Does a Trunnion Mounted Ball Valve Work ?

A trunnion mounted ball valve consist of 4 main parts:
1. An actuator lever
2. A stem
3. A ball
4. A trunnion

The trunnion forms the base onto which the ball is mounted. At the top end, the ball is linked to the stem. And the stem is connected to an exterior actuator lever. In a flanged trunnion ball valve, there are spring-loaded seats and a polymer ring insert between the trunnion and the ball. The springs put pressure on the ball to keep it in place. Together with the polymer ring, they also reduce friction when the ball is rotating.
To facilitate the flow of media, the ball is made hollow in the middle. It can either be a full bore or a partial bore. A full bore is a ball whose hollow part is the same size as the pipeline it is installed in.
When the actuator is turned, the stem connected to it also turns. These actions cause the ball to rotate on the trunnion to an open or closed position. During and after fluid flow, seals in the seats and stem prevent the fluid from leaking out of the pipeline. An adjustable gland packing box also helps the valve take on different capacities of pressure. A typical trunnion ball valve would also have 2 bleeders for purposes of depressurization.

Pros and Cons of a Trunnion Mounted Ball Valve

Pros:
It requires less torque to operate.
It can be applied in both large or small scale operations.
Less friction during trunnion ball valve operation helps mitigate wear and provides full-proof sealing.

Cons:
Due to the fully-welded or bolted-together design, trunnion ball valve is difficult to be repaired in-line. Therefore, repair will interrupt normal pipeline operations.
If maintenance is not carried out as required, welded parts could begin to operate with higher friction leads to efficiency decline.