An Introduction To The Floating And Trunnion Ball Valves

A ball valve is a quarter-turn valve that encompasses a perforated ball that controls the flow of media. In an open position, the ball aligns with the pipelines to allow liquids or gases. In the closed position, the valves handle turns the balls perforation away from the pipeline outlet and seals the flow. Ball float valves or floating ball valves are a popular type of valves used in many industries. In the floating ball valve, the ball is compressed into position with the help of two elastomeric seats. As its name indicates, the ball can float freely within the space created by the seats as it is connected only to a stem. A Trunnion ball valve is the stark opposite of the floating valve. Inside a trunnion ball valve, the ball connects to a stem on one end and a shaft on the other end. This design ensures the internal ball is held firmly in place and cannot float around like the ball float valve.

Yellow painted industrial ball float valves arranged in a workshop for dispatch

Comparing ball float valves and Trunnion ball valves

The design and operating mechanism

The floating ball valve:

In the floating valve, the seats are fixed inside the valve's body. When it is in operation, the internal ball is pushed against the downstream seat due to the pressure caused by the moving medium, thus causing the ball to float in place. When the valve is closed, the ball remains pressed against the surface of the sealing.

Also Read : Leakage In Ball Valves: Reasons Given By Top Ball Valve Manufacturers

In floating valves, the torque increases when the operating pressure and the valve size increases and if the seats are made of robust materials like metals. In this design, the ball is rotated by a shaft connected to a handle or an automatic actuator. Due to the floating nature of the ball, the design is applicable for valves in smaller sizes and lower pressures. In rare instances, the fluid pressure exerted on the ball can exceed surpass the seat's ability to hold the ball in place.

The standard bore size for the floating valve design is DN25 or NPS 1 up to DN 50 or NPS 2.

The trunnion ball valve:

The trunnion is a pin that protrudes from the bottom of the ball and sits within a cylindrical bearing in the base of the valve's body. In the trunnion ball valve, the internal ball cannot move because it is fixed between the stem and the trunnion. The in-line pressure presses the seats against the ball, indicating that it is enough to generate a lower torque than what is required for a floating ball valve. The stem shaft and the trunnion control the ball's rotation and maintain it at a vertical axis. Due to this control, the ball remains firmly in place regardless of the flow pressure.

Applications

The floating ball valve:

These valves are suitable for medium and low-pressure applications as they are smaller in diameter and capable of bi-directional shutoff. They are used in homes for water distribution and in other applications that do not require high pressure.

The trunnion valve:

The trunnion ball valve's design makes it more suitable for high-pressure applications and those that require bigger dimensions. Because the trunnion is connected to a drain connection, it is suitable to operate as a dual safe instrument. It is also apt for applications where the force of the central cavity is higher than the pressure of the seats. In such cases, it automatically functions as a relief valve. The structural design of this valve also makes it a popular choice for applications involving valve automation.

The lower operating torque and the lesser wear and tear of the valve seats make the trunnion valve suitable for refineries and oil and gas plants. The valve can be used in high-pressure industrial environments and is available in sizes upto 60 inches.

Oilway, Singapore: Expert manufacturers of ball float valves

Oilway has long reigned as the leading industrial valve suppliers in Singapore and a host of other countries such as India, Indonesia and China. We offer a unique range of industrial valves designed to perfection and manufactured with the highest quality raw materials. We also hold a high reputation for delivering orders right on time with strict adherence to quality standards and customer requirements.