Ball Valve Design and Operation

Batu Valve ball valves convey, divert or stop the medium by the rotation of a ball inside the body; the ball is rotated to open or shut off the flow, providing quick shut-off.

The production range covers split body, fully welded and mono-block designs, floating and trunnion mounted balls, and full bore and reduction bore valves. Connection, operation and safety options are given below.

The rotation of the lever or gearbox is transmitted to the ball through the stem. The ball, which has a bore through its centre, is rotated to open or shut off the flow. On lever operated valves the lever lies in the direction of flow when the valve is open.

At high pressure the medium acts behind the seat ring, pushes the ring against the ball and provides the seal itself. When the pressure drops this force decreases; the spring supporting the ring then takes over and contact is maintained. In a ball valve the difficult condition is not high pressure but sealing at low pressure.

Seat materials: PTFE (standard), glass fibre reinforced PTFE (RPTFE), graphite-filled PTFE, PEEK and Devlon. PEEK and Devlon are used in the high pressure classes.

Floating ball valves have a ball that is not fixed to the stem; it “floats” freely inside the valve body. When line pressure is applied, the ball is pushed towards the downstream sealing surface and forms a secure seal. Trunnion mounted ball valves carry the ball on the stem at the top and on a lower bearing (trunnion) at the bottom; the operating torque is low.

In Batu Valve catalogs the floating and trunnion dimensions are given together for the same pressure class.

Full bore valves have a ball bore equal to the inside diameter of the pipe; the flow passes without restriction. Reduction bore valves have a ball bore one size smaller than the pipe diameter.

• Manual: lever, T-handle or gearbox operated.
• Actuated: pneumatic, hydraulic or electric actuator.

In the API 6D series, valves of 4" and below are fitted with a lever and larger valves with a handwheel gearbox. The actuator mounting flange on top of the body is to ISO 5211 dimensions; an actuator can also be fitted at a later date.

Fire-safe design. Soft seat material is damaged in a fire. In the fire-safe design, when the PTFE and O-rings burn away, a metal-to-metal seal forms between the secondary metal seat and the ball; the graphite gaskets between the body and closure withstand high temperature. It is required on lines carrying flammable media such as oil and LPG.

Anti-blowout stem design. The stem is designed with a wide lower shoulder; even if the stem retainers and seals are removed, pressure cannot eject the stem.

Antistatic design. On lines carrying flammable media, static charge must not build up on the ball. The spring and ball in the stem conduct any charge through the body to the pipeline.

Drain and vent. When the valve is closed, pressurised medium remains in the body cavity. The drain at the bottom and the vent at the top are provided for releasing it safely; they are specified in the order.