球閥的閥芯是球形體，由圓形通孔通過軸線，當球旋轉90度時，在進、出口處呈現球面，從 而截斷流體，反之即呈現通孔，供介質通過。球體的內腔為介質提供了小阻力、全通徑的流道。
The ball valve trim is a sphere shape with a round hole passes the valve stem, when the ball rotates 90 degrees, the inlet and outlet port will shows a spherical surface, and becomes a flow channel when it rotate back. The spherical inner cavity provides a small resistance and full port for medium.