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　　Working principle of heat preservation ball valve
One, opening process
1 in the closed position, the ball is subject to the mechanical pressure of the valve stem, the pressure on the valve seat.
2 when the handwheel counterclockwise, the stem is the reverse movement, the bottom of the angular plane to disengage the ball seat.
3 the valve stem continues to increase, and with the valve stem guide pin in the groove interaction, so that the ball began to rotate without friction.
4 until the full open position, the valve stem to the limit position, the ball to the full open position.
Two, closing process
1 when the hand wheel is closed, the valve stem begins to fall and the ball is left in the valve seat.
2 continue to rotate the hand wheel, the valve stem is embedded in its spiral groove on the role of the guide pin, so that the valve stem and the ball at the same time to rotate 90 degrees.
3 is about to close, the ball has been in contact with the valve seat without contact with the case of 90 degrees rotation.
4 the last few laps of the hand wheel rotation, the bottom of the valve stem from the angle of the machine to press the ball to the ball, so that it closely pressed on the valve seat, to achieve complete sealing.