Plug valve internal pressure balancing

摘要

The preferred embodiment comprising a truncated cone valve plug, or a truncated cone with curved sides as in the tractrix valve is described. A step is fabricated into the large end of the valve plug. A secondary seal, called a Veri-Seal, is placed on the large end of the valve plug on the step at an intermediate location between the outer diameter of the plug and the stem. Pressure forces acting downward on the step on the top of the valve plug balance the pressure forces acting upward in the channel through the valve plug. By placing the Veri-Seal at this intermediate location on the top of the plug, the spring force can be minimized and the resulting torque to open and close the valve is consequently reduced.