Valve for controlling slurry flow

A valve for controlling flow of fluid containing solid material, comprising:

• a valve body defining a valve chamber and having an outer wall formed with an opening,
• a valve seat located within the valve chamber and defining an orifice,
• a valve plug located within the valve chamber and moveable relative co the valve seat for opening and closing the valve,
• a valve actuator located outside the valve body,
• a valve stem extending through said opening and coupling the valve actuator to the valve plug, and
• a flexible valve stem seal positioned outside the valve body and sealing the valve stem to the valve body, the valve stem seal defining a seal chamber that is in communication with the valve chamber, whereby the seal chamber and the valve chamber form an essentially closed space for the fluid,
• and wherein the opening formed in the outer wall of the valve body is of substantially greater cross-sectional area than the valve stem, whereby contact between the valve stem and the valve body is avoided, the valve body comprises an interior partition that is spaced from the outer wall and divides the valve chamber into first and second vessels, the first vessel is of substantially greater cross-sectional area perpendicular to the valve stem than the opening formed in the outer wall of the valve body, the valve body has an inlet that opens into one of said first and second vessels and an outlet that opens from the other of said first and second vessels, the outer wall bounds the first vessel, the valve seat is located in the first vessel and is attached to the interior partition, the valve plug is located in the first vessel and is moveable in the first vessel relative to the valve seat for opening and closing the valve, and the second vessel is of substantially greater cross-sectional area perpendicular to the valve stem than the orifice in the valve seat.