How many types of gate valves are there? How are they classified?

Ⅰ.Classified into two categories based on gate plate construction

1. A parallel-type gate valve is a gate valve in which the sealing surfaces are parallel to the vertical centerline, meaning the two sealing surfaces are parallel to each other. Parallel-type gate valves are further classified into double-disc and single-disc types. They are also categorized as having or not having a flow-through orifice.
2. A wedge gate valve is a type of gate valve in which the sealing surfaces are set at an angle to the vertical centerline, forming a wedge shape. Wedge gate valves are further classified into double-disc, single-disc, and elastic-disc types.

Ⅱ.Classified into two categories based on the construction of the valve stem

1. A rising-stem gate valve is a type of gate valve in which the stem nut is located on the bonnet or bracket, and the stem is raised or lowered by rotating the stem nut to open or close the gate.
2. A concealed-stem gate valve is a type of gate valve in which the valve stem nut comes into direct contact with the medium inside the valve body, and the gate is opened and closed by rotating the valve stem.