Types of cryogenic gate valves can be classified into wedge‑gate plate gate valves and parallel‑gate plate gate valves based on sealing‑surface configuration. Wedge‑gate plate gate valves are further divided into single‑gate plate, double‑gate plate and flexible‑gate plate types. Parallel‑gate plate gate valves consist of single‑gate plate and double‑gate plate versions. When categorized by the thread position of the valve stem, cryogenic gate valves fall into two types: outside‑screw‑and‑yoke (OS&Y) gate valves and inside‑screw‑and‑yoke gate valves.
When a cryogenic gate valve is closed, its sealing surfaces can rely merely on medium pressure for sealing. The medium pressure pushes the sealing face of the gate plate firmly against the opposite valve seat to achieve tight sealing, which is known as self‑sealing. Most gate valves adopt forced‑sealing structure. External force is applied to press the gate plate against the valve seat when the valve closes so as to guarantee reliable sealing performance of the sealing surfaces.
A gate valve whose gate plate moves linearly together with the valve stem is referred to as a rising‑stem gate valve, also known as an outside‑screw‑and‑yoke (OS&Y) gate valve. The rising stem is generally equipped with trapezoidal threads. The nut mounted at the valve top and guide grooves on the valve body convert rotary motion into linear motion, which transforms operating torque into pushing force for valve operation.
The fluid passage becomes fully open when the lifting height of the gate plate equals the nominal diameter of the valve. However, this exact position cannot be observed during actual operation. In practical applications, the uppermost position of the valve stem where the handwheel cannot turn further is regarded as the fully‑open position. To prevent jamming caused by temperature variations, operators usually back‑off the handwheel by 1/2‑1 full turns after the stem reaches its top‑end position. Therefore, the fully‑open state is defined according to the travel of the gate plate.
Certain gate valves install the stem nut on the gate plate. Rotation of the handwheel drives the valve stem to spin and lift the gate plate. Such products are called non‑rising‑stem gate valves or inside‑screw‑and‑yoke gate valves.