The flexible gate prevents the disc from binding in the seat - lilyscoggins/ffxivgil GitHub Wiki

Gate valves and knife valves are advantageous in applications involving slurries, because their “gates” can trim right throughout the slurry. They are also utilized in applications that entail viscous liquids including heavy oils, light grease, varnish, molasses, honey, cream along with non-flammable viscous liquids. They can be bought in large sizes to increase handle thick flow. However, gate valves have low-pressure limitations, and so are not optimal in applications that want cleanliness or sanitary conditions. They are wonderful for use anywhere a shutoff valve is essential. When needed, they could also be used where throttling capabilities are desired, although not generally recommendGate Valve imageed as erosion in the seat and disc occurs due to vibrations from the disk in throttling applications.

ball valve and knife valves are built to minimize pressure drop through the valve within the fully opened position preventing the flow of fluid completely. The direction of fluid flow won't change, plus the diameter whereby the process fluid passes is actually equal to that from the pipe. Hence, they tend to have minimal pressure drop when opened fully.

For a valve in the non Rising Stem type, there's no upward stem movement when the valve is opened. The stem is threaded in the disk. As the handwheel about the stem is rotated, the disk travels up or down the stem for the threads as the stem remains vertically stationary.

Flexible Wedge: A Flexible Wedge gate valve includes a disk having a cut throughout the perimeter. A shallow cut gives less flexibility. A deeper cut provides more flexibility. Flexible Wedge gate valves in many cases are used in steam systems. The flexible gate prevents the disc from binding in the seat in the event the lines are heated that could cause some distortion from the valve bodies

Split Wedge: Split Wedge gate valves are of ball and socket design. In a split wedge gate valve, both the disk halves have no choice but outward up against the body seats using a spreader following disk has become fully lowered into its seating position.