It seals the bore causing a full closure in the valve from aoaltwar's blog

A gate valve is a kind of type of bidirectional valve that your wide variety of different industries and process plants use. The primary function of an gate valve is always to stop or start the flow of resources by way of a pipeline. Typically, gate valves may be fully open or fully closed while in use gate valve . They are ideal for situations which require minimal flow restriction and straight-line flow of fluid and so are suitable for high-pressure and temperature applications. To learn regarding the primary elements of a gate valve needed for its effective operation, consult the guide.

The gate valve, as illustrated in around the right, generally is made gate-like disc, actuated by way of a screwed stem and hand-wheel which moves top to bottom at right angles towards the flow. In the closed position, the disc seats against two faces to seal off flow. To support the fluid inside the pipeline, a gland is provided that is supplied with some kind of packing to resist leakage.

Gate valves incorporate three major components: body, bonnet, and trim. The body is normally connected for the piping through flanged, screwed, or welded connections. The bonnet, containing the moving parts, is joined on the body, generally with bolts, to allow for cleaning and maintenance. The valve trim includes the stem, the gate, the wedge, or disc, as well as the seat rings.

The main operation mechanism is a snap. When the hand-wheel is turned, it rotates the stem, that is translated into your vertical movement of the gate via threads. They are considered multi-turn valves because it takes many 360° choose fully open/close the valve. When the gate is lifted on the path from the flow, the valve opens when it returns to its closed position, it seals the bore producing a full closure on the valve.

On opening the gate valve, the flow path is enlarged inside a highly non-linear manner with regards to percent of opening for more . This means that flow rate isn't going to change evenly with stem travel.Also, a partially open gate disk has a tendency to vibrate in the fluid flow. Most on the flow change occurs near shutoff which has a relatively high fluid velocity causing disk and seat wear and eventual leakage if employed to regulate flow.