Threaded gate valve

Threaded gate valve, also known as shut-off valve, is a widely used type of valve. Its popularity is due to the low friction between the sealing surfaces during the opening and closing process, the small opening height, easy manufacturing, and convenient maintenance. It is not only suitable for medium and low pressure, but also for high pressure. Its closing principle is to rely on the pressure of the valve stem to tightly fit the sealing surface of the valve disc with the sealing surface of the valve seat, preventing the flow of the medium

Threaded gate valves only allow one-way flow of the medium and have directionality during installation. Its structural length is greater than that of a gate valve, and at the same time, it has high fluid resistance. During long-term operation, its sealing performance is not strong

Threaded gate valves are divided into three categories: straight through, right angle, and straight through diagonal globe valves

When the threaded gate valve is opened, the opening height of the valve disc is 25% to 30% of the nominal diameter. When the flow rate has reached a large level, it indicates that the valve has reached the fully open position. Therefore, the fully open position of the globe valve should be determined by the stroke of the valve disc

Threaded gate valves belong to forced sealing valves, so when the valve is closed, pressure should be applied to the valve disc to force the sealing surface not to leak. When the medium enters the valve body from below the valve disc, the resistance that the operating force needs to overcome is the frictional force between the valve stem and the packing, as well as the thrust generated by the pressure of the medium. The force required to close the valve is greater than the force required to open it, so the diameter of the valve stem should be larger, otherwise the valve stem bending fault may occur

The opening and closing component of a threaded gate valve is a plug shaped valve disc, with a flat or conical sealing surface. The valve disc moves in a straight line along the centerline of the fluid. The movement form of the valve stem includes a lifting rod type (the valve stem is lifted and lowered without the handwheel lifting), as well as a lifting rotating rod type (the handwheel rotates and lifts together with the valve stem, and the nut is set on the valve body). The bellows globe valve is only suitable for fully open and fully closed, and is not allowed to be adjusted or throttled

The bottom of the threaded gate valve adopts a flat bottomed valve seat design similar to that of the water pipe, which does not produce debris accumulation, has a low flow resistance coefficient, and a smooth channel. The threaded gate valve body is coated with epoxy resin both inside and outside to prevent corrosion and rust. It can be used not only for domestic water but also in sewage treatment systems. Widely used as regulating and throttling devices on fluid pipelines such as tap water, sewage, construction, petrochemicals, food, medicine, textiles, electricity, ships, metallurgical energy systems, etc

In recent years, with the emergence of self sealing valves, the flow of medium in globe valves has shifted from above the valve disc into the valve chamber. Under the pressure of the medium, the force required to close the valve is small, while the force required to open the valve is large, resulting in a corresponding reduction in the diameter of the valve stem. Meanwhile, under the influence of the medium, this type of valve is also relatively tight. The "Three Modernizations" of valves in our country once stipulated that the flow direction of globe valves should be from top to bottom

Advantages of Threaded Gate Valve:

1、 The structure is simple, and manufacturing and maintenance are relatively convenient

2、 Small work schedule and short opening and closing time

3、 Good sealing performance, low friction between sealing surfaces, and long service life

Disadvantages of Threaded Gate Valves:

1、 The fluid resistance is high, and a large amount of force is required for opening and closing

2、 Not suitable for media with particles, high viscosity, and easy coking

3、 Poor regulation performance

The types of threaded gate valves are divided into external thread type and internal thread type according to the position of the valve stem thread. According to the flow direction of the medium, there are straight through, direct current, and angular types. Globe valves are classified according to their sealing forms, including packing bellows gate valves and bellows sealed globe valves

Installation and maintenance of threaded gate valve:

The bellows globe valve operated by handwheel and handle can be installed at any position in the pipeline

Handwheels, handles, and moving mechanisms are not allowed for lifting purposes