Forged steel valve means closing member (shutter) movable in vertical direction centerline of the valve passageway. The main valve in the pipeline for cutting. Forged steel gate valve is a valve using a very broad, general caliber DN≥500mm cutting device have chosen it, and sometimes a small diameter valve cutting device also selected. As a lower-level gate valves, are more common. First, the advantages of a gate valve, fluid resistance. 2, the opening and closing force required is small. 3, the flow of media is not limited. 4, when fully open, the sealing surface by erosion of the working medium is smaller than the cut-off valve. 5, is relatively simple shape, good casting process. Second, the disadvantage of a gate valve, and the opening height dimensions are larger. Larger space required for installation. 2, the opening and closing process, the relative friction between the sealing surface, easy to cause abrasions. 3, the valve generally has two sealing surface, to processing, polishing and maintenance of some additional difficulties. Gate structure according to the sealing surface configuration can be divided into wedge gate-type valve and parallel gate-type valve, wedge gate-type valve can be divided into: a single gate type, double plate and flexible gate type; parallel gate-type valve can be divided into single-gate type and double plate. 1) Parallel Gate Valve: sealing surface and the vertical centerline parallel, that is, two valve sealing surfaces parallel to each other. In a parallel-type valve, the structure with a thrust wedge most common, both in the middle of a two-sided thrust wedge gate, this valve for low pressure small-caliber (DN40-300mm) gate. Also with a spring in between the two gate, to the clamping force of the spring can produce beneficial gate seal. 2) wedge gate valve: sealing surface and the vertical centerline into some sort of angle, that is, two sealing surface into wedge gate valves. The inclination angle of the sealing surface are generally 2 ° 52', 3 ° 30', 5 °, 8 °, 10 °, etc., the size of the angle depends on the medium temperature level. As higher operating temperature, the greater the angle should be taken to reduce the likelihood of wedged temperature changes occur. In the wedge gate valve, a further single gate, double plate and the flexible gate points. Single wedge gate valve, simple structure, reliable operation, but higher on the sealing surface angle accuracy requirements, processing and maintenance more difficult, the possibility of temperature changes wedged great. Double plate wedge gate valve to use more water and steam in the media line. Its advantages are: the lower the angle of the sealing surface accuracy, temperature changes are unlikely to cause wedged phenomenon, when the sealing surface wear, you can add shim compensation. But this structural parts are more easily bonded viscous medium, affect the seal. But mainly on the lower bezel is easy to produce long-term corrosion, gate easily. Resilient wedge gate valve, which has a single wedge gate valve structure is simple, use * advantages, but also produce small amounts of elastic deformation of the sealing surface to compensate the deviation angle generated during processing and improve manufacturability, has been a large number of adoption. Construct a stem) stem gate valve: the valve stem nut cover or stand on the opening and closing gate with a rotary valve stem stem nut to achieve lift. This structure of the valve stem lubrication Advantageously, the closing level significantly, so it is widely used. 2) dark bar valve: the valve stem nut body, direct contact with the media. When opening and closing the gate, the rotary valve stem to achieve. The advantage of this structure are: the total height of the gate remains unchanged, so a small installation space, suitable for large diameter or restricted valve installation space. Such structure should be equipped with open and close indicator to indicate the degree of opening and closing. The disadvantage of this structure are: stem thread lubrication is not only impossible, but also directly accept the medium erosion, easy to damage.