The opening and closing part of the sluice gate valve is the ram. The direction of movement of the ram is perpendicular to the direction of the fluid. The gate valve can only be fully open and fully closed, and cannot be adjusted and throttled. The gate has two sealing faces. The two sealing faces of the most common mode gate valves form a wedge shape. The wedge angle varies with valve parameters, usually 50, and is 2°52' when the medium temperature is not high. The gate of the wedge gate valve can be made into a whole, called a rigid gate; it can also be made into a gate that can produce a small amount of deformation to improve its processability and compensate for the deviation of the sealing surface angle during the machining process. The board is called a resilient shutter. working principle When the fire gate valve is closed, the sealing surface can be sealed only by the medium pressure, that is, the sealing surface of the shutter is pressed against the valve seat on the other side by the medium pressure to ensure the sealing of the sealing surface, which is self-sealing. Most of the gate valves are forced to seal, that is, when the valve is closed, the external force is forced to press the gate to the valve seat to ensure the sealing of the sealing surface. The gate of the fire gate valve moves linearly with the valve stem, called the lift gate valve (also called the open gate valve). Usually there is a trapezoidal thread on the lifting rod, and the rotary motion is changed into a linear motion by the nut at the top end of the valve and the guide groove on the valve body, that is, the operating torque is changed to the operating thrust. When the valve is opened, when the lifting height of the gate is equal to 1:1 times the diameter of the valve, the passage of the fluid is completely unblocked, but this position cannot be monitored during operation. In actual use, the apex of the valve stem is used as a mark, that is, the position where the valve is opened, as its fully open position. In order to consider the temperature change, the lock phenomenon is usually turned on to the apex position, and then back to 1/2-1 turn as the position of the fully open valve. Therefore, the fully open position of the valve is determined by the position of the shutter (ie stroke). In some gate valves, the stem nut is arranged on the gate plate, and the rotation of the hand wheel drives the valve stem to rotate, and the shutter is lifted. This valve is called a rotary lever gate valve or a dark rod gate valve. A, the working principle of the fire gate valve: Turning the handwheel, through the advancement and retreat of the thread of the handwheel and the stem, lifting or lowering the valve plate connected with the valve stem to achieve the function of opening and closing According to the sealing surface configuration, the type of gate width can be divided into wedge gate valve and parallel gate valve. The wedge gate valve can be divided into: single gate type, double gate type and elastic gate type; parallel gate type gate valve Can be divided into single gate type and double gate type. According to the thread position of the valve stem, it can be divided into two types: open gate valve and dark gate valve. The following matters should be noted for the installation and maintenance of the sluice gate valve: The handwheel, handle and transmission mechanism are not allowed to be used for lifting, and collision is strictly prohibited. The double gate gate valve should be installed vertically (ie the stem is in the vertical position and the handwheel is on the top). The gate valve with the bypass valve should open the bypass valve before opening (to balance the differential pressure between the inlet and outlet and reduce the opening force). The gate valve with transmission mechanism is installed according to the product manual. If the valve is used frequently, it should be lubricated at least once a month. Structural features: The general gate valves used in the market have been leaking or rusting for a long time. The company introduced the high-grade rubber sealing valve produced by European high-tech rubber and valve manufacturing technology, which overcomes the defects of general gate valve sealing, rust and other elastic seats. The sealing valve uses the elastic ram to produce a slight elastic deformation compensation effect to achieve a good sealing effect. The valve has the advantages of light switch, reliable sealing, good elastic memory and long service life. Can be widely used in tap water, sewage, construction, petroleum, chemical, food, pharmaceutical, textile, electric power, shipbuilding, metallurgy, energy systems and other body pipelines as a regulating and intercepting device. B, the characteristics of the fire gate valve: Light weight: The body is made of high-grade ball black cast iron, and the weight is reduced by about 20%~30% compared with the traditional gate valve, which is convenient for installation and maintenance. Flat-bottomed gate: Traditional gate valves are often deposited in the groove of the valve bottom due to foreign objects such as stones, wood blocks, cement, iron filings, debris, etc. after the water is washed, which is easy to close and form a leak. The bottom of the elastic seat sealing gate valve adopts the same flat bottom design as the water pipe machine, which is not easy to cause debris accumulation, so that the fluid is unobstructed. Integral encapsulation: The ram is made of high-quality rubber for the whole inner and outer rubber. The first-class rubber vulcanization technology in Europe enables the vulcanized ram to ensure precise geometrical dimensions, and the rubber and spheroidal cast slabs are secure and not easy to fall off. Flexible memory is good. water Precision cast body: The valve body is precision cast, and the precise geometry allows the valve body to be sealed without any finishing. C, the fire gate valve has the following advantages: 1. The fluid resistance is small, and the sealing surface is less brushed and eroded by the medium. 2, opening and closing is more labor-saving. 3. The flow direction of the medium is not restricted, and it does not disturb the flow and does not reduce the pressure. 4. Simple shape, short structure length, good manufacturing process and wide application range. D, the shortcomings of the fire gate valve are as follows: 1. Erosion and abrasion are easily caused between the sealing surfaces, and maintenance is difficult. 2. The external dimensions are large, and a certain space is required for opening, and the opening and closing time is long. 3. The structure is more complicated. Performance comparison The gate valve is a kind of valve which is widely used in pipelines and mainly functions to connect and cut off the medium. It is not suitable for adjusting the flow rate of the medium, but it can judge the flow rate according to the height of the valve stem lifting (such as the elastic seat sealing gate valve for fire protection with the opening and closing scale). Compared with other valves, gate valves have a wide range of applications for pressure, temperature, and caliber. The gate valve can be divided into two types according to the internal structure: wedge type single gate type, elastic gate type, double gate type and parallel gate type. According to the different stem brackets, it can be divided into: open gate valve and dark rod gate valve. The main performance advantages of the gate valve are as follows: 1. The fluid resistance of the valve is small. Since the valve body of the gate valve is straight-through type, the flow of the medium does not change direction, so the flow resistance of other valves is smaller. 2, the sealing performance is better than the stop valve, the opening and closing is also less labor-saving than the stop valve. 3, a wide range of applications, in addition to the use of steam, oil and other media, but also for the use of granular solids and a medium with a high viscosity, also suitable for use as a valve for venting valves and low vacuum systems. 4. The gate valve is a valve with dual flow direction, which is not restricted by the flow direction of the medium. Therefore, it is suitable for the pipeline where the medium may change the flow direction, and is also easy to install. The main performance shortcomings of the gate valve are as follows: 1. The shape design is high in size and the opening and closing time is long. When opening, the valve plate needs to be lifted to the upper part of the valve cavity. When closing, the valve plate needs to be completely dropped into the valve seat, so the valve plate has a large opening and closing stroke and a long time. 2. Since the sealing surfaces of the valve plate and the valve seat of the gate valve have friction during the opening and closing process, the sealing surface is easily scratched, which has an impact on the sealing performance and the service life, and is difficult to repair. Performance comparison of several different types of gate valves: (1) Wedge type single gate valve a, the structure is simpler than the elastic gate valve b. At higher temperatures, the sealing performance is not as good as that of the elastic gate valve or the double gate valve. c. Suitable for high temperature medium that is easy to coke. (2) Elastic gate gate valve a, which is a special form of wedge type single gate valve. Compared with the wedge gate valve, the sealing performance is good at high temperature, and the ram is not easily caught after being heated; b. It is suitable for steam, high temperature oil and oil and gas medium, and is suitable for frequent switching parts. c. Not applicable to media that are easy to coke. (3) Double gate valve a, sealing performance is better than wedge gate valve. When the angle of inclination of the sealing surface and the valve seat are not very accurate, it still has good sealing performance. b. After the sealing surface of the ram is worn, the metal pad at the bottom of the spherical top can be replaced after use. Generally, it is not necessary to weld and grind the sealing surface, which is an advantage that the single ram and the elastic ram do not have. c. It is suitable for steam, high temperature oil and oil and gas media, and is suitable for frequent switching parts. d. Not applicable to media that are easy to coke. (4) Parallel gate valve a, sealing performance is worse than other forms of gate valve. b. Suitable for media with low temperature and pressure. c. The processing and maintenance of the sealing surface of the gate and the valve seat are simpler than other types of gate valves.
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