The structure form of a resilient seat seal gate valve: 1. Stem sealing structure The stem seal uses a three-way O-ring structure, as shown in Figure (a). The third O-ring reduces the pressure at the gland, and at the same time enables the pipeline to replace the upper two seals when there is medium pressure (replacing the stem seal and packing with pressure is dangerous, so this practice is not recommended). The O-ring seal construction can effectively reduce the opening and closing torque of the valve compared to the use of stuffing box construction [Figure (b)]. In the water supply industry is generally not recommended to use the form stuffing box structure, especially in the direct buried gate valve, is not allowed to use, because the stuffing box structure needs to be lubricated with outward seepage of water, and the stem seal can not use materials containing asbestos, etc. O-ring sealing structure on the stem processing accuracy and surface roughness accuracy requirements than the packing structure, otherwise there will be cut O-ring situation. The trapezoidal thread of the stem should be extruded, with high surface hardness and a small friction factor. The requirements for rubber material, process, and performance must...
As the electric valve is a combination of valve and electric device, so when the valve is determined how to correctly select the electric device is an important factor related to the actual use of whether it can meet the needs of the project. The selection of an electric device should not only consider the aforementioned working environment, electrical control, and general technical performance but also the comprehensive technical performance of the electric device should also be considered comprehensively. 1. The output torque and speed of the electric device The output torque value is one of the important technical parameters of the electric device, and it is also an important parameter to be selected in use. If the output torque of the electric device is too large or insufficient, it is not desirable to use the electric valve. Because in general, the electric device manufacturers need to test and adjust the output torque value when the product leaves the factory, which is relatively accurate. If you choose too much output torque margin, will make the electric valve has a great potential danger, once the control protection failure will easily cause damage to the valve (stem bending, valve body rupture) phenomenon,...
The slow-closing check valve is a special variety of check valves, which reduces water hammer pressure by slow-closing form. The slow-closing check valve has a variety of structure types, this article introduces three of them: two-stage slow-closing check valve, built-in cylinder damping slow-closing check valve, and water resistance controlled slow-closing check valve. First, two-stage slow-closing check valve This is a kind of side resistance slow-closing check valve with a double-cylinder damper, its structure principle is shown in Figure 1, the valve body is an ordinary swing check valve, but the rocker shaft of the valve flap is thicker and longer, wearing out the valve body outside, through the connection mechanism and the cylinder damper on both sides of the placement, the connection mechanism consists of the rocker arm, slide fork, and cross pin. When the pump stops, the valve flap is closed in two stages from the fully open position. Firstly, the flap falls down by its own weight, the cross pin of the rocker’s arm is lowered to the lowest point from high in the guide groove of the sliding fork, and the cylinder damper does not work, which is the fast closing stage, accounting for...
Definition of Check Valve: The check valve is a device that prevents the flow of liquid or gas in one direction only. It is used in plumbing and in industrial processes. The check valve is a one-way valve, which lets water drip through it but no air can go through it from below. The check valve also provides a non-return function because it has two discs with holes on each end and when you press down on one disc, it closes off any holes above it so there’s no way for air to get into your pipes even if you have some leaks! The check valve consists of a disc or flapper valve that closes when the fluid flow reverses (i.e., when water flows up instead of down). It works by allowing for a complete seal against backflow when opened so that anything trying to come up will not be able to pass through unless there’s pressure pushing hard enough against them all at once.” Working Principle of Check Valve The working principle of the check valve is simple: When the input pressure or flow exceeds a given value, the diaphragm will be compressed,...
Top 3 Things for selecting a electric Valve. In the pipeline project, the correct choice of electric valves is one of the conditions to meet the requirements of use. If the electric valve used is not properly selected, not only will affect the use, and can also bring adverse consequences or serious losses, therefore, in the design of pipeline engineering should be the correct choice of electric valves. 1. Working environment Electric valves should pay attention to the pipeline parameters, but also should pay special attention to the environmental conditions of their work, because the electric device in the electric valve is electromechanical equipment, and its work is greatly affected by its working environment. Usually, the electric valves are located in the following working environment: ① indoor installation or outdoor use with protective measures; ② outdoor open-air installation, wind, sand, rain, sunlight, and other erosion; ③ with flammable, explosive gas or dust environment; ④Humid tropics, dry tropics area environment; ⑤Pipe medium temperature up to 480℃ or more; ⑥The ambient temperature is below -20℃; ⑦easily flooded or immersed in water; ⑧ With radioactive materials (nuclear power plant and radioactive materials test equipment) environment; ⑨ on ships or docks (with...
The globe check valve is a valve that can cut off the fluid and act as a check valve, and the connection between the stem and the valve flap is designed to be disconnected. Figure 1 shows the globe check valve to play the role of the check, in essence, is a lift check valve, its working principle, and lift check valve. When closing the valve, the stem moves downward to push the valve flap, so that the valve plays a closing role of the globe valve. When the valve is opened, the stem and valve flap are disconnected, and the valve flap can move up and down along the stem, which is equivalent to the lift check valve, when the fluid backflow, the valve flap can be closed under the action of self-weight and backflow pressure to prevent the media backflow. The globe check valve shown in Figure 1 is essentially a swing check valve, and its working principle is the same as the swing check valve. When closing the valve, the stem moves downward to push the valve flap, so that the valve plays a closing role in the shut-off valve. When the valve is opened,...
What is a 200X Pressure Reducing Valve? The 200X pressure reducing and stabilizing valve consists of a main valve, a pilot valve, a needle valve, a ball valve, a micro filter and a pressure gauge to form a hydraulic control connection system. When a fire breaks out, a large amount of water is urgently needed for firefighting, and domestic water is cut off immediately to ensure sufficient firefighting water; when the pressure of water for firefighting stops decreases, the valve automatically opens and assumes a normally open state to restore domestic water supply. The valve makes the system unnecessary to set up a special separate water supply pipe network for fire protection, which greatly saves the construction cost and water consumption. This product is self-controlled by a pilot valve, does not require other devices and energy sources, is easy to maintain, has high pressure control accuracy, is less affected by inlet pressure and flow, and is reliable in reducing pressure and stabilizing pressure. This series of valves are widely used in high-rise buildings, living areas and other water supply pipe network systems and urban water supply projects. working principle: When water is supplied to the valve from the...
The difference between bellow seal globe valve and ordinary globe valve Features of bellow seal globe valve: Bellows globe valve is also called bellows seal globe valve, through automatic seam welding, a metal barrier is formed between the fluid medium and the atmosphere to ensure the design of zero leakage of the valve stem. Compared with traditional globe valves, it has the following advantages: Double sealing design (bellows + packing) If the bellows fails, the valve stem packing will also be avoided; the sturdy and durable bellows seal design ensures zero leakage of the valve stem and provides maintenance-free conditions. Reasonable structure, reliable sealing, excellent performance and beautiful appearance. There is no fluid loss, reducing energy loss and improving plant equipment safety. The sealing surface is surfacing with Co-based cemented carbide, which has good wear resistance, corrosion resistance, good anti-friction performance, long service life, reduces maintenance times and reduces operating costs. The sturdy and durable bellows seal design ensures zero leakage of the valve stem and provides maintenance-free conditions. The bellows globe valve stem is quenched and tempered and surface nitrided, which has good anti-corrosion and anti-friction performance; The characteristics of ordinary sealing globe valve introduction: Globe valve is also called...
Introduction Do you want to know the difference between a globe valve and a ball valve? You should use ball valves for high-pressure applications where you need a quick response time and can’t afford any leaks. If you’re working on something that requires precise adjustments to flow rates, use globe valves. The purpose of this article is to help you understand the differences between these two types of valves so that you can choose which one is best for your needs. Structure The primary difference between these two valves lies in their construction: Globe valves have both an open side and a closed side—one chamber is always open and another always closed (except when being adjusted). Ball Valves only have an open side—there’s no closed side like there is with globe valves; rather than using two separate chambers like globe valves do though. The discs in a globe valve are flat, while the discs in a ball valve are spherical. The seats of both types of valves are made of metal, but they have different shapes. Globe valves have three-edged seats that allow movement in three directions. Ball valves have four-edged seats that allow movement in...
The opening and closing member (valve flap) is driven by the valve stem, along the seat (sealing surface) axis of the valve to do linear lifting movement is called the globe valve. A Globe valve is generally composed of the main parts such as the driver (hand wheel), stem, valve body, valve cover, valve flap (closing member), and packing device. The globe valve is widely used, mainly for higher pressure and smaller caliber occasions, generally only produced to DN400 (NPS116), the larger diameter specifications only for special pipelines. For example, large oxygen pipeline, due to the existence of other valve friction prone to static fire, so the use of a large-diameter stainless steel globe valve. Although sizes up to NPS148 (DN1200) globe valve has been produced and put into use, however, the American Petroleum Institute guidance document API 615 “Valve Selection Guide” on the selection of globe valve is described as follows: “Although large bore and high-pressure rating may also be appropriate, the standard globe valve with a pressure rating of 150 pounds class is suitable for nominal size not to exceed NPS 112 for the 300-pound class, NPS 110 for the 300-pound class, and NPS 18 for the 600-pound...
