Introduction to liquefied gas shut off valves, the use of pneumatic shut off valves

When the medium enters the valve six from the bottom of the valve disc, the resistance that the operating force needs to overcome is the friction force of the valve stem and the packing material and the thrust generated by the pressure of the medium, and the force of closing the valve is greater than the force of opening the valve, so the diameter of the valve stem should be larger, otherwise the fault of the top bend of the valve stem will occur. In recent years, after the emergence of the self-sealing valve, the medium flow direction of the globe valve has been changed from the top of the disc to enter the valve cavity, at this time, under the action of medium pressure, the force of closing the valve is small, and the force of opening the valve is large, and the diameter of the valve stem can be reduced accordingly. At the same time, under the action of the medium, this form of valve is also tighter.

China's valve "three to give" has stipulated that the flow direction of the globe valve is all top-down. When the liquefied gas shut-off valve is opened, the opening height of the disc is 25% of the nominal diameter When 30%, the flow rate has reached the maximum, indicating that the valve has reached the full open position. Therefore, the fully open position of the globe valve should be determined by the stroke of the disc.

Here are some of the well-known brands recognized in the valve industry, which are widely recognized and have a high reputation. While rankings may vary depending on time and market conditions, the following brands are generally considered to be among the top brands in the valve industry:

The following influential first-line brands of water system valves and industrial valves can be used as a reference, but for reference only: Suzhou Neway Valve, Shanghai Guanlong Valve, Shanghai Qizhong Valve, Sanhua, Su Yan, Shentong, Su Valve, Nanfang, Jiang.

First, the word Yao. The above manufacturers are only estimates and references, and the specific situation may vary or fluctuate at any time due to changes in a series of factors such as changes in the market, the size of the competition pattern, and the stability of product quality. As an indispensable key device in industrial production and civil facilities, the quality and reputation of the valve brand directly affect the satisfaction and trust of users.

These brands are known in the valve industry for their innovative technology, high-quality products and reliability. It is important to note that the market and industry are evolving rapidly, and different rankings may vary depending on time and region. For the most up-to-date ranking information, it is recommended to refer to industry reports, professional organizations or market research data for more detailed and accurate information.

This article analyzes in detail the use of pneumatic globe valves, as well as the difference between them and gate valves. If you think the answer is helpful to you, please raise your hand and give the American Weidun VTON valve stop valve a thumbs up!

The opening and closing parts of the stop valve (globe valve) are plug-shaped discs, which are flat or sea cone surfaces on the seal, and the disc moves in a straight line along the center line of the valve seat. The movement form of the valve stem, (common name: dark rod), there are also lifting and rotating rod types, which can be used to control the flow of various types of fluids such as air, water, steam, various corrosive media, mud, oil, liquid metal and radioactive media.

As a result, this type of shut-off valve valve is ideal for shut-off or regulation and throttling. This type of valve is very suitable for regulating the flow rate because the stem opening or closing stroke is relatively short, and because it has a very reliable shut-off function, and because the change of the seat port is proportional to the stroke of the disc.

Shut-off valves can be used in most material step system software. It has developed various forms of globe valves for various main purposes in petrochemical industry, electric power engineering, metallurgical industry, urban construction, chemical plants and other units.

The application of globe valve is extremely extensive, but because the opening and closing torque is very large, the structure length is long, the general nominal pipe diameter is limited to DN250m or less, and it also reaches DN400mm, but it is necessary to pay attention to the direction of the inlet and outlet when using. In general, most of the shut-off valve materials below DN15OMM are injected directly below the piston valve, while most of the shut-off valve materials above DN250m are injected from the top of the piston valve. It is fully considered to be triggered by the shut-off torque of the gate valve.

In order to reduce the torque of opening or closing, the shut-off valve above 250m is generally equipped with an internal bypass valve or an external intake valve.

Shut-off valves can also be used for flow regulation.

(1) Function:

The inlet pressure is reduced to a required outlet pressure through adjustment, and when the inlet pressure and flow rate change, the outlet pressure is automatically kept within a certain range by the energy of the medium itself.

2) Principle: When the pressure reducing valve leaves the factory, the adjusting spring is in an uncompressed state, at this time the main valve disc and the valve disc are in a closed state, turn the adjusting screw clockwise when using, compress the adjusting spring, and make the membrane flap move to the top to open the valve disc, the medium enters the piston from hole A through the valve seat to hole B, and the piston moves downward to push the main valve disc away from the main valve seat under the action of medium pressure, so that the medium flows to the back of the valve. At the same time, it enters the diaphragm below by the C hole, when the pressure behind the valve exceeds the set pressure, the diaphragm is pushed up to compress the adjusting spring, and the valve disc moves to the closing direction accordingly, so that the medium flowing into the piston above decreases, and the pressure also decreases, and the main valve disc moves up and down under the promotion of the spring force of the main valve disc at this time, so that the gap between the main valve disc and the main valve seat is reduced, and the medium flow rate is also reduced, so that the pressure behind the valve also drops to a new equilibrium, on the contrary, when the pressure behind the valve is lower than the set pressure, the gap between the main valve disc and the main valve seat increases, The flow rate of the medium also increases, which increases the pressure behind the valve to a new equilibrium.

Liquefied gas pressure reducing valve: It is a valve applied to liquefied gas.

The operation of the liquefied gas pressure reducing valve is controlled by the pressure behind the valve. When the pressure sensor detects that the valve pressure indication is rising, the valve opening of the pressure reducing valve decreases; When the pressure reducing valve is detected, the pressure decreases and the valve opening of the pressure reducing valve increases to meet the control requirements. Liquefied gas pressure reducing valve – the pressure reduction ratio of this valve must be higher than the system value to a certain extent; It should be able to respond to positive or negative control signals even at maximum or minimum flow rates.

These valves should be selected for the useful control range, i.e. 20% to 80% of the maximum flow rate. Normal is isometric or has isometric characteristics. These types of valves inherently have the optimal flow characteristics and flow range required for proportional control.

It should be checked and replaced frequently, otherwise it will affect your normal use.

The definition of "valve" is a device used to control the direction, pressure, and flow of fluid in a fluid system. A valve is a device that allows the flow of media (liquids, gases, powders) in pipes and equipment to flow or stop, and controls its flow.

The valve is a control component in the pipeline fluid transportation system, which is used to change the channel section and the direction of medium flow, and has the functions of diversion, cut-off, regulation, throttling, check, diversion or overflow pressure relief. Valves for fluid control, from the simplest globe valves to the most complex automatic control systems used in a variety of valves, its varieties and specifications, valves from the very small instrument valve to the diameter of 10m for industrial pipelines. The valve can be used to control the flow of various types of fluids such as water, steam, oil, gas, mud, various corrosive media, liquid metal and radioactive fluid, the working pressure of the valve can be from ultra-high pressure to 1000MPa, and the working temperature is from ultra-low temperature of -269 to high temperature of 1430.

The control of the valve can adopt a variety of transmission modes, such as manual, electric, hydraulic, pneumatic, worm gear, electromagnetic actuation, electromagnetic hydraulic, electro-hydraulic, gas-hydraulic, spur gear, bevel gear drive, etc.; Under the action of pressure, temperature or other forms of sensing signals, it can act according to predetermined requirements, or simply open or close without relying on sensing signals, and the valve relies on a drive or automatic mechanism to make the opening and closing parts lift, slide, swing or slew movement, so as to change the size of its flow channel area to achieve its control function.

The opening and closing parts of the liquefied gas shut-off valve are plug-shaped discs, the sealing surface is flat or conical, and the disc moves in a straight line along the center line of the fluid. The movement form of the valve stem has a lifting rod type (the valve stem is lifted, and the handwheel is not lifted), and there is also a lifting and rotating rod type (the handwheel and the valve stem rotate together to lift the god beat, and the nut is located on the valve body). The shut-off valve is only suitable for full opening and full closing, and is not allowed to be adjusted and throttled.

The liquefied gas shut-off valve is a forced seal valve, so when the valve is closed, pressure must be applied to the disc to force the sealing surface not to leak.