Globe valve is a kind of plug-shaped disc, the sealing surface is flat or conical, and the disc moves linearly along the center line of the valve seat. The movement form of valve stem (commonly known as hidden rod) and lifting rotary rod can also be used to control the flow of various types of fluids such as air, water, steam, corrosive medium, mud, oil, liquid metal and radioactive medium. Therefore, this type of cut-off valve is very suitable for cutting off or adjusting and throttling. Because the opening or closing stroke of the valve stem is relatively short, and it has a very reliable cutting function, and because the change of the valve seat opening is proportional to the stroke of the disc, it is very suitable for flow regulation.
Classification:
According to the channel direction
1) Direct cut-off valve
2) Direct-flow cut-off valve: In direct-flow cut-off valve or Y-shaped cut-off valve, the flow passage of the valve body and the main flow passage form a diagonal line, so that the damage degree of the flow state is smaller than that of the conventional cut-off valve, and the pressure loss through the valve is correspondingly smaller.
3) Angle cut-off valve: In the angle cut-off valve, the fluid only needs to change direction once, so that the pressure drop through this valve is smaller than that of the conventional cut-off valve.
4) Plunger globe valve: This type of globe valve is a variant of the traditional globe valve. In this kind of valve, the disc and seat are usually designed according to the plunger principle. The disc is polished into a plunger connected with the valve stem, and the sealing is realized by two elastic sealing rings sleeved on the plunger. The two elastic sealing rings are separated by a collar, and the sealing rings around the plunger are firmly pressed by the load exerted on the bonnet by the bonnet nut. The elastic sealing ring can be replaced and made of various materials. Valves are mainly used for "opening" or "closing", but they are equipped with special plungers or special collars, which can also be used to adjust the flow.
Position of threads on the valve stem
1) Threaded stem globe valve: Thread of globe valve stem.
Outside the valve body. Its advantage is that the valve stem is not corroded by medium and is easy to lubricate. This structure is widely used.
2) Lower threaded stem globe valve: The thread of the globe valve stem is in the valve body. The valve stem thread of this structure is in direct contact with the medium, which is easy to be corroded and cannot be lubricated. This structure is used in places with small diameter and low temperature.
There are many manufacturers of globe valves in China, and the connection dimensions are mostly different. Mainly divided into the following categories: general category based on JB/T 2203- 1999 stop valve structure length. At present, most domestic manufacturers of globe valves design and produce according to this standard. However, this standard is not perfect and the specification is not complete. The maximum nominal diameter of single gate globe valve is DN 1200, and that of double gate globe valve is DN 1500. According to the specifications of stop valves produced by manufacturers and existing data, the minimum nominal diameter of angle stop valves is DN 15, and the nominal diameter of Z-type straight-through stop valves reaches DN2000. After textual research, the connection dimensions of various manufacturers are not uniform. In order to have a unified standard, users can exchange the same specifications when selecting and installing. It is suggested that China General Machinery Research Institute revise JB/T 2203- 1999 "Structural Length of Stop Valve". It is suggested that design institutes and users should choose according to standards, and manufacturers of globe valves should design and manufacture according to standards.
According to the purpose
The fluorine-lined globe valve is suitable for aqua regia, sulfuric acid, hydrochloric acid, hydrofluoric acid, various organic acids, strong acids and strong oxidants with various concentrations at -50 ~ 150℃, and also suitable for pipelines with various concentrations of strong alkali organic solvents and other corrosive gases and liquid media.
International globe valve is the most commonly used product in globe valve series. API American globe valves implement ANSI and API standards. The sealing surfaces of disc and valve seat are made of stellite with different hardness, which has the advantages of reliable sealing, high hardness, wear resistance, high temperature resistance, corrosion resistance, good scratch resistance and long service life.
Needle valve is a kind of small-caliber instrument valve, which plays the role of opening and closing and accurate flow control in instrument measurement pipeline system, mainly including power station instrument series, oilfield special series, American standard series and so on.
Low-temperature cut-off valve usually refers to the valve with working temperature lower than-1 10℃, which is widely used in low-temperature industries such as liquefied natural gas and liquefied petroleum gas. Since 2008, globe valves with the applicable temperature of-196℃ can be manufactured, and all parts are pretreated with liquid nitrogen at low temperature, thus completely avoiding the seal deformation and leakage during use.
Plunger valve is also called plunger globe valve, and its sealing surface adopts radial sealing structure. The load exerted on the valve cover by two elastic sealing rings sleeved on the polishing plunger through the connecting bolt between the valve body and the valve cover compresses the elastic sealing rings around the plunger, so as to seal the stop valve.
Insulation jacket globe valve adopts insulation jacket design, and uses external heat source to heat circularly outside the valve, which can effectively prevent the temperature loss of the medium when it passes through the valve and ensure the temperature of the medium.
Forged steel globe valves are designed and manufactured according to API 602 standard, and three bonnet design forms are provided: bolted bonnet, welded bonnet and pressure self-sealing bonnet. Users can choose different forms according to their needs, and provide three connection methods: RF flange, NPT thread and SW welding.
The oxygen special cut-off valve is made of silicon brass or stainless steel with excellent material, which has the advantages of high mechanical strength, wear resistance and good safety. Used in oxygen pipeline, it has the best explosion-proof and flame-retardant performance, eliminates the unsafe factors in oxygen pipeline, and is widely used in the pipe network of oxygen engineering such as steel, metallurgy, petrochemical and chemical industry. In addition to the functions of ordinary valves, it has its own characteristics. Strict oil prohibition measures are adopted during manufacturing, and all components are strictly degreased before installation.
Bellows globe valve is designed with molded stainless steel bellows. The bellows has been tested by 10000 times, and the sealing performance is reliable. Suitable for industrial and mining with flammable, explosive, toxic and harmful media, which can effectively prevent valve leakage.
The installation and maintenance of stop valve should pay attention to the following matters:
1, the stop valve operated by handwheel and handle can be installed anywhere in the pipeline.
2. Handwheels, handles and micro-motion mechanisms are not allowed to be used for lifting.
3. The flow direction of the medium should be consistent with the arrow direction shown on the valve body.