Medium of initial conditions, the valve closed pipe into the valve body, with big holes on the disc into the disc lumen, start the drive, the stem drive small disc first open, open the seal, medium through a small disc, the valve on both ends of the differential pressure decreases rapidly, continue to open small disc until fully open) (about a third of the valve, the valve stem continues to rise to drive the disc open, open the seal, and valve fully open. The stem force of the force needed to open a small disc and the function of the medium on the large disc force (gravity negligible), the small disc opens, the pressure differential between the valve import and export decrease (mainly depends on sealing area ratio between inside and outside), the open large disc, medium forces acting on the large disc far less directly using single disc medium forces acting on the disc, the valve stem of total force decreases, and the stem diameter smaller, lumen size smaller, the overall structure of the valve is reduced, the weight, and at the same time open the valve drive thrust decreases, and at the same time reduces the valve and a driving gear manufacturing costs, Improve the use economy of the valve to achieve the purpose of energy saving.

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The closing principle of the cast steel globe valve is that relying on the pressure of the valve stem, the sealing surface of the disc and the sealing surface of the valve seat are closely fitted to prevent the flow of the medium.

Ⅰ. Structures of the cast steel globe valve

The length is longer than that of the gate valve, the fluid resistance is large, and the sealing reliability is not strong during long-term operation.

As one of the most important shut-off valves, the cast steel globe valve plays an important role in the aerospace field. As an important component of aerospace equipment, the cast steel globe valve realizes the functions of medium transportation, cutoff and adjustment, and its sealing performance directly affects the safe and reliable operation of aerospace equipment.

The study of the influencing factors and rules of the sealing characteristics of typical cast steel globe valves has guiding significance for the structural design of the valve sealing pair, thereby improving the sealing performance and reliability of the valve.

Ⅱ. What is the selection standard of the cast steel globe valve?

1. Cast steel globe valves should be selected for pipelines or devices of high temperature and high-pressure medium. For example, cast steel globe valves are suitable for high temperature and high-pressure pipelines of thermal power plants and petrochemical systems;
2. On the pipeline where the convection resistance requirements are not strict, that is, the place where the pressure loss is not considered;
3. Cast steel globe valves can be selected for small valves, such as needle valves, instrument valves, sampling valves, pressure gauge valves, etc.;
4. There is flow adjustment or pressure adjustment, but the requirements for adjustment accuracy are not high, and the diameter of the pipeline is relatively small. For example, on the pipeline with a nominal diameter of ≤ 50mm, a cast steel globe valve or throttle valve should be used;
5. For water supply and heating projects in urban construction, for pipelines with smaller nominal diameters, cast steel globe valves, balance valves or plunger valves can be applied, such as pipelines with a nominal diameter less than 150mm;
6. Applicable to medium pipelines such as steam below DN200;
7. Not suitable for medium with high viscosity;
8. Not suitable for media containing particles that are easy to precipitate;
9. It is not suitable for vent valve and valve of low vacuum system.

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Application scope of globe valve

The opening or closing stroke of the stem of the globe valve is relatively short, which has a very reliable cut-off function. The stroke between the opening and closing of American Standard globe valve disc is small, and the sealing surface can withstand multiple opening and closing. Therefore, the globe valve is fit for switching on & off frequently, which can be used in most media process systems. Globe valve is widely used in petrochemical, electric power, metallurgy, urban construction, chemical industry and other industries.

Installation direction of globe valve

The chamfered flat disc is between flat and conical in terms of its shape. If the opening height of the disc is very small and the bottom of the disc is not higher than the seating surface, the formula of conical disc can be used. If the opening height is large, and AK value is close to the data determined by the formula of plane sealing disc, at this time, the opening height of disc shall be calculated according to the distance between the bottom of disc and the seating surface.

When it is viewed from both sides of the globe valve, the downward raised part of the valve stem is “low”. On the other side, the channel connected to the valve chamber slightly higher (relative to “low”) is “high”. Globe valve: DN ≤ 200mm and PN ≤ 4. Globe valve of 0mpa adopts method of low inlet and high outlet. When DN > 200 mm, method of high in and low out should be selected. When the diameter is larger than 200 mm, due to the larger flow rate and the large pressure on the unit area, a large opposite force is needed to ensure the sealing when using the method low inlet and high outlet.

The structure of globe valve body includes straight through type, straight flow type and right angle type. Straight through is the most common structure, but its fluid resistance is the largest. Direct flow fluid has less resistance and is mostly used for fluid with solid particles or high viscosity. The right angle valve body is mostly forged, which is suitable for the globe valve with small diameter and high pressure.

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Working principle of globe valve

Generally, the stem of globe valve is rotated and lifted, and the handwheel is fixed on the top of the stem. When the handwheel is rotated clockwise, the stem thread is screwed down, the sealing surface of the disc is in close contact with the valve seat, and the globe valve is closed. When the handwheel is rotated counterclockwise, the stem thread is screwed up, the sealing surface of disc and valve seat is separated, and the globe valve is opened.

Features of globe valve

Advantages of globe valve

a.Compared with the gate valve, the globe valve is simple in structure with only one sealing surface on the valve body and disc. The sealing area is small, no expensive materials are used, with low cost, so the manufacturing process is relatively good, and it is simple to maintain.

Disadvantages of globe valve

• a. The length of the structure is large.
• b.The opening and closing torque is large, and it takes time to open and close. When the valve is closed, the movement direction of the disc is opposite to the action direction of the medium pressure, and the force of the medium must be overcome, so the opening and closing torque is large.
• c.The flow resistance is large. The medium channel in the valve body is tortuous, the flow resistance is large, and the power consumption is large. In the hydraulic device, the pressure loss is particularly obvious. Among all kinds of block valves, the block valve has the largest flow resistance.
• d. The flow direction of the medium is limited. When the medium flows through the globe valve, it can only flow from the bottom to the top or from the top to the bottom at the valve seat channel, so the medium can only flow in one direction and can not change the flow direction.
• e.When the valve is closed, solid particles in the fluid medium may be trapped between the sealing surfaces
• f. Inconvenient installation.

Operation characteristics of globe valve

The sealing form of globe valve is forced sealing. When the valve is closed, sufficient force must be applied to the valve disc to achieve the effect of sealing, and the sealing can be realized only when the specific pressure is sufficient.

Sealing force and medium pressure are on the same axis. When the medium enters from the lower part of the valve disc (low in and high out), the closing torque of the valve is greater than the opening torque due to the opposite direction of the medium pressure and the sealing force, and the maximum stress on the valve rod is the pressure stress, so there must be sufficient strength and rigidity, otherwise the valve rod will be deformed.

Therefore, when the size of the globe valve is larger than DN150 (NPS 6), in order to reduce the operating torque of the valve and reduce the diameter of the valve stem, the medium is usually flowed to the upper part of the valve disc to enter (high in and low out). At this time, the direction of medium pressure and sealing force is the same. Under the action of medium pressure, the valve can be sealed more easily. The closing torque decreases and the opening torque increases, the maximum stress on the valve stem is tensile stress, and the valve stem diameter can be reduced accordingly.

When the globe valve is opened, when the opening height of the disc reaches 25-30% of the nominal size of the valve, the flow has reached the maximum, that is, the valve has reached the full open position, so the full open position of the globe valve should be determined according to the stroke of the disc.

When the globe valve is closed and reopened, it is similar to the forced seal gate valve, that is, after the valve is closed, sufficient operating force shall be applied on the sealing surface to achieve the effect of sealing. Therefore, the closing torque of the valve should be increased to the specified value based on the operating torque. When the valve is opened again, the opening torque of the valve is usually larger than the closing torque due to the influence of static friction, thermal expansion and other factors, thus, the valve can be opened reliably, and it should be considered in the design.

In order to reduce the high impact pressure formed in the opening and closing valve, the globe valve should be operated slowly, in a sense, it should have a rate of change consistent with the flow rate.

The operating torque of the globe valve has the following characteristics:

“Low inlet and high outlet openings”

When “low inlet and high outlet” is adopted, the valve is closed from the fully open position. The resistance that the operating force needs to overcome is the friction resistance of the stem and packing and the thrust caused by the medium pressure on the disc section (axial). With the falling of the valve disc, the pressure difference between the front and the back of the valve disc is formed, which prevents the valve disc from falling, and the resistance will increase rapidly with the falling of the valve disc. With the valve completely closed, exerts a forced sealing force is applied by the valve rod, and the pressure difference between the front and back of the valve disc reaches the maximum working pressure of the medium, at this time, the valve rod bears the maximum closing torque.

During valve opening, medium pressure, or thrust caused by pressure difference between front and back of disc the same as direction of closing valve. However, it should be noted that at the moment of opening, the opening operating torque may exceed the closing torque due to the large static friction torque between sealing surfaces.

“High inlet and low outlet openings”

When “high inlet and low outlet” is adopted, the valve is closed from the fully open position. The above two forces are still needed to overcome the operating force. With the decrease of the valve disc, the pressure difference before and after the valve disc is conducive to the valve closing before the valve is closed.

When the valve is opened, the situation is just the opposite. The thrust caused by the medium pressure and the pressure difference between the front and the back of the disc is opposite to the opening direction of the valve, so the operating torque required for the opening process of the valve is much larger than the closing torque.

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Flow Characteristics of Globe Valve

The opening and closing parts of the stop valve (globe valve) are plug-shaped discs, their sealing surface is flat or conical, and the discs move linearly along the center line of the fluid. For valve stem movement, there are lifting rod types (the valve rod is raised and lowered, and the hand wheel does not rise and fall) and lifting and rotating lever types (the hand wheel and the valve stem are rotated and raised together, and the nut is provided on the valve body). The globe valve is only suitable for full opening and full close. It is not allowed for adjustment and throttling.

All globe valves have an inherent flow characteristic that defines the relationship between ‘valve opening’ and flow rate under constant pressure conditions. Please note that ‘valve opening’ in this context refers to the relative position of the valve plug to its closed position against the valve seat. It does not refer to the orifice pass area. The orifice pass area is sometimes called the ‘valve throat’ and is the narrowest point between the valve plug and seat through which the fluid passes at any time. For any valve, however, it is characterized, by the relationship between flowrate and orifice pass area is always directly proportional.

Valves of any size or inherent flow characteristic which are subjected to the same volumetric flow rate and differential pressure will have exactly the same orifice pass area. However, different valve characteristics will give different ‘valve openings’ for the same pass area. Comparing linear and equal percentage valves, a linear valve might have a 25% valve opening for a certain pressure drop and flow rate, whilst an equal percentage valve might have a 65% valve opening for exactly the same conditions. The orifice pass areas will be the same.

1. Needle globe valve

It is used for precise flow control. The valve disc is usually integrated into the valve stem, and it has a needle makeup head that cooperates with the valve seat with high accuracy. In addition, the thread pitch of the needle-type globe valve stem thread is smaller than that of the ordinary valve. Under normal circumstances, the size of the needle seat valve seat hole is smaller than the size of the pipe. Therefore, it is usually limited to pipelines with small nominal diameters and is more commonly used for sampling valves.

Features of Needle Globe Valve

• A compact but extremely sturdy design for high-pressure-temperature service.
• Available types: Stop, Stop check, Needle, and Flow control.
• Available with bolted or welded bonnet.
• Packing rings are precompressed to 4000 psi to provide a high-integrity seal.
• Repairable 2-piece stem drive.
• Available with double packing, leak-off connection, and live-loading.

How are Needle Valve and Globe Valve Different?

2. DC globe valve

The stem and channel of the DC-type globe valve form a certain angle, and the sealing surface of the valve seat and the inlet and outlet passage also has a certain angle. The valve body can be made integral or separated. The globe valve that has a separate valve body uses two valve bodies to sandwich the valve seat in the middle for easy maintenance. This type of stop valve allows the fluid to hardly change the flow direction, and the flow resistance is minimized in the globe valve. The sealing surface of the valve seat and valve disc can be welded with hard alloy to make the entire valve more resistant to erosion and corrosion, which is very suitable for pipeline control in the alumina production process, and it is also suitable for pipelines with coke and solid particles.

3. Angle globe valve

The biggest advantage of the angle globe valve is that the valve can be installed at the corner of the piping system, which is easy to operate and not necessary to use 90 ° elbow. Therefore, this type of valve is most suitable to be used in synthetic ammonia production systems and refrigeration systems in fertilizer plants. For example, J44H-160, J44H-320, L44H-160, and L44H-320 are completely designed for synthetic ammonia production systems.

Classification of Angle Globe Valve

These valves can be classified depending on various parameters:

• Design of Valve Disc: Conventional or Ball disc, Composition disc, and Plug type disc.
• Disc–Stem configurations of Valve: Rotating Stem with Integral or Non-Integral Disc and Non-Rotating Stem with Integral Disc or Non-Integral Disc.
• Valve Stem Screw: Inside and Outside stem screw.
• Bonnet Design of Valve: Bolted Bonnet, Welded Bonnet, Flanged Bonnet, Union ring Bonnet, and Pressure seal Bonnet

How does an angle globe valve work?

The angle globe valve’s opening and closing sections are plug-shaped valve discs, the sealing surface is smooth or conical, and the flap travels linearly down the fluid’s centerline. The inlet and outlet channels of an angle globe valve, also known as an angle valve, are not in the same direction, creating a 90° right angle. This form of globe valve allows the medium flowing through it to change its flow path, resulting in a pressure drop.

4. Steel-ball or porcelain-ball sealed globe valve

The structural feature of the valve is that the valve body is divided into one-piece type and split type. The valve disc is a STL hard alloy steel ball, or a ceramic ball made of amorphous material by powder forming, high temperature sintering and fine development. The rolling envelope ball at the lower end of the valve stem is inside the valve hole. When the ball is rotated three-dimensionally in the ball hole of the valve stem, countless seal lines can be generated, which increases the service life of the sealing surface and can also ensure a reliable sealing.

Due to the limitation of the ball seal, this valve is generally used for smaller nominal passages, about 6-25mm. The valve is suitable for high-temperature and high-pressure steam pipelines in nuclear power plants and thermal power plants, instrumentation pipelines for sampling and sewage systems, and temperature-resistant, pressure-resistant, wear-resistant and corrosion-resistant pipelines in petrochemical and chemical systems.

5. High-temperature and high-pressure power station globe valve

The structural feature of the valve is that the connection between the valve body and the valve cover adopts a pressure self-tight seal type or a clamp type. The connection form of the valve body and the pipeline is a butt welding connection. The material of the valve body is mostly chrome molybdenum steel or chrome molybdenum vanadium steel, and the sealing surface is mostly welded with hard alloy.

Therefore, this type of valve is resistant to high temperature and pressure with good heat resistance; the sealing surface is resistant to wear, abrasion, corrosion, and it has good sealing performance and long life. It is most suitable for high-temperature and high-pressure and superheated steam pipelines in thermal power industry systems, petrochemical systems and metallurgy.

6. Fluorine lined globe valve

The opening and closing member of the fluorine-lined globe valve is a plug-shaped disc. The sealing surface is flat or conical, and the valve flap moves linearly along the center line of the fluid. For the movement form of the valve stem, there are lifting rod type (the valve rod is raised and lowered, and the hand wheel does not rise and fall) and lifting rotating rod type (the hand wheel and the valve rod are rotated and raised together, and the nut is provided on the valve body).

The globe valve is only suitable for full open and full close. It is not allowed to used for adjustment and throttling. The fluorine-lined stop valves is suitable for aqua regia, sulfuric acid, hydrochloric acid, hydrofluoric acid, and various organic acids, strong acids and strong oxidants at -50 to 150 ° C. It is also suitable for various concentrations of strong alkali organic solvents and other corrosive gas and liquid medium pipelines.

7. Insulation globe valve

The opening and closing piece of the insulation glo valve is a plug-shaped disc. The sealing surface is flat or conical, and the valve flap moves linearly along the center line of the fluid. For the movement form of the valve stem, there are lifting rod type (the valve rod is raised and lowered, and the hand wheel does not rise and fall) and lifting rotating rod type (the hand wheel and the valve rod are rotated and raised together, and the nut is provided on the valve body).

The corrugated globe valve is only suitable for full open and full close, and it is not allowed to be used for adjustment and throttling. The insulation globe valve is mainly used in petroleum, chemical, metallurgy, pharmaceutical and other systems to transport high-viscosity media that will solidify at room temperature. The insulation jacket of the DC jacket insulation globe valve is welded between the two flanges of the valve, and two connection ports of the insulation jacket are provided on the side and bottom of the valve. The DC insulation globe valve is particularly suitable for pipelines in the chemical and fertilizer industries. The steam contained in the jacket can prevent the medium from crystallization. Insulated globe valves are widely used in various systems such as petroleum, chemical, metallurgy and pharmaceuticals.

8. Electric flange globe valve

Electric flange globe valve and flange gate valve is the same type of valve. It consists of electric actuator or pneumatic actuator and shut-off valve. The difference is that the closing part of the electric flange globe valve is a valve body. The valve body is rotated around the center line of itself to open and close the valve.

The gate valve is mainly used to cut off, distribute and change the flow direction of the medium in the pipeline. It has a wide range of applications, from several millimeters to large meters, and can be applied from high vacuum to high pressure.

9. API stop valve

This type of globe valve is designed in strict accordance with the ASMEB16.34 standard; the connection between the valve body and the bonnet, the stuffing box, the installation of the stem nut, and the upper seal are all designed in strict accordance with API600. The valve material fully meets the requirements of API600. Its structural length conforms to ASMEB16.10; flange connection dimensions conform to ANSI / ASMEB16.5a. The inspection and test of the valve is carried out strictly in accordance with API598. Therefore, the valve is widely used in petrochemical pipelines, and it is also suitable to be used in power, metallurgy, textile and other systems.

10. Stop valve for oxygen pipeline

11. Petroleum liquefied gas stop valve

This valve is specially designed for the pipeline or device of petroleum liquefied gas, focusing on the fire protection requirements in structure. The packing is made of polytetrafluoroethylene, which has a reliable sealing and never leaks. The sealing sub-material is made of polytetrafluoroethylene or nylon on the valve body, which is soft and reliable. This valve is suitable for the liquefied petroleum gas pipeline system as an opening and closing device, and also suitable for other pipelines with a temperature ≤80 ° C.

12. Upper threaded stem globe valve

Upper threaded stem globe valve: the thread of the stem of the globe valve is outside the valve body. The advantage is that the valve stem is not affected by the medium and is easy to lubricate. This kind of structure is commonly used.

The stem of this type of stop valve does not directly contact the working medium. It is suitable for different working conditions according to the different materials of the casing, the material of the sealing pair, the material of the packing and the material of the valve stem. If the material of the valve body and valve cover is carbon steel, the sealing sub-material is alloy steel, the filler is flexible graphite, and the material of the valve stem is Cr13 series stainless steel, which is suitable for water, steam and oil pipelines. If the valve body and bonnet material are 1Cr18Ni9 or 0Cr18Ni9, the sealing sub-material is the valve body material or hard alloy, the filler is polytetrafluoroethylene, and the valve stem material is Cr17Ni2, which is suitable for corrosive medium pipeline and device based on nitric acid. However, the maximum nominal through diameter of this type of stop valve is 200mm, and a bypass valve or an internal bypass structure should be provided on the stop valve above 200. Generally, the inlet end of a DN ≥200mm globe valve is above the valve disc, that is, high in and low out. This is to prevent from using great effort when closing it and a thick stem.

13. Lower threaded stem globe valve

Lower threaded stem globe valve: the thread of the globe valve stem is in the valve body. This structure of the valve stem thread directly contacts with the medium, susceptible to erosion, and cannot be lubricated. This structure is used in places with small diameter and low temperature.

The stem thread of this type of globe valve is in direct contact with the working medium and directly eroded by the medium, which makes the stem thread susceptible to rust and causes laborious opening and closing. The globe valve in this structure has a relatively small nominal passage, generally between 6 and 50 mm, and is mostly used for instrument valves and sampling valves.

14. API602 forged steel globe valve

This type of globe valve is designed according to American Petroleum Institute standard API602. The body and bonnet are forged from carbon steel or stainless steel. The valve body and the bonnet are connected with a bolt connection, a screw connection and welding, and are divided into an upper threaded stem and a lower threaded stem. The sealing sub-material is Cr13 steel, stainless steel acid steel to STL hard alloy. The filler is flexible graphite or polytetrafluoroethylene. Connection methods include flange, thread, socket welding and butt welding. The pressure level is CL150 ～ CL1500, and the nominal pass is 1/4 ～ 2in.

This type of globe valve is widely used in the equipment and pipelines of petrochemical, power, chemical and other departments. The working medium is steam, oil, and corrosive media. The structure length is according to ASMEB16.10, the flange connection size is according to ASME / ANSIB16.5a, the welding end size is in accordance with ASMEB16.25, the socket welding hole size is in accordance with ANSIB16.11, and the screw connection end size is in accordance with ANSIB1.20.1.

15. Plunger globe valve

This type of plunger valve is a radial seal, which is realized by two elastic sealing rings sleeved on the polished plunger. The two elastic sealing rings are separated by a collar, and the elastic sealing ring around the plunger is pressed firmly by the load applied to the valve cover by the valve body and the valve cover connecting bolts to ensure the seal. The material of the valve is composed of carbon steel for the housing and Cr13 stainless steel for the plunger. Flexible graphite for sealing ring can be used for water, steam and oil pipelines. If the shell is made of stainless acid-resistant steel, the plunger is made of stainless acid-resistant steel, and the sealing ring is made of polytetrafluoroethylene, which is suitable for acid and alkali corrosive media.

The valve has the advantages of reliable sealing, long life and easy maintenance; the disadvantage is slow opening and closing speed. This type of valve is widely used in urban construction systems, water and steam pipelines in urban heating system.

16. Bellows globe valve

The bellows globe valve is also called a bellows sealed globe valve. Through automatic roll welding, a metal barrier is formed between the fluid medium and the atmosphere to ensure a zero leakage design of the valve stem. The bellows globe valve uses a bellows structure inside, and the lower end of the stainless steel bellows is welded to the valve stem to prevent the process fluid from eroding the valve stem. The other end is placed between the valve body and the valve cover to form a static seal. For dual seal design, if the bellows fails, the valve stem packing will also prevent leakage. The corrugated pipe welding and the valve stem maintain stable running performance to avoid valve stem vibration caused by valve plug vibration. It is most suitable for pipelines of steam, flammable, explosive, thermal oil, high purity, toxic and other media.

17. Direct globe valve

The inlet and outlet channels of media of the straight stop valve are in the same direction at 180 °. This type of globe valve has relatively small damage on the flow state, so the pressure loss through the valve is correspondingly reduced. It relies on the pressure of the valve stem to tightly combine the sealing surface of the valve disc with the sealing surface of the valve seat to prevent the medium from flowing. During the opening and closing process, the friction between the sealing surfaces is small, wear-resistant, the opening height is small, and the manufacturing process performance is good. Compared with gate valves, globe valves have a simpler structure and are more convenient to be manufactured and maintained. It is the most widely-used valve in the industrial sector.

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1. Introduction of pneumatic globe valve

Pneumatic cut-off valve, widely used in the important system of mine and nuclear power plant, is an important key equipment to ensure the safety production of power plant. In the actual operation, many factors such as the setting of manual mechanism, packing failure, improper operation, insufficient air intake flow lead to many failures, which threaten the safe and stable operation of the power station. In this article, taking the pneumatic globe valve produced by SEREG as an example, analyze the working principle of typical pneumatic globe valve for power station, and describe the setting of neutral point in detail. It provides a basis for the operation and troubleshooting of SEREG pneumatic globe valve or similar pneumatic globe valve used in the power station.

2. Introduction to the working principle of pneumatic globe valve 

Working principle of pneumatic globe valve: most of the valves which uses compressed air as power source adopt remote control. The main control room manually or automatically triggers the action command to make the intake and exhaust solenoid valve act to supply and exhaust compressed air to the actuator. Compressed air acts on the piston or diaphragm to overcome the friction of valve action and the spring force on the stem. Press down (Loss of air pressure, open the valve J ) or lift up (Loss of air pressure, open the valve F1) the valve rod, driving the valve core up and down to open or close the valve. When the air pressure is lost in the valve and the driving head compresses air, the valve will be in the safe position of full opening or full closing according to the requirements of the system. The air supply pressure of the service instrument is generally 4-9 bar. Before entering the valve, filter and purify the compressed air through the filter, and then reduce the pressure through the pressure reducing valve. The reading of the inlet pressure gauge is not more than 4bar. The adjustment can be realized by adjusting the adjusting screw installed on the top of the pressure reducing valve, and the protective cover shall be loosened before adjustment.

The four most common and widely used types of pneumatic globe valves are: the valve closed by air loss of handwheel, the valve opened by air loss of handwheel, the valve closed by air loss without handwheel, and the valve opened by air loss without handwheel.

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Installation regulations for power station globe valve:

• 1. Pay attention to the flow direction of the medium when installing the power station globe valve, and it must be installed in the direction indicated by the flow direction of the valve.
• 2. The power station globe valve can be installed at any position on the pipeline, but the material needs to be selected according to the medium and the operating temperature.
• 3. The globe valve of electric power station should be installed vertically with the valve stem facing up.

High-temperature and high-pressure power station globe valve

• 1. Valve bodies below DN50 are die forgings, and valve bodies above DN65 are die forgings and steel castings.
• 2. There are three types of valve sealing surfaces: flat seal, spherical seal and tapered seal.
• 3. The connection form of valve body and bonnet: DN10 ~ DN25 is open-loop connection; DN32 ~ DN65 is screw connection; DN80 and above is pressure self-sealing structure.
• 4. The material of the valve stem is nitriding steel, which has the following advantages: long service life, high hardness, corrosion resistance and wear resistance.
• 5. The sealing surface of valve seat and valve disc adopts surfacing welding of cobalt chromium tungsten cemented carbide or ion spray welding, so it has the advantages of high hardness, wear resistance, abrasion resistance and long service life.

Material of parts of the power station globe valve with DN≤50

Material of parts of the power station globe valve with DN≥65

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What is a Stainless Steel Globe Valve?

Stainless steel globe valve is a type of globe valve that is made of stainless steel. This type of valve is meant for throttling, opening, or closing fluid flow. The stainless steel globe valve manufacturers mostly use stainless steel material to make the body, bonnet, disc, and stem. This helps to make the valve very strong and resistant to impact damage as well as able to withstand high pressure and high temperatures. Other parts of the stainless steel globe valves such as seats can be made of other materials such as plastic and or rubber. Stainless steel globe valves can be either soft seated or metallic seated valves. Metallic seated valves are the ones in which the seat is made of soft material like rubber and or plastic. Metallic seated stainless steel globe valves are the ones in which the seat is made of metallic material like stainless steel. Stainless steel globe valves use linear motion when closing or opening fluid flow. The closing member of a stainless steel globe valve is known as a disc. The disc fits on the seat to block fluid flow when the valve is closed. Stainless steel globe valve manufacturers design these valves to be either manual or automatic.

Structure of Stainless Steel Globe Valve

Stainless steel globe valves are heavy duty, outside screw & yoke type, bolted bonnet, rising stem, and hand wheel. Valves are highly efficient for services requiring frequent operation and throttling. The internal passage within the valve diverts flow through 90° changes of direction resulting in pressure drop and turbulence. The most advanced design features provide the ultimate in dependable, economic flow control. They are available in a wide range of sizes and weights. Globe valves are generally considered where moderate control or regulation of flow is required.

API 602 Forged Globe Valve

A comprehensive range of small forged gates, globe, check, angle, and bellows seal valves with unique design features.

Globe Valve Flow Direction

The most important thing to understand about globe valve direction flow is that they have specific flow directions. Depending on the application, a globe valve will have fluid flow above or below the disc.

Globe Valve Direction Flow Globe valves designed to have the pressure flowing under the disc are used in low-pressure and low-temperature applications such as general plumbing. This type of flow direction lets the disc rotate freely on the valve stem. This allows the disc to fit properly against the seat as the valve closes, which results in less seat leakage

Globe valves can also have pressure flow above the seat when applied as part of high-pressure and high-temperature systems. This type of flow direction helps to prevent the stem from contracting when it cools down and will keep the disc from lifting off the seat.

To determine the globe valve flow direction, simply look at its body. Here, you should find an arrow indicating the valve flow direction.

Features of Stainless Steel Globe Valve

1. The stainless steel globe valve structure is simpler than the gate valve, making it easier to manufacture and maintain.
2. The sealing surface is not easy to be worn and scratched, and the sealing property is good. There is no relative sliding between the valve flap and the sealing surface of the valve body when opening and closing, so it is not serious for the wear and scratch of the valve, with the features of good sealing performance, and long service life.
3. When opening and closing, the valve flap stroke is small, so the globe valve height is smaller than the gate valve, but the structure length is longer than the gate valve.
4. The opening and closing torque are a large, laborious, and long time.
5. Large fluid resistance. Because of the tortuous medium channel in the valve body, the fluid resistance is large, with huge power consumption.
6. Medium flow direction: When the nominal pressure is PN≤16MPa, the flow direction is usually downstream, and the medium flows upward from the valve flap. When the nominal pressure is PN≥20MPa, it is usually counterflow, the medium flows downward from above the valve flap, which increases the sealability. When in use, the medium can only flow in one direction and cannot change the flow direction.

Applications of Stainless Steel Globe Valve

Stainless Steel Globe valves are adequate for all service media. Valves are marked with flow direction since they are recommended to install with flow and pressure under the disc. It can also be installed in reverse conditions depending upon the conditions. The stainless steel globe Valve is generally faster to operate due to less travel. But requires much force to operate compared to Gate valves.

The stem axis of the stainless steel flange globe valve is perpendicular to the seat sealing surface. The valve stem opens or closes at a relatively short stroke, and the J41W globe valve has a very reliable shut-off action, making this valve suitable for use as a medium for shut-off, adjustment, and throttling. Once the J41W series stainless steel globe valve is open, there is no contact between its seat and the disc sealing surface, so its sealing surface is less mechanically worn. Since the valve seat and disc of most globe valves are easier to repair or replace the sealing element, it is not necessary to remove the entire valve from the pipe, which is ideal for the case where the valve and the line are welded together. The flow direction of the medium as it passes through such a valve will change, so the flow resistance of globe valves is higher than other valves.

Ten articles before and after

The differences between forged valves & casted valves – Zeco | API 602 forged valve manufacturer

Brief introduction of forging methods – Zeco | API 602 forged valve manufacturer

The features of forged steel gate valve – Zeco | API 602 forged valve manufacturer

Forged Steel Ball Valve vs Cast Steel Ball Valve – Zeco | API 602 forged valve manufacturer

Needle valve: a kind of valve that can be precisely adjusted – Zeco | API 602 forged valve manufacturer

Brief Introduction of Ball Valve – Zeco | API 602 forged valve manufacturer

Butterfly Valves with Extended Stem – Zeco | API 602 forged valve manufacturer

3-Way & 4-Way Plug Valves – Zeco | API 602 forged valve manufacturer

The Reasons for the Aging of Rubber Seals – Zeco | API 602 forged valve manufacturer

The Advantages of V-type Ball valves – Zeco | API 602 forged valve manufacturer

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