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Ball Valves vs Globe Valves,Which Valve is Best for You?

There are many different types of valves available for different applications. With so much choice it can be difficult to decide which valve is most suitable for your application. In this article, STV Supplies explores the merits of ball valves versus globe valves.

 

 

 

 

WHAT IS THE MAIN DIFFERENCE BETWEEN BALL AND GLOBE VALVES?

The main difference between ball and globe valves is the way they close. Ball valves have a stem and ball, which turns horizontally, and are commonly referred to as “rotational” valves. Whereas, globe valves have a stem and plug, which strokes linearly, and gives them their other name of “stroke” valves. Ball valves are best suited to applications requiring on/off control without pressure drop. While globe valves excel at regulating flow.

HOW DOES A BALL VALVE WORK?

Ball valves are designed with a ball inside the valve. A ball valve is a form of quarter-turn valve which uses a hollow, perforated and pivoting ball (called a “floating ball”) to control flow through it. It is open when the ball’s hole is in line with the flow and closed when it is pivoted 90-degrees by the valve handle. The handle lies flat in alignment with the flow when open, and is perpendicular to it when closed, making for easy visual confirmation of the valve’s status.

HOW DOES A GLOBE VALVE WORK?

Globe valves were for many years the industry standard in control valves. They are named for their spherical body shape, with the two halves of the body being separated by an internal baffle. This has an opening that forms a seat onto which a movable plug (or disc) can be screwed in to close the valve. Typically, automated globe valves use smooth stems rather than threaded and are opened and closed by an actuator assembly.

WHICH IS BETTER: A BALL VALVE OR GLOBE VALVE?

Ball valves are durable, performing well after many cycles, and reliable, closing securely even after long periods of disuse. These qualities make them an excellent choice for shutoff applications, where they are often preferred to gates and globe valves. On the flip side, ball valves do lack the fine control in throttling applications offered by globe valves.

STV SUPPLIES STOCKS BALL AND GLOBE VALVES

 

 

STV stock a wide range of ball valves, from quarter-inch to six-inch at our works in Bishopbriggs. From general purpose two-piece ball valves, v-ball control valves, hygienic valves, to heavy duty ball valves for steam; we have a variety of sizes, end connections and materials to suit many applications. We also stock globe valves up to six-inch in size, and can supply many size and material variants on a next-day basis.

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What is a Gate Valve

The gate valve is a fairly common valve that can be seen in the piping systems of many homes and structures. It is the preferred valve for houses because it is rather easy for any homeowner to operate. It can also be used for more industrial purposes and are instantly recognizable.

Since this particular valve’s design is for it to either be opened all the way or closed all the way, the drop in pressure across the actual valve is extremely limited when opened, making it possible for fluid to flow through nearly seamlessly and the seal that exists between the valve’s disk and the valve’s seat is strong enough to resist any pressure that may be coming from the fluid.

Like with any other kind of valve, the gate valve has its advantages and disadvantages and recognizing what these are will provide any potential user the ability to make a better informed choice in what kind of valve they should use. Also, knowing the pros and cons can make the user know what to expect and what needs more looking after.

One of the advantages of gate valves is its high capacity as well as its ability to seal tightly, making the shutoff of any flow possible and any leakage nearly impossible. This particular kind of valve is also known to be very cost effective, which is probably why it is a popular choice for countless residences. Gate valves also have low friction loss because there is almost nothing obstructing the flow of the fluid when the valve is fully opened, creating little resistance to the flow.

As earlier mentioned, gate valves are meant to be fully opened or fully closed and partially opening the valve is bound to cause vibration which in turn leads to damage to the valve. Another thing that needs to be taken into consideration is that the valve disks and valve seats go through a great deal of wear and tear, making it necessary to replace them more often than compared to other kinds of valves. Because it is either fully opened or fully closed, gate valves are thought to have difficulty in controlling flow.

Overall, the gate valve remains a great choice as a control valve for any piping system that does not need to be constantly turned on or off. It is able to handle large flows of fluid, making it work for industrial purposes as well. Gate valves can also work with several materials such as oil, gas, air, steam, heavy and corrosive liquids, non-condensing gases, and slurries, making it a versatile selection.

The most important thing to remember when gate valves are used in a piping system is how it is maintained. According to an article entitled how to maintain a gate valve, the proper maintenance of gate valves can help ensure that they function properly and last for years so making sure that these valves are taken care of accordingly enables there to be more pros than cons.

 

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To Understand About Parts Of A Ball Valve

While contemplating on the brand and type of ball valve to purchase for use in your shut off application or flow control system, be in the know of its various parts. Having an adept knowledge of its parts will give you an idea of how the valve entirely works when it is installed.

1. Body :

This part is regarded as the principal part of a valve, regardless of its shape and type. It is the part that gives framework to the whole valve because it holds all the other parts intact. It also serves as the pressure boundary of the valve because it is the first line of resistance against the volume and pressure of the liquid flowing through all the pipes connected to it.

2. Bonnet:

This part covers the opening in the valve’s body. It also serves as the second pressure boundary. Valve bonnets are usually bolted and screwed with the body. It is also usually made of the same material as the body to make the whole valve firmer and stronger.

3. Trim:

This part is a collection of differentinternal valve parts such as disk, seat, stem and sleeves. Because of these internal parts, the valve can perform basic motions to provide flow control. The disk together with the seat is important in determining the performance of the valve system. In most designs, the disk serves as the third layer of pressure boundary. It can permit and prohibit fluid flow due to its pressure-retaining capacity.

The seat, also called as seals ring provides an interface to where the disk is seated. The seal rings can either be forged within the body by welding or by machine. The stem is responsible for positioning the disk. It connects the actuator and the disk usually though welded joints.

4. Actuator:

This part works in conjunction with some internal parts located in the valve trim. This part is responsible for running the stem and disk. There are many types of actuator that are available in the market today. Some are handwheels, levers, motors, solenoids, pneumatic operators or hydraulic arms. Most valve manufacturers’ provide a design where the actuator is mounted with the bonnet through a yoke.

5. Packing:

This part commonly prevents leaks from the space between the valve stem and bonnet. The valve packing can be made from fibrous materials like flax or some other materials like Teflon. Regardless of the valve packing composition, it should be able to form a seal between the internal parts and the outer valve environment where the stem extends from the valve body. The packing must be properly placed to prevent leaks that can cause further damages to the entire valve system. The packing must neither be too loose nor too tight.

In summary, knowledge of the different parts of a ball valve will give you a generalized idea of how it will work during the entire span after it has been installed by your designated workforce. It will also help you to have a rough estimate of the cost of implementing a flow control system with the use of a ball valve.

 

 

 

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how to select Gate Valve

Knowing the right kind of gate valve to select depends greatly on how you are planning to use it in your piping system. A professional’s advice and guidance can help whittle down the choices and recommend which one will work best in your precise setup.

There are two basic types of gate valves that can be purchased and installed as part of the plumbing system of a structure. These two types depend on the manner in which the disk is designed in the actual gate valve. As mentioned in the article parts of a gate valve, the gate valve disk is basically the gate that can seal shut when the valve is closed, meaning no water flow is possible, and can open when the valve is opened, allowing water pressure to pass through.

The two basic types of gate valves are:

1. Parallel Gate Valve

 

The parallel gate valve is used in valves that have parallel valve seats. The two halves of the parallel disk can either be thrust together or spread apart and there is often a spring-like mechanism that assists in the proper sealing of the disks to the seats. There is a variety of designs that use the parallel gate valve but the bottom line for each design is to make sure that there is optimum sealing that occurs between the disks and the seats.

2. Wedge Gate Valve

 

The wedge gate valve is separated into three categories:

  • Solid Wedge: The solid wedge gate valve is considered to be the most commonly used disk and is known for the simplicity in its design that belies its strength. The solid wedge gate valve functions well in any position it is placed in and can handle almost any kind of fluid.
  • Flexible Wedge: The flexible wedge gate valve is a singular disk whose perimeter has a cut around it in order to be able to fit better in the valve seats. The cut depends on the design of the valve seats and the flexible wedge gate valve works best with steam systems since heat can cause expansion and cold can cause contraction, making it necessary for more flexibility to occur within the disk.
  • Split Wedge: The split wedge gate valve has a ball and socket design that are able to self-adjust and self-align to the valve seats’ surfaces. This makes it possible for half the disk to adjust and align itself if the other half is unable to do so due to something being lodged that makes it impossible for it fit snugly into the valve seat. The split wedge gate valve is appropriate for systems that handle non-condensing gases and liquids.

Knowing the right kind of gate valve to select depends greatly on how you are planning to use it in your piping system.One particular type of design may work specifically for plumbing purposes in a home while another type of design may work better in an industrial setting. This is why it is important to have the correct information on each type of gate valve and whether they will meet your specific requirements and needs. A professional’s advice and guidance can help whittle down the choices and recommend which one will work best in your precise setup.

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how to maintain a gate valve

Like other mechanical products, valves also need maintenance. This work well, can extend the service life of the gate valve, the following will introduce the maintenance of the Gate valve.

1. Gate Valve storage and maintenance

The purpose of storage and maintenance is not to damage the valve or reduce the quality. In fact, improper storage is one of the important reasons for valve damage.
The Gate valves should be kept in good order. The small valves should be placed on the shelf. The large valves can be arranged in order on the ground of the warehouse. They should not be stacked disorderly. The flange connection surface should not contact the ground. This is not only for the sake of beauty, but also to protect the valve from damage.
Due to improper storage and handling, broken handwheel, crooked valve stem, loose nut between handwheel and valve stem, etc., these unnecessary losses should be avoided.
Asbestos packing should be taken out for valves not to be used for a short time to avoid electrochemical corrosion and damage of valve stem.
Check the valve just entering the warehouse. If there is rain or dirt in the process of transportation, wipe it clean and then store it.
The inlet and outlet of the valve should be sealed with wax paper or plastic sheet to prevent dirt.
The valve surface that can rust in the atmosphere should be coated with antirust oil for protection.
The outdoor Gate valves must be covered with rain proof and dust-proof materials such as linoleum or tarpaulin. The warehouse where the Gate valves are stored should be kept clean and dry.

2. Gate valves operation and maintenance

The purpose of operation and maintenance is to extend the service life of the valve and ensure the reliability of opening and closing.
Stem thread, often with the stem nut friction, to apply a little yellow dry oil, molybdenum disulfide or graphite powder, lubrication.
Do not often open and close the valve, but also regularly turn the hand wheel, add lubricant to the stem thread to prevent seizure.
For outdoor valves, theGate valves stem shall be protected from rain, snow, dust and rust.
If the Gate valves is mechanical, add lubricating oil to the gearbox on time.
Always keep the valve clean.
Always check and maintain the integrity of other parts of the valve. If the fixing nut of the hand wheel falls off, it should be matched and can not be used properly, otherwise it will grind the square on the upper part of the valve stem, gradually lose the reliability of matching, and even can not start.
Do not rely on the Gate valves to support other heavy objects, do not stand on the Gate valves.
The valve stem, especially the thread part, should be wiped frequently, and the lubricant that has been contaminated by dust should be replaced with a new one, because the dust contains hard debris, which is easy to wear the thread and the surface of the valve stem, affecting the service life.

3. Maintenance of valve packing

The packing is directly related to the key seal of valve leakage when opening and closing. If the packing fails, causing leakage, the valve will be equivalent to failure, especially the valve of urea pipeline, because of its high temperature, corrosion and easy aging of packing. Strengthening maintenance can prolong the life of packing.
When the valve leaves the factory, in order to ensure the elasticity of the packing, it is generally subject to the static pressure test without leakage. After the valve is installed into the pipeline, due to the temperature and other factors, the leakage may occur. At this time, the nuts on both sides of the packing gland should be tightened in time. As long as there is no leakage, the leakage can occur again in the future. Do not tighten it once, so as to avoid the loss of elasticity and sealing performance of the packing.
Some valve packing is filled with molybdenum disulfide grease. When it is used for several months, the corresponding grease should be added in time. When it is found that the packing needs to be supplemented, the corresponding packing should be added in time to ensure its sealing performance.

 

4. Maintenance of valve transmission parts

In the process of valve opening and closing, the original lubricating oil will be continuously lost. Coupled with the effect of temperature, corrosion and other factors, the lubricating oil will continue to dry up. Therefore, the transmission parts of the valve should be checked frequently, and the lack of oil should be added in time, so as to prevent the increase of wear due to the lack of lubricant, resulting in inflexibility of transmission or failure of case

 

5. Maintenance of valve during grease injection

When the Gate valves is greased, the amount of grease is often ignored. After the grease gun is filled with oil, the operator selects the valve and grease connection mode to carry out the grease injection operation. There are two situations: on the one hand, the amount of grease injection is less, and the sealing surface is worn faster due to the lack of lubricant. On the other hand, excessive fat injection causes waste. The reason is that there is no accurate calculation for the sealing capacity of different valves according to the valve type. The sealing capacity can be calculated according to the valve size and type, and then a reasonable amount of grease can be injected.
When the valve is greased, the pressure problem is often ignored. During the operation of fat injection, the pressure of fat injection changed regularly from peak to valley. If the pressure is too low, the seal leaks or fails, if the pressure is too high, the grease injection port is blocked, the grease in the seal is hardened, or the seal ring is locked with the valve ball and valve plate. Usually, when the grease injection pressure is too low, the injected grease flows into the bottom of the valve chamber, which usually occurs in small gate valves. On the one hand, check the grease nozzle, if the grease hole is blocked, judge the situation and replace it; On the other hand, it is the hardening of grease. It is necessary to use cleaning fluid to soften the failed sealing grease repeatedly and inject new grease for replacement. In addition, seal type and seal material also affect the grease injection pressure. Different seal forms have different grease injection pressure. Generally, the grease injection pressure of hard seal is higher than that of soft seal.

When greasing the valve, pay attention to the problem that the valve is in the on / off position. Ball valve maintenance is generally in the open state, special circumstances choose to close maintenance. Other valves can not be treated as open. The gate valve must be closed during maintenance to ensure that the grease fills the sealing groove along the sealing ring. If it is open, the grease will directly fall into the flow channel or valve cavity, causing waste.

When the Gate valves is greased, the effect of greasing is often ignored. During the operation, the pressure, amount and switch position were normal. However, in order to ensure the effect of valve greasing, sometimes it is necessary to open or close the valve, check the lubrication effect, and confirm that the surface of valve ball or ram is evenly lubricated.
Attention should be paid to the blowdown of valve body and the pressure relief of screw plug during grease injection. After the pressure test of the valve, the gas and water in the valve chamber of the sealing chamber will be increased due to the rise of the ambient temperature, and the blowdown and pressure relief should be carried out before the grease injection, so as to facilitate the smooth progress of the grease injection. The air and water in the sealing cavity are fully replaced after grease injection. The pressure of the valve chamber is released in time, which ensures the safety of the valve. After grease injection, the drain and pressure relief plugs must be tightened to prevent accidents.
When injecting fat, pay attention to the problem of even fat. During normal fat injection, the nearest fat hole to the fat injection port first gets fat, then goes to the low point, finally to the high point, and then gets fat one by one. If not in accordance with the law or not out of fat, prove the existence of blockage, timely clearing treatment.
When greasing, the valve diameter and sealing ring seat should also be observed. For example, for ball valve, if there is open position interference, the open position limiter can be adjusted inward, and it can be locked after confirming that the diameter is straight. The adjustment of the limit should not only pursue the position of the opening or closing side, but should be considered as a whole. If the opening position is flush and the closing position is not in place, the valve will not be closed tightly. In the same way, the corresponding adjustment of the opening position should also be considered when adjusting the closing position. Ensure right angle travel of the valve.
After the grease injection, the grease injection port must be sealed. Avoid impurities entering or lipid oxidation at the grease injection port. The cover shall be coated with anti rust grease to avoid rusting. So that it can be applied in the next operation.

When greasing, we should also consider the specific problems in the future oil sequential transportation. In view of the different quality of diesel and gasoline, the scouring and decomposition capacity of gasoline should be considered. In the later valve operation, in case of gasoline section operation, timely add grease to prevent wear.
When greasing, do not ignore the greasing of the valve stem. There is sliding sleeve or packing on the valve shaft, which also needs to be lubricated to reduce the friction resistance during operation. If the lubrication can not be ensured, the torque will be increased during electric operation, and the worn parts will be worn, and the switch will be laborious during manual operation.
Some ball valves are marked with arrows on the valve body. If there is no English fiow handwriting attached, it is the direction of action of the sealing seat, not as a reference for the flow direction of the medium. The direction of self discharge of the valve is opposite. In general, double seat sealed ball valve has two-way flow direction.
During valve maintenance, attention should also be paid to the problem of water inflow in the electric actuator and its transmission mechanism. Especially in rainy season. One is to rust the transmission mechanism or shaft sleeve, the other is to freeze in winter. When the electric valve is operated, the torque is too large, and the transmission parts will be damaged, which will make the motor no-load or over torque protection jump off, and the electric operation cannot be realized. The transmission parts are damaged, and manual operation cannot be carried out. After the over torque protection action, manual operation is also unable to switch, if forced operation, the internal alloy parts will be damaged.
Valve maintenance should be treated with a scientific attitude in order to achieve the desired effect and application purpose. In order to make the production run normally, reduce the shutdown and increase the economic benefits, we must do these three things well in the aspect of valves

Correct selection of valves is the foundation.
Correct use of the valve is the key.
Correct maintenance is the guarantee.

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Gate valve Overview

Overview of gate valve standard: the opening and closing part of gate valve is gate.

The movement direction of the ram is perpendicular to the direction of the fluid.

The gate valve can only be fully opened and fully closed, and cannot be adjusted or throttled. The gate has two sealing surfaces. The two sealing surfaces of commonly used gate valves are wedge-shaped, and the wedge angle varies with the valve parameters. Wedge gate valve gate can be made into a whole, known as the rigid gate; It can also be made into a ram that can produce a small amount of deformation, so as to improve its processability and make up for the deviation of sealing surface angle in the processing process. This kind of ram is called elastic ram.
Working principle of gate valve: when the gate valve is closed, the sealing surface of flange gate valve can only be sealed by medium pressure, that is, the sealing surface of gate valve is pressed to the valve seat on the other side by medium pressure to ensure the sealing of secret cover, which is self sealing. Most gate valves use forced sealing, that is, when the valve is closed, the gate must be pressed to the seat by external force to ensure the sealing surface. Gate valve gate and stem linear movement, lifting stem gate valve (also known as rising stem gate valve). Generally, there is a trapezoidal thread on the lifting rod, which passes through the nut on the top of the valve and the guide groove on the valve body. The rotary motion becomes linear motion, that is, the operating torque becomes the operating thrust.

When the gate valve is opened:
When the lifting height of the flange gate valve is equal to 1:1 of the valve diameter, the fluid passage will be completely unobstructed, but this position cannot be monitored during operation. In practical use, the apex of the stem is used as a mark, that is, the position where it cannot be opened, as its fully open position. In order to consider the locking phenomenon caused by temperature change, it is usually opened to the top position, and then returned to 1 / 2-1 circle as the position of full open gate valve. Therefore, the full open position of the valve is determined by the position (i.e. stroke) of the ram. In some gate valves, the stem nut is installed on the gate valve, and the handwheel rotation drives the stem to rotate, so as to lift the gate. This kind of valve is called rotary stem gate valve or Non rising stem gate valve.

Gate valve type: according to the configuration of sealing surface, flange gate valve can be divided into wedge gate valve and parallel gate valve. Wedge gate valve can be further divided into: single gate type, double gate plate type and elastic gate type; Parallel gate valve can be divided into single gate plate and double gate plate. According to the thread position of the stem, it can be divided into two types: rising stem gate valve and Non rising stem gate valve.

Gate valve structure features:

1. Gate valve fluid resistance is small, sealing surface is less media scrubbing and corrosion.

2. The workload of opening and closing is saved.

3. The flow direction of the medium is not limited, it will not interfere with the flow, and it will not reduce the pressure.

4. Simple shape, short structure length, good manufacturing process and wide application range.

Application scope of gate valve: gate valve is widely used in domestic steel plant, petroleum, chemical, natural gas, boiler, paper making, textile, medicine, food, transportation, water supply and drainage, energy, polysilicon, electric power and other industrial pipelines for medium cutting and circulation. Flange gate valve is suitable for pipes with nominal pressure of pn1.6 ~ 6.4Mpa and working temperature of – 29 ~ 600 ℃. It can cut off or connect pipeline medium without adjustment and throttling. The applicable medium of gate valve is water, oil, steam, acid medium, etc.

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STV Delivers Wafer Check Valves to a Thailand Customer

China dual check valve,spring loaded check valve,Wafer Check Valve,Wafer Swing Check Valve,stainless steel check valve Manufacturer with high quality and competitive price

The valve made by stainless steel ASTM A351 CF8

We just delivered some special material check valves to a Thailand customer.

Generally:
Dual-plate check valve, wafer type
***design as per API 594
***for mounting between two flanges, as per ASME B16.5

***body: ASTM ASTM A351 CF8
***disc: ASTM ASTM A351 CF8
***trim: ASTM A182 F304
***spring: INCONEL X750
***body seat: stellite

10″-150 LB    25pcs
10″-150 LB    25pcs

China Dual Plate Check Valve,Hub type double disc swing check valve,Lug type double disc swing check valve,Axial flow Check valve,Double flanged type tilting disc check valve,Wafer type single disc lift check valve, single disc swing check valve,Wafer type single disc swing check valve,Wafer type tilting disc check valve,Double fanged type double disc swing check valve,Lug type double disc swing check valve,Wafer type double disc swing check valve

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