Globe valves have become a necessary instrument in controlling fluid flow. They are used for two major functions as they also operate as on-off valves. These valves have a wide range of applications in several industries, such as water systems, turbine seals, and fuel oil systems.
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However, the design of the globe valve results in resistance to fluid flow, and this leads to high-pressure drops in the fluid. Therefore, before selecting a globe valve, factors such as pressure drop at positions within the valve and valve sizing should be considered.
This post discusses the function of the globe valve, its parts, installation and maintenance requirements, and other factors to be considered before buying an industrial globe valve.
Globe valves are valves whose disc or plug moves in a straight line to allow, restrict or regulate the media flow. The vertical movement of the globe valve disc is called linear motion, which is why globe valves are called linear motion valves.
As the disc moves linearly down the valve, the globe valve seat opens to accommodate the discs. The globe valves are primarily used, because of their design, for throttling and regulation of flow through the valve. Still, they can also be used in the on/off services of totally allowing or restricting media.
During passage through the globe valve, the fluid moves up on the side of the seat and against the valve disc before continuing its flow; this cleans the disc and reduces dirt in the valve body.
However, the fluid flow rate and direction are altered and therefore result in a substantial pressure drop as the fluid moves.
The globe valve symbol is composed of two triangles meeting at a point. A solid circle is inserted at the meeting point of the triangles, and solid horizontal lines extend from the opposite sides of the triangle.
The horizontal lines show that the globe valve is a two-way inline valve used for throttling and on-off applications.
The globe valve symbol used in piping and instrumentation diagrams (P&ID) is a modification of the valve symbol, which is the same symbol without the solid circle at the meeting point of the two triangles.
The three isometric symbols in the diagram indicate symbols for butt-welding end connections, flanged ends, and socket ends connections.
Globe valves are of various types and can be differentiated based on their valve body design and body-bonnet connection.
Globe valves can be differentiated into three types based on their body design: Angle pattern globe valve, Standard or T-pattern globe valve, and Oblique or Y-pattern globe valve.
This valve is a commonly used industrial globe valve. The valve seat is set horizontally so that the disc moves perpendicular to the flow through the pipe flanges.
The standard pattern globe valve obstructs flow in several places in the valve body, leading to a high-pressure drop during the fluid passage. This pattern offers the highest obstruction to flow among the three patterns, and it also has the lowest flow coefficient.
The T-pattern globe valve is used in extreme throttling cases. For example, they are used in processing plant operations in bypass lines required around control valves. Also, they are used in flow regulation operations where pressure losses in the fluid are not important.
This pattern is a modified version of the T-pattern. The angle pattern globe valve has its ends at a right angle, and fluid flows after a 90-degree rotation. Angle pattern globe valves have a higher flow coefficient than the standard pattern globe valves.
Because of the ability of the globe valves to handle slug flow of fluid, it is used commonly with fluids of periodic variations and pressure changes. The angle pattern globe valve offers lower obstruction to fluid flow than the standard valves.
Also, when installed near pipeline ends, they decrease the number of pipe joints required and function as a pipe elbow in changing the direction of the fluid flow.
The oblique pattern globe valve, out of the three globe valves, offers the least obstruction to fluid flow. Because it least obstructs flow, this results in a decreased fluid pressure drop.
The valve seat is positioned at 45 degrees to the stem, contributing to the direct fluid flow through the valve and the reduction in fluid pressure drop.
TheY-pattern globe valves are not easily susceptible to erosion, even after long periods of fluid flow. During early operation periods, the oblique globe valve is used for flow regulation. Their ability to be cleaned off of sludges when operating in closed lines gives them an advantage over some other valves.
Bonnets are components of the globe and gate valve placed on top of the valve body. The bonnet connects the valve body to the manual lever device or the actuators and grants entry into the valve trim components.
Industrial valve manufacturers uncouple the bonnet from the body for repair and maintenance of globe valves. The body-bonnet connection is important for easy maintenance, checking the seal’s integrity, valve size selection, etc.
Below are the types of globe valves based on the bonnet connection to the valve body :
The bolted bonnet globe valve is also called the screwed-in globe valve. It is the most common and economical connection. The bonnet should not be uncoupled from the valve body often as it may damage the joining areas of the bolts.
The bonnet joints of these valves require large torque in screwing into the valve body and are usually used on valve sizes that are not large.
The welded bonnet globe valve is created by welding the bonnet to the valve body. The bonnet is usually welded completely to the valve body when made of a weldable material.
The welded bonnet connection can be applied to most valve sizes and is functional in different operating conditions.
However, a major disadvantage of the welded bonnet is that uncoupling the connection could damage the bonnet and valve body. Hence, this bonnet connection is used in cases where the valve body can be discarded.
Flanged bonnet globe valves have bolts spread over the connection area. The extra bolts help hold the connection tighter and are more evenly spread than in the bolted connection globe valves. It also allows the flanged bonnet connection to be applied to various sizes of valves and demanding operating conditions.
However, for larger valve sizes, the flanged connection may be welded for safer operations.
In the union ring bonnet globe valve, the bonnet is joined to the valve body with a union ring. The contact areas for the joints in this bonnet connection are not affected by frequent unscrewing. However, it is used in valve sizes that are not large.
This bonnet connection is most suitable for high temperature and pressure conditions. The pressure seal bonnet globe valve uses fluid pressure to tighten the joint between the bonnet and valve body.
Globe valves are usually compared to the gate and ball valves. While the gate and ball valves function as on-off valves, the globe valve functions as a throttling device in on-off operations. Here are some of its other advantages in piping operations:
The vertical movement of the valve disc to the valve seat encourages the good throttling ability of the globe valve. As the valve is closed, the space between the disc and seat reduces gradually over a short distance, contributing to good flow regulation.
The globe valve has a simpler construction than the gate valve. With one sealing surface and minimal sealing area, the globe valve reduces construction costs and saves production material.
Maintenance of the globe valve is easy, and it offers a better production process because the valve saves cost and material.
There is little or no sliding between the valve seat and disc surfaces, leading to less friction between the two surfaces. Therefore, the sealing surfaces experience less wear over a long period and provide good sealing operations.
Also, because the valve seat and disc do not wear easily, the service life of the globe valve is longer than some valves.
Other advantages of the globe valve include:
These are some disadvantages experienced while using the globe valve:
The fluid pressure is overcome by the valve disc from the opposite end, requiring large torque to close this valve. Also, to lift the globe valve disc and open the valve, large torque is required.
Shutoff valves offer the highest resistance to flow. This resistance occurs because there are various obstructions to fluid flow in the valve. The high resistance also leads to high-pressure losses in the fluid.
Globe valves restrict the movement of flow to one direction. Fluids can only move from the bottom up or down without changing direction.
Other disadvantages of globe valves include:
Globe Valves function in on-off operations as blocking or isolation valves and in throttling operations to regulate flow. They are largely designed to operate as flow regulators but are also functional when fully open or closed to restrict fluid flow.
As a result of the small height of the globe valve compared to the gate valve, the globe valve disc moves a short distance to the valve seat when opening or closing. The ability of the valve to decrease the space between the valve seat and disc gradually makes it suitable for throttling operations.
Also, globe valves are less likely to be damaged by fluid flow when in a partially open position; this contributes to its effectiveness as a throttling device.
When used in on-off operations, the globe valve disc design is carefully selected to ensure sealing reliability. Linear motion valves such as gate, needle, and globe valves can be applied in many operations with suitable conditions.
The parts of the globe valve include the actuator, stem, disc (plug), valve body, seat, and bonnet.
The valve disc is the main part of the globe valve responsible for allowing, restricting, or controlling fluid flow within the pipeline. The valve disc pulls up or moves down in reaction to the stem rotation.
Globe valve discs are designed in three ways: Plug disc design, Composition disc design, and Ball disc design.
These discs have an end that narrows to a flat surface. They are better for use in flow regulation than the ball and composition disc.
Composition discs are suited for water systems because they are hardly eroded. They have a wider surface than the plug and ball disc and are replaceable.
This design is mostly used for on-off operations. It has a narrowing lower end and is usually used in low pressure and temperature conditions.
The valve seat is the sealing surface for the disc. It is made to accommodate the valve disc as it drops down to close the valve. The globe valve seat can be made with the valve body or screwed. The valve disc connects with the seat at a right angle, resulting in a more reliable seal.
A globe valve back seat is the sealing point for the stem and bonnet above the disc. It holds the media pressure from reaching the valve packing as the valve disc rests on it when fully open.
The stem connects the disc with the valve actuator. It is usually joined to the bonnet, and the disc can be connected to the stem in two ways: slipping over the stem or screwing into it.
For faster action, the globe valve stem is designed to allow the disc to move in the direction of the fluid as it closes.
This part of the globe valve protects the internal components of the machine. The globe valve is designed to have a simple but solid body construction.
The valve actuator rotates the stem, which controls the movement of the valve disc. The opening and closing of the valve are determined first by the actuator. The globe valve actuator is classified into two types based on the requirements of the valves. The types are:
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Bonnets are components of the globe valve placed on top of the valve body. The threaded stem passes through the bonnet through a hole, and the bonnet connects the valve body to the manual lever device or the actuators.
The function of the globe valve is to allow, restrict, or control the flow of media through the pipe from one area to another. To accomplish this, the globe valve uses a valve disc and a valve seat.
The globe valve seat is positioned parallel to and at the center of the pipe. When the handwheel is turned or the actuator is operated automatically, the valve stem is rotated, and the valve disc moves.
For on-off operations, the globe valve disc, controlled by the stem, is either lowered fully to seal with the valve seat and hence block the flow of media or raised fully to allow the flow of media. When the valve disc is raised fully, the fluid flow is at its highest rate, and when it is lowered fully, fluid flow is shut off completely.
For throttling operations, the disc is not fully raised, and the fluid flow occurs in direct proportion to the lifting of the valve disc.
Proper installation of globe valves decreases premature wear and tear and ensures proper operation of the valves. Upright installation of the globe valves and waste removal inside the valve are some proper installation practices. Some others are:
Maintenance of globe valves increases their service life and ensures they work at optimal conditions. Here are some maintenance practices that enable globe valves to last longer:
Globe valves are selected based on their suitability to conditions such as temperature, pressure, type of fluid, etc. Therefore selecting the suitable globe valve is based on the valve size, material type, pressure rating, standard, and design of the valve, to select the appropriate globe valve.
Various materials such as cast iron, steel, and plastics, are used in producing globe valves because of their application in most industries. Selecting an appropriate globe valve requires knowledge of the qualities of the media passing through the valve.
Globe valves made with stainless steel are usually used for high-temperature conditions as it is resistant to seizing and galling. Manufacturers should be consulted to know the specific globe valve for different conditions.
Globe valve designs are classified into two types: Valve Body Design and Disc Design. The globe valve body design includes the standard pattern, angle pattern, and oblique pattern.
The standard pattern valve offers the most obstruction to flow, leading to a higher fluid pressure drop in this valve, while the angle pattern valve is suitable for fluids with slug flow. The oblique pattern valves are hardly susceptible to erosion. (These patterns have been explained in detail under globe valve body types)
The globe valve disc design includes the composition disc, plug disc, and ball disc. The composition disc is best suited for water system operations, while the plug discs have the best flow regulation of the three designs. The ball disc is appropriate for low temperature and pressure conditions. (These, too, have already been discussed above under globe valve parts)
Valve sizing is essential for throttling valves as the sizes determine how fluid flows through the valve. Selecting the globe valve size requires research and knowledge of the requirements. Usually, the manufacturer sizes the valve for a buyer. Sizing a globe valve is different for each of its functions.
As a throttle valve, the globe valve size is important for calculating the pressure drop at specific positions in the valve.
While functioning in on-off operations, the pressure drop is not monitored as the globe valve functions to allow or restrict fluid. However, a smaller valve size may restrict the flow, but it is a more economical option than the larger valve sizes.
Below are some important standards used in petrochemical industries for the globe valve:
Choosing the right globe valve for your system requires careful consideration. Many factors influence how effectively the valve operates for your needs. For example, understanding what your system requires is crucial. You should evaluate aspects such as pressure, temperature, flow, and the weight of the fluid. These details are especially vital in demanding environments like chemical plants or high-temperature systems.
The material of the valve is also significant. If you choose the wrong material, it may rust or leak, leading to faster wear and tear. Additionally, selecting the right size and pressure rating is essential to prevent issues or failures. Finally, examining how the valve operates ensures it functions optimally for your configuration. By taking all these factors into account, you can ensure that you choose the right globe valve, which will enhance your system’s performance, maintain safety, and extend its lifespan.
Knowing what your system needs is the first step. Globe valves are great for controlling flow accurately. Their design helps make small, precise adjustments. Industries like chemical plants or water treatment use them often. They are trusted for shutting off flow and preventing leaks.
Different flow types also matter for your system. Quick-opening valves are best for on-off tasks. Linear flow valves work well with steady pressure drops. Equal percentage valves handle changing pressure losses better.
Flow Type What It Does Quick Opening Reaches high flow fast; good for on-off tasks. Linear Flow matches valve opening; great for steady pressure drops. Equal Percentage Flow increases evenly as valve opens; handles changing pressures.Choosing the right flow type makes your system work better and saves energy.
Picking the right material keeps your valve safe and lasting longer. Wrong materials can rust, leak, or break the system. Stainless steel works well in chemical areas. Cast iron is better for less harsh uses.
Use guides like ASTM Piping Materials Match Table to check materials. These tools help you pick the right body, bonnet, and trim materials. Good material choices stop damage and lower repair costs.
Getting the right size and pressure rating is very important. A valve too big or small can cause problems. Big valves may not control flow well. Small ones might not handle enough flow.
A good-sized valve is usually smaller than the pipe. It should open 60%-80% at full flow and not less than 20% at low flow. Follow standards like ANSI B16.34 or ISO to ensure proper size and pressure.
Standard What It Covers ANSI B16.34 Rules for valve design, thickness, and size. ISO Dimensions for metal valves in pipe systems.By picking the right size and pressure, your system will run smoothly and avoid problems.
Understanding actuation is key when picking a globe valve. Actuation decides if the valve works manually or automatically. The right actuation helps your system work well and meet needs.
There are three main actuation types: manual, electric, and pneumatic. Each type has its own advantages and fits different uses.
Tip: Think about your system’s needs, like how often it runs, the environment, and your budget. Picking the right actuation improves the valve’s performance and lifespan.
Choosing the best actuation ensures the valve works properly and fits your system.
Knowing the fluid’s properties is very important for valve choice. Fluids can affect valves differently based on their type. For example, soft-seated valves work in low pressure but fail in high heat. Metal-seated valves are better for high pressure and heat, lasting longer.
Not considering fluid properties can cause problems like:
Choose valves that match the fluid’s type to improve system reliability.
Picking the wrong valve size can mess up flow control. Big valves may drop pressure too much and cause vibrations. Small valves might block flow, making control harder.
Problems from wrong sizing include:
Make sure the valve size fits the system’s needs. Correct sizing reduces wear and keeps the valve working longer.
Skipping maintenance can lead to expensive fixes and delays. Cheap valves often need replacing more, raising costs. Old manuals or staff changes can make upkeep harder.
Issues from poor maintenance include:
Regular checks and following schedules keep valves working well. Buying good valves with clear guides saves money and time later.
Choosing the wrong way to control your globe valves can cause problems. It may lead to safety issues, wasted money, and poor performance. There are three main types: manual, electric, and pneumatic. Each has its own pros and cons. Knowing these differences helps you avoid mistakes.
Manual control is good for simple systems with rare changes. But it’s not safe for high-pressure or hard-to-reach places. For example, in a hot system, manual control can put workers at risk.
Electric controls are precise and work well in automated setups. However, they might fail in dangerous areas with flammable gases. In such cases, pneumatic controls are better. Pneumatic systems use air, making them safe in risky places. But they need a steady air supply, which isn’t always possible.
Tip: Think about your system’s safety, how often it runs, and its environment. This helps you pick the best control type for your globe valves.
The wrong control type can also make maintenance harder. Electric systems often need experts to fix them, causing delays. Manual controls wear out faster if used too much, leading to higher costs.
Choosing the right control type improves how your globe valves work. It also saves money and makes your system last longer.
Choosing the right globe valves is very important in oil and gas. These systems often face high pressure and harsh fluids. Strong and reliable valves are needed to handle these conditions. High-pressure globe valves control flow well and lower failure risks. Materials like stainless steel or special alloys resist corrosion from chemicals and gases.
Think about how the valve will be operated. Pneumatic actuators are common in oil and gas because they are safe and reliable. They don’t use electricity, so there’s no spark risk in flammable areas. Picking valves made for these tough conditions improves performance and reduces downtime.
Chemical plants need valves that can handle harsh and rough fluids. The material of the valve must match the fluid type. Anti-corrosion materials help the valve last longer and stop leaks. Studies show that fixing issues like seal wear and material mismatch lowers failure rates a lot.
Controlling flow precisely is also very important. Globe valves are great for adjusting chemical flow. Regular care, like checking and oiling parts, keeps valves working well. Focusing on these things ensures safe and smooth chemical processing.
In power plants, globe valves manage steam and hot fluids. These systems need valves that handle high heat and pressure without failing. Studies show better valve designs can reduce problems like pressure drops and cavitation. For example, computer models improve flow and make valves more efficient.
Check the valve’s flow coefficient (CV) too. This affects how well it controls flow and pressure. Research shows picking the right CV saves energy and boosts efficiency. Using globe valves made for power plants ensures good performance and cuts costs.
Globe valves are important in water treatment systems. They control water flow, manage pressure, and stop backflow. This helps the system run smoothly. These valves are used in key areas like raw water intake, chemical dosing, and sludge removal. Their precise control keeps water clean and systems working well.
Why are globe valves so useful in water treatment? These systems often face changing flow rates and pressures. The right valve ensures smooth operation and avoids problems like leaks or pressure spikes. For example, in chemical dosing, globe valves let you adjust flow rates accurately. This ensures the right amount of chemicals mixes with water, reducing waste and improving efficiency.
When picking a globe valve for water treatment, consider key factors. These include pressure limits, flow rates, and the type of fluid. The table below shows important metrics to check:
Metric What It Means Design pressure The highest pressure the valve can handle. Flow rate How much fluid moves through the valve in a set time. Media flowing through the valve The type of liquid or gas passing through the valve. Allowable pressure drop The biggest pressure loss allowed during use. End connection type How the valve connects to the pipes.Knowing these details helps you pick the right valve. For example, if your system uses harsh chemicals, choose a valve made from materials that resist corrosion. This choice reduces damage and makes the valve last longer.
Tip: Take care of your globe valves with regular cleaning and checks. This keeps them working well, lowers repair costs, and prevents downtime.
Choosing the right globe valves for water treatment improves system performance. It also lowers risks and meets water quality rules. By focusing on your system’s needs, you can make smart choices that benefit your operation.
Picking the right globe valve for your industry needs careful thought. You must check your system’s needs, material fit, size, and control type. Talking to experts or manufacturers can help you decide. Experts often talk to suppliers and users to get honest advice. This method gives correct and useful information.
Parameter What It Means Market Drivers and Restraints Looks at what helps or slows the market grow Raw Material Scenario Checks supply and price changes Regulatory Scenario Explains current and future rules Capacity Analysis Shows how much more can be added by Forecasting Methodology Uses models to predict short and long-term trendsHere’s how to start:
Tip: The right valve boosts efficiency and cuts repair costs and delays.
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