A Brief Introduction to Valves

author: ATHENA GROUP -09-04 Valves are mechanical devices used to control the flow of fluids (liquids, gases, or slurries) through a system by opening, closing, or partially obstructing the passage. They play a crucial role in various industries, including manufacturing, oil and gas, water treatment, and more.  

Basics of Valves

  The valves are available in various types: gate, globe, plug, ball, butterfly, check, diaphragm, pinch, pressure relief, control valves, etc. There are a number of models available for each of these types, each with its own functional capabilities. In some cases, valves are operated manually, while in others, they are operated by an actuator, pneumatics, or hydraulics.  

The Functions of Valves Are as Follows

  Flow Regulation: Valves control the flow rate of fluids or gases within a system, allowing operators to adjust the volume and speed of flow as needed.
Shut-Off: Valves can completely stop the flow of fluids or gases, providing a means of isolating sections of a pipeline or system for maintenance, repairs, or emergencies.
Pressure Control: Some valves are designed to regulate and control the pressure of fluids or gases within a system, helping to maintain safe operating conditions.
Directional Control: Valves with multiple ports enable directional control, determining the path of fluid or gas flow within hydraulic, pneumatic, or other systems.
Backflow Prevention: Check valves specifically prevent backflow, ensuring that fluids or gases flow in one direction only to prevent contamination or damage to upstream components.
Various types, models, and designs of valves have been developed for a wide range of industrial applications. Each satisfies one or more of the functions outlined above. It is important to specify the right valve for the function and to build it from the right material for the process liquid, since valves are expensive items.
In general, all valves are composed of the following basic components: the body, bonnet, trim (internal elements), actuator, and packing.   

Valve Body

  The valve body, often referred to as the shell, serves as the primary enclosure for a pressure valve. It plays a central role in the valve assembly as it provides the structural framework that holds all the valve components together.
Functioning as the initial pressure boundary of a valve, the valve body withstands fluid pressure loads from the connected piping. Inlet and outlet piping are connected to the valve body through threaded, bolted, or welded joints.
The valve body's ends are designed to facilitate the connection of the valve to the piping or equipment nozzle using various types of end connections, including butt or socket-welded, threaded, or flanged connections.
Valve bodies are manufactured through casting or forging processes, and each component within the valve body serves a specific function and is constructed from materials suitable for that purpose.  

Valve Bonnet

  The bonnet is the second most important boundary of a pressure valve. Like valve bodies, bonnets are available in a wide variety of designs. A bonnet acts as a cover on the valve body, and is cast or forged of the same material as the body. Most common connections are threaded, bolted, or welded. When the valve is manufactured, the internal components, like the stem, disk, etc., are put into the body, and then the bonnet is attached to hold the whole thing together.
There is always a pressure boundary at the attachment point of the bonnet to the body. In other words, the bolts or weld joints that secure the bonnet to the body act as pressure-retaining parts. Although valve bonnets are an integral part of most valves, they are also a source of concern. As well as complicating valve manufacture, bonnets can increase valve size, contribute to the cost of valves, and can cause leaks.  

Valve Trim

  An valve's trim is a term used to describe the parts that can be replaced. The trim of a valve includes a disk, a seat, a stem, and sleeves used to guide the stem.
A valve's performance is determined by the disk and seat interface and the relationship between the disk position and the seat. It is possible to control flow and perform basic motions through the trim. Rotational motion trim designs change the flow opening by sliding the disk closely past the seat. In linear motion trim designs, the disk lifts perpendicularly away from the seat, forming an annular orifice.  

Valve Disk and Seat(s)

  The valve disk and seat(s) are critical components within a valve assembly that play a crucial role in controlling the flow of fluids or gases through the valve. Here's a brief overview of these components:
Valve Disk (or Valve Closure Element):
Function: The valve disk, often referred to as the closure element, is the part of the valve that opens or closes to regulate or block the flow of fluids or gases. It acts as a barrier that can be moved into or out of the flow path to control the flow rate.
Design: Valve disks come in various designs, including flat disks, balls, plugs, and more, depending on the type of valve. The shape and design of the disk are selected based on the specific requirements of the application.
Materials: Valve disks are typically made from materials that can withstand the conditions within the valve, such as pressure, temperature, and the nature of the fluid or gas being controlled. Common materials include metals like stainless steel, brass, or plastics.
Sealing: When the valve is in the closed position, the disk forms a tight seal against the valve seat to prevent fluid or gas from passing through. The quality of this seal is critical to prevent leakage and maintain system integrity.
Valve Seat(s):
Function: The valve seat is a stationary component within the valve body against which the valve disk seats when the valve is in the closed position. It provides a sealing surface for the disk, ensuring a tight closure to prevent fluid or gas leakage.
Design: Valve seats are designed to be highly precise and often feature a sealing material or coating that enhances the sealing capability. The design of the seat may be flat, conical, or spherical, depending on the valve type and application.
Materials: Valve seats are typically made from materials that are compatible with the valve disk material and are resistant to wear and corrosion. Common materials include various types of metal alloys, elastomers, and polymers.
Maintenance: Valve seats can wear over time due to friction and the abrasive nature of some fluids. Regular inspection and maintenance may be required to ensure the continued effectiveness of the sealing surface.  

Valve Stem Packing

  Packings are used to seal the stem and the bonnet, and they are equipped with components such as:
The gland follower is a sleeve that compresses the packing by a gland into the stuffing box.
The gland is a kind of bushing that compresses the packing into the stuffing box.
The stuffing box is a chamber that compresses the packing.
There are several types of packing, such as Teflon®, elastomeric material, fibrous material, etc.
When the valve is fully open, a backseat provides a seal between the stem and bonnet, preventing system pressure from building up against the valve packing. It is commonly used in gate and globe valves.
Most valves, like standard Ball, Globe, Gate, Plug, and Butterfly valves, have their sealing assemblies based on shear force, friction, and tearing.
As a result, valve packaging must be properly done to keep the stem from being damaged and fluid or gas loss from occurring. If the packing is too loose, the valve will leak. If the packing is too tight, the valve will be difficult to move, and the stem may be damaged.  

Best Instrument Valve Manufacturer 

  ATHENA GROUP is a prominent manufacturer of fluid system components, with a global presence and a well-deserved reputation for producing high-quality products and providing exceptional customer support. The company is headquartered in Milan, Italy, and has a strong foothold in the industrial market.
Over the years, ATHENA GROUP has evolved from being a regional valve and level gauge manufacturer to becoming a robust and diversified global group with a significant presence in the industrial sector.

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What Are Valves and How Do They Work? 

At their most basic, valves are devices that work to control, regulate or direct flow within a system or process.

They often feature a range of characteristics that help to define their ideal application.

However, whether you&#;re looking to control flow, provide safety in a system that is piping liquids, solids, gasses or anything in between, there are likely stainless steel valves available to help.

Valves provide several functions, including:

• Starting or stopping flow based on the valve state
• Regulating flow and pressure within a piping system
• Controlling the direction of flow within a piping system
• Throttling flow rates within a piping system
• Improving safety through relieving pressure or vacuum in a piping system

Valve Opening Methods Explained

While many valves accomplish similar goals, how they do so mechanically can vary.

How a valve opens and closes will not only impact the overall performance but also determine how much control you have over the flow and how quickly the valve can operate.

Most valves fit into one of three categories:

• Multi-Turn valves: Think of these valves like a screw or piston. You crank the handle and the plug, plate, membrane, or other controlling obstruction moves into the path of the pipe blocking access. Depending on the valve, these can have higher or lower differentials allowing you to open or close them at various speeds.
• Quarter turn valves: Quarter-turn valves offer a full range of motion in a 90-degree turn of the handle. This makes them ideal for situations where precision isn&#;t as important as rapid action and easy opening or closing.

On top of the mechanical motion involved with a valve, also consider the method of actuation. In most cases, valves fall into one of three categories:

• Manual Valves: Typically adjusted by hand, these valves use handwheels, hand levels, gear wheels, or chains to actuate.
• Actuated Valves: Often connected to electric motors, air or pneumatic systems, hydraulic systems, or solenoids, these valves allow remote control and automation for high-precision or large-scale applications.
• Automatic Valves: Some valves activate when a specific flow condition is met. Examples include check valves closing during backflow or pressure release valves activating when an over-pressure condition is detected.

Common Valve Types and Their Applications

Valves feature a range of characteristics, standards, and groupings the help to give you an idea of their intended applications and expected performance. Valve designs are one of the most basic ways to sort the huge range of valves available and finding a good fit for a project or process.

Common types of valves include:

You might also see valves classified by function instead of design.

Common functional designations and their common design types include:

• Isolation Valves: Ball, butterfly, diaphragm, gate, pinch, piston, and plug valves
• Regulation Valves: Ball, butterfly, diaphragm, globe, needle, pinch, and plug valves
• Safety Relief Valves: Pressure release and vacuum relief valves
• Non-Return Valves: Swing check and lift check valves
• Special Purpose Valves: Multi-port, float, foot, knife gate, and line blind valves

Valve Sizing Explained: Keeping Things Flowing

While valves might be a small part of your piping process or system in terms of space, they&#;re often a substantial portion of the design and build budget. They also have a significant impact on long-term costs and overall system performance.

Choosing a proper valve size is essential to both optimizing costs and ensuring safe, accurate, and reliable operation.

The first thing to consider is the overall size of the valve -- both in terms of physical dimensions and in terms of internal size and flow rates (CV).

Are you interested in learning more about Valve Opening Key? Contact us today to secure an expert consultation!

Choosing a valve that does not fit properly in the space required could result in added costs. Choosing a valve which does not provide the ideal flow rate can lead to inaccurate flow control at the least and complete system failure at worst.

For example, if your valve is too small, it could cause reduced flow downstream while creating back-pressure upstream. If the valve is too large, you&#;ll find that flow control is drastically reduced the further you move from fully open or fully closed.

When choosing the proper size, be sure to consider both the connector diameter and the overall flow rate of the valve compared to your needs. Some valves offer excellent flow while others constrict flow and increase pressure.

This means sometimes you must install a larger valve to adjust for flow than the adapter diameter alone might imply.

Valve End Connections: The Key to a Good Fit and Proper Operation

With sizing and design out of the way, it&#;s also important to consider valve end connections.

While the most obvious implication here is choosing an end connection compatible with your piping, there are also functional characteristics to common end types that might make one valve more suited to your needs than another.

Common valve connections and ends include:

• Screwed or Threaded: Often used in instrument connections or sample points
• Flanged: The most common ends for piping use
• Butt Welded: Typically used in high-pressure or high-temperature operations
• Socket Welded: Commonly used on small bore piping where threaded connections are not permitted
• Wafer and Lug: Often used for compact valves installed in systems with limited space

Valve Materials: Ensuring Safety and Long-Lasting Performance

Depending on your intended use, the materials with which your valves are made might be a critical aspect in ensuring safe operation and reducing maintenance and replacement costs over the life of your operation.

Stainless steel valves are excellent options in a range of processing environments, including those involving corrosive media (such as chemicals, saltwater, and acids), environments with strict sanitation standards (such as food and beverage manufacturing and pharmaceuticals), and processes involving high pressure or high temperatures.

However, if you are processing solvents, fuels, or volatile organic compounds (VOCs), choosing a valve material from a non-sparking material -- such as brass, bronze, copper, or even plastic -- is often a better option. In addition to selecting the correct body material, internal (wetted) trim parts should be evaluated for chemical compatibility as well. If your valve contains elastomers, they should also be evaluated for their chemical compatibility as well as pressure and temperature limitations.

Valve Standards: Meeting Compliance and Regulatory Concerns

Depending on your intended usage, you might find that valves must adhere to particular standards to meet regulatory requirements for safety, sanitation, or other concerns.

While there are too many standard organizations and potential regulations to cover in detail, common general standard organizations include:

• CSA Group (CSA)
• The American Society of Mechanical Engineers (ASME)
• The American National Standards Institute (ANSI)
• The American Society for Testing Materials International (ASTM International)
• The Manufacturers Standardization Society (MSS)
• The International Organization for Standardization (ISO)
• The Public Health and Safety Organization (NSF)
• NACE International (NACE)
• The American Petroleum Institute (API)
• American Water Works Association (AWWA)

There are also industry-specific standards to consider.

Major standards organizations by industry include:

• ASHRAE Valve Standards
• ASME BPVC Valve Standards
• ASSE Valve Standards
• ISA Valve Standards
• NFPA Valve Standards
• SAE Valve Standards

Final Thoughts

Choosing the right valve for your project might seem complex. However, by starting with general characteristics -- such as valve design, valve size and actuation method -- you can quickly limit your options to determine the best valves for your needs.

Whether you&#;re designing a new processing system or looking to make upgrades to or maintain an existing system, Unified Alloys&#; selection of valves and fittings can help you find the ideal solution for your application and usage environment. As a leading provider of stainless steel alloys, valves, flanges, and more, our experts have helped industries across Canada and North America for more than 4 decades. Need assistance or have a question? Contact us for personalized help.

If you want to learn more, please visit our website Non-Sparking Flat Chisel Tools.