How To: The Top 10 things to consider when selecting industrial valves

So you have been tasked with selecting industrial valves for project or maintenance work and given a list of what valves, sizes and specifications. Great!!

However, how much thought has been given to whether the specification is right, the valves will be suitable, and if they will be right for the job?

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There are many assumptions around valve selection, the most common of which are:

• &#;this is what we used before&#;  &#; on an entirely different process

• &#;contractor x said this is what we need to use&#; &#; based on what? 

• &#;the site standard is x&#; &#; but what if that type of valve wont work on this application

• &#;this is what we have always used&#; &#; but have been experiencing downtime and regular failures

Getting your valve selection right from the get go is really important and in this article I will walk you through a simple 10 step process to help you ensure your valve selection is based on facts rather than assumptions.

1. What is the purpose of the valve?

Valves can be used on various different duties and perform a variety of different functions.  The best starting point when selecting any valve for industrial use is to decide what purpose it will serve.  Some things to consider might be:

• Will it be used to control or isolate media?

• Will it be used many times a minute or every few months for maintenance?

• How critical is it to your process and what would happen if it failed?

• Is it a valve that will need to work in an emergency?

Having this clear in your mind will make it a lot easier to select the right valve for the job!!

2. What is the pressure of the media going through the valve?

In deciding what valve will be most suitable for your application you should always ascertain the pressure. On high pressure applications, specialist valves will be the norm, and these types of valves typically have thick wall diameters to cope with the pressure. They also have specialist sealing arrangements like you would find on Trunnion Mount Ball Valves. On low pressure applications where bubble tight shut off is not imperative, a valve may not be the best solution at all. A good example of this is on low pressure air/exhaust applications where a &#;damper&#; would be more cost efficient and lighter in weight.

3. What is the temperature of the media going through the valve?

Temperature is also a minimum requirement for selecting Valves. Valves that are seeing extremes of temperature will often be &#;bespoke&#; as opposed to &#;off the shelf&#;.  The two main considerations with temperature, are (a) whether the materials of construction will be suitable and (b) whether the valve will seal against the temperature. Your supplier can advise you on the most suitable body material and sealing design. A good reference point here is the use of pressure/temperature charts which show how the temperature limitation of a valve will decrease as the pressure rises. These are available for most types of valves.

4. What media will be going through the valve?

Some things to consider when it comes to media:

• Are you processing something self-lubricating like food oil or engine oil?
• Is it something abrasive like sand or powder?
• Could it be something dry like air or gas?
• Is bubble tight shut off something you definitely need, or can this be sacrificed in order for the valve is used more like a &#;barrier&#; or &#;gate&#;?
• What are your expectations regarding maintenance, and can you invest in a higher specification &#;fit and forget&#; valve which will mean less maintenance down time?

There are a lot of questions around media but ascertaining this at the outset and communicating this to your supplier will mean the right valve is selected and minimise downtime as a result.

5. What are the environmental conditions where the valve will be situated?

Not all valves are going to be situated indoors in an ambient, dry and dust free environment.  Therefore think about where your valve will be fitted.  Could it be on the end of a Jetty in a saline environment? In the middle of a dry, sandy desert in extreme heat for most of the day? Submerged in water? It isn&#;t the end of the world if the valve location is not hospitable.  It just means that the materials and particularly the exterior coatings and internal seals will need to be suitable to withstand the environment. 

6. Is the valve likely to be noisy?

Sometimes valves can be noisy and a good example of this would be a Control Valve on high pressure steam.  This doesn&#;t matter if the valve will be located inside in an area that is well noise insulated, but could be an issue outside when in close proximity to houses and other buildings.  Low noise trims are available on such valves to mitigate some of this noise but its best to get this clarified at design stage as it can be something that catches engineers by surprise.

7. Will the valve be manually operated or automated?

Most modern plants are moving towards automation, but in some instances valves that are rarely used, or just used for maintenance or isolation are kept as manual valves.  Where you are looking to automate a valve, there are a few points worth considering:

• Will you actuate with an Electric or Pneumatic Actuator?
• What will the pressure, temperature and media be (for correct actuator sizing)?
• What is the supply voltage or instrument air pressure available?
• Do you need open/closed feedback indication to your control room?
• Would you like to control the opening and closing 24VDC/110VAC/240VAC?
• Does ATEX apply to the area in which the valve will be situated?

8. Do you need to use the valve for control?

Control is easily achieved in an actuated valve and the easiest way of achieving crude control on a ball or butterfly valve is with a 4-20mA Electro Pneumatic Positioner or a 4-20mA Potentiometer Card (in the case of an Electric Actuator).  Another great option for greater control is a V-Ball or Ball Sector control valve.  Where very accurate control is required, it will be worth considering a rotary control valve, or linear globe style control valve which is sized on a bespoke basis. These will generally be more costly but where control is critical they are generally the best option.

9. Valve dimensions.

Sometimes valves arrive on site for fitting and at that point the fitters realise that there is not enough space. The hand-wheel fouls on adjacent pipework, the valve actuator is hitting a tank, or the lever is hitting some steelwork.  The majority of valves have a dimensional datasheet available, so always get a copy of this and double check that the valve will fit into the space you have available.  There is nothing more disheartening than that call from a frustrated fitter with a hefty quotation for altering pipework.

10. Weight & Supports

Valves by their very nature can be heavy &#; very heavy in fact. Large bore valves with actuators and additional controls can weigh over 500kg.  This puts quite a lot of stress on pipework, so always factor this in when you are designing a system that is likely to have large valves installed.  A common place where this can become an issue is ducting and HVAC type installations where the ducting is quite lightweight. As with valve dimensions your supplier should be able to supply you a datasheet with valve weights in kilograms. With actuated assemblies they will calculate for you a weight with actuator, valve, switchboxes and other ancillaries combined.

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Table of Contents

1. Type of Valve

2. Actuator Type

3. Material Compatibility

4. Pressure and Temperature Ratings

5. Flow Requirements

6. Sealing Performance

7. Control and Connectivity

8. Maintenance and Repair

9. Certifications and Standards

10. Cost of Ownership

Actuated valves are critical components in various industries, controlling the flow of liquids and gases with precision. Whether you're in the pharmaceutical, food processing, petrochemical, or water treatment industry, selecting the right actuated valve is crucial for your operations. This comprehensive guide will outline the top 10 factors to consider, ensuring you make an informed decision that enhances efficiency, safety, and productivity.

1. Type of Valve

When delving into the intricacies of actuated valves, understanding the various types available and their specific applications is paramount. This knowledge ensures the selection of the most appropriate valve, which is a critical determinant of your system&#;s efficiency, reliability, and safety. Here, we explore the common types of valves used in actuated systems, highlighting their unique features, advantages, and typical applications. For example:

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Ball Valves

Ball valves feature a spherical disc with a hole through it, which controls the flow through the valve when the ball is turned. This design allows for full, unrestricted flow with a quarter turn of the valve handle, leading to minimal pressure drop. Ball valves are renowned for their durability and excellent sealing capabilities, making them a preferred choice for applications requiring tight shut-off. They can handle a wide range of fluids, pressures, and temperatures, making them versatile for many industries.

Butterfly Valves

Butterfly valves consist of a disc mounted on a rotating shaft. When the valve is closed, the disc is turned so that it completely blocks off the passageway; when it is open, the disc is rotated a quarter turn to allow nearly unrestricted flow. This type of valve is known for its compact design and low weight, which makes it easy to install and requires less support. Butterfly valves are suitable for handling large flow volumes and are commonly used in water and wastewater treatment, as well as in HVAC applications.

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2. Actuator Type

Actuators are the mechanisms that operate the valve, and they can be pneumatic, electric, or hydraulic. Pneumatic actuators are known for their fast response time and are suitable for explosive environments. Electric actuators offer precise control and are ideal for remote operation. Hydraulic actuators provide high force with minimal space requirements. The choice of actuator will depend on your operational requirements, including speed, force, and control needs. For example:

Pneumatic Actuators

Pneumatic actuators use compressed air to generate force to move the valve. They are characterised by their fast response time and reliability. These actuators are particularly well-suited for environments where spark prevention is critical, making them a safe choice for explosive or flammable atmospheres. Pneumatic actuators are cost-effective for applications requiring a large amount of force, such as large valve operations in the oil and gas industry.

Electric Actuators

Electric actuators use an electric motor to operate the valve mechanism. These actuators offer precise control over valve positioning and are easily integrated into digital control systems, making them ideal for applications requiring accurate flow modulation. Electric actuators are suitable for a wide range of environments, including hazardous areas, provided they are equipped with the appropriate enclosures. They are typically used in water treatment plants, HVAC systems, and anywhere precise electronic control is needed.

Hydraulic Actuators

Hydraulic actuators use fluid pressure to generate force to move the valve. They are capable of producing a very high force output from a relatively small footprint, making them suitable for heavy-duty industrial applications where space is limited. Hydraulic actuators provide smooth, consistent control over valve movement and can maintain valve position even when hydraulic pressure is removed, offering a fail-safe operation. They are commonly used in applications where reliability and high force are crucial, such as in the petrochemical industry.

Factors to Consider When Choosing an Actuator Type

• Speed and Response Time: Pneumatic actuators typically offer the fastest response time, followed by electric and hydraulic actuators.
• Control and Precision: Electric actuators provide the highest level of control and precision, especially beneficial for modulating valves.
• Force Requirements: Hydraulic actuators are unmatched in their ability to generate high force, making them ideal for moving large, heavy valves.
• Environment: Consider the operational environment, including the presence of explosive gases, which may favour pneumatic or specially enclosed electric actuators.
• Availability of Utilities: Electric actuators require electricity, while pneumatic actuators need compressed air, and hydraulic actuators depend on a supply of hydraulic fluid.
• Cost: Initial installation costs, operational costs, and maintenance needs vary across actuator types, influencing the total cost of ownership.

3. Material Compatibility

Material compatibility is a cornerstone consideration in selecting actuated valves, directly impacting their durability, functionality, and suitability for specific applications. The materials chosen for both the valve body and the internal components must be able to withstand the operational environment, including the type of media flowing through the valve, the temperature range, and any potential corrosive or abrasive conditions. Let&#;s explore the importance of material compatibility in more depth and the considerations involved in selecting the right materials for your actuated valves.

Understanding Material Compatibility

Material compatibility is critical for ensuring the long-term performance and reliability of actuated valves. The right material selection can prevent common issues such as corrosion, erosion, and material degradation, which can lead to valve failure, leakage, and operational inefficiencies.

Common Valve Materials

• Stainless Steel: Highly resistant to corrosion and can withstand a wide range of temperatures, making it suitable for a variety of applications, from water to harsh chemicals.
• Brass: Often used in applications where corrosion resistance is needed but at a lower cost than stainless steel. Suitable for water, gas, and some mild corrosive environments.
• PVC (Polyvinyl Chloride) and CPVC (Chlorinated Polyvinyl Chloride): Plastic materials that offer excellent resistance to corrosion and chemical attack. Ideal for applications in water treatment and chemical processing where metallic valves might corrode.

Factors Influencing Material Selection

• Type of Media: The chemical properties of the fluid or gas, such as acidity (pH level), corrosiveness, and solvent properties, dictate the material choice to ensure compatibility.
• Temperature and Pressure: High temperatures and pressures can compromise the integrity of some materials. It&#;s essential to choose materials that can maintain their properties under the expected operational conditions.
• Abrasion and Wear: For applications involving abrasive materials, such as slurry services, material selection must consider resistance to wear and erosion.

4. Pressure and Temperature Ratings

Understanding the pressure and temperature ranges within your system is vital. Actuated valves are rated for specific operating pressures and temperatures. Choosing a valve with inappropriate ratings can lead to failure, posing safety risks and operational downtime. Always ensure the valve you select can withstand the maximum expected pressure and temperature of your system.

Pressure Ratings

Pressure ratings indicate the maximum pressure at which a valve can safely operate without risking damage or failure. These ratings are determined by various factors, including the valve's material, design, and size. Exceeding these ratings can lead to catastrophic valve failure, posing safety risks and potential damage to the broader system.

Factors Affecting Pressure Ratings:

• Material Strength: Different materials can withstand different levels of stress. For instance, metal valves typically have higher pressure ratings than plastic valves.
• Valve Design: The design and thickness of the valve body and components affect its ability to withstand pressure.
• Temperature: The valve's pressure rating can change depending on the temperature, as materials may weaken or expand at higher temperatures.

Temperature Ratings

The temperature rating specifies the range of temperatures within which the valve can operate effectively. It is determined by the materials used in the valve's construction, including the body and sealing elements. High temperatures can affect the elasticity of seals, leading to leaks, and can alter the material properties of the valve body.

Considerations for Temperature Ratings:

• Thermal Expansion: Materials expand at different rates when heated. This expansion can affect the fit and sealing capabilities of valve components.
• Material Degradation: Prolonged exposure to high temperatures can cause materials to degrade or change properties, potentially leading to failure.
• Seal Material: The type of seal material (e.g., PTFE, EPDM, Viton) has a significant impact on the valve's temperature tolerance. Each material has its own strengths and temperature range.

5. Flow Requirements

Understanding and accommodating flow requirements is essential when selecting actuated valves, as it ensures the valve not only fits within the system but also performs its intended function efficiently and effectively. The flow requirements of a system dictate the size and type of valve needed to manage the fluid dynamics appropriately. Here&#;s an in-depth look at the considerations surrounding flow requirements.

Understanding Flow Coefficient (Cv)

The flow coefficient (Cv) is a critical specification that measures how much fluid can pass through a valve at a given pressure drop. It's defined as the number of gallons of water at 60°F that can flow through a valve per minute with a pressure drop of 1 psi. The Cv value is an essential indicator of the valve's capacity to deliver the required flow rate for your application.

Sizing the Valve

Correctly sizing the valve is pivotal to meeting the flow requirements of the system. An undersized valve can lead to excessive pressure drop, reduced flow rate, and inefficiency in the system operation. Conversely, an oversized valve may cause control issues, including poor regulation or valve hunting, leading to instability in the system.

Factors Influencing Valve Sizing:

• Flow Rate: The desired flow rate of the medium (liquid, gas, or steam) through the system is the starting point for determining the appropriate valve size.
• Pressure Drop: The acceptable pressure drop across the valve when it is fully open is a key factor. A higher allowable pressure drop can permit the use of a smaller valve, but this needs to be balanced against the overall system requirements and efficiency.
• Type of Media: The physical properties of the media (viscosity, density) affect flow characteristics and must be considered when selecting and sizing the valve.

Type of Operation

The intended function of the valve within the system also influences the flow requirements. Valves can be used for on/off control, throttling, or as part of a safety mechanism. For example, a valve used for throttling purposes will need precise control over a wide range of flow rates, whereas an on/off valve may only need to minimise pressure drop when fully open.

6. Sealing Performance

Leakage can significantly impact process efficiency and safety. When selecting an actuated valve, consider the sealing technology it uses. Soft seals, such as PTFE, offer tight sealing but may wear out faster with high-temperature applications. Metal seals withstand higher temperatures but might not provide as tight a seal. The right choice will balance sealing performance against operational conditions.

Types of Seals in Actuated Valves

• Soft Seals: Made from materials such as PTFE (Polytetrafluoroethylene), EPDM (Ethylene Propylene Diene Monomer), and NBR (Nitrile Butadiene Rubber), soft seals are known for their excellent sealing capabilities at lower pressures and temperatures. They provide tight shut-off but may wear faster under harsh conditions or with frequent cycling.
• Metal Seals: Constructed from stainless steel, alloy, or other metals, metal seals are suitable for high-temperature and high-pressure applications. While they offer durability and can withstand aggressive media, metal seals might not provide as tight a shut-off as soft seals and could require greater actuation force.

Considerations for Seal Selection

• Media Compatibility: The seal material must be compatible with the media being handled to prevent degradation, swelling, or other forms of deterioration that could impair sealing performance.
• Pressure and Temperature: The operating pressure and temperature range of the system influence seal selection. High pressures and temperatures may necessitate the use of metal seals or specially engineered soft seals.
• Valve Cycling Frequency: Valves that open and close frequently require durable seals that can withstand wear and tear without degrading the sealing performance.
• Regulatory and Environmental Concerns: In applications where leakage could have serious environmental or health impacts, such as in the chemical or pharmaceutical industries, the choice of seal and its performance is especially critical.

7. Control and Connectivity

In the context of actuated valves, control and connectivity encompass the methods and technologies used to operate, monitor, and integrate valves into broader system controls and automation strategies. As industries advance towards more automated and intelligent systems, the importance of sophisticated control and connectivity options for actuated valves has significantly increased. Here&#;s a closer look at the nuances of control and connectivity for actuated valves.

Control Mechanisms

• On/Off Control: The most basic form of valve control, where the valve is either fully open or fully closed. This is commonly used in applications requiring simple flow shutoff or isolation.
• Proportional Control: Enables the valve to modulate flow by adjusting the valve position between fully open and fully closed. This is critical in applications requiring precise flow control, such as in process industries where maintaining specific process conditions is essential.
• PID Control (Proportional, Integral, Derivative): A more advanced form of control that adjusts the valve position based on the difference between a setpoint and the process variable. PID control is used for maintaining precise control over complex processes by correcting overshoot and stabilising the process flow.

Connectivity Options

• Wired Connections: Traditional connectivity method involving direct wiring to control systems. This includes 4-20 mA signals for analog control or digital signals like HART, Foundation Fieldbus, and Profibus, which offer the advantage of transmitting data along with control signals for diagnostics and monitoring.
• Wireless Technologies: Emerging technologies like WirelessHART and ISA100.11a allow for remote control and monitoring of valves. Wireless solutions reduce installation costs, improve flexibility in system design, and enhance the ability to access hard-to-reach or hazardous locations.
• Ethernet/IP and Modbus TCP/IP: For integrating valves into industrial networks, protocols like Ethernet/IP and Modbus TCP/IP facilitate communication over industrial Ethernet. This connectivity supports high-speed data exchange and enables integration with modern Industrial Internet of Things (IIoT) platforms.

8. Maintenance and Repair

Maintenance and repair considerations are pivotal in ensuring the long-term reliability and efficiency of actuated valves within any industrial system. The ease with which a valve can be maintained and repaired impacts not only its operational lifespan but also the overall productivity and safety of the system it serves. An effective maintenance strategy minimises downtime, reduces operational costs, and prolongs the service life of the valve.

Importance of Maintenance

Regular maintenance is essential for detecting and mitigating wear and potential failures before they escalate into more significant issues. It involves routine inspections, cleaning, lubrication, and adjustments to ensure optimal performance and to prevent unexpected shutdowns.

Predictive Maintenance

Advancements in sensor technology and connectivity have paved the way for predictive maintenance strategies. By monitoring key performance indicators such as temperature, pressure, and flow rates, as well as specific valve conditions like stem movement and actuator performance, operators can predict potential failures before they occur, scheduling repairs at convenient times to minimise operational impact.

Accessibility

The design and installation of actuated valves should consider ease of access for maintenance and repair activities. Valves that are difficult to reach or require extensive disassembly of the system for access can significantly increase maintenance time and costs. Modular designs that allow for the easy replacement of components without the need for complete valve disassembly are highly beneficial.

9. Certifications and Standards

Certifications and standards play a pivotal role in ensuring the quality, safety, and compatibility of actuated valves with specific industry requirements. Adherence to recognised standards and obtaining the relevant certifications signify that a valve has been rigorously tested and meets the established criteria for performance, durability, and safety. This not only facilitates trust in the product's reliability but also aids in compliance with regulatory and industry-specific requirements. Here&#;s a closer exploration of the importance of certifications and standards for actuated valves.

Why Certifications and Standards Matter

• Quality Assurance: Certifications provide assurance that the valve has been manufactured to meet high-quality standards, ensuring reliability and performance in critical applications.
• Safety Compliance: Safety standards ensure that valves are capable of operating safely under the designated conditions, protecting both personnel and the environment from potential hazards.
• Regulatory Compliance: Many industries are subject to stringent regulations that require the use of certified valves. Compliance with these standards is crucial for legal operation and avoiding potential fines.
• Interoperability: Standards ensure compatibility between valves and other components within a system, facilitating integration and smooth operation.

Common Certifications and Standards for Actuated Valves

• ISO (International Organisation for Standardisation): ISO provides various standards for quality management systems (ISO ), environmental management systems (ISO ), and specific product standards for industrial valves (ISO for valve testing, ISO for actuator mounting).
• API (American Petroleum Institute): API standards are crucial in the oil and gas industry, with specifications like API 6D and API 598 governing pipeline valves and valve inspection and testing, respectively.
• ANSI (American National Standards Institute)/ASME (American Society of Mechanical Engineers): ANSI/ASME standards such as B16.34 provide specifications for valve materials, design, and pressure-temperature ratings, ensuring valves are suitable for their intended service conditions.
• PED (Pressure Equipment Directive) in the European Union and ASME Boiler and Pressure Vessel Code in the United States: These regulations govern the design, manufacture, and testing of pressure equipment, including valves, to ensure they are safe for use at specified pressures and temperatures.
• ATEX and IECEx for Explosive Atmospheres: Certifications ensuring that equipment, including actuated valves, is safe to use in potentially explosive environments by preventing ignition sources.
• NSF/ANSI Standards: Particularly relevant in the food, water, and pharmaceutical industries, these standards ensure that valves do not contaminate the media they control and are safe for use in these critical applications.

10. Cost of Ownership

The cost of ownership of actuated valves encompasses not only the initial purchase price but also a variety of other expenses incurred throughout the valve's life cycle. This holistic view of costs is crucial for making informed purchasing decisions that optimise both financial outlay and operational performance. Understanding and effectively managing these costs can lead to significant savings and more efficient system operations over time. Here's a comprehensive look at the factors contributing to the total cost of ownership for actuated valves.

Initial Purchase Price

• Acquisition Costs: The upfront cost of purchasing the valve, which can vary significantly based on the type, size, material, and specific features of the valve.

Installation and Commissioning Costs

• Installation: Costs associated with integrating the valve into the system, including any necessary modifications to piping or infrastructure.
• Commissioning: Expenses related to the initial setup, calibration, and testing of the valve to ensure it operates correctly within the system.

Operating Costs

• Energy Consumption: For electrically actuated valves, the cost of electricity to operate the actuator can impact overall expenses, especially in systems with frequent cycling.
• Compressed Air: Pneumatic actuators require compressed air, the production of which can contribute to operating costs.

Maintenance and Repair Costs

• Routine Maintenance: Regular inspections, cleaning, lubrication, and adjustments are necessary to keep the valve functioning efficiently.
• Unscheduled Repairs: Costs associated with unexpected breakdowns or failures, including parts replacement, labor, and potential system downtime.
• Spare Parts: Inventory costs for keeping essential spare parts on hand to minimise downtime during repairs.

Downtime Costs

• Production Losses: The loss of productivity or output due to system shutdowns for valve maintenance or repairs.
• Operational Inefficiencies: Costs incurred from operating the system at reduced capacity or efficiency while dealing with valve issues.

Strategies to Optimise Total Cost of Ownership

• Selecting Quality Products: Investing in higher-quality valves may have a higher initial cost but can lead to lower maintenance and repair costs, longer service life, and better performance.
• Preventive and Predictive Maintenance: Implementing a maintenance strategy that prevents failures and predicts issues before they occur can significantly reduce downtime and repair costs.
• Energy Efficiency: Choosing valves and actuators that are energy-efficient can lower operating costs, especially in systems with high usage rates.
• Standardisation: Using standardised valves across a facility can reduce spare parts inventory costs, simplify maintenance procedures, and streamline training for maintenance personnel.

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