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Selecting the Right Flow Control Valve: A Guide for Operators
Selecting the Right Flow Control Valve: A Guide for Operators
Water flows, winds flow, and manufacturers prefer flow production, a term to describe the smooth and orderly movement of materials and components through the facility. The flow production method promotes efficient, streamlined output, and that means all components and systems must work in concert to achieve these efficiencies.
Flow control valves, although small components, are mighty in terms of keeping production flowing smoothly in chemical processing and other industry segments, as they regulate and direct the flow of liquids, gases, or slurries through piping systems, preventing disruptions and maintaining optimal process conditions.
Some of the most common industries that regulate gas flow for example, in addition to chemical processing, includes the food and beverage sector, pharmaceutical and biotechnology applications, water/wastewater management, oil and gas, industrial gas, and the energy and power industry.
At the heart of any well-designed system is a minor yet critical component'the flow control valve. Flow control valves not only control the flow, as the name implies, but also the volume, direction, rate, and pressure of fluids and gases. As such, the flow control valve impacts the plant's safety and efficiency, its production and profitability.
However, selecting the appropriate flow control valve can pose a complex and challenging task due to the need to balance multiple, often competing system requirements and operating conditions. This selection of a seemingly simple component is complex due to:
- The multiple factors requiring consideration, such as flow rate, pressure, fluid properties, control characteristics.
- System-specific needs that might require a tailored valve solution.
- Potential for unintended and undesirable consequences from an improper selection.
- Technical expertise required to properly evaluate and size the valve.
- Evolving system conditions over time.
The flow control valve needs to be carefully matched to the unique and sometimes changing demands of the fluid system. All the relevant specifications and known or anticipated operating conditions must be considered and balanced to select a valve for the most reliable, efficient and safe operation.
Properly sizing and matching the valve
As an operator, the biggest hurdle when choosing a flow control valve is selecting the proper size and matching it to specific system requirements. The wrong selection could generate many issues ' from insufficient flow capacity to excessive pressure drops, control instability to premature wear and reliability problems. Carefully evaluate the key factors to select the proper flow control valve for optimal performance and long, trouble-free service life, for a true 'set it and forget it' component.
- Determine your flow requirements The first and most fundamental step is to accurately define your flow requirements. This means knowing the minimum, maximum and ideal flow rates you need the valve to handle. Consider not just your current needs, but any potential future changes or expansions to your system. Underestimating your flow requirements can lead to an undersized valve unable to meet your process demands. Conversely, overestimating can result in an oversized valve that creates excessive pressure drops and control challenges.
- Evaluate fluid properties The physical properties of the fluid flowing through the valve can impact valve selection and performance. Factors like fluid viscosity, density, temperature and phase (liquid, gas, or two-phase) must be considered.
More viscous or dense fluids will require larger valve sizes to maintain the same flow rates as less viscous fluids. The potential for issues like cavitation and flashing must also be carefully evaluated based on the fluid's vapor pressure characteristics.
- Assess pressure requirements Closely related to a system's flow requirements are the pressure conditions. Operators should know the upstream and downstream pressures and the maximum allowable pressure drop across the valve. These pressure parameters will help dictate the valve size, trim and actuator needed to provide the required flow control while maintaining suitable pressure conditions. Ignoring pressure requirements can lead to control instability, component damage and safety hazards.
- Factor in valve sizing and materials With the flow, pressure and control parameters defined, you can begin sizing the valve. This requires careful hydraulic or pneumatic calculations, computerized flow modeling, and close collaboration with the valve manufacturer like CPV Manufacturing.
The right valve size is critical ' too small and you will restrict flow, too large and you will battle instability and cavitation. The valve materials of construction must also be compatible with your process fluids to ensure long-term reliability and avoid corrosion or erosion issues.
- Do not forget installation and maintenance Even the most carefully selected valve can underperform if the installation and maintenance practices are suboptimal. Factors like upstream and downstream pipe configurations, valve orientation, and accessibility for servicing must all be considered during the installation phase. Ongoing monitoring, adjustment and preventative maintenance are also essential to keep your flow control valve operating at peak efficiency throughout its service life.
The consequences of getting it wrong
Selecting the wrong flow control valve for your application can have serious consequences. An undersized valve will be unable to meet your flow demands, potentially starving critical equipment and disrupting your entire process. An oversized valve, on the other hand, can create excessive pressure drops, control instability, and cavitation-induced damage. Both scenarios can lead to reduced efficiency, higher energy consumption and compromised system reliability.
Partnering for success
Given the complexity involved, operators are well-advised to work closely with experienced valve manufacturers and distributors when selecting flow control valves. Their technical expertise, application knowledge and sizing tools can be invaluable in ensuring you choose the right valve for your specific needs. Do not be afraid to lean on their guidance ' it could mean the difference between a smoothly running, reliable fluid system and one plagued by persistent control and performance issues.
CPV Manufacturing focuses its efforts on fabricating and supplying high-quality valves, fittings and supplemental equipment for demanding applications like the naval and aeronautics industries. CPV can offer tailored solutions crafted with care, or more standard valves in a wide range of sizes.
By partnering with our experienced team of engineers, we can collaborate with your team to select and meet your unique requirements for reliable, precise flow control of industrial gases or liquids. Learn more about our extensive product line of valves and fittings. Or speak to a member of our staff to discuss the specifications for your next project.
Be thorough in your analysis and do not hesitate to seek expert support. Get the valve selection right, and you will enjoy trouble-free operation and optimal performance from your fluid system for years to come.
Want more information on flow control valve do? Feel free to contact us.
Automatic control valves, much like everything else we purchase these days, are not all created equal. Some fall into the high quality bracket with pricing to match, while others hover closer to the lower quality and price sensitive end of the scale. Unfortunately, when evaluating control valve prices, it is not always clear what you are being offered and what standards the valve actually meets. Here are a few questions to consider and ask the supplier to ensure you get years of trouble free operation that lasts longer than it takes the sales person to drive out of your parking lot!
Q 1 What materials are being used?
Make sure you know what the different components of the valve are made of, as this will certainly affect the life of your valve, specifically:
Body Material ' is the valve body cast iron or ductile iron? Traditionally valves were cast iron but ductile iron has become the new standard due to its superior physical properties that are much better at weathering the elements.
Body Coating ' Most of the world insists on fusion bonded coating of a valve, inside and out. Unfortunately here in North America, that is not always requested. This just makes common sense for valves that are constantly wet and sit in locations that are not always dry and pristine. A valve should last for many years, so insisting on a coated valve is a wise choice.
Seat Material ' bronze is typically the common material for seats but over time, depending on water quality and velocities, bronze wears resulting in the need for replacement. This is time consuming and expensive as seat replacement requires a complete disassembly of the entire valve. Ideally go for stainless steel.
Valve Internals ' Most valve manufacturers utilize stainless steel for their valve stems. Make sure that you ask what grade of stainless you are getting as not all stainless steel is created equal. 316 SS is always the best choice because it is harder and least likely to corrode.
External Fasteners ' Over time valves experience condensation or flooding and this can play havoc with coated studs or bolts. There is nothing worse than trying to remove heavily rusted studs out of an old valve to perform maintenance. Request stainless steel fasteners as this will ensure that bolts will be removable at any age.
Q 2 Does the valve supplier fully understand your application?
Too frequently a specification will be requested and a valve is supplied that is simply the wrong valve for the job. It may also be the case that there is just a better solution. Ensure you give your valve supplier all the necessary pressure and flow details including details of the actual application and what you want this valve to do. Having the wrong valve for the wrong application, at best case will result in a significantly shorter life and worst case, a malfunction that can result in destruction of the valve and other parts of your water distribution system.
Q 3 Will this new valve fit into my existing piping layout?
Don't be tempted to just stay with brand X because that is the valve you may be replacing and has the same lay lengths. Most manufactures can be quite innovative on providing solutions to combat varying lay lengths so explore all of you options rather than just settling because you think it may be easier.
Q 4 Do you need specialty tools for maintenance?
Nobody wants to have to carry around a specific tool that only performs one task. Ensure that your valve can be maintained with everything you would carry in regular tool kit. Some valve manufacturers require specialized seat removal tools, or vice jaws installed with copper jaws to protect valve stems. While these are great ideas, they are certainly not things that the average operator has in his toolkit.
Q 5 Will your personnel receive complimentary factory qualified training?
Control valves are not so difficult to understand and once taught, most operations personnel can easily perform maintenance. Ensure that you will not be reliant on the additional cost of having to bring out a factory person every time your valve requires maintenance. Request that a factory-trained representative is on site when the valve is commissioned. This will allow your operators to be schooled in the regular maintenance needs, know what to look for if things go awry and how to start up a valve in a new system or after service. Simple tricks like removing air out of the pilot system are valuable lessons to see in practice.
Q 6 Does your valve have a solid warranty?
These days having a product with the long term back up of the factory is important. Three years should be the standard to ensure there are no manufacturing faults.
Q 7 Can I make changes to the valve if required
Having a valve 'expansion ready' for the future can save you money and make your decisions a whole lot easier. For example, can you add a limit switch or a position indicator easily? Or, if you need to move the pilot system to the other side of the valve, can you do it, or is it not possible because the valve body does not have the required connections? Things always change and a flexible valve gives you more options to keep your now perfect valve, perfect down the road.
Q 8 Does your valve meet industry standards?
There are third party accreditations that ensure your valve was built to the correct specifications. For example; NSF 61, WRAS, UL/FM, AWWA, ISO et.al. They are important because they ensure that the valve has been built to a given standard so the user can be assured they meet approval for such things as low lead content, bacterial growth tests, functional tests etc.
Q 9 Do you have local and factory support?
Make sure there is someone in the area that is factory trained and available to come out and assist when you have questions or problems. This sounds like a given but it's best to ensure the local agent will in fact be there for you when you need him. When a valve fails, timing is usually of the essence so you should know whom to call prior to such an event.
Q 10 Is the valve solution offered able to handle future needs?
In the world of 'low bid wins', a supplier may be tempted to squeeze as small a valve as possible into the application in order to reduce price. Make sure that the offered solution will supply your needs for the foreseeable future without the burden and additional cost of having to change a valve in a couple of years.
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