Category Archive: Check Valves

Check Valve Selection 101: Types & Applications

Check valves, sometimes called non-return valves, are valves with two openings or ports that allow fluid flow in only one direction. Fluid enters through one port and exits the valve through the other. Industrial fluid systems in power plants, chemical plants, water and wastewater treatment facilities, oil fields, refinery applications, and other industries rely on check valves to prevent fluid flow back to the source. For instance, check valves are often used to transfer fuel and an oxidizer in separate lines to a mixing vessel without the fuel or oxidizer flowing back into the initial gas or oxidizer cylinders. 

Selecting the right check valve for a specific application is essential to achieving optimal performance, reliability, and service life. Here, we will explore the various check valve types and applications to help you decide on the best option for your project.

Important Check Valve Selection Criteria

When selecting a check valve for an application, consider the following:

• Initial Costs: Consider the cost of the valve and any installation costs associated with the check valve.
• Maintenance Costs: The cost of maintenance or repairs can vary depending on the complexity of the valve. Improper, oversized check valves can add dramatically to life cycle maintenance costs.
• Head Loss and Energy Costs: Head loss is a characteristic of check valves determined by the internal valve design and degree of opening. Restriction in the valve opening (compared to the pipeline opening) will result in increased head loss, which can lead to higher energy costs.
• Non-Slam Characteristics: Proper valve selection is critical in preventing water hammer and slamming during operation. Consider a check valve that offers compatible closing characteristics to the dynamics of the pumping system.
• Fluid Compatibility: Certain valves are designed for different fluid viscosities, sediment, and particles. Select the valve that is compatible with the medium passing through it.
• Sealing Ability: Consider the proper sealing for your application, whether it’s gas-tight, bubble-tight, or drop-tight sealing.
• Flow Characteristics: Every check valve has its distinct flow characteristics. Matching the right characteristics to your needs can minimize the potential for reverse flow or surges on sudden pump shutdown.
• Valve Size and Pressure Rate: Check valves come in a variety of sizes and pressure classes. Ensure your valve is sized appropriately for the system’s flow rate and can withstand the operating pressure. Undersized or oversized valves may lead to inefficiencies or even system failure.
• Materials Selection: Based on certain criteria such as compatibility of the fluid type, temperature, and corrosiveness, material selection is crucial for the reliability of the valve.
• Installation Orientation: Consider the orientation of the check valve installation. Some check valves cannot be installed both horizontally or vertically.
• Application Considerations: Different applications have unique requirements, such as sanitary standards for food or fire safety for oil and gas. Ensure your check valve complies with any specific industry regulations.

Types of Check Valves and Their Applications

There are several types of check valves designed for distinct applications. Some of the most common check valves include lift, swing, and ball check valves.

Lift Check Valves

Lift check valves are economical, automatic valves with no external moving parts for reliable operation. Specific types of lift check valves include nozzle check valves, in-line check valves, and piston check valves. The main closure mechanism in a lift check valve is typically a disc that lifts off the valve seat when subject to inlet pressure, allowing normal fluid flow past the disc and seat, then through the outlet port. The motion of the disc is guided in a straight line, so the valve can later reseat properly. A spring or gravity moves the disc back into the seat when the upstream fluid pressure drops, stopping the fluid flow. DFT® check valves can be installed in any orientation: horizontal, vertical flow up, or vertical flow down. These types of valves are commonly found in applications where backflow prevention is critical.

Swing Check Valves

Swing check valves are one of the most common types of check valves due to their low cost. Because the valve operates entirely from flow pressure and gravity, it relies on the change of flow direction to close. This means swing check valves can only be used for horizontal or vertical “up” lines and are very susceptible to slamming and water hammer. These types of valves are commonly used in wastewater, sewage systems, and predictable flow water pumping applications.

Ball Check Valves

Ball check valves are often very small and simple in that the closing member is a spherical ball and the valve has no external components. The rotation of the ball during operation prevents particles from getting stuck on the ball. Some designs are spring-loaded and some do not have springs, instead relying on reverse flow to move the ball to the seat for sealing. Ball check valves are used in many applications and are often found in liquid or gel mini-pump dispenser spigots, hydraulic systems, and sprayer devices.

Contact Our Experts for Your Check Valve Needs

With many check valve types to suit various applications, it is vital to consider your fluid system’s needs when selecting the best check valve. Some of these deciding factors include cost, fluid compatibility, sealing, non-slam characteristics, and installation orientation. DFT® manufactures world-class silent check valves and severe service control valves for critical industries, from oil and gas to food and beverage to wastewater processing. We pride ourselves on collaborating closely with customers to solve their unique challenges. Our check valves are world-renowned for eliminating or preventing water hammer issues in diverse fluid systems. 

Browse our catalog of check valves to find the best product for your system. Additionally, you can download our eBook, Design for Flexibility: Key Considerations to Make When Designing Fluid or Gas Flow Systems. Contact us or request a quote to speak with a specialist about your check valve needs. 

Webinar Q and A: Carbon Capture and Role of Engineered Check Valves

As a follow-up from our webinar “Carbon Capture & the Role of Engineered Check Valves“, we are sharing, in this post, a few of the questions received from the audience.

During the webinar, we discussed what carbon dioxide is and how it impacts the environment, the critical methods of capturing carbon dioxide, how carbon dioxide is transported from producers to storage sites, technologies involved in carbon dioxide sequestration (storage), and how carbon dioxide is used for enhanced oil recovery.

We also explored the selection of appropriate check valves within the different carbon capture processes, including valve materials and pressure classes, highlighting their importance in maintaining optimal system performance and efficiency.

This webinar was presented by Stephen O’Neill, Director of Sales & Marketing at DFT^® Inc.

If you missed this webinar, you can now view it on demand from the DFT^® website, just click this link.

Below, our host answers a variety of questions that came in during the webinar:

Q: What is the difference between WLC^® BF and WLC^®?

A: The WLC^® BF was engineered for the extreme conditions of boiler feed applications. The WLC^® BF body comes standard as WC9 material with 410 trim in class 600 and 900/1500, 2 1/2″ to 10″. The WLC^® materials available are Carbon Steel or Stainless Steel and sizes range from 1″ to 10″ in classes 150 to 2500.

Q: DFT^® PDC^® valve, is this designed to be used entirely without a pulsation dampener or does DFT^® still recommend the use of a separate device?

A: The PDC^® has a built in pulse dampening chamber so there is no need for a separate pulsation dampening devise.

Q: What are the primary advantages of Excalibur^® over GLC^® designs?

A: The primary differences between the Excalibur^® and the GLC^® are that the Excalibur has a 2-piece body and ASME B16.10 face-to-face dimensions, a direct replacement for a swing check valve. The GLC^® has a short patterned body, therefore a lesser weight than the Excalibur^®. The GLC^® also meets API6D and is available in a larger range of sizes than the Excalibur^®.

Q: Which plant absorbs co2

A: In general plants remove carbon dioxide from the air naturally, and trees are especially good at storing CO2 removed from the atmosphere by photosynthesis.

Q: Do you have any mining applications with DFT^® Valves?

A: Yes, DFT^® has installations of check valves in many mining applications such as Autoclaving, mine dewatering, pump isolation, discharge, along with many others. We have the following resources on Mining that can be downloaded from our website:

An application guide with a section on Mining here:
DFT-Check-Valve-Application-Guide-2.pdf

Also, you can find success stories on dewatering and water hammer in mining here:
DFT_Mining-AppGuide_1-1.pdf

Q: Can the springs on the non-slam axial flow check valves be modified by factory to crack at a higher DP?

A : Yes, DFT^® is able to custom size the internals of our valves to your application, which does include being able to modify cracking pressures as needed.

Q: What is the value of stiffness of springs

A: Spring rate (K) is the proportion of a spring’s force (pounds or newtons) to one unit of travel (inch or millimeter). It is a constant value which helps to calculate how much load you will need with a specific distance traveled and it will also help you calculate how much travel you will achieve with a certain load.

Q: Is there a standard guideline on where to install check valves in piping systems?

A: In keeping with generally accepted piping and valve installation guidelines, the DFT^® Axial Flow, Nozzle Check Valve should be installed a minimum of 5 diameters downstream of a flow impediment, i.e. valve, reducer or bend etc, to ensure a good flow pattern at the entry to the check valve. The DFT^® Axial Flow, Nozzle Check Valve should also be installed at least 5 diameters upstream of a bend or reducer to allow flow to even-out and avoid choked flow conditions which can prevent the full opening of the check valve.

DFT^® has a technical sheet with diagrams that is available on our website in the resources section that can be downloaded. Go to WWW.dft-valves.com to download

Q: What advantages do axial flow non-slam check valves have versus swing check in reducing the effects of water hammer?

A: Swing checks rely on gravity or reverse flow to close and these conditions contribute to water hammer. Axial flow check valves are designed to close upon decreasing differential pressure, not reliant on reverse flow. This reduces or eliminates the likelihood of it slamming shut.

Axial flow, spring assisted, non-slam check valves can be installed horizontally or vertically flow up or flow down, whereas swing checks cannot be installed vertical flow down.

Q: What does Sweetened natural gas mean?

A: Gas Sweetening is a process that removes Hydrogen Sulfides (H2S) and is sometimes referred to as amine treating.

Resulting in Sweet Gas, which is non-corrosive, less acidic, and requires little refining.

Whereas Sour Gas must be sweetened to remove H2S and CO2, which have a corrosive effect on gas pipelines and is toxic to humans.

Q: Why is valve sizing important?

A: The most appropriate-sized valve must be chosen in order to render the best service. An undersized valve will cause higher pressure losses and create excessive noise and vibration, and an oversized valve can lead to a premature wear and failure of the valve’s internal components. Choosing the best valve will ensure proper flow, optimize overall efficiency, and enhance the integrity and longevity of any fluid handling system.

DFT^® will also work with customers to “engineer” the right valve for their application. DFT^® will help you by providing the right valve solution.

Hospital Building Systems and the Role of the Check Valves

Hospitals and healthcare environments serve thousands of employees, patients, and visitors 24/7. It is essential that these large campus systems are properly constructed and maintained to produce a safe, effective, and efficient environment for the benefit of all who use these facilities.

These facility systems are complex and include utility services that provide power, heat, water, steam, air, and gas. It is important that appropriate design considerations are taken to ensure system maintainability, economic and energy efficiency, and the ability to adapt to future changes or expansions. Check valves are common throughout all these systems and play an important role in providing protection to pumps and compressors, as well as preventing reverse flow and water hammer.

Utility Services Where Check Valves Are Installed

Power House Systems in Hospitals: Medical campuses use a large amount of energy for equipment such as high-power lighting in operating rooms, air exchange, filtration, and other uses. They rely on continuous supply and backup power systems. There are different types of systems in use, from gas and steam turbines to thermal heat and solar power. 

A steam turbine power generation plant is a common type of power plant today. This type of plant converts heat into electricity typically by using a boiler and a turbine to operate an electric generator.

Chiller Systems: These systems are used to create a comfortable interior environment. They use pumps, fans, and other components to provide chilled air via air-cooled or water-cooled condenser systems. 

Air & Gas (Nitrous Oxide) Pumping Systems: Industrial check valves are also used in the transport of air and gas throughout hospital systems. They need to be reliable to prevent leakage and minimize the risk of fire and explosion. 

Industrial Boiler Systems in Hospitals: Most hospitals use steam boilers to economically heat buildings quickly. These boilers are relied upon for consistent and safe operation, responsible for heating, hot water, humidification, and sterilization, among other vital hospital tasks. They need to keep up with demand, so downtime is not an option.

How a steam boiler works to heat a facility:

1. Feed water intake—transferred from the main supply to the boiler system
2. Dirt and debris are removed
3. A deaerator removes the air from the water
4. The water goes into the boiler tank for heating
5. Steam is produced by boiling the water
6. The steam is sent through pipes and used for heating areas
7. Through condensation, the steam turns back into water for reuse 

Steam Boiler – Deaerator

DFT® has an extensive installed base in hospitals, medical centers, and universities throughout the U.S. Our check valves are used in many different applications throughout these campuses. 

What differentiates DFT® check valves from other check valves is the distinctive spring-assist technology that prevents reverse flow, reduces the potential for water hammer and vibration, and protects pumps and other valued equipment. Additionally, the low maintenance and long service life provide long-term savings and superior performance.

Check valves play an important role in preventing water hammer and its effects within hospital systems. They also protect pumps within the system from reverse flow. DFT® provides complimentary check valve sizing analysis to ensure stable, maintenance-free operation. This quick and easy DFT® sizing process will ensure significant improvement in check valve performance and reliability. In addition, our sizing process has proven to provide our customers with the lowest cost of check valve ownership far beyond any other commodity-type checks used in most plants today.  

DFT® Check Valves Used in Boiler Systems and Building Maintenance

Boiler feedwater systems are challenging due to the potential for high pressure and temperature. DFT® has designed the WLC® Boiler Feed Wafer Style Axial Flow Non-Slam Check Valve for just this application.  The WLC® Boiler Feed Check Valves can handle pressures up to 3,705 PSI and Temperatures up to 800 °F.

The WLC® BF wafer check valves provide excellent performance and protection in boiler feedwater systems. 

Features:

• A one-piece body that has a ribbed construction
• A welded disc and stem
• 410 stainless steel trim 
• Spring-assisted axial flow design
• Center guided non-slam construction
• The WLC® BF is available in:
  • Sizes 2½ through 10 inches
  • Pressure classes 600/900/1500

DFT® can also offer the Excalibur® or GLC® Check Valve designs if flanged construction is required.

Condensate return systems are integral to boilers. These systems tend to operate at lower pressures and temperatures than feedwater applications. They also tend to have smaller diameter piping. The SCV® can handle pressures up to 2,570 PSI and temperatures up to 510 °F depending on the materials of construction and Cold Working Pressure ratings.

The SCV® provides excellent performance and protection in boiler condensate systems.

The SCV® threaded valves feature:

• Stainless steel construction
• NPT or socket weld ends
• Body guided disc 
• Spring-assisted axial flow design
• The SCV® is available in:
  • Sizes ½ through 3 inches
  • 750 and 3600 Cold Working Pressure

DFT® has many types of check valves designed for use in steam and steam condensate systems, depending on the size, flow, and temperature of the application. 

For more information on DFT® check valves and sizing for your application, contact us.

Threaded Check Valves Guide

Threaded check valves are a type of valve that features either internal or external threaded end connections. The term “threaded” refers to the valve end connection, which is the component of the valve that connects with the piping system. This type of valve is typically easy to install and performs very well in applications with various pressures and temperatures. Most often, threaded valves are four  inches or under. These components are available with either male or female connections and can be tapered or straight. Tapered threaded valves (NPT ends) will provide a direct seal, while straight threaded valves (NPS ends) will require auxiliary components to provide a seal.

Uses for Threaded Valves

Threaded valves are widely found in applications with stable pressures and temperatures. They can be used in liquid, gas, or steam applications. Industries that commonly utilize threaded valves include:

• Boiler
• Food and beverage
• Power generation
• Pharmaceutical
• Municipal
• Pulp and paper
• Chemical processing
• Water treatment
• Mining
• Test laboratories
• Textiles
• Primary metals
• Gas transmission
• Petroleum production and refining
• Building maintenance

Applications

Threaded valves can be found throughout all industries but are common within the petrochemical  industry and can often be found in refineries. They are also a popular choice for boiler and steam applications. In these cases, the environment will typically feature very high temperatures coupled with low pressures.

It is also possible to use threaded valves in applications related to gas or oil production. Unlike steam and petrochemical applications, gas and oil production will feature extremely high pressures, prolonged opening and closing times, and harsh environmental conditions.

Factors to Consider Choosing the Right Threaded Valve

To protect the long-term performance of your piping system, it is important to choose the appropriate threaded valve. There are several factors to consider when making this decision. A significant consideration is the amount of pressure that the valve must withstand. For applications with high pressure, an externally threaded valve is the optimal choice, as it will have a thicker wall than an internally threaded valve.

It is also important to determine whether the valve must provide a direct seal. Applications that require a fluid-tight seal will generally necessitate the use of a tapered valve, as this will provide a seal without the need for any additional components. National Pipe Thread Tapered (NPT) valves are the U.S. standard for applications requiring tapered valves.

Factors to consider when choosing a threaded valve include:

• Temperature
• Pressure
• Tight seal (metal or soft seat)
• Size and weight
• Adherence to industry and plant standards
• Valve permanence
• Ease of installation
• Ease of removal
• Budget
• Inventory simplification

Threaded Check Valves from DFT Valves

Since 1943, we at DFT Inc. have been engineering and manufacturing world-class, in-line check valves for use in a wide array of industries, from petroleum refining to food and beverage.

Our check valves can be installed vertically or horizontally and play an integral role in steam condensate management systems. These systems help maintain high-quality steam, thus preventing the development of many issues within the pipe and valve. In particular, our line of SCV threaded check valves is ideally suited for use in steam condensate applications. These valves feature a range of qualities, including corrosion resistance and longevity, that ensure their high performance in applications of this type.

For over seven decades, our priority has been preventing threaded check valve failures. We are dedicated to providing our customers with threaded valves that are both sized appropriately and suited to the unique needs of each application. To learn more about our offerings, browse our Threaded Valves Catalogue or contact us today.

DFT Threaded Check Valves are available in the following types and sizes:

SCV Check Valves – 1/2” to 2” – 750 & 3600 CWP

SCV-R – ½” to 2” –

Basic Check – ¼” to 2 ½”

Restrictor Check – ¼” to 2 ½”

Vacuum breakers – 1”” to 4”

DFT®’s ALC® and WLC® Wafer Check Valves

Water hammer is a problem that can occur in piping systems that use pumps or valves to control liquid or steam flows. It is commonly caused by a sudden closure of a valve or shutdown of a pump and presents as a loud banging or knocking sound in the pipes. If the problem is severe enough, water hammer can cause damage to pumps, pipe ruptures, or broken gaskets or welds, creating a safety hazard for anyone in the vicinity.

To eliminate water hammer from your system, we first must understand the various harmful effects it can have and what solutions are available to resolve them.

The Harmful Effects of Water Hammer

Water hammer occurs when a fluid in motion suddenly stops or changes direction. The fluid sends a shockwave—called hydraulic shock—through the system, causing vibration or banging in the pipes immediately following shutoff.

Water hammer is an issue that can cause damage to your flow system and overall operation. The most common consequences are:

• Pump and flow system damage: Water hammer can cause pumps, valves, and other instruments to be damaged. Seals and gasketed joints can fail, and the integrity of welded joints and pipe walls can be compromised.
• Ruptured pipes: Local pipeline failure as a result of extreme pressure spikes can lead to complete rupture, which can be costly and time-consuming to repair.
• Accidents: Ruptured pipes can endanger maintenance staff and other employees. In some facilities, such accidents can put them at risk of electrocution, slips, and falls.
• Leaks: When pressure waves hit the pipes, they can damage connections, joints, and fittings, leading to leaks. These weak spots may go unnoticed or grow slowly over time, exposing surrounding equipment to potential damage.
• External property damage: The water from a ruptured pipe can cause external damage or corrosion to infrastructure and electrical devices.
• Unscheduled downtime: If a pipe ruptures or causes property damage, repairs can be lengthy. This can lead to lost production and other financial losses related to the repair.

Our Solution

DFT® is a world-class manufacturer of check valves for a wide range of industries and applications. Our ALC® and WLC® are wafer-style check valves that help to prevent water hammer and reverse flow. They can be a direct replacement for failing double-door or dual-plate check valves. DFT® non-slam, spring-assisted, and center-guided check valves are designed to maximize the service life of your flow system.

The ALC® Wafer Check Valve is a compact, lightweight spring assisted valve with API 594 face-to-face dimensions that fit between mating flanges. The body is constructed from corrosion-resistant stainless steel and carbon steel, and it can be used in vertical or horizontal installations. Compatible with steam, gas, or liquid process flows, the ALC® check valve features spring-assisted silent closing.

The WLC® Wafer Check Valve is a lightweight, spring-assisted valve suitable for a wide range of pressures, temperatures, and fluids. With a carbon steel and stainless steel body, the WLC® features a protected Inconel spring and dual-guided stem. Optional body materials such as Alloy 20, Hastelloy®, Duplex SS, Titanium, and Inconel® 625 are available.

Benefits of Our ALC® and WLC® Wafer Check Valves

To eliminate water hammer and reverse flow from your industrial piping system, look no further than DFT®’s ALC® and WLC® Wafer Check Valves. These non-slam check valves do not rely on gravity or reverse flow for their closure. Instead, as the forward velocity of the fluid slows, the spring assist on the valve starts to close ahead of flow reversal. The DFT® spring-assisted operation ensures that the valve does not slam shut, thus preventing water hammer and its associated noise and damage. Here is an overview of the features and benefits of each product line.

ALC® Wafer Check Valves

• Available in sizes 2” to 24”, Class 150 & 300
• Meets API 594 face-to-face dimensions
• Center-guided
• Suitable for gas, liquid, or steam applications
• Can be installed vertically or horizontally
• Can be custom-sized to your application
• Low maintenance, long service life
• Tapped holes in the body to aid installation (only 10” or larger)
• Download the ALC Cut sheet

WLC® Wafer Check Valves

• Available in sizes 1” to 10”
• Class 600 & 900/1500 RF meets API 594 face-to-face
• Class 150 & 300 RF meets MSS 126 face-to-face dimensions
• Center & dual-guided stem
• Works with a wide range of temperature/pressure combinations and fluids
• Can be installed vertically or horizontally
• Can be custom-sized for your application
• Available for Severe Service (WLC® SS) and Boiler Feed (WLC® BF) severe duty applications
• Low maintenance, long service life
• Download the WLC Cut sheet

Prevent Water Hammer With DFT® Check Valves

For more than 75 years, DFT® has been solving our customers’ check valve issues, preventing check valve failures, and eliminating water hammer problems. We offer cost-effective rapid prototyping, engineering assistance, and fast production turnarounds. Instead of merely meeting line size, DFT® specializes in producing in-line check valves that meet our customers’ specific requirements. As an engineered valve manufacturer, we have the capability to size to the application and solve unique problems by making adjustments to our valves to suit your application.

DFT® can evaluate your valve sizing requirements and answer any questions you may have about our WLC® and ALC® valve product lines. Browse the ALC® and WLC® product pages, or contact us today.