Category Archive: Check Valves
When planning a check valve installation, the primary goal is to achieve a valve and piping system that offers the longest service life at the lowest cost. Accomplishing this goal while also ensuring that the system operates effectively and efficiently requires several considerations.
As a world-class manufacturer of high-quality check and control valves, DFT® understands the challenges of choosing the optimal valve for a piping system. To facilitate the selection process for our customers, we put together the following guide outlining how to choose and implement the right valve.
Principles of Piping Design
In general, optimal piping system designs follow three basic principles:
- There must be a 5-10x nominal pipe size (NPS) of straight pipe on either side of the valve, i.e., both the upstream and the downstream sides of the valve.
- The minimum pressure to open a check valve is referred to as the cracking pressure. However, to fully operate a valve, the system requires twice the differential pressure.
- While many styles of check valves will work in horizontal piping, only axial flow (“silent”) check valves are suitable for use in vertical piping. Whenever possible, a horizontal line is preferred since it rules out gravity, but vertical piping must be considered for flows that require up or down transport.
Common Piping Design Mistakes
Following the above principles facilitates the proper configuration of check valves in a piping system with minimal need for maintenance and maximum reliability. However, many industry professionals may find it challenging to navigate the nuances of pipeline design. Some of the most common mistakes made when designing a pipeline involve:
As mentioned in Principle #1, valves should have enough clearance—i.e., straight pipe—on either side from other pipeline components, such as pumps, elbows, expansion joints, and other valves, to function properly. When positioned upstream, these components can cause turbulence, which affects the performance of the check valve and can cause increased wear and, consequently, failure. The same can be said of other types of valves, such as ball valves and control valves; they perform best when the media flow is laminar, not turbulent.
Axial flow check valves can be installed close to the inlet of an isolating value if it is full port and fully open.
As outlined in Principle #2, there must be enough pressure to keep the valve fully open under minimum, normal, and maximum flow conditions. It is not enough to match the valve size to the pipe; it is necessary to do the sizing calculations to pick the right sized valve for the given flow conditions.
Vertical Pipe Runs
Avoid using swing check valves in vertical pipes. The downward flow keeps the valve open, and the upward flow leads to water hammer from the disc slamming against the seating. As specified by Principle #3, use only axial flow check valves in vertical pipes. The strong spring of the axial flow check valve avoids water hammer by ensuring that the valve closes before the reverse flow happens.
Choosing the Best Check Valve for Your Application
There are several factors to keep in mind when choosing a valve for a piping system. These selection considerations include:
As required by Principles 1 & 3 above, the location of a valve is important; horizontal piping is preferred for all valves except axial flow check valves, and there must be sufficient straight piping on either side of the valve.
Check valves remain open only when there is sufficient pressure in the line. Therefore, the pressure available with minimum flow must be considered along with maximum and normal flow conditions while selecting the valve. This is the requirement per Principle #2 above.
When choosing a valve material, the main focus is on choosing one that is compatible with the characteristics of the piping and requirements of the application (i.e., temperature, pressure, corrosion resistance, etc.). This generally results in the body material of the valve matching the flange material of the pipe. For example, a carbon steel line typically features a carbon steel valve body. Carbon steel is the most commonly employed valve material, with cast iron and stainless steel following close behind.
Types of Valves Used in Industrial Piping
Valves find use in a variety of industrial piping system applications. Typical applications include:
- Preventing reverse flow (check valves)
- Managing the flow of process fluids, including concentrated acids and bases
- Redirecting flow from one line to another
- Restricting flow for system balancing purposes
- Controlling cooling rates to regulate temperature
- Stopping flow during a system failure
Industry professionals employ a wide range of valves to fulfill the above functions, depending on the requirements and restrictions of their unique application. Some of the most common valve types used are:
- Check valves have a disc, stem, or a similar moving part that closes if the flow reverses or stops.
- Ball valves are the most common type of valve and feature a ball with a round hole in the center. When aligned with the pipe, the valve is ON. When turned 90°, it is OFF.
- Diaphragm valves are used for precise flow control, especially when the media contains solids.
- Flanged valves use bolts to secure the connection and a gasket to seal the joint.
- Gate valves turn flow ON and OFF with a vertical disc that moves up and down.
- Globe valves regulate flow with a disk that moves relative to a stationary ring seat.
- Needle valves are similar to a globe valve, but they use a tapered plug for finer flow control.
- Relief valves are safety valves that prevent excessive pressure buildup in the system.
- Wafer valves in general have a smaller footprint in the system.
In addition to the valves listed above, there are many other types available, each of which is suitable for varying industrial applications.
If you need a valve for your pipeline, DFT®, Inc. delivers. With over 75 years of experience manufacturing high-quality check valves and control valves, we can provide you with a valve solution that meets your needs. Check out our product page to find out about our valve offerings or contact us today with your questions or project specifications.
In sanitary manufacturing applications that employ the use of fluid systems, such as in the pharmaceutical industry, regulating fluid flow and pressure is essential to maintaining high product and production quality. Common issues—such as backflow, water hammer, and cleanliness – significantly affect the overall effectiveness and efficiency of the system. For these situations, DSV® sanitary check valves serve as an ideal solution.
Why Are DSV® Sanitary Check Valves Important?
Unlike other check valves available on the market, DSV® sanitary valves meet 3A sanitary standard and are designed for use in applications with high sanitation requirements. As such, they are ideal for the manufacturing operations of products intended for consumption or direct contact with consumers, where unsanitary conditions can result in illness or injury. 316L stainless steel offers the corrosion resistance needed to prevent the contamination of process fluids.
By eliminating crevices and cavities from the valve design and achieving smooth, polished finishes on internal and external surfaces, we minimize the risk of material and bacteria buildup in our valves. We test 100% of our check valves before shipping them out to customers.
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Additional Information on DSV® Valves
The valve consists of seven main components: body, seat, disc, spring, guide, clamp, and body gasket. Both the disc and seat are lapped to ensure tight shutoff capabilities.
For full valve construction, check out our eBook.
- Horizontal Valves. The horizontal valve models are suitable for use in horizontal piping lines that require a self-draining valve.
- Vertical Valves. The vertical valve models are designed for use in vertical piping lines or horizontal piping lines that do not require a self-draining valve.
- Meets 3A Standard 58-02
- 32 Ra or 15 Ra finish
- Clean-in-Place Design
- And more…
- Condensate lines
- Vacuum breakers
- Purified Water
- And more…
A DFT® DSV® Sanitary Check Valve Success
A major engineering firm contacted us on behalf of several pharmaceutical companies. The firm needed to find a check valve solution for their noncorrosive medical waste drain system. The check valve needed to operate at 20 psig or less with a flow of 3 GPM, have sanitary end connections, provide tight shutoff, have a low cracking pressure to open and be able to be steam cleaned in place.
The check valve had to withstand high temperatures, as the firm used 330°F steam to clean the entire medical waste process system 3 times a day. The valve also needed an extremely smooth finish to maintain sanitary conditions.
Responding to the challenge, a DFT® 2 inch DSV® vertical check valve was specified. Designed to prevent flow reversal, this non-slam, full-body valve came equipped with a 0.1-psi cracking pressure spring. We also designed it with tri-clamp connections for ease of disassembly. The product was so successful that… Get the full story in our eBook!
For additional information about our DSV® valves and how they suit the needs of the pharmaceutical industry, download our eBook today.
Cryogenic valves are intended for use in extremely cold applications, the term cryogenic generally is applied to temperatures below -50oC. Valves for cryogenic service have to be constructed of materials that retain their ductility at these very cold temperatures as well as special gaskets and seals that are suitable for extremely cold temperatures. Industries that deal with liquefied and compressed natural gas, as well as liquid Oxygen, Nitrogen or Helium rely on these specialty valves frequently to move cryogenic liquids and gases safely and reliably.
Usually, cryogenic check valves use the pressure of the fluid flow to push the valve into an open position, which allows gas, the media to flow through. When fluid flow pressure decreases, the valve will close again and form a seal in order to prevent leakage through the valve.
Special Cleaning and Concerns
Cryogenic valves require special cleaning and degreasing by the valve manufacturer. This is accomplished with special solvents to degrease and remove any organic contaminants, and often by using ultrasonic cleaning solutions. Some services like oxygen or chlorine service require very high levels of cleanliness to insure that no organic materials or lint fibers are present after cleaning. Properly cleaned and certified valves are placed in double sealed polyethylene bags to insure that the valve remains cleaned until it is time to install the valve.
Operators should always thoroughly inspect cryogenic valves before installing them. This is critical to ensure that no oil or grease has been accidentally introduced into the valve. Some specialized lubricants are approved for oxygen service; their presence may be allowable, but this varies by application.
As mentioned earlier, cryogenic valves must also be kept free of lint. Generally speaking fibers greater than 1/8” in length are not allowed to be present in the cleaned valve. In many cases, absolutely no fibers or lint can are allowed to be present regardless of length. Debris like this can prove dangerous in oxygen systems. Many industry professionals utilize blacklight testing to help detect fibers.
Finally, inspectors must regularly check cryogenic valves and oxygen systems for both internal and external leakage. Internally, leakage can be prevented by ensuring that the proper valve is in place and that it has a well proven sealing design. Cryogenic conditions in particular require robust seals to boost longevity. External leakage is also a significant concern. Often times weld end designs are required. These can be in the form of butt weld ends or socket weld ends on the valves.
How DFT® Can Help
DFT® offers high quality, In-Line, Axial Flow designed check valves as well as a full line of severe service control valves. Our customers often specify weld-end valves for a greater sense of security, but flanged and wafer-style valves are also used. DFT’s GLC, WLC and BNC model check valves and our HI-100 model control valves are suitable for a wide variety of cryogenic applications.
Learn More About DFT’s Valve Solutions
With over 75 years of experience in valve manufacturing, DFT® is proud to offer our clients world-class products at affordable prices. Our certified, knowledgeable staff helps customers overcome obstacles and create custom solutions that will maximize the potential of their valve systems. If you would like to learn more about cryogenic valves, keep an eye out for our upcoming eBook, “Cryogenic Valves 101.”
Check Valve Installation & Piping Design Guidelines
As a follow up from our webinar “Solutions to your check valve problems”, we are sharing, in this post, a few of the questions received from the audience. A variety of questions came in which are answered here by our host Arie Bregman, vice president and general manager of DFT® Inc and a 35-year industry veteran, who is an active member in the U.S. Valve Manufacturers Association (VMA), serving on the group’s education, training, and technical committees.
During the webinar Arie discussed the different factors that go into a well-functioning piping system and ways to prevent water hammer and related issues before they become serious, time-consuming problems. Many times valve problems are not a function of the valve at all, but problems with the piping system design, valve location, poor installation practices or selecting the wrong valve for the application. In the webinar you will hear about check valves within piping design, best practices of installation, choosing the right check valve for the application and even a section on gasket installation best practice.
If you missed this webinar, you can now view it on demand from the DFT website, just click this link.
Below, our talented host answers some common questions regarding check valve applications to help you find the right type and fit.
Q: Can you explain leakage rates for various types of check valves?
A: All of our check valves must meet one of the two most common standards for valves: MSS SP61 and API 598. To test leakage rates, we usually perform the test with either air or water, although water tends to be the more difficult medium. If you’re using your valve in an application that involves gas, you might want to choose the MSS SP61 standard and use gas testing.
Q: Can I use check valves with 50% caustic soda solution? If so, what the minimum temperature?
A: It may be a challenge to use any check valve with such a solution because the caustic soda will likely cause the parts to gradually bind. If you need to use a caustic soda solution, however, we recommend using a special coating such as Xylan on any internal parts that will need to be able to move relative to one another.
Q: How closely does a full bore gate valve approximate a straight pipe? Can this count towards the straight pipe run recommendation?
A: Although a full bore gate valve will have a fairly high flow coefficient, it will still cause flow turbulence. Therefore, you should still place it after the check valve if you plan to use it in place of a straight pipe.
Q: What is the effect on pressure drop for an axial flow check valve?
A: A pressure drop will result in higher flow resistance in an axial flow check valve than it would in a swing style check valve because of the internal pressure within the flow stream. Greater flow resistance, however, isn’t necessarily a problem, particularly if the volumetric flow rate through the collective piping system is also high. You simply need to ensure that the differential pressure created by the axial flow valve enables the valve to completely open at normal flow conditions.
Q: Can you provide a ranking of check valve types from the smallest to the largest pressure drop in the fully open position?
A: Unfortunately, this type of ranking isn’t possible because of the number of variables among the valves. Generally, the highest coefficient by line size would be with a swing style valve, followed by tilting disc, double door (dual plate), and then axial flow valves.
Q: How does cracking pressure relate to pressure drop across the valve?
A : The cracking pressure will be the absolute minimum pressure loss that the valve will experience when in operation. If you need a more precise estimate of the amount of pressure that will be lost, you must do valve-sizing calculations for your specific application.
For more than 70 years, DFT® Inc. has helped customers find and install the right check valves for their unique applications. From world-renowned DFT® Silent Check Valves to the innovative DFT HI-100® Control Valves, we have the products you need and a team of valve experts with decades experience in a range of industries, including power generation, petroleum, construction, chemical processing, steam, water treatment and many more
New Webinar From DFT®: Solutions to Your Check Valve Problems — Important Valve Installation and Piping Design Guidelines
Even one minor mistake in an otherwise well-designed piping system can cause serious, high-maintenance problems — such as water hammer — that can damage pumps and other components. At DFT®, we’ve seen best-case scenarios, and we’ve seen catastrophes, especially involving the installation and maintenance of check valves.
To help understand the many factors that go into a well-functioning piping system and to prevent water hammer and related issues before they become serious, time-consuming problems, we’ve created a comprehensive webinar, “Solutions to Your Check Valve Problems — Important Valve Installation and Piping Design Guidelines.” This presentation will review installation, maintenance, and piping design tips, as well as key guidelines to keep in mind to ensure the most efficient installation and use of check valves.
The upcoming webinar will explain the basics of piping design and the fundamentals of valve sizing, with an emphasis on sizing check valves for specific application conditions, rather than selecting a valve based solely on line size.
- Date — May 23, 2018
- Time — 2 p.m. EDT (11 a.m. PDT)
- Duration — 1 hour
- Presenter — DFT®
- Speaker —Arie Bregman, vice president and general manager of DFT® Inc. A 35-year industry veteran, Bregman is active in the U.S. Valve Manufacturers Association (VMA), serving on the group’s education, training, and technical committees. He also is a member of the VMA Board of Directors. Bregman holds a Master of Science degree in mechanical engineering from Worcester Polytechnic Institute in Worcester, Mass.
- Learn general check valve and piping design rules
- Understand how piping design can impact valve reliability and maintenance costs
- Explore best practices and review check valve installation and valve maintenance guidelines
- Learn how to choose the best check valve for your application
- Hear about common valves myths vs. reality