The purpose of check valves is to prevent backflow within a piping system. Check valves are unidirectional valves that provide unobstructed flow in one direction as long as flow pressure remains constant and protect the piping system against reverse flow. The three main types of check valves we offer are ball, piston, and stop check valves.
Piston Check Valves
Also part of the lift check valve family, piston check valves incorporate a weighted piston (or disc) to prevent backflow. These function in a manner similar to ball check valves, allowing for flow as long as flow pressure remains steady, but applying gravitational closure when flow pressure decreases to a point where it no longer has the force to lift the valve.
The valve bore maintains and guides piston alignment throughout its travel. Depending on flow conditions, piston check valves sometimes include spring assistance to aid in closure. Common cases employing piston check valves include:
- Feed water control in the nuclear industry
- Dump lines
- Make-up water
- Miscellaneous process systems
- N2 systems
- Monitoring and sampling systems
Ball Check Valves
Ball check valves are lift check valves, and use a weighted ball rather than a disc to allow flow and inhibit backflow. Once the cracking pressure is attained, the ball lifts up from its seat, allowing flow to occur. When there is a reduction of flow pressure, it falls back into place to prevent backflow.
Applications of ball check valves include instances where high-pressure and high-velocity flows are critical and backflow may damage upstream components (Applications similar to piston check valves, but more suited to those for more viscous media).
Stop Check Valves
Stop check valves combine the benefits of lift check valves with the positive closure functionality of globe valves. These features allow for the control of flow regardless of direction. The main purpose of stop check valves is to prevent damage to pump or boiler systems upstream of the valve in the piping system. Common case applications of stop check valves include:
- Heat recovery steam
- High-temperature service
- Geothermal service
- High-pressure safety service
- Safety systems
- Shutdown cooling
- Petroleum production and refining
- Hydrocarbon processing
Check Valve FAQ
What are some advantages/disadvantages of check valves?
The primary advantage of a check valve is they prevent reverse flow while typically requiring no external actuation. They also provide a fast-acting solution to preventing backflow. Some disadvantages include the inability to determine the condition of the valve and its status, limitation(s) on its installation configurations, and the possibility of sticking in the open position (not often a problem associated with ball and piston types).
How do you choose the right check valve?
There are several factors to consider when deciding on a check valve for your needs:
- Material Selection: Material used for valve construction must stand up to piping system and media demands associated with the specific type of gas or liquid flowing through the piping system.
- Performance Requirements: Performance considerations include the capability of the valve to handle various temperature and pressure instances.
- Type and Size: Selection of the right check valve includes control considerations, typically related to increased safety in hazardous applications as well as sizing the valve to properly accommodate the piping system’s flow conditions.
- Maintenance: In addition to considering the frequency of maintenance or replacement, operators must also think about the valve’s resistance to clogging, jamming, or otherwise malfunctioning.
- Special Requirements: Check valve selection also includes several special requirements unique to their function, including response time, cracking pressure, normally closed vs. normally open, vertical vs. horizontal mounting, flow direction (upward or downward) and fluid density.
How do you prevent check valves from failing?
One of the disadvantages of check valves is the difficulty of determining the condition of the enclosed valve. Consequently, there are certain measures necessary for recognizing their failure and preventing it. Several indicators that signal failure or potential failure include valve vibration (chattering), measured reverse flow, excessive component wear, audible indications of leakage (water hammer), and leaking. You can prevent failure by:
- Proper sizing
- Routine inspections for cleanliness
- Proper installation
- Replacing valves as needed
Check valves play an important role in controlling flow within high-performance piping systems. Selecting the right check valve provides greater piping system efficiency and improves operational safety.
Conval is a leading global provider of check valves specifically designed to meet the unique needs of our customers. Contact us to learn more about the solutions we offer or request a quote to get started on your next project.
Many industrial facilities operate under severe conditions. When harsh operating conditions are present, using an improper valve can lead to persistent and widespread problems.
As a cheaper valve begins to deteriorate, the efficiency of the whole system stands to decrease—and that’s only a minor consequence compared to the potential for failure, injury, downtime and product loss.
Common operating conditions that will impact valve function and service life may include:
- Extreme temperatures and pressures
- Corrosive chemicals
- Erosive / abrasive conditions
- Lethal media
- High cycle applications
All of the above factors can irreparably damage general-use valves.
Severe Service Valves are engineered to perform under harsh conditions. Incorporating special base materials, innovative sealing mechanisms, and advanced protective coatings, Severe Service Valves survive where other valves would fail. They are a sound investment for facilities that would otherwise incur constant repair or replacement expenses.
Conval, an industry leader in Severe Service Valves for decades, has drawn on that experience to develop the most resilient, cost-effective valves on the market. Our products are designed to withstand the toughest industrial challenges. When maintenance is warranted, Conval products can be serviced in-line.
All of these features allow our valves to boast the lowest lifecycle cost of any comparable product.
What are Severe Service Valves?
Severe Service Valves (SSVs) are rugged, durable and designed to withstand prolonged exposure to challenging environmental conditions. They are also suitable for applications that require frequent cycling. Standard valves, under such demands, often wear down prematurely and require replacement.
While there is no single industry standard that defines a severe service valve, they do tend to share some key characteristics that facilitate their longevity. For instance, materials of construction for Severe Service Valves are selected based on their ability to withstand extreme temperatures, pressures, corrosive environments, erosive conditions, or high cycle needs based on the specific applications.
At Conval, we employ a comprehensive process of testing, analysis to optimize every feature of a new valve from its materials of construction to its sealing integrity.
When You Need Severe Service Valves
There are many applications requiring Severe Service Valves. Most designs are intended for use in the following cases:
- Extreme temperatures. A general-purpose valve is simply not sufficient in applications where piping frequently reaches temperatures below -100° F or above 1,200° F. Severe Service Valves are designed to withstand temperature extremes without leaking or failing.
- High pressure. Most valves are susceptible to leakage at very high pressures or when pressure conditions fluctuate. Severe Service Valves are designed to maintain sealing integrity.
- Abrasive media. Solids, sediments, or particulate matter of any kind pose a significant risk to general-purpose valves. Even small solids can abrade a valve’s surface, increasing susceptibility to further damage (e.g. erosion). The sealing surface of a Severe Service Valve will generally be treated to mitigate this risk.
- Corrosive service. Corrosion-resistant materials and surface treatments are essential if a valve is to function under chemical exposures.
Industries for Severe Service Valves
There are a number of industries that are more likely to incur these challenges. Some of the best candidates for Severe Service Valves include the following industries:
- Process plants
- Chemicals and Petrochemicals
- Metal and Mineral mining
- Oil & Gas (including Upstream, Midstream, and Downstream operations)
- Power generation
- Nuclear plants
This list is far from complete, so any company that operates a high-risk process can benefit from replacing their valves with more durable severe service options.
Selecting Severe Service Valves
It’s important to consider a facility’s processes before investing in Severe Service Valves. Not all applications warrant the same interventions, and not all Severe Service Valves are created equal.
One consideration is the degree to which valves will be exposed to erosive and corrosive influences. High-velocity flow and corrosive chemical transport present substantial obstacles in terms of component lifespan, so it’s critical to assess Severe Service Valves carefully to ensure that they can withstand these demands.
In particular, look for Severe Service Valves that are forged from appropriate alloys, and consider carefully what pressure and temperature ratings are necessary for your application.
Common Severe Service Conditions
Any Conval valve can be ordered to customer specifications, ensuring that our valves are suitable for the specific conditions of an application. Conval’s use of modular design and interchangeable parts make it easy to alter a standard valve to be even more resistant to severe service conditions.
Some of the application challenges with which we have experience include the following:
- Particulate matter
- Lethal media
- High pressures
- Extremely high or low temperatures
- High cycle
The combination of these variables should be the key determinant when choosing the components used in your final valves. A Conval representative can guide you toward the optimal choices.
Conval’s Severe Service Valves
Conval’s state-of-the-art Severe Service Valves are appropriate for any and all of the applications discussed above. We also offer a variety of standard valve configurations to accommodate various process conditions, further increasing the versatility of our product offerings.
CLAMPSEAL® Globe Valves
For harsh conditions, we offer CLAMPSEAL® globe valves in a Y, Angle, and T-pattern body styles, including both stop and stop check options. An Integral Gland Wrench (IGW) makes packing adjustments simple with no tools required.
Our globe valves are streamlined with a single-piece gland, eliminating unnecessary complexity while still incorporating the IGW. The low-emission design is complemented by a full range of accessories and end connections to allow easy installation into any system.
Swivldisc® Gate Valves
The Conval Swivldisc® wedge gate uses an innovative flexible disc to achieve optimal alignment between seating surfaces, forming a tighter seal than a standard wedge gate can permit.
Our gate valves exemplify the same commitment to quality and in-line reparability as our other offerings while still incorporating innovative features like an advanced pressure-actuated backseat and a high-performance graphitic packing system.
Camseal® Ball Valves
Conval’s Camseal® Top Entry single forged body design effectively eliminates the potential for leakage due to pipeline stresses, unlike two-piece, end entry or side entry designs. The top entry design allows for rebuilding the valve in line, without any welding or stress relieving.
The proprietary coating and finishing process ensures reliable performance through thermal cycles, operational cycles and erosive system fluids. An easy-to-read stem and ball alignment indicator ensures sustainable shutoff and accurate instrumentation adjustment.
Clampseal strainers are simple and rugged pipeline components, engineered to efficiently entrap entrained solids flowing within process pipelines.
Utilizing a wide range of strainer element hole sizes, they are available in angle, Y or T body configurations and feature in-line disassembly for element cleaning or change out . As with all Clampseal products, the internals are standard subassemblies, interchangeable within all body patterns.
Conval Whisperjets promise a safe, affordable mechanism for handling pressure drops that can otherwise lead to erosion, and cavitation. To do this, the Whisperjet directs an input stream through a series of pressure-reducing stages that minimize the velocity and pressure of the media. These devices also address noise issues, and like all Conval products, perform excellently for years.
Clampseal® Check Valves
Lightweight Conval check valves use just two moving parts to allow or deny fluid flow, enabling simple and smooth operation year after year. Piston, ball, and stop checks are available in a variety of body styles.
Use Conval Severe Service Valves to Safeguard Piping Systems
Conval’s in-line repairable valves, are the most trusted name in Severe Service Valves. Conval offers the most customizable high-performance products in the industry. If you expect your valves to experience high pressures, extreme temperatures, or corrosive conditions, Conval Severe Service Valves are the best investment you can make to increase the longevity of your piping system.
Our products quickly pay for themselves by extending the service life and minimizing the need for regular maintenance. Please contact us for more information about what the transition would look like for you.
Users report that Conval valves offer superior performance in HRSG combined cycle plants.
When Heat Recovery Steam Generator (HRSG) combined cycle plants were first designed and built several decades ago, many of the originally-installed actuator/valve packages included lower-quality, foreign made globe, gate and ball valves. Time and experience have now shown that these inferior valves only last 4-5 years or less. By comparison, where Conval’s were specified and installed, typical valve life has been more like 16-20 years. Based on this real-life experience, more HRSG maintenance supervisors and planners are choosing to replace original lower-quality, foreign made valves with new Conval Camseal ball valves, Swivldisc gate valves and Clampseal globe valves. Sometimes these plants already stock Conval valves. If they do not, factory deliveries are good. If the original valves are actuated, Conval can match the footprint of the actuator for easy replacement. Based on users’ experience, Conval valves are being used in such key HRSG combined cycle cations as isolation, vents, drains, and feedwater. By their very nature, these plants frequently cycle up and down, on and off, which is very difficult on any mechanical equipment. Most OEM valves simply cannot perform in these highly demanding circumstances. Plant managers and their staffs are discovering that Conval is the smartest, most economical valve choice from a total life cycle standpoint.
Conval’s family of product literature is now available to download in pdf format.
A two year old power plant originally chose a competitor’s globe and gate valves. However, the Plant Engineering Department wasn’t satisfied with the valves. By October of that year the valves had pressure seal gasket and packing leaks, forcing the plant to replace the faulty valves.
Having used Conval’s CLAMPSEAL® globe valves at other power plants in the past, they turned to Conval. Their Conval sales representative informed them about the Conval Swivldisc® Gate valve; the valves were replaced and the problem was solved permanently.
Conval continues to set the industry standard with high-pressure, high-temperature valves that have the industry’s lowest lifetime costs.
To better serve our customers, our Conval CLAMPSEAL® Valve Servicing Instructions are included on our website. Our main goal is to provide our customers with up-to-date information, which enables them to maintain our CLAMPSEAL® valves, in a timely manner. We hope the information contained in our Servicing Instructions will give customers the instant support that they require.