by Matt Migliore
|Online specification tools, such as ASCO’s Redundant Control System (RCS) configurator (pictured here), allow users to build virtual valve assemblies with a variety of options, including diagnostics capability, materials, manual resets, and SIL ratings. Such tools are designed to enable specifying engineers to more quickly and accurately select the valve solution that is most appropriate for a given application.|
When specifying valves for a given application, it is important to first determine the intended function. This may seem a rather obvious observation, but, unfortunately, a lack of functional understanding is often where valve performance issues begin. The user, rather than fully considering the application in which the valve will operate, moves forward on a purchase, only to find later on that the valve isn’t all that well suited to meet the needs of the job it is being asked to do.
To avoid such problems, Ron Fletcher, a technical support representative for ASCO Valve (www.ascovalve.com), recommends users answer a few simple questions when considering a valve purchase:
• What is the valve controlling (air, water, gas, etc.)?
• What size valve is needed?
• Will the valve connect to tubing or hard piping?
• What is the desired volume?
• What is the max./min. pressure of the process?
• Where is the application (inside or outside)?
• What is the voltage (AC or DC)?
• Are there any special features required?
In addition, Fletcher says there are also some common pitfalls users should be aware of when specifying valves. For example, he says users often select valves with internal or body materials of construction that are not compatible with the fluid being handled and/or the application environment. He says this scenario results in a situation where the valve surfaces degrade at a rapid rate and ultimately compromise the performance of the device.
Fletcher says users must also be cognizant of the effect flow restrictions have on the performance of valves. If the application or related equipment hinders the ability of the process to meet the valve’s minimum pressure differential, performance will suffer.
Finally, Fletcher says users must be careful to properly filter the material going through the valve, as unfiltered media will often result in buildup in the internal passages of the valve and hamper operation. For example, in air service, Fletcher says failure to place an upstream filter makes the process susceptible to debris or particulate contamination, which could affect the lifespan of the valve.
In an effort to help end-users with specification and care, ASCO provides an information sheet for each valve it manufactures, detailing best practices for installation, maintenance, and rebuild. For all of its valves, ASCO recommends users filter process media to avoid contamination and buildup, as well as maintain process pressure within the valve’s specified pressure rating.
Regarding installation, Fletcher says the most common mistakes users make typically revolve around improper piping arrangements, which often lead to insufficient pressure differential for consistent performance. For example, a poor piping arrangement might create a situation where the lack of pressure differential between the pressure and the exhaust ports will not allow the valve to shift properly.
ASCO also stresses the importance of valve sizing when consulting end-users. The company offers sizing software on its Web site, which looks at three specific application characteristics — volume (i.e., flowrate), pressure drop, and Cv rating — to determine the valve size needed for a given use. If the user knows two of these parameters, the software can calculate the third to provide an accurate size estimate for the application under consideration.
Fletcher says oversized and undersized valves lead to their own unique set of problems. For example, he says an undersized valve will be incapable of providing the needed volume no matter how much pressure is provided. Meanwhile, he says, an oversized valve will exhibit erratic behavior — sometimes failing to open, sometimes failing to close — because there just isn’t enough volume passing through the valve to ensure proper operation, which can also cause premature valve failures.
Though users must be diligent when it comes to specification and maintenance best practices, valve manufacturers continue to develop new valve technologies to support more application flexibility and higher levels of performance. ASCO, for example, is now embedding microchips into the coils of its solenoid valves to enable improved pressure ratings, lower power consumption, noise reduction, and increased operating voltage range. “In recent years we’ve made tremendous progress improving solenoid valve performance by incorporating advanced electronics into our designs,” says Nick Buccheri, vice president of engineering for ASCO Valve. For example, he says ASCO’s RedHat Next Generation Electronic Valve features DC pressure ratings 100 percent to 500 percent higher than today’s standards; consumes up to 80 percent less power than traditional solenoid valves; eliminates the hum associated with typical AC solenoid valves; operates across broad voltage ranges; and includes built-in surge suppression.
Buccheri also cites the evolution of online configurators as a major advance for the valve industry, as such systems now provide feature-rich capabilities that allow specifying engineers to easily use Web-based software to “build” a valving system that meets their specific needs. For example, ASCO’s Redundant Control System (RCS) configurator allows users to create a dual-pilot valve assembly for process control applications with a variety of options, including diagnostics capability, materials, manual resets, and SIL ratings.
Going forward, Buccheri anticipates valve performance will continue to improve as engineers employ design tools, such as finite element analysis, computational fluid dynamics, electromagnetic field simulation, mold flow analysis, and others. He expects improvements will come in the form of increased flow, higher pressure ratings, smaller envelope size, and expanded temperature ratings. He sees valve selection becoming faster and easier as well, as the use of online product configurators continues to rise.
Regarding entirely new forms of valve technology, Nicolo Accordino, an analyst with The Freedonia Group (www.freedoniagroup.com), says it is unlikely there will be any revolutionary designs to come to market in the valve space in the immediate future. “Typically, advances in industrial valve technology occur at a slower, more evolutionary pace than in more technology-intensive industries,” says Accordino. “Because of this, valve producers usually alter minor parameters, such as changing the materials of construction — for example, using plastics instead of metals — or tweaking the design — developing, for instance, high-performance butterfly valves with better features than standard butterfly valves.”
Accordino does, however, see a lot of activity brewing in the area of “smart” valve technology, such as wireless actuators. “While still in its infancy, the main advantage for [wireless] is that it effectively eliminates wires and the costs associated with installing and maintaining a vast network of wiring in a modern factory setting,” he says.
Specifically, Accordino sees the recent release of the HART 7 protocol, which includes a framework for enabling wireless diagnostics, as an area of potential for new valve technology. He says, “The HART 7 protocol and the advantages that it presents are in line with those of other smart valve devices, with WirelessHART allowing the system to be controlled from an even more remote location.”
ASCO Valve’s online sizing software is available at
Matt Migliore is the editor of Flow Control magazine. He can be reached by phone at 610 828-1711 or via e-mail at email@example.com.