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Technical

Control Valve Positioner Performance Diagnostics

There has been discussion for some years about the accuracy of measuring control valve travel with the use of the original equipment manufacturer (OEM) measuring element versus the use of independent valve analyzers.

In this article, we will define these devices, as well as relate how they work and how they influence measurements in the various diagnostics programs that use them.

Although many types of digital positioners exist, only a few types of travel feedback sensors are available. This forms the basis of our discussion, which includes the pros and cons of travel sensors and how they measure the travel.


Magnetic Particle Examination: Not the Only Way to Test for Flaws

Magnetic Particle Examination (MT) is a popular, relatively low-cost method to perform nondestructive examination on ferromagnetic materials. As defined by ASME V, ferromagnetics are simply “magnetic” materials that can be magnetized and are strongly attracted by a magnetic field. MT is defined as a method that verifies the presence of defects on the surface of a component (or just below the surface).

MT was first introduced during early 1920s, after workers noticed that metallic grindings appeared to be arranged in patterns around cracks on components under machining. The technique was the result of exploiting the principles of magnetism. The ferromagnetic powder-to-steel parts allowed a more visible indication of discontinuities and defects. MT was first introduced in the railroad industry and quickly replaced other rudimental surface NDEs like “oil and whiting.”

Turning the Tables on Valve Corrosion

Multiple valve manufacturers and users worldwide are finding the value of valve preservation centered on vapor corrosion inhibitor (VCI) technology and related strategies. These strategies reduce manufacturing cycle time, counter the use of products hazardous to the environment and provide more effective corrosion protection than traditional methods.

Design Considerations for High-Temperature Sealing

With growing pressure to combat fugitive emissions and meet strict industry regulations, understanding the latest sealing technologies and design considerations for component solutions in severe applications is becoming increasingly critical. As operating conditions continue to subject valves to ever more extreme temperatures and pressures, sealing them effectively poses a challenge that cannot be met with traditional elastomer and polymer-based gaskets. In these extreme environments, metal seals have much greater design flexibility to address critical issues regarding temperature, pressure, fire safety, leak rate and process compatibility. As a result, metal seals often are the sealing solution of choice in modern valve applications, but numerous design considerations must be taken into account to ensure the seal will perform as expected in these increasingly harsh environments.

The Many Layers of Valve Qualification

While there has been much rhetoric from the new U.S. administration over the past two months about “deregulation,” Cameron’s This email address is being protected from spambots. You need JavaScript enabled to view it. pointed out in his presentation at VMA’s 2017 Technical Seminar there is much more to achieving approved status for valves than meeting governmental regulations.

Daglio joked that there are many terms in use now to attempt to convey just how important valves are. Whether they’re called “supercritical” or “ultracritical” or just “critical,” the bottom line is that valves are essential to the operation of many systems. They must also function in increasingly high pressures and temperatures, as well as in unconventional and extreme environmental conditions, while being robust enough to stand up to highly corrosive chemicals and meet end-user requirements for near-zero leakage, especially valves in gas service.

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