Advances in valve-control improve functionality

Dec. 2, 2008
Contributing Editor Sheila Kennedy reports that advances in valve-control materials, design and construction improve performance, reduce costs and simplify maintenance.

One area that’s changing is the techniques valve operators use to recognize valve positioning, says Ed Hardin, owner of Hardin Consultants in Charlotte, N.C. “It’s not enough to expect a valve to open or close. You need to know whether the open or close happened. According to Murphy’s Law, the most critical valve will have a problem of indicated position most frequently.”

“Too often the indicator is a direct-action micro switch, which is subject to physical change or damage causing loss of reliability,” Hardin explains. “Secondary operator devices often can resolve this problem but introduce secondary reliability concerns. Visual or light transmission devices can mitigate some of these concerns, but then protection from blockage, dirt, trash and alternate sources become critical.”

Fieldbus networks allow continuous access to device positioning, performance and condition information so that quick action can be taken. Metso Automation recently introduced the first Foundation Fieldbus safety valve controller. Its Neles ValvGuard VG9000F leverages Foundation Fieldbus communication to automatically deliver status changes and generate real-time alarms, without requiring external wiring or I/O cards.

Lower-cost materials

New polymer materials are a low-cost, lightweight alternative to metal for flow regulation. Festo has developed technopolymer-based, one-way flow control valves, solenoid-operated valves and valve terminals for high-volume industrial control markets. The VB12 valves are composed of a 50% glass-fiber reinforced polyarylamide compound. A rigorous R&D program including X-ray and thermal analysis demonstrated high strength, rigidity and dimensional stability. The products also exhibited creep resistance at high stress levels, good leakage values, environmental resistance and electrical insulation properties.

Festo’s injection-molded valves supply air flow rates from 200 liters to 1,000 liters per minute and provide full reliability at ambient temperatures as high as 122°F. The VB12 valves are available as individual components or as fully assembled valve manifolds.

Extended life

Longevity is improved with a recent solenoid valve offering. Humphrey’s new 320 Series ¼-in. ported three-way direct-acting solenoid valves are said to offer exceptionally long life through a controlled, short-stroke balanced poppet design. The valves are lubrication-free, tolerant of impurities and have achieved multimillion cycle capability with rapid cycling and positive sealing and flow characteristics. The valves can be inline mounted or inserted into Humphrey’s custom valve manifolds.

Improved temperature control

A new three-way valve accurately controls the temperature and pH of industrial fluids such as water, oils and steam. The Fisher GX 3-Way control valve and actuator system from Emerson Process Management, available with integrated FIELDVUE digital valve controller technology, offers consistent temperature controllability in a rugged, high-capacity design that is compact in size.

Suited for heat exchangers and lubricating skids, the Fisher GX 3-Way valve features a patented flow cavity engineered for linear stability. It accommodates flow mixing (converging) and flow splitting (diverging) applications without requiring extra parts. It has both side-port and bottom-port common trim, unlike other three-way valves. The internal valve trim, screwed seat ring and one-piece plug and stem design make for easy maintenance. In addition, because the actuator is automatically matched to the valve, the need for actuator sizing is eliminated.

Easy installation and repair

Significant time and money is spent maintaining plug valves, particularly in the seawater desalination industry. Flowserve’s new Durco PlugSeal can be repaired without removing the welded valve from the reverse osmosis desalination process line, and no special equipment or training is required. The corrosion-resistant, PFA-coated plug design eliminates the need for a sleeve. Worn plugs can be easily removed and replaced in-line, and adjustor bolts are accessible so that the plugs can be adjusted in-line.

To prevent external leakage, the stem-sealing system uses a reverse lip PFA diaphragm that is self-adjusting and self-energized when line pressure forces liquid to the stem seal area. The Durco PlugSeal can be welded in the pipeline in its entirety or the internal components can be removed and, following the welding process, reassembled and tested before start-up.

Valves should always be tested first, particularly when venturing into uncharted territory. “Before you commit to a large number of unknown valves for a new or unusual application, test them first to ensure they will indeed be functional and serviceable,” Hardin advises.

E-mail Contributing Editor Sheila Kennedy, managing director of Additive Communications, at [email protected].

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