Valves Earn the Title of Process 'Workhorses'
Tour any process plant and one of the first stops is the control room. The implied message, ''This is where the work takes place.'' But if you really want to see where the work takes place, chances are you will need to visit the plant's basement, climb over pipes, and peek behind vessels because that's where the workhorses of the process industry are located. EXPANDED VERSION ON-LINE
Tour any process plant and one of the first stops is the control room. The implied message, 'This is where the work takes place.' But if you really want to see where the work takes place, chances are you will need to visit the plant's basement, climb over pipes, and peek behind vessels because that's where the workhorses of the process industry are located. That's where you find control valves.
During June 2002, Reed Research Group, using an independent firm, invited a select group of Control Engineering subscribers to participate in an online survey regarding control valves. Survey results are based on responses received from persons involved in the specification, recommendation, and/or purchase of control valves.
Specific survey areas of interest included:
Applications and media;
Manufacturers purchased from;
Dollars spent; and
Future purchasing plans.
Among those specifying, recommending, and/or purchasing control valves, 75% do so for in-plant requirements, 16% purchase for original equipment manufacturer (OEM) needs, and 10% purchase for both in-plant and OEM requirements.
Control valves are used in a wide variety of continuous and batch processing applications and flowing media. (See 'Where and How Control Valves are Used' graph.)
The survey asked responders to indicate which actuator type is most used with different control valve types. Without exception, pneumatic actuators dominate every control valve type.
In 1998, fieldbus wars were just ending and end-users were still maintaining a 'wait and see' posture. Four years later, users have begun deploying control valves on fieldbus networks, but no clear fieldbus dominance has yet emerged.
Apparently recent consolidations and divestitures within this industry has end-users confused. Despite providing a list of control valve manufacturers to assist responders to complete a purchasing related question, more than a few responders chose 'other' and listed brand names rather than company names.
Looking ahead, 73% of participants indicate future control valve purchases will remain about the same as the past 12 months.
Many articles about reducing variability chide end-users for not taking better care of their control valves. Control Engineering used this opportunity to learn more about control valve repairs.
To the question, 'What is the frequency of your average control valve repair/service?' Repair services are fairly evenly distributed across one, two, and three or more year increments at 30%, 38%, and 30% of those surveyed, respectively.
One surprise is that 71% of control valve repairs are being performed by the company's own maintenance shop. Another, 14% use a third-party service provider, 11% use factory repair services, and 4% indicate 'other,' though it's hard to imagine what 'other' might be.
Control valve surroundings are often hot, dank, and dirty, the flowing media passing through is frequently corrosive and nasty, and one-third of the time it's three or more years before someone spends any time examining a valve's internals. If you want your process 'workhorses' to perform better, perhaps they should be treated better.
Control valve products
To request information on these products, circle the following numbers in this issue or visit www.controleng.com/freeinfo. For more manufacturers of these products, visit the Control Engineering Buyers Guide at www.controleng.com .
Valve incorporates most sought features
Marshalltown, IA - Standard features in the recently introduced Fisher D2 Flo-Pro control valve include 1-in. NPT end connections; ASME Class 900 (2,250 psig, 155 bar) pressure rating; solid Alloy-6 erosive service trim; full pressure drop capability; Enviro-Seal D2 packaging system; low temperature (-50 °F /-46 °C) materials; field-reversible actuator; and corrosion-resistant powder coat paint. The D2 Flo-Pro's field-adjustable maximum flow rate feature allows setting of 2, 4, or 6 Cv flow rates using just one port size.
www.emersonprocess.com/fisher Emerson Process
Valve family receives major improvements
Elyria, OH - Parker Hannifin's DFW Series proportional directional control valves use improved coil technology to increase maximum flow capacities to 47 l/min (12.5 gpm) for the D1FW and 170 l/min (45 gpm) for the D3W. Connection option improvements include conduit boxes with wire leads, flying leads, or DIN-type connectors as standard choices. Special lead terminations are available in OEM quantities.
www.parker.com Parker Hannifin
Valve engineered for turbine bypass control
Stafford, TX - Dresser Measurement and Control recently reengineered the Masoneilan SteamForm steam-conditioning valve to handle rigorous cyclical operation of turbine bypass applications while maintaining tight shutoff and repeatability expected of severe service control valves. SteamForm uses a patented water-injection design to achieve maximum turndown within the shortest downstream distance. A patented dual-nozzle system, made up of multiple flat and hollow cone nozzles, varies the mass of water droplets. www.masoneilan.com Dresser Measurement
3-way control valve reduces downtime
Tampa, FL - Leslie Controls Class DOT 3-way control valve is suitable for converging and diverging liquid flow services. Class DOT 3-way valves are available with cast iron or bronze bodies in 1- through 3-in. sizes, and threaded or flanged end connections. Cage-guided trim reduces stem load, increases valve stability, and is easily removed from the top of the valve, eliminating the need to remove the DOT from the line for maintenance.
www.lesliecontrols.com Leslie Controls
Bidirectional valve designed for high cycles
Spartanburg, SC. -Hoke's 7223D RotoBall bidirectional valve series is designed for extended duty cycles in the range of 50,000 to 100,000 cycles. The 7223D Series offers high flow with a Cv of 3.4 using a 0.375-in. orifice. Its maximum operating pressure is 5,000 psig (345 bar) at 70 °F (21 °C) with a temperature range of -65 to 400 °F.
Patented stem seal reduces fugitive emissions
Cincinnati, OH - Using ball-joint-like technology, the spherical S2 seal allows Xomox's new Tufline process ball valves to compensate for minor stem movement caused by side loading or seal component wear. Tufline valves are available in one and two-piece flanged, and three-piece screwed, socket-weld, and butt-weld end models. Sizes range from 0.5 through 8 in. in ANSI class ratings of 150, 300, and 600. Tufline valves provide tight shutoff from high vacuum through-rated pressure at temperatures of -20 to 450 °F (-20 to 232 °C).
Plastic control valve features bellow seals
Angleton, TX. - Collins Instrument's Model 1000B series plastic low-flow control valves are offered with a wide selection of Cv values, energy-dissipating trim, limit switches, and pneumatic or electronic operation. The permeation-resistant PTFE bellows seal is designed for use in hazardous or corrosive environments and includes a back-up stem seal packing arrangement.
www.collinsinst.com Collins Instrument
- Malcolm Broderick, Reed Research, also contributed to this article.
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The three most important features in Control Engineering's 1998 and 2000 valve studies-reliability, low maintenance, and repeatability-remain the same in 2002. (See ''Feature Importance'' graph.)
Four years ago, 20% of control valve survey respondents indicated low emissions as an important feature. Two years ago 29% ranked low emissions as an important feature; in 2002 low emissions remains relatively low on the importance curve at 18%.