Valve Survey Says, ‘Cost Less Important than Support’

TRENDS IN VALVES

Pneumatic actuators

Fieldbuses

Microprocessor-based positioners

Embedded feedback devices

Contestants on the show Family Feud won points and eventually prize money for correctly matching their answer to audience survey responses. The valve survey recently conducted by Control Engineering is less animated, but financial rewards for properly selecting, applying, using, and maintaining valves can be much greater than won on Family Feud.

Control Engineering ‘s survey was conducted by sending 1,500 surveys to a selected portion of our 45,000 North American readership audience. Four-hundred and six responses were returned (27%) with 95% of the respondants being those who specify, recommend, or buy valves for their own in-plant requirement, or for use in customer facilities. The latter group includes contractors, integrators, consultants, and OEM’s (original equipment manufacturers).

Survey responders produce specialty and fine chemicals; petrochemicals; food and beverages; stone, clay, and glass; textiles; machinery; and furniture producers, to name just a few. Industrial valves in these plants fit one of two categories: on/off valves, and control valves.

In developing the list of industrial valves to include in the survey, the list grew long. Fearing inclusion of every conceivable valve type might cloud survey results, the list was limited to: ball, butterfly, diaphragm, gate, globe, needle, plug, and pinch valves. We purposely omitted emergency shutdown valves, relief valves, fire-safe valves, and safety related valves.

On/off valves would be seen in plant applications needing to allow or prevent the flow of liquids, gases, powders, and other media into and out of vessels, pipes, retention ponds, cooling towers, boilers, and thousands of other applications.

Control (throttling) valves frequently are connected to controllers assigned to maintain pressures, flows, temperatures, etc. Control valves are expected to provide smooth, precise, repeatable changes in media flow when valve parts move from closed to open and back again.

Liquids, gases, slurries

When asked what media flows through plant valves, our audience provided multiple answers. Liquids slightly beat air and gases, 86% to 76%. Slurries finished a distant third at 32%. Only 10% of valves handle dry materials, and less than 7% appear in cryogenic applications.

Which actuators are installed most often on certain valve types? Survey respondants say, pneumatic actuators are mounted on diaphragm and butterfly valves 42% of the time. Thirty-seven percent of ball valve installations, 30% of installed globe valves, and 23% of installed plug valves are equipped with pneumatic actuators.

Not surprising, manual actuators are used on 49% of needle valves, 46% of gate valves, and 31% of ball valves.

Electric actuators reside on 13% of installed butterfly valves. Ten percent of ball valves, diaphragm valves, and gate valves also are fitted with electric actuators.

According to information provided by Limitorque Valve Actuators & Controls (Lynchburg, Va.), electric actuators frequently are applied to on/off valves 4-inch diameter and larger, and/or installed where conditions are unsafe for people, or there just isn’t enough room to “man-handle” the valve to its open/closed position. Electric actuators efficiently move big valves, operating in processes where quick movements can be detrimental, such as super-heated steam in a 24-inch header. In this sort of application, closing a 24-inch valve in 60 seconds works just fine.

When asked about accessories available in electric actuators, Paul Boeckerman, Limitorque marketing manager explains, “Electric actuators of the past offered a lot of options, but required sorting through a “mountain” of diagrams and instructions to enable the features needed. Today electric actuators include microprocessors that can be interactively programmed to activate the features the user requires. Through buttons and a display mounted on the actuator, users perform “soft wiring” to enable and set the features required.”

When valves are installed in hazardous processes, fail-safe concerns arise. Pneumatic activated valves generally use springs to force the valve to a full open or full closed position. Electric actuated valves generally fail-in-place.

Discussions about control valves often include suggestions on using variable speed pumps as control valve replacements; a seemingly good alternative. When Control Engineering asked valve and valve accessory manufacturers, “What impact are competing technologies, such as variable speed pumps, having on valve markets?” the nearly universal response was “very little.” Jon Monsen, product manager for Neles Controls added an interesting twist when he explained that “Even when economics of energy cost dictate the use of variable speed drives, it’s wise to include a control valve (operating fully open), to assume control in event of drive failure.”

Valves communicate & accessorize

Control Engineering reports on a variety of communication networks (fieldbuses), so it seemed appropriate to determine what communications, if any, dominate connection to valves.

Slightly less than half, 48%, of respondents use network communications between valves and other devices or systems with 4-20 mA dominating those communication users (see Networks used graph).

Valve and valve accessory manufacturers anticipate growth in the use of digital fieldbus technologies as users better understand the benefits available when deploying microprocessor based valve accessories. Included in the category of valve accessories is pneumatic valve positioners, or the newer term being promoted…valve controllers.

Technically, traditional pneumatic valve positioners are valve controllers, because they use feedback control.

Through mechanical connection to the valve stem, feedback of actual valve position is provided. A desired valve position (setpoint) is received from an external controller, such as a distributed control system. Mechanical linkages, bellows, and flappers determine if the actual valve position matches the desired position. If there is a mismatch, the positioner adds, for example, instrument air to the valve actuator, thus forcing the valve to a new position. The difference between positioners and I/P (current-to-pressure) transducers is positioners work as amplifiers (boosters). Supplied with 80 psi instrument air, a positioner will keep adding instrument air to the actuator until the stem moves or until the pressure on the actuator diaphragm equals 80 psi. I/P transducers, by contrast, generally provide operating pressure in the 3-15 psi range. Thus, 15 psi is the maximum force that could be applied to an actuator diaphragm.

Positioners are available in a variety of styles from those providing proportional only control, to units that include a cam that can be characterized to compensate for nonlinearity in the process and/or final control devices.

Experienced instrument engineers developed opinions of what worked and what didn’t and passed those opinions down as “rules-of-thumb” for determining when to apply traditional positioners. Considerations included use:

On slow loops only;

When packing box friction is high;

When using unbalanced valve plugs; and

If spring and diaphragm hysteresis is high.

Analytical studies conducted by Fisher Controls (Marshalltown, Ia.) (and published in the Fisher Controls Control Valve Handbook) indicate using or not using a positioner is completely independent of the old “rules-of-thumb” with one exception. When stem friction, or stickiness, is unusually high, it becomes increasingly important to ignore the old “rules” and follow fast loop/slow loop principles for positioner application.

Introduction of microprocessor-based positioners (controllers) is further challenging old “rules.” Smar International (Houston, Tex.) explains it well. “These new positioners offer faster response, adjustable gains, and adjustable actuation times, making them suitable for application on fast and slow loops. Instead of mechanical cams and springs, soft-cams are used for characterization and split-ranging. Elimination of mechanical cams and springs ensures parts cannot stick or gall. Also errors, caused by cam wear, are eliminated resulting in greater accuracy, less failures and longer operational life. Dead band caused by mechanical imprecisions is avoided.”

Considering the increasing interest and use of microprocessors and digital communications to and from field devices, limit switches and position feedback devices are taking on new appearances, and some manufacturers are embedding feedback devices in the valves. Users choosing these new technologies have more data available to their control system. The trick is converting data to information, and vendors are offering solutions via software designed to periodically interrogate valves (and other field devices) and report abnormal developments. Available solutions vary in implementation designs from stand-alone applications running on PCs to expert systems designed to detect abnormal situations (see “How to Avoid Abnormal Situations,” September 1998, Control Engineering ).

Features desired

Features respondants most wanted in control valves was reliability at 31%, with low maintenance second at 26% (see Features wanted in control valves graph).

A total of 147 respondents purchased $18,579,480 worth of valves in the past 12 months. Fisher Controls captured the leading sales position at $6,411,200 on 1,379 units sold to 58 respondents. If 58 respondents seem low, there were 92 valve companies listed in the survey responses.

Valtek Inc. (Springville, Ut.) was second in terms of sales dollars, selling 749 units to 14 respondents and receiving $3,931,500 for its efforts.

The third position went to Neles Controls selling $1,962,000 to 18 respondents and delivering 1,296 units.

For units purchased in the past 12 months, 92 companies delivered 12,452 valves to 147 respondents. What’s the future for valve sales? One-half of those survyed predicts their control valve purchases will remain about the same during the next 12 months. Another 23% are uncertain about the outlook for valve purchases. Seventeen percent anticipate their control valve spending will increase in the upcoming year. Only 6% believe their control valve purchases will decrease.

What would valve manufacturers like to advise those who specify and purchase valves? The responses were quite prolific, but boiled down to:

When specifying valves, do not get “locked into” specifying the same as last time. Consider the application and remain open to new technologies designed to improve valve performance and reduce process variability;

Sizing is more important than some users appreciate. Installing an oversized valve, in anticipation of future process requirements, will likely introduce unnecessary variability;

Be realistic in specifying valve requirements. For example, specifying bubble-tight shut-off or requiring special certification on every valve adds unnecessary cost.

While cost was fifth in importantance when ranked against other important characteristics it was still ranked important by 65% of our respondants (see What’s important graph).

New gas shutoff valve

Loveland, Colo. -Designed to provide gas flow shutoff in less than 75 msec at pressures between 100 and 900 psia, with pressure drops of less than 7 psid at 25,000 lb/hr flow rate. Designed with a straight through flow design, the GSOV25 keeps moving parts and seals out of the flow stream. The normally closed valve is designed for emergency and normal shutdown services and incorporates a seal design in the main piston to extend operating life, prevent leaks, and obtain Class VI shutoff ratings. Woodward Governor Co.

Pinch valve with a brain

Carnegie, Pa. -Combining pinch valve and microprocessor technologies produces a valve suitable for abrasive and highly corrosive applications to be controlled with accuracy and repeatability. Mounting a HART compatible positioner on a pinch valve offers digital control to lime slurry, sludge, mine tailings and other abrasive processes. Red Valve Co.

Relief valve handles high back pressures

Wrentham, Mass. -Incorporating a balanced bellows design allows JBS-E and JLT-JBS-E to provide optimum performance when the developed back pressure in exhaust systems or discharge manifolds becomes excessive. Mounting the guide, spindle, spring and other components in the bonnet chamber they are protected from corrosive fluids that could prevent valve operation. Components most likely to be affected by corrosion are constructed of 316L Stainless Steel to improve reliability. Crosby Valve Inc.

Valve trim reduces noise 40 dBA

Marshalltown, Ia. -Utilizing laser-machined discs stacked and permanently fused into a rigid cage assembly surpasses noise attenuation capability of conventional designs by 25% to 30%. WisperFlo trim addresses problems when extreme control valve noise threatens employee safety or causes “bad neighbor” situations. Extreme noise levels also may warn of valve instability and pipeline vibrations that can shorten equipment life. Fisher Controls International

Economical titanium ball valves

Houston, Tex. -Developed as a bi-directional valve with interchangeable soft or metal seats using a cast 3-piece design makes the 3-D Titanium valves suitable for corrosive and erosive services. Sizes from 1/4 to 1-in. with pressure ratings to ANSI Class 1500 are available with any combination of standard or custom end connections. Noble Alloy Valve

Ball valve is actuator ready

Matthews. N.C. -Designed to simplify process automation, Apollo-AR valves are shipped with an ISO-5211 mounting pad. Offered in Conbraco

Smart interface for modular valve system

Irvine, Calif. -Provided with multi-pin connections, this pneumatic valve system is compatible with fieldbus protocols including DeviceNet, Interbus S, Profibus DP, Profibus PA, CAN and ASI Bus. Three size groups are offered: 10 mm, 18 mm, and 32 mm with up to 96 valves using one address on the network. Three-way and/or 4-way valves can be mounted on a common manifold with threaded or push-in connections. Using rocker arm actuators in place of up/down plunger designs improves reliability, providing cycle life in excess of 100 million cycles with nonlubricated air. Burkert Contromatic

Programmable electric actuator

Lynchburg, Va. -Accutronix MX electronic valve actuator incorporates external and internal features to make valve control setup easier. A 32-character LCD display “speaks” six languages, and uses on-screen menus with “yes/no” guided dialogues. A patented absolute encoder provides 100% repeatable valve position tracking, without batteries. Electronic torque sensing provides torque or position seating, and prevents valve and actuator damage caused by torque overload. Limitorque

Color-coded seals simplify maintenance

New Britain, Conn. -The simplicity of color-coded seal inserts offers added measure of valve life performance by eliminating seal misapplication. Thirteen seal materials are available to cover applications such as inert gas, corrosive fluids, refrigerants, high temperature, high-pressure corrosive fluids, and more. A unique compensating plunger design permits the top insert to move up and down, providing a bubble-tight top orifice seal. Peter Paul Electronics

High pressure gas valve actuators

Rochester, N.Y. -Designed specifically to meet demands of gas pipelines, HPG quarter-turn actuators use unregulated natural gas as actuator power and are intended for use in remote areas and hostile environments. Rugged construction, special sealing materials, and attention to surface treatments enable a life of 200,000 cycles in ambient temperatures of–60 to 200°F (–50 to 95°C). Actuators can be specified with control options including remote open and close signaling with a high/low pressure close down priority. Control components are housed in lockable steel enclosures. Rotork Controls

Valve controller delivers high performance

Spring House, Pa. -Modular design of the ValvePAC valve controller minimizes stocking requirements, while allowing flexibility to assemble a variety of valve controllers. To the base pneumatic platform, modules to provide additional capabilities such as: HART interface; feedback signals, including limit switches, 4-20 mA, proximity sensors, and potentiometer (slidewire); and a second PID loop are available. The second loop forms a cascade control strategy with the primary PID valve controller. Bias, gain, and ratio can be utilized, and alarms can be assigned. Manipulation of loop setpoint and other performance adjustments can be made from another controller, a setpoint from a control system, a HART hand-held configurator, or local push-buttons. Moore Process Automation

Miniature gate valves

Woburn, Mass. -Offered with aluminum or stainless steel bodies in sizes from 5/8 to 2-in., Series 01 gate valves provide 50,000 cycles before requiring service. To accommodate fast mounting and minimal flange-to-flange centering, a choice of standard CF, ISO-KF flanges, or a quick-change flange with integral ISO centering rings and clamps are available. Manual and pneumatic actuators are available. VAT Inc.

Really big chemical-resistant valve

Houston, Tex. -Extending the size range the Series 22/23 valve line now offers high performance butterfly valves in sizes from 2-inch to 24-inch diameters. Available in wafer and lug bodies coated with epoxy for chemical resistance, these valves are certified and marked 3.1.B. Increased sizes use patented energized stem sealing system that isolates the valve body and stem from the line media, creating a bubble-tight shut off with high C v values. Bray Valves & Controls

Ambient temperature sensing control valve

Willow Grove, Pa. -Fully self-contained, self-actuating ambient temperature stainless steel control valve minimizes steam consumption is automatically controlling flow in steam-traced lines, instrument enclosures, unit heaters, and other temperature control applications. The TL valve uses low friction, solid-liquid phase thermal actuator to maintain accurate setpoint control with narrow deadband. Ogontz Corp.

Modular pilot operated security relief valve

Avon, Mass. -Comprised of few components, the MPV uses a self-cleaning pilot seat design, making it tolerant to icing and dirty operating conditions. Available as a modulating pilot and a pop pilot within a single assembly, permits conversion from one design to the other. Suitable for gas or liquid processes, MPV provides an adjustable blowdown feature. MPV’s main valve design is API 526 compliant. Dresser Valve & Controls Div.

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