A Changing Landscape

Control valves continue to be most often fitted with pneumatic actuators, but electric, hydraulic, and electro hydraulic actuators are the fastest growing actuator types, especially for ball and v-ball valves. Meanwhile, reliability, low maintenance, low leak-through-rate, and repairability were listed as the top four features, respectively, that users most seek in control valves.

By Dave Harrold December 1, 2003
  • Electric actuators

  • Smart positioners

  • Availability

  • Repairability

Control valves continue to be most often fitted with pneumatic actuators, but electric, hydraulic, and electro hydraulic actuators are the fastest growing actuator types, especially for ball and v-ball valves. Meanwhile, reliability, low maintenance, low leak-through-rate, and repairability were listed as the top four features, respectively, that users most seek in control valves.

These are among the findings from a Control Engineering and Reed Research Group survey designed to learn where reader/subscribers are using and what they looking for when they buy control valves. Over time, “Product Focus” research shows definite patterns and trends.

Who’s buying

Control Engineering subscribers represent a broad number of industries and have many job titles, thus they are buying, specifying, and/or recommending control valves for use in diverse applications including chemical, food and beverage, pulp and paper, and waste treatment.

Analyzing results of the past four (1998, 2000, 2002 and 2003) control valve “Product Focus” surveys and Control Engineering’s 2002 purchasing study indicates subscribers most likely to be involved in applying control valves have a title of control and/or instrument engineer, specify one to five units per year for use in continuous and batch processes, and pay an average of $3,885 per unit. During the next 12 months, they expect their control-valve spending to remain about the same. Respondents were widely distributed, but the largest number, by state and company type, work in Texas for an end-user company.

Gains and loses

Pneumatic actuators continue to dominate the actuator technology users purchase; however, since the 1998 study, electric actuator’s share has moved from 11% to 45% and hydraulic and electro hydraulic have moved from near zero to 28%.

Survey analysis reveals other dynamics in the accessories users are specifying. From 1998 to 2003, the need for limit switches and solenoid valves dropped 24% and 42% respectively.

In the area of current to pneumatic transducers (I/Ps), survey analysis indicates the death knell may be ringing for traditional force/balance I/Ps. Forty percent of all control valves were being specified with traditional I/Ps in 1998. That number dropped during each survey period and by 2003 only 16% of control valves are being specified with traditional I/Ps.

Despite a few factors moving around, the top three remain unchanged and provide valuable insight to suppliers as to what’s really important to those specifying, buying, and/or recommending control valves.

Managing valve assets

A slight decline from last year’s number (71% to 62%) indicates more end-user companies are now using outside service providers to maintain and repair control valves.

According to ARC Advisory Group ( www.arcweb.com ) analyst David Clayton, control valve suppliers are actively gearing up to assume more control valve maintenance, repair, and upgrade services to end-user companies.

Regardless of who provides the services, reaping the greatest benefits requires the establishment and administration of a control valve asset management strategy, such as ARC’s collaborative asset lifecycle model (CALM).

Models like CALM help manufacturers address long- and short-term control valve lifecycle planning.

Long-term planning includes establishing decisions on how to extend valve life. Short-term planning identifies who and how specific control valve health, performance, and maintenance activities will be conducted and coordinated.

A well-designed control valve asset management plan addresses scenarios for:

  • Running to failure;

  • Time or use based (preventive) maintenance;

  • Performance analysis (predictive) maintenance; and

  • Operational impact (functional) maintenance.

Poor control valve performance can often negate the expected gains of advanced process control (APC) applications. Ensuring control valves perform correctly is a critical step to profitability, and an effective control valve lifecycle strategy helps achieve that assurance.

Clayton says, “By minimizing unnecessary maintenance and maintaining process variables as near as possible to setpoint, the CALM model helps manufacturer’s lower maintenance costs and reduce rework and waste.”

ARC’s CALM model recommends end-users:

  • Conduct a valve audit to identify each valve’s operational performance criticality;

  • Invest in digital positioners, especially on critical and APC controlled valves;

  • Consider investing in asset management software capable of accessing control valve performance data; and

  • Work toward the adoption of a common fieldbus communication protocol capable of providing control valve data into a common database.

Control valve products

For more manufacturers, visit www.controleng.com/buyersguide . To request free information from vendors, www.controleng.com/freeinfo .

Comments? E-mail dharrold@reedbusiness.com

Supplier selection
The 2000 and 2003 surveys asked respondents to rank the following seven factors when choosing a control valve supplier.

Factor 2000 2003
Source: Control Engineering
Despite a few factors moving around, the top three remain unchanged and provide valuable insight to suppliers as to what’s really important to those specifying, buying, and/or recommending control valves.
Availability from stock 1 1
Repairability 2 2
Cost 3 3
Manufacturer’s reputation 6 4
Factory technical support 4 5
Local technical support 5 6
On-line ordering 7 7

Rotary valve delivers longer life

Emerson Process Management’s Slurry Vee-ball control valve features rugged construction, wear-resistant trim materials, and an unrestricted straight through flow path for controlling the most abrasive of slurries. Slurry Vee-ball is available in 3-, 4-, 6-, 8-, 10- and 12-in. sizes. Emerson Process-Fisher , www.emersonprocess.com .

Soft seated, tight shutoff valves

Parker-Hannifin’s C200 Series of soft-seated valves are designed for steam, hot or cold water, and air and inert gas applications requiring bubble-tight shutoff. Using stainless steel reinforced PTFE rings on the stem, C200 valve bodies are machined from high grade Navy-M bronze with stainless steel stem and seats, spring-loaded packers, and stainless steel spiralwound gaskets. Available in a variety of sizes, C200 valves have a maximum operating pressure of 400 psi (28 bar). Valve temperature range is -40 to 400 °F (-40 to 204 °C). Parker-Hannifin , www.parker.com .

Smart control valves

Metso Automation’s nelesCV control valves integrate three matched components: a process specific valve, a double diaphragm actuator, and an intelligent valve controller with smart communications for on-line performance and predictive condition monitoring diagnostics. The scope of offering includes nelesCV Finetrol, nelesCV Globe, nelesCV Neldisc, and nelesCV Segment control valves. Metso Automation , www.metsoautomation.com .

Valve available with high thrust actuator

Valtek’s Trooper valve is designed for use in ANSI Class 150 or 300 service applications with temperatures ranging from -20 to 650 °F (-30 to 345 °C). Trooper’s compact, high thrust, reversible diaphragm actuator is optionally available with integral I/P or P/P positioner. The integrally mounted positioner eliminates external tubing requirements, reduces pinch points, and keeps moving parts safe from external dirt and damage. Reversing actuator action is achieved without tubing changes or additional parts. Flowserve-Valtek , www.flowserve.com .

Ball valve offers a characterized seat

Worcester’s C-Flow rotary control valve combines the simplicity of a process ball valve with a characterized seat. This combination provides high rangeability; bubble tight shut-off; compact, lightweight design; minimized hysteresis; and in-house maintainability. Flowserve-Worcester , www.worcestercc.com .

General service butterfly valve

DeZurick/Copes-Vulcan’s BGS II butterfly valve seat is made of a wear resistant elastomer with a phenolic backup ring on the 2-14 in. sizes and aluminum on sizes 16-36 in. The soft, elastic seat is designed not to collapse under vacuum or high velocity service and it eliminates a need for flange gaskets. The stem seals consist of a primary seal between the spherical disk and seat hub. Secondary seals are o-rings at the top and bottom of the stem to retain lubrication and prevent atmospheric corrosion. Pneumatic, hydraulic, or electric actuators with solenoids, positioners, and limit switches can be installed for automated operation. DeZurick/Copes-Vulcan , www.dezurik.com .

Port design improves performance

Samson’s incorporation of a port in its type 3310-segmented ball valve reportedly provide benefits similar to those of a V-port plug valve. The 3310 posts specifications of 100:1 rangeability, high KVS values, and characteristic of linear or equal percentage valves—depending on the direction of rotation. The hardened-steel segmented ball remains in contact with the seat ring over the entire control range, ensuring that any foreign deposits are wiped clean. PTFE soft seals are used to achieve leakage class VI requirements. In the fully open position, the flow path is unobstructed. Samson , www.samson-usa.com .

Self-aligning plug ensures shutoff

Dresser-Masoneilan’s Camflex II provides ANSI Class 600 flangeless and Class 150 and 300 flanged body ratings. A straight through flow pattern provides high flow capacities and an integral extension bonnet allows usage in -320 to 750 °F (-196 to 399 °C) fluid-temperature applications. Camflex’s self-aligning eccentric rotating plug provides tight shut off and low dynamic forces. Slurry packages are available in all sizes, and a highly visible indicator shows valve position. Dresser-Masoneilan , www.masoneilan.com

Control valve provides linear flow

RKL Controls LEF Series pre-pinched control valves provide a smooth, unobstructed design that produces linear flow characteristics from 15% to 80% valve openings. LEF has a high C v rating and provides minimal pressure drop when in full-open position. The valve body is available in cast iron, aluminum, or ductile iron. Available in 1-16-in. sizes, valve sleeves come in pure gum rubber, Neoprene, Hypalon, chlorobutyl, Buna-N, EPDM or Viton. Red Valve-RKL Controls , www.redvalve.com/rklcontrols .

Resilient seated knife gate valve

Burbach’s MF Series of resilient seated knife gate valves are designed for use in pulp stock, sewage, soft solids, coal dust, emulsions, granulates, powders, and paste applications. MF Series includes bi-directional zero leakage, a no-packing design, self-adjusting transverse seals to prevent atmospheric leakage, and a flow profile that enables natural flushing. MF Series uses a low-profile gate radius design to minimize solids build-up. Burbach www.bnaknifegate.com .

High-cycle pneumatic actuator

A-T Controls Triac TR Series pneumatic valve actuators are designed for high-cycling applications. TR Series actuators include dual travel stops, an ISO5211 wide base mounting design, and traceability serialization. Providing up to 36,000 lb-in. of torque, and 100 degrees of rotation, TR Series actuators can be fitted on butterfly valves, ball valves, and damper applications. A-T Controls , www.a-tcontrols.com .

Self-diagnosing positioner

Siemens’ Sipart PS2 electro-pneumatic digital positioner features manual or automatic tuning, entry of maintenance information, electronics replacement without retuning, and binary input for safety cut-off. PS2’s internal diagnostic parameters include limit values for travel integral, number of direction changes, and dead-zone and top and bottom hard stop monitoring. PS2 is available with Profibus-PA or HART communication protocol. Siemens Energy and Automation, www.sea.siemens.com/ia .