20 Innovative & Elegant Engineering Improvements for Pneumatic Valve Positioners

Kinetrol AP Pneumatic Positioner
Kinetrol AP Pneumatic Positioner
on top of a Kinetrol Vane Actuator
A valve positioner is an instrument attached to a valve to ensure the valve is at a desired position of opening or closing as per the control signal. Positioners sense the valve position through a position feedback mechanism connected to valve stem. There are many types of valve positioners. Some utilizing pneumatic signals (referred to as pneumatic positioners) and some using electrical current as the signal (referred to as electro-pneumatic positioners). Many manufacturers stake claim over design and performance enhancements, but one pneumatic positioner stands out because of its elegant design. The Kinetrol AP Positioner.

The AP pneumatic positioner combines the smoothness and accuracy of Kinetrol’s proven mechanical positioner technology (using a proportional spool valve driven by a simple, accurate and robust force balance mechanism) with new advances in convenience and simplicity of use, derived from the unique innovative design both of the internal mechanism and of the overall package. 

The result is a positioner with unparalleled performance and real industrial robustness, sweet and easy to calibrate and characterize, and adaptable to the whole range of applications with its unbeatable list of options – high flow valves, direct mount or industry standard discrete mount housings, 4-20mA angle retransmit, limit switches, Clear Cone position monitor and I/P convertors (either simple or with various explosion proof options).

20 Innovative & Elegant Engineering Improvements
  1. ENCLOSURE – robust die-cast metal with tough corrosion-resistant epoxy coating and O-ring sealing. Layout gives easy access to all adjustments on removal of lid.
  2. LID – shown with optional Clear Cone sealed angle monitor. Epoxy coated die–cast metal held on by four captive screws gives quick access to the interior.
  3. CARRIER PLATE ASSEMBLIES – integrated assemblies carrying the feedback shaft and cam plus angle retransmit drive and pot (when specified). Easily removed for conversion or maintenance.
  4. FEEDBACK POT DRIVE – zero backlash, proven trouble free for life.
  5. OPTIONAL ANGLE RETRANSMIT CIRCUIT – externally powered (8–30v DC) linear 4-20mA feedback, rangable down to 30ยบ for full 4-20mA span. Easily accessible zero and span adjustment.
  6. RETRANSMIT POT – high quality conductive plastic servo–type with ball bearings. Proven long life and high precision.
  7. ACTUATOR INTERFACE – options include NAMUR standard (shown), Kinetrol male square or Kinetrol direct mount female square. Quick external conversion allows bracket mounting to any rotary or linear actuator.
  8. INTERCHANGEABLE PORT PLATES – easily convertible for different flowrate options.
  9. INTERNAL ANGLE SCALE – with adjustable indicator for easy field calibration.
  10. EXHAUST SNUBBER SCREWS – allow travel speed reduction down to 1/ 3 x full speed, independently in each direction, by screwing in to restrict exhaust air flow.
  11. GAUGE PORT – as standard.
  12. SPAN ADJUSTMENT – quick and easy thumbwheel setting with slotted locking screw.
  13. ZERO ADJUSTMENT – quick and easy thumbwheel setting with slotted locking screw.
  14. STRAIGHT–LINE MECHANISM – unique geometry allows cw/ccw change over by simple cam inversion.
  15. FEEDBACK CAM – quick and easy reversal ( for rotational sense handing) or replacement (to change the response characteristic) of the cam is facilitated by a spring loaded retention device.
  16. FEEDBACK SHAFT – innovative collet connection permits quick– fit/release of the actuator interface and eliminates backlash.
  17. 3–TERMINAL DIN PLUG – retrofit-able option available for 4-20mA angle retransmit. Allows fully external connection with rapid connect/disconnect capability.
  18. AIRFLOW CHANGEOVER BLOCK – allows selection of direction in which positioner moves (for direct mount models).
  19. SPOOL VALVE – highly reliable, all metal, 5 port proportional valve controls the air flow. Three versions, with different flowrates, are easily interchangeable.
  20. UNIT IDENTIFICATION – each positioner carries a unique serial number and is CE marked.

Kinetrol Actuators on Thermoplastic Valves

Kinetrol Actuator on Thermoplastic Valve
Kinetrol Actuator on
Thermoplastic Valves
Thermoplastic valves are becoming the material of choice for more and more chemical process applications. Benefits are numerous: affordable cost, ease of installation, superior chemical resistance, abrasion resistance, light weight, ability to meet high purity standards, and long life expectancy.

The thermoplastics used for valves include Polyvinyl chloride (PVC), Acrylonitrile-Butadiene-Styrene (ABS), Glass Fibre Polypropylene (GRPP), Anti-Static Polypropylene (ASPP), and Polyvinylidene fluoride (PVDF). Plastic valves are proving themselves time and again in commercial and industrial applications such as wastewater treatmentwater distribution, primary metalsfood and pharmaceuticalschemical processing, power generation, and oil refineries.

For example, many chemicals used to treat drinking water and wastewater use plastic valves because they stand up to the caustic and aggressive chemicals such as sodium hypochlorite, sodium hydroxide, sodium bisulfite, hydrofluosilisic acid and potassium permanganate.
Kinetrol Actuator on Thermoplastic Valve
Kinetrol Actuator on
Thermoplastic Valves

In the high purity industries such as the semiconductor industry, fluoropolymer valves are required for aqueous chemicals, solvents and slurries.  In these applications chemical contamination must be less than 100 parts per trillion (ppt) total contamination from the entire piping system (including valves, fittings, tubing, filters and instrumentation). Other ultra-pure application examples are microelectronics, medical devices and pharmaceutical production.

Thermoplastic valves are sensitive to temperature changes and experience a higher degree of thermal expansion and contraction than their metal counterparts, but most agree the advantages far outweigh these concerns.

The key to actuating plastic valves is like any other valve system - understanding the operating requirements of system. It's important to remember that since most plastic valves are used on corrosive media, there's a fair chance the actuator may be exposed to corrosives as well. Effects on the actuator housing, internal parts, and any springs have to be considered. In most cases the actuator will have to be specially coated or come with a corrosion-resistant epoxy finish. Kinetrol actuators fit the bill as they come standardly with an epoxy stove enamel finish and stainless steel internal and external hardware, and Kinetrol spring units are totally sealed from the atmosphere, protecting the spring element and assuring long life.

Kinetrol Actuators on Dilute and Dense Phase Conveying Diverters

kinetrol on diverter valves
Kinetrol actuator on dense phase diverter valves
Pneumatic conveying systems transfer powders, granules, and other dry bulk materials through an enclosed horizontal or vertical conveying line. Pressure differential and air flow is the motive force in pneumatic conveying. Through control of pressure or vacuum and the airflow inside the conveyor, the system can successfully move material.

Pneumatic conveying systems are classified into two types by their operating principle: dense phase and dilute phase.

The most common is dilute phase pressure conveying. Used for powders or granules, and most often with non-abrasive, non-fragile materials that have a light bulk density. Common examples are plastic granules, sugar,  flour, corn starch, activated carbon, zinc oxide, hydrated lime, and sodium bicarbonate. Dilute phase vacuum conveying is for materials that compress under pressure, for toxic materials, and are conveyed over short distances at low capacities.

kinetrol on diverter valves
Kinetrol on diverter valves
Dense phase pressure conveying is best for conveying fragile or abrasive materials over long distances. Commonly handled materials include feldspar, fly ash, silica sand, alumina, sorbitol, dextrose, carbon black, resins, cocoa beans, nuts, and certain cereals. Dense phase pressure conveying moves materials at a relatively low speed to reduce materials degradation, air consumption, and wear and tear on mechanical systems.

Diverters are used to direct the flow of conveyed material to branch lines. Because they are handling materials such as sand, gravel, whole grains, stone, cement, and coal, the diverter must be designed for handling very abrasive materials and for high cycles. Not only must the diverter be designed for this service, but the pneumatic actuator must also meet theses demanding requirements.

Kinetrol actuators have become the preferred quarter-turn pneumatic actuator for conveying diverters because of their dependability and ability to withstand tough operating environments. Kinetrol actuators are virtually immune to the high vibration, dusty atmospheres and provide years of maintenance free operation.

Kinetrol Actuators in Wood Power Pole Manufacturing

steam valve
Wood treatment steam valve
Wooden utility power poles must be chemically treated to protect against pests, rot, and decay. The manufacturing process to apply the chemicals requires heat, vacuum, pressure, and harsh chemicals.

The pressure treatment process varies everything from full vacuum to prepare the poles to accept the treatment, to positive pressure and elevated temperatures (using steam) to force the chemical treatment into the pole.
pole treatment vessel
Pole treatment vessel

There are three areas where automated valves are required: 

1) Steam control valve
2) Vacuum pump valve
3) Chemical flow control valve

The steam line at one plant was unreliable and very expensive. It was costing the plant about $4000. To help come up with a better, more economical solution, a  Kinetrol USA Distributor was invited in and specified a Kinetrol actuator, positioner and custom brackets for the existing steam line valve. 

wood treatment chemical line
Look carefully to see (2) Kinetrol
Actuators on chemical feed lines.
The retrofit was completed with the new Kinetrol actuator and positioner at a fraction of the previous actuator package cost. The customer was delighted the Kinetrol package gave them better control in a package that was much easier to service.