How to Install the Optional 4-20 mA Feedback Mechanism on the the Kinetrol AP Pneumatic Positioner

This video describes how to install the optional angle retransmit circuit  (4-20 mA feedback mechanism) on the Kinetrol AP pneumatic positioner.

The angle retransmit circuit is an externally powered (8–30v DC) linear 4-20mA feedback module, rangeable down to 30 deg. for full 4-20mA span. The module's retransmit pot is a high quality conductive plastic servo–type with ball bearings, coupled with a zero-backlash feedback pot drive. The combination provides long life and high precision.

The Kinetrol AP positioner moves an actuator to a position set by a 3-15 psi control signal and holds it there. It is designed to drive a rotary or linear actuator to a position set by a 3-15 psi (0.2 to 1.0 bar) signal and hold it there until the signal changes.

For more information, contact Kinetrol USA by calling 972-447-9443 or visiting https://kinetrolusa.com.

Control Valve Positioner and Control Valve Actuator Basics

Control Valve Loop*

Control valves control fluid in a pipe by varying the orifice size through which the fluid flows. Control valves contain three major components, the valve body, the positioner, and the valve actuator.

The valve body provides the fluid connections and movable restrictor comprised a valve stem and plug that is in contact with the fluid that varies the flow.

The valve actuator is the component that physically moves the restrictor to vary the fluid flow.

Their are two general categories of control valves - linear and rotary. Three actuator types are used in linear control valves including spring and diaphragm, solenoid, and motor operated. Three actuator types are used in rotary control valves including pneumatic, electric, and electro-hydraulic. Rotary actuators are sometimes referred to as "quarter-turn" or "partial-turn".

Pneumatic positioner with
rotary vane actuator
on ball valve.

The valve disc (restrictor) controls flow through the valve body. A positioner receives information from a supervisory controller advising wether or not the flow condition is satisfactory. The positioner then provides a signal to the actuator that provides the force to open and close the valve.

Each type of positioner works in response to a process signal. Some positioners (linear) use a 3-15 PSI pneumatic process signal. The pressure is exerted on a large diaphragm creating downward force that is applied against a spring which moves the restrictor up and own. Other types of positioners use a 3-15 PSI pneumatic signal to regulate a higher supply pressure (such as 0-60 PSI) to move pistons or vanes back and forth (rotary). 

The variable 3-15 PSI control signal can be provided directly by a pneumatic controller connected directly to the process, or in other cases the 3-15 PSI is regulated by an electropneumatic device called an I/P or E/P (current to pressure or voltage to pressure) transmitter. These transmitters receive their signal from a supervisory control as a 0-10VDC or 4-20mA and then throttle the 3-15 PSI output to open/close the valve. 

* Image courtesy of Tony R. Kuphaldt from "Lessons In Industrial Instrumentation"

Kinetrol P3 On/Off Positioner

Kinetrol P3 On/Off Positioner

The Kinetrol P3 On/Off positioner consists of an electronic positioning circuit mounted in a robust all-metal enclosure, which controls a 1⁄4-turn rotary pneumatic actuator via standard on-off solenoid valves direct-mounted on the actuator’s own interface.

The P3 circuit is designed so that its assembly can be mounted inside a standard Kinetrol limit switch box (either ULS-type, or explosion proof XLS-type), using only two screws. The P3 assembly is complete with feedback potentiometer and anti-backlash gear drive, which engages with gear teeth on the limit switch coupling to read the actuator’s position. The limit switch coupling complete with gear teeth needs to replace the standard coupling if a standard box is being retrofitted with a P3.

The positioner circuit is powered by the mid-point input voltage. It functions by comparing the actual mid-point position (read by the feedback potentiometer) with the set position (set via an on-board preset, or a remote preset, or a remote 4-20mA signal). The positioner circuit uses its solid-state switched outputs to power solenoid valves which drive the actuator towards the position where the set position corresponds with the actual position. When it gets there, the solenoids are switched to hold that position.

 Need More Information?

Contact Kinetrol USA at

www.kinetrolusa.com

or call 972-447-9443.

The positioner circuit incorporates a unique power supply allowing it to be powered by any of 24vDC, 48vDC, 115vAC or 230vAC, 50/60 Hz, without the need for any change. The supply maintains full isolation of the low voltage control circuit from the power input line (up to 5Kv). Switching of the solenoid valve outputs is achieved through opto-isolated solid state switches which operate at all the above voltages – only the solenoid coils themselves need to be adapted specifically to the supply voltage. The use of solid state switching avoids any limitations on relay contact life.

Double acting models are available as fail-free (standard), fail-down (moves clockwise on loss of electrical power if air supply is still present) and fail-hold (holds position on loss of electrical and / or air supply) variants. Spring return models move in the direction of the spring on loss of electrical failure, but hold position on loss of air. An external pressure switch (which cuts electrical power on loss of air pressure) should be fitted by the customer if spring function is required on loss of air and / or electrical power.

An optional angle retransmit (AR) circuit can be retrofitted by plugging it into the top of the positioner circuit and fixing with three screws. The AR circuit is a 2-wire loop-powered 4-20mA device, which reads the position of the positioner’s feedback pot. It is fully functional whether or not the positioner circuit is powered, and the feedback signal is electronically isolated (ie. floating) relative to the low voltage positioner circuit (which in turn is electrically isolated from the power supply and solenoid connections).

Extra solid-state switches have been incorporated on the positioner board to allow supply to both solenoid valves via a single cable for movement to the upscale position when the positioner is in spring-return or fail-down mode, while still allowing the positioner to control the two valves independently for the mid position. If the mid-position input is energised, then these extra switches isolate the solenoids from the upscale/downscale inputs.

The three power input lines (for up, mid, down positions) are independently fused using plug-in miniature fuses on the positioner circuit board.

External connections are made via a multi-option connector board, which allows simultaneous connection of up to four changeover limit switches, three control supply inputs plus neutral/negative, and a single low-voltage signal. This connector board, like the positioner circuit assembly, mounts in either the standard ULS or XLS box using two screws.

If an angle retransmit circuit is fitted using the low voltage signal terminal, optional 4-20mA inputs or external setpoint pot wires can be connected either directly to the terminal block on the positioner circuit or, if only three or less limit switches are in use, relayed through an unused limit switch terminal on the connector board.

The limit switch box is fitted with a ground terminal which must be connected to a suitable external ground.

Industrial solenoid valves which permit the use of standard quality air supplies (instrument quality air is not required) are direct-mounted on adaptor blocks on the side of the actuator, and electrically connected via steel-armoured flying leads with DIN sockets on the solenoid end. At the positioner end, they connect to two 2-way terminal blocks on the circuit board. A range of solenoid valve options are available, determined by the function required, the supply voltage, and whether or not the unit requires hazardous area certification. 

KEY FEATURES

• Robust modulating actuator, control tolerant of standard air quality (instrument air quality is not necessary).
• Three position rotary control using only three electrical inputs plus air supply.
• Two endstop positions + adjustable mid position anywhere in angular range of actuator (90 or 180°).
• Control circuit mounts inside standard all metal industrial quality Kinetrol ULS or XLS limit switch boxes without disturbing limit switches – available fully assembled, or (on non-explosion proof models only) for user retrofit to existing boxes.
• Direct mounting onto full range of Kinetrol 1⁄4 turn actuators. Namur mounting options available.
• Uses direct-mounting standard solenoid valves outside box to position actuator.
• Easy adjustment of mid position set point by switch–selectable choice of methods: on-board pot, remote pot or 4-20mA input signal.
• Explosion proof options available (approved to IECEX, ATEX; FM (for USA & Canada) standards pending) by use of XLS housing plus standard explosion proof solenoid valves.
• All new positioner circuit – runs on any of 24vDC, 48vDC, 115vAC or 230vAC power without any change required.
• Solid-state universal-voltage solenoid switching – no mechanical contacts.
• Three separate on-board mains fuses for three inputs.
• Switchable selection of mid-point setting method (on-board preset, remote preset, remote 4-20mA signal).
• Switchable selection of double acting or spring return operating mode.
• Power input isolated from signal inputs and outputs for all voltage options.
• Moulded reinforced plastic internal circuit cover for insulated safety.
• Positioner has user-adjustable zero, span, deadband and damping parameters via preset pots for easy optimization of positioning performance.
• Damping parameter gives velocity-proportional setpoint advance to allow better stabilization of fast-moving or high inertia loads while maintaining resolution and repeatability.
• Retrofittable isolated loop-powered 4-20mA angle-retransmit circuit available – just plugs in inside same enclosure – with its own user-adjustable zero and span presets.

Need More Information?

Contact Kinetrol USA at

www.kinetrolusa.com

or call 972-447-9443.

20 Innovative & Elegant Engineering Improvements for Pneumatic Valve Positioners

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 30º 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.

A Cheesy Application for a Kinetrol Actuator & Positioner

Kinetrol Actuator, Positioner and Spring on
Steam Line in Cheese Making Plant

High above the cheese factory floor, mounted to a 1-1/2 steam supply pipe is a lonely V-ported ball valve with a Kinetrol 097-120 actuator, spring  unit, and positioner. The valve is controlling 180 PSIG steam at 375 Deg. F. with the ambient air surrounding the actuator, positioner and spring unit at a constant 135 deg. F.

Its a tough application, and critical to keep running. Losing steam supply is very costly because of production losses and access to the valve is difficult.

The plant maintenance people tried a few of the more well-known valve/actuator packages without success. These packages would last a few weeks (a couple months at best), before failing. Frustrated and out of answers, the maintenance crew turned to a local Kinetrol Distributor salesperson for advice.

Knowing Kinetrol actuators, spring units and positioners are designed for the toughest applications, the salesperson specified the 097-120 on top of a Triad v-ported ball valve. Hopeful, but with little optimism, the maintenance crew installed the 1-1/2 control valve on the steam line and fired the system up.

For 11 months now (without any downtime), 24 hours a day, this lonely control valve, powered by a Kinetrol positioner and vane actuator, accurately throttles the steam supply and reliably keeps the cheese process line running.

Problem solved by Kinetrol!