Electropneumatic Valve Positioner Offering Precise Control, Smooth Operation, and Fast Response

Features of the Kinetrol EL positioner (click on image for larger view).

The Kinetrol EL is one of the valve automation industries best performing electro-pneumatic positioners available. It combines the precision and adaptability of a digital electronic control circuit with the smoothness and efficiency of Kinetrol's proven proportional servo valve, to give the best available 4-20mA positioning performance from rotary pneumatic actuators.

To compliment this unbeatable performance, the EL combines the easiest available setup procedure, easiest access to all functions and options, easy connectivity, and a compact all-metal housing, unique easy-set isolated angle retransmit, and limit switch options inside the same enclosure.

The EL positioner is designed to smoothly and precisely drive a rotary or linear actuator to a position set by the 4-20 mA input signal, and then accurately hold it there until the signal changes.

Inside the EL, a microprocessor in the loop powered 4-20 mA positioner circuit reads signal via one channel of a 12-bit A-D convertor, reads the position voltage from tie pot via the second channel of the A-D convertor, and compares the two. If an error between desired position and actual position exists, the EL changes it's output to the servo valve in order to drive the actuator in the direction required to eliminate the error.

In sync with the movement of the actuator, the feedback pot voltage changes, and the microprocessor continually calculates how to adjust the servo valve in order to guide the actuator accurately into position. Because the servo valve is a fully proportional device, it can be adjusted precisely and smoothly to slow the actuator to a stop exactly at the required position.  Programmed in the microprocessor is an advanced algorithm that allows this critical dynamic valve adjustment to be made correctly, giving optimal results with any actuator/load combination. Slow or fast responding, high friction or low friction, high inertia or low inertia, all can be optimized by PGAIN and DAMP parameters via the positioner circuit pushbuttons. The 12-bit A-D conversion gives the amazing resolution of approximately 1/40 of a degree angular.

For more information, contact Kinetrol USA by calling 972-447-9443 or visit their web site at https://kinetrolusa.com.

More Kinetrol Vane Actuators Hard at Work!

Here is a another short video of Kinetrol pneumatic vane actuators taking on some of the toughest industrial valve and damper applications.

Kinetrol engineered the first rotary vane actuators in 1958. The rotary design is based upon a single moving part which eliminates additional parts required to convert linear motion to rotary motion. This simple and innovative design provides a highly accurate and extremely reliable actuator for operating valves, drives and dampers, and is perfectly suited for the most demanding process control control applications.

For more information visit http://www.kinetrolusa.com or call 972-447-9443.

What Is a Vane Actuator?

Inside view of a vane actuator showing the clam-shell
design, internal chamber layout, and double-sided vane.

Vane actuators use pneumatic or hydraulic power to open, close, or modulate quarter-turn valves, dampers, louvers, as well as for precise movement of ergonomic lifting equipment.

Linear motion gas/hydraulic cylinder or piston actuators use gears to convert linear to rotary motion. Vane actuators employ a rigid vane inside a sealed chamber that is connected directly to the drive shaft at one end with no gears. The result is much smoother rotary movement and greater cycle life.

Vane actuators operate by introducing a fluid or gas to either side of it's enclosure through inlet/outlet ports, creating the force required for movement. Advanced vane actuators utilize double sided vanes that allow for pressurization of both sides, allowing for bi-directional movement. The vane itself provides an arc movement in the far side (opposite the shaft) of the actuator, translating rotary movement back to its integrated shaft.

The vane actuator shaft is designed to connect directly to a device (valve, damper, ergo mechanism) for the transfer of movement. In advanced design vane actuators, the shaft is completely sealed from the pressurized side of the vane via “lip seals” which act to prevent the loss of air/gas/oil through shaft seals or bearings. With the help of spring steel supports, the lip seals are kept in constant contact with the inner surface of the chamber wall at all times during rotation. A side benefit of lip seals are the self-cleaning or sweeping action they provide to the inside chamber surfaces.

Since the double-sealed vane separates the vane actuator chamber in two sides, movement in either direction can be changed merely by creating a pressure differential on either side of the vane. Inlet/outlet ports allow for the pressurization and de-pressurization for either side. As gas or fluid is introduced to one side, the vane is forced away, toward the opposite side. By reversing the pressure and vent ports, and pressurizing the opposite chamber, the actuator moves in the opposite direction.

When vane actuators use only gas or fluid as their source for movement in both directions, they are referred to as “double acting”. When an optional spring is used to provide the power in one direction (open or close) they are referred to as “spring return”.

For more information on vane actuators, visit http://www.kinetrolusa.com

Tighter Boiler Emissions Control with Pneumatic Vane Actuator Damper Drives

Pneumatic rotary vane damper drive.

In order to ensure efficient, reliable, and safe boiler operation, it is critical to accurately control the flow of the boiler's combustion air and flue gas. Poor control of airflow results in inefficient burning (wasting money), erratic cycling, flame-outs and even the possibility of toxic and hazardous emissions. In order to reduce the likelihood  of these situations, accurate airflow control is critical.

In the United States, the Environmental Protection Agency's introduction of the MACT (Boiler Maximum Achievable Control Technology) Rule requires operators to institute maintenance procedures annually or bi-annually in an effort to force plant operators toward compliance. This strict new legislation has a large impact on how companies' control their emissions from industrial boilers, process heating systems and furnaces. 

Typical drive applications and designs
(click for larger picture).

Industrial boilers use dampers and louvers to control the quantity of air admitted to the furnace. Tighter boiler draft control significantly improves combustion. Any improvement in controlling the position of the dampers and increasing the positioning speed improves boiler efficiency. Damper operation needs to be precise and fast for the accurate control. 

There are an estimated 15,000 boilers, furnaces, and process heaters running in the USA, and many are using an outdated primary component to control their lovers and dampers - the electric damper drive. Electric damper drives utilize motors and gear-boxes to move and position flue gas and combustion gas dampers. However, because of the inherent movement (sometimes referred to as hysteresis) between gears, linkages and other assorted mechanisms, these drives may not provide the accuracy, power, or signal response time required for optimum control.

Enter the pneumatic vane actuator damper drive. Pneumatic vane actuator drives are a newer, but still proven, method to provide high speed, accurate, and continuous modulation of air dampers for precise control. Replacing outdated electric damper drives with fast acting, pneumatic rotary vane damper drives offers measurable improvement to burner efficiency and cleaner emissions.

Switching out electric drives with their better performing pneumatic cousins is fairly simple. Downtime is not an issue.  The old drive footprint, lever positions, connecting rods, and operational envelop are considered with every design. Any existing mechanical or electrical connection placements are matched. Since the new drive mates to all existing mounting and connections, and the envelope size is typically smaller, installing the pneumatic drive is usually a matter of pulling the old one out, and dropping the new one in.

At the heart of the pneumatic damper drive is the stalwart pneumatic rotary vane actuator. With hundreds of thousands of these devices operating in the toughest process applications around the world, their reputation is well earned. These actuators are known for their incredibly long life, ability to withstand very high cycle rates, and smooth “bump-less” control. They are also designed to handle high ambient temperatures, high vibration, and very dusty environments, typical of where boiler dampers are located. Additionally, rotary vane actuators are available with direct mount pneumatic and electro-pneumatic positioners, manual overrides, network communication modules, limit switches, and spring modules. The direct mount design eliminates external brackets and coupling, and keeps the overall package size small.

Pneumatic vane actuator damper drives are a significant improvement over traditional electric damper drives. They provide fast response to input signal changes, very accurate positioning, a reduction in plant air consumption, and they lower fuel consumption. Engineers tasked with increasingly rigorous boiler emissions requirements must consider pneumatic vane style drives as a compelling alternative to the electric drive. They truly are an example of better form, fit, and function.

Does Your Valve or Damper Need More Than 90 Degrees Rotation?

180 degree actuator

Kinetrol’s 180° actuator is produced by adding a 2:1 step-up linkage onto the output shaft of well proven 90° vane actuators.

Factory fitted, direct mount linkage units are available to suit model 02, 03, 05, 07, 09, 12, 14 and 16 actuators, giving a neat single unit with no mount kits or brackets. The linkage’s unique geometry gives constant 2:1 step-up so that the output torque remains constant throughout the actuator's travel.

The all-steel mechanism of the linkage employs rolling contacts to minimise frictional losses and wear, and to maximise life. The linkage is lubricated for life, and encased in a robust, fully sealed die cast alloy casing. Exterior surfaces are protected by a corrosion resistant epoxy stove enamel finish. Standard adjustable endstops on the 90 degree actuator can be used to set the angle of travel. The other end of the 90 degree actuator allows the full range of Kinetrol modular accessories to be fitted directly.

• Simple compact unit - No external moving parts
• Unique linkage design - converts to 180° travel 120° option available 
• Constant gear-up ratio through travel range - Hence constant output torque 
• Rolling contact linkage mechanism - Ensures low wear, long life, low friction 
• Linkage sealed for life - Protected from the environment, long maintenance free life 
• Compatible with all Kinetrol modules - Direct mounted spring returns, limit switch boxes, positioners etc.
• Adjustable endstops

180 Degree Rotary Vane Actuator from Kinetrol USA

Louver and Damper Control with Vane Actuators

Besides pneumatic valve actuation, Kinetrol vane actuators are used widely on controlling industrial and commercial louvers and dampers.

The video below gives you a short visual demo of a louver being opened, closed and positioned with a Kinetrol vane actuator and electro-pneumatic positioner.

Louvers and dampers are used to stop or regulate the flow of air inside a duct, chimney, air handler, or other air handling equipment.

Some varieties of dampers are:

• Louvered Inlet Box Dampers
• Radial Inlet Dampers
• Variable Inlet Vane (VIV) Dampers
• Vortex Dampers
• Discharge Dampers

Industries that use dampers include:

• Petrochemical
• Oil & gas
• Power generation
• Construction industries