6 Reasons Why Pneumatic Vane Actuators are Superior to Rack and Pinion Actuators

Rotary vane actuators offer distinct design and performance advantages.

1. Rotary vane actuators do not convert linear motion to rotary motion, unlike rack and pinion actuators. No additional gearing is required and no side loading is transferred to the actuator housing.
2. Vane actuator lip seals are the key to long life. The double opposing lip seal design, with stainless steel expanders, provides unmatched service life by using air pressure to improve the actuators seal-to-enclosure contact, and provide a “self cleaning” effect on the epoxy or PTFE internal finish.
3. The elimination of pressure bearing o-ring shaft seals. Rack and pinion actuators require shaft sealing o-rings that are exposed to the full supply air pressure used to operate the actuator. These o-rings wear, causing leaks, a drop in efficiency, and wasted energy through air consumption. Vane actuators' double opposing lip seals isolate the supply air pressure from the actuator shaft, requiring only a low friction bearing on the shaft.
4. Rotary vane actuators provide superior modulating accuracy. Because of the integral vane and shaft (machine from a single casting), lost motion or hysteresis is reduced dramatically which intern provides much tighter modulation and control. The vane actuators inherent low friction also reduces hunting and sticking.
5. Direct mount, modular design for springs, positioners, switches, and solenoids reduce space requirements and lower inventory costs. Since vane actuator accessories direct mount to various size actuators, there’s no need to inventory and keep track of mounting kits. 
6. Rotary vane actuator spring return units are designed to be virtually indestructible. Using low stress, clock springs reduces spring tension loss and metal fatigue. The housing for vane a actuator springs are sealed from the atmosphere, preventing corrosion of internal parts. Most importantly, these type of spring units provide the lowest torque loss which enables the section of smaller (less expensive) actuators.

Tough Actuator Service on Paper Plant Green Liquor Line

Pulp and Paper Plant

It's said the only thing a pulp and paper plant doesn't reuse is the "shade the building casts". The processes used in the production of pulp and paper are very efficient when you consider the reuse of energy and by-products. The efficiency comes at a cost though - through very hostile atmospheres and demanding operating conditions for process equipment.

For example, the "kraft process" (also known as the sulfate process) is the method to convert wood chips into pulp and then to cellulose fibers. This is done by mixing the wood chips with sodium hydroxide and sodium sulphate, soaking, cooking and processing.

Here's a very basic explanation of the kraft process. Wood chips are soaked and processed in sodium hydroxide and sodium sulphate mixture known as "white liquor".  After the wood chips are impregnated with white liquor, they are then cooked in digesters to break the wood down into cellulose. The solid pulp is then separated and the remaining fluid is referred to as "black liquor". Black liquor is further processed to remove solids and chemicals which are to be re-used in the pulping process. One of the final by-products is "green liquor" which contains sodium carbonate and sodium sulfide and is then reacted with lime to regenerate more white liquor.

All of these steps expose process equipment, piping, and valves to very tough environments. Kinetrol actuators are preferred in these situations because they don't allow corrosive atmospheres to penetrate the actuator or springs, their long cycle life,  and their epoxy stove enamel finish.

Below is a picture of a Kinetrol model 14 double acting actuator on a 8” full-port ball valve on a green liquor line. The valve cycles 2 times per day to direct green liquor flow and weak wash (weak white liquor) alternatively from one pipe to another in order to prevent solids build up in the pipelines.

Kinetrol Model 14 in Green Liquor Line

Don't Get Racked Up ... Use Kinetrol Vane Actuators

Little video "commercial" about the virtue of Kinetrol Vane actuators over pneumatic rack and pinions actuators ...

Kinetrol vane actuators provide:

• Single moving part - Simplest and most reliable mechanism for quarter-turn rotary actuation.
• Close couple control modules - Fail-safe spring returns, limit switches, positioners and solenoid valves all close couple to the actuators.
• No cranks or gearing - No power loss or backlash - allows accurate positioning.
• Durable corrosion resistant finish
• Long maintenance-free life - Up to 4 million operations guaranteed.
• Compact - space saving - efficient: Best torque/size package available, fast operating speeds, best air consumption, proven design.

The Virtues of the Pneumatic Vane Actuator Damper Drive

Pneumatic damper drives

Pneumatic damper drives significantly improve the reliability, precision, and efficiency of industrial boilers and furnaces. Accurate control of combustion air and flue gas provide many cost savings benefits to plant operators. A pneumatic damper drive’s precision and rapid response greatly improve fuel efficiency, reduce emissions, lower fuel consumption, and provide better boiler draft control.

Recent “Boiler MACT” (Boiler Maximum Achievable Control Technology) regulations require regular maintenance to optimize boiler performance. Air-to-fuel mixing and CO emissions are two areas where fine tuning and precise control yields dramatic improvement in burn efficiency. Old electric drives do not provide the precision, speed or torque needed for accurate control, so a retrofitting program that replaces electric drives with pneumatic units is an easy way to improve efficiency and gain better performance.

In the application outlined below, several dual-arm damper drives, using Kinetrol Model 18 actuators, were specified to replace aging Bailey electric damper drives in a power plant in the southwest USA. These specific drives are used to control the desuperheater and reheater temperature at a gas fired plant. Not only was there a need for optimized performance for better fuel consumption and lower emissions, but the customer was also very concerned about reliability. The plant needed to know the new Kinetrol-based damper drives were immediately available, and ready for drop-in replacement as the Bailey drives failed. This was easily managed by designing pedestals and frames that matched the bolting patterns and envelope size of the existing Bailey units. The Kinetrol drives were designed to match the legacy footprint exactly, have the drive shaft and drive lever in the exact position, and provide a drive shaft and lever with the same dimensions as the Bailey drive.

The result is a high duty cycle, highly precise, long-life, fast acting, responsive, easily maintained, and easily automated damper drive.

The Principles of Rotary Actuators

Variation of the rotary actuator.
(Kinetrol pneumatic vane actuator.)

A rotary actuator is an output device for a fluid power system that delivers an oscillating motion over a limited range in less than one full revolution of the circle.

A true rotary actuator produces work by direct action of fluid pressure against internal vanes. Work is defined as a force applied over a distance. Rotary actuators produce a special type of rotational work called torque.

Torque occurs when a force acts on a radius. Since rotary actuators operate at low speed with high torque, torque output rather than the horsepower is used for the rating and identification purposes. Speed is a secondary consideration when choosing a rotary actuator for a particular application.

The typical units of measurement for torque are foot pounds (lb·ft). For example, if a rotary actuator with an arm length or radius of two feet were used to lift the two hundred-pound weight, then the resultant torque required to accomplish the work would be 400 lb·ft.

Understanding the relationship between the output torque required and the physical set up a fluid system enables designers to determine the appropriate rotary actuator for each unique application.

The following video does an excellent job of illustrating the mechanics and the physics behind rotary actuators.

Water Recycling Application at Iron Ore Mine

Mining corporations need water - a lot of water - to make bare rock give up its valuable minerals.

Water is used for the extraction of minerals that may be in the form of solids, such as coal, iron, sand, and gravel. The category includes quarrying, and milling (crushing, screening, washing, and flotation of mined materials).

Not only is water used to expose the mineral, it must be carefully managed to prevent the release of contaminated water back into the environment.

There are multiple processes involving the management of water that require piping, valves and automation for water management.

• The reuse of water used to extract the minerals from the other solids.
• Managing surface water from rain, snow, and streams.
• Capturing and recycling water from the mine site.
• Storing water in evaporation ponds.

At a large Midwest iron ore mining facility, a Kinetrol Distributor was contacted to look at ways to lower the overall consumption of water in the main water treatment plant.

The Distributor designed and provided this characterized butterfly control valve, with a Kinetrol actuator, pneumatic positioner, and cone indicator.  The valve is used to recycle processed water back into the plant for reuse in the extraction process. The valve and actuator experiences a very high cycle rate (400 cycles per day).

Intercepting and diverting surface water

• Intercepting and diverting surface water (rain and snowmelt runoff, streams, and creeks) from entering the mine site by building upstream dams to reduce the potential for water contamination from exposed ore and waste rock
• Recycling water used for processing ore in order to reduce the volume of water requiring treatment
• Capturing drainage water from precipitation at the mine site through the use of liners and pipes and directing the water to tailings dams in order to prevent potentially contaminated water from entering groundwater or flowing off site
• Allowing the water to evaporate in ponds to reduce the volume of contaminated water; in dry regions, enough water may be evaporated that no water needs to be discharged, resulting in the containment of contaminates at the mine site
• Installing liners and covers on waste rock and ore piles to reduce the potential for contact with precipitation and contamination of groundwater

- See more at: http://www.miningfacts.org/Environment/How-is-water-managed-and-treated-in-mining/#sthash.0qMpVdHr.dpuf

Segment Ball Control Valve with Vane Actuator, Pneumatic Positioner, and I/P Transmitter

Actuator and Positioner

Ball, plug and butterfly valves all belong to a class of valves commonly referred to as "quarter-turn" valves. This refers the 90 deg (angular) rotation required to go from full closed, to full open position.

In most cases standard ball, plug, or butterfly valves are not the best choice as control valves (where the process media has to be modulated or throttled). Standard ball, plug and butterfly valves usually introduce very non-linear, dynamic flow coefficients. Furthermore, they can introduce undesirable turbulence to your piping system.

As a means to linearize flow coefficients and reduce turbulent flow, the machining, or characterization, of the valve disk is done so that the machined shape allows for more optimized flow.

For ball valves in particular, machining the ball's flow port with a "V", or even by machining the ball more radically, can deliver excellent flow curves. A term for a more radically machined ball is the "segment ball" (sometimes called "segmented").  In the following video you can see how a Kinetrol pneumatic actuator, postioner, and I/P transmitter team up with a segment ball valve foe an excellent control valve.