Showing posts with label Hytork. Show all posts
Showing posts with label Hytork. Show all posts

Thursday, July 6, 2017

Added Safety For Pneumatic Actuators

pneumatic actuator for industrial process control valve
XL Series Pneumatic Actuator
Courtesy Emerson - Hytork
Manufacturers of industrial process control gear keep the safety of their customers as a high priority item when designing products. There is much at stake in industrial operations, so every instance where the probability or impact of failure can be reduced is beneficial.

Pneumatic valve actuators utilize pressurized air or gas as the motive force to position a valve. A common version of these air powered actuators employs a rack and pinion gear set that converts the linear movement of air or spring driven pistons to rotational movement on the valve shaft. When one side of the piston is pressurized, the pinion bearing turns in one direction. When the air or gas from the pressurized side is vented, a spring (spring-return actuators) may be used to rotate the pinion gear in the opposite direction. A “double acting” actuator does not use springs, instead using the pneumatic supply on the opposing side of the piston to turn the pinion gear in the opposite direction.

From time to time, service or maintenance operations for the actuator may require opening of the pressure containing case. This is a potentially hazardous step and confirmation that the case is not pressurized when disassembly is undertaken is essential to a safe procedure. Many pneumatic actuators have cases assembled with numerous threaded fasteners. Hytork, an Emerson brand, employs a keyway and flexible stainless steel key to affix the end caps to their XL Series pneumatic actuators. This method provides a number of benefits, not the least of which is preventing the removal of the key and end cap if the case is pressurized.

Find out more about the XL Pneumatic Actuators in the illustrated piece provided below. Share your industrial fluid control challenges with industrial valve and automation specialists, combining your own process experience and knowledge with their product application expertise to develop effective solutions.


Thursday, May 11, 2017

Rack and Pinion Actuator - Double Acting vs. Single Acting

pneumatic valve actuator
Pneumatic rack and pinion valve actuator
Courtesy Emerson - Hytork
Automating industrial valve operation requires numerous considerations in selecting the correct power source, drive type, torque range, and much more. The widest range of possible operation conditions should be anticipated and accommodated by the actuator selection to assure safe and effective valve operation under normal and adverse conditions.

The use of compressed air or gas as the energy source for valve positioning has been in use for many years and remains popular to this day. Among the perceived advantages of this energy source are the ability to store it in pressurized vessels for emergency short term use and the absence of any potential ignition source, as may be the case with electric powered actuators.

A rack and pinion valve actuator delivers a linear torque output throughout its full range of travel. The movement of a piston causes movement of the rack. The rack is toothed, and drives the pinion, converting linear movement of the rack into rotational movement of the pinion. The pinion is connected to the valve shaft, providing re-positioning of the valve. Adjustable stops, part of the actuator, limit the travel of the valve trim.

spring return and double acting valve actuator diagrams
Double acting pneumatic rack and pinion actuator (left) on its inward stroke. Spring return actuator (right) on its
outward or air powered stroke  (Illustrations courtesy of Emerson - Hytork) 

There are two common configurations of rack and pneumatic pinion actuators. A double acting actuator has provisions for delivering or exhausting air from both sides of the piston. Small control valves coordinate the delivery and removal of pressurized air or gas to drive the pistons inward or outward, producing torque in a clockwise or counterclockwise direction. Its operation could also be described as "air to open, air to close".

The single acting version of the pneumatic rack and pinion actuator provides air driven movement in only one direction. In this case, reversing the direction of travel is accomplished with a spring installed within the chamber on one side of the pistons. The spring powered movement provides a fail safe positioning of the valve in the case of control air pressure loss. This actuator provides "air to open, spring to close" operation, although, in some cases the fail safe position can be changed.

This is the simple version. Share your process control challenges with a valve expert, combining your own process knowledge and experience with their product application expertise to develop effective solutions.



Tuesday, January 31, 2017

The Rack and Pinion Style Pneumatic Actuator

pneumatic rack and pinion valve actuator
Pneumatic Rack and Pinion Valve Actuator
Courtesy Emerson - Hytork
Three primary kinds of valve actuators are commonly used: pneumatic, hydraulic, and electric.

Pneumatic actuators can be further categorized as scotch yoke design, vane design, and the subject of this post - rack and pinion actuators.

Rack and pinion actuators convert linear movement of a driving mechanism to provide a rotational movement designed to open and close quarter-turn valves such as ball, butterfly, or plug valves and also for operating industrial or commercial dampers.


Rack and Pinion Animation
Courtesy Wikipedia
The rotational movement of a rack and pinion actuator is accomplished via linear motion and two gears. A circular gear, known as a “pinion” engages the teeth of one or two linear gears, referred to as the “rack”.

Pneumatic actuators use pistons that are attached to the rack. As air or spring power is applied the to pistons, the rack changes position. This linear movement is transferred to the rotary pinion gear (in both directions) providing bi-directional rotation to open and close the connected valve.

Rack and pinion actuators pistons can be pressurized with air, gas, or oil to provide the linear the movement that drives the pinion gear. To rotate the pinion gear in the opposite direction, the air, gas, or oil must be redirected to the other side of the pistons, or use coil springs as the energy source for rotation. Rack and pinion actuators using springs are referred to as "spring-return actuators". Actuators that rely on opposite side pressurization of the rack are referred to as "direct acting".

Most actuators are designed for 100-degree travel with clockwise and counterclockwise travel adjustment for open and closed positions. World standard ISO mounting pad are commonly available to provide ease and flexibility in direct valve installation.

NAMUR mounting dimensions on actuator pneumatic port connections and on actuator accessory holes and drive shaft are also common design features to make adding pilot valves and accessories more convenient.

Pneumatic pneumatic rack and pinion actuators are compact and effective. They are reliable, durable and provide good service life. There are many brands of rack and pinion actuators on the market, all with subtle differences in piston seals, shaft seals, spring design and body designs. Some variants are specially designed for very specific operational environments or circumstances.

Share your process valve control and automation challenges with application experts, and combine your process experience and knowledge with their product application expertise to develop effective solutions. 

Tuesday, December 29, 2015

Pneumatic Actuator For Corrosive Environments

Corrosion Resistant industrial valve pneumatic Actuator disassembled
Commando XL Corrosion Resistant
Pneumatic Valve Actuator
Courtesy Hytork - Emerson
Industrial process control operations sometimes call for equipment to be placed in physical locations or environments that are not conducive to a long and productive component lifespan. Extremes of temperature, humidity, and vibration can have substantial effect on equipment performance and longevity. Deleterious impact can also arise from elements of the process itself, in the form of corrosive liquid or vapor prevalent in the processing area. While most industrial equipment is provided with some level of protection, there are instances where standard coatings and protective materials may not provide adequate resistance to the deteriorating impact of their installation environment.

Valves of many types are used throughout industrial processes to provide control of fluid flow, with quarter turn movement being one of the more prevalent.
Pneumatically powered quarter turn valves have an actuator option that provides a high level of corrosion resistance, along with the field proven performance of a recognized leading product. 
Hytork™, an Emerson brand, offers their XL line of actuators with a special treatment to withstand aggressively corrosive environments. The corrosion resistant version has been labelled "XL Commando" and, in the company's own words, has...
A durable Fluoropolymer impregnation (using CORROGARD-CG941) of the actuator body parts (inside and out) for maximum corrosion resistance. This durable impregnation can best be achieved in cast aluminum parts (all XL COMMANDO body parts are cast aluminum). As the aluminum metal grains are expanded under heat the CORROGARD-CG941 is applied, entering the grain structure and, upon cooling, is locked at the surface, integral with the grain structure. Extruded surfaces can only be coated and are more susceptible to scratches and other mechanical deterioration.
You can review the performance range, sizes, and other features of these pneumatic valve actuators through a review of the document included below. Bring your process challenges to a valve application specialist and combine your process knowledge with their product application expertise to achieve a solid practical solution.



Tuesday, November 24, 2015

Special Solenoid Valve for Pneumatic Valve Actuators

Industrial Valve With CATS Solenoid Valve Control
Industrial Valve Actuators With
CATS Solenoid Control
Courtesy Emerson Hytork
In our industrial process control operations, we strive for uninterrupted reliable operation of control valves to maintain safe conditions and produce the desired process outcomes. Let's look at pneumatic valve actuators and their control solenoids. Hytork™ has a well thought out solution to enhancing actuator performance and longevity with their CATS solenoid valve. Instead of paraphrasing, I share the manufacturer's own words describing the operational benefits...

Hytork™'s 'CATS' (Clean Air To Springs) is a solenoid valve designed specifically for superior operation of pneumatic actuators. 
All spring return actuators that use a 3-way solenoid valve require air to enter and leave the spring chambers. As compressed air is introduced to the actuator to push the pistons apart, air from the spring chambers must be allowed to vent. During the fail or spring stroke, the compressed air between the pistons must exhaust to permit the springs to drive the pistons together. This piston movement creates a vacuum in the spring chambers which is usually filled by ambient air that may contain dirt, abrasives, corrosives and moisture of which are bad for the actuator - reducing its performance and life. 
A wrong solution for this problem is the use of a 4 way solenoid valve (sometimes referred to as "air assist"). It does prevent the ambient air from entering the actuator, but it will also pressurise the spring chambers. The actuator now acts like an air to open, air to close unit. In the unlikely event of a spring breakage or if the valve torque increases, due to line media build up within the valve, the actuator would still appear to operate normally until its fail action was needed in an emergency. At this most critical time, with supply air not available, the actuator could not perform as intended and it's function as a safety device would be defeated.
Hytork™'s CATS solenoid valve prevents this undesirable action from happening.
As the solenoid is de-energised, permitting the springs to push the pistons together, an internal by-pass in the CATS valve permits some of the exhausting air to fill the spring chambers at atmospheric pressure while the remainder exhausts to atmosphere. No ambient air enters the actuator.
Only clean supply air gets into the actuator - Air that was normally planned to be vented!-There is no pressure build up that can lead to false torque availability on the fail stroke, as in the case of air assisted springs! No extra clean compressed air is used!
The solenoid valves are available in a number of configurations to accommodate almost any installation. To summarize, the advantages include:

  • Maximises actuator life.
  • Reduces installation and initial costs.
  • Prevents actuator seal failure.
  • Prevents corrosives from entering actuator.
  • Prevents dirty air from entering actuator.
  • Proves that the actuator springs are working correctly every stroke.
  • NAMUR standard - Easiest assembly possible - only two mounting screws.
  • Eliminates brackets and tubing - mounts directly to the NAMUR pad on the actuator.
  • Only one style of solenoid valve required for Spring Return and Double Acting actuators - reducing inventory costs.
To explore how these solenoid valves can improve your pneumatic valve actuator operation and longevity, contact a product specialist and share your requirements. Combining your process expertise with the product application knowledge of a professional sales engineer will move you quickly toward a good solution.

Monday, September 14, 2015

No Compressed Air? Use Water to Power Your Valve Actuator.

Hytork XLW Water Powered Valve Actuator
XLW Water Powered Valve Actuator
Courtesy Hytork
Air is everywhere, but very little of it is compressed for our use in powering a valve actuator. Sometimes, possibly at sites located remotely, a reliable source of compressed air is unavailable for process control valve actuation. Installing an air compressor at the site may be an option, but one with impact on the reliability of the installation deemed undesirable. One possible solution is a water powered valve actuator. With mains water available, pressurized within the range of 60 to 100 psi (4-7 bar), actuator power can be derived and valve operation successfully achieved.

Water always presents its own set of special considerations, not the least of which is that it tends to corrode most metals used in construction of actuator parts over time. Of additional concern are the particulates present in water systems which can cause premature deterioration of seals and scoring of cylinders in the actuator. Directional control solenoid valves will also function more reliably with a water supply free of larger particulates. While this is a concern, the solution is simply to place an inexpensive filter upstream of the devices, eliminating the contaminates from the water supply.

While it is possible to employ some "standard" actuators in a water powered setting, there are special adaptations that can be applied to common actuator design to better suit the use of water power. One manufacturer, Hytork, has done just that with their XLW Series of water operated actuators. The XLW Series is a water powered adaptation of the company's successful XL Series actuators. Special coatings are applied to critical parts to provide necessary protection for water applications. There are other differences between the compressed air and water versions of the actuator, detailed in the installation and operating instruction manual shown below. The manual is short enough to be read in a couple minutes (really, just a couple minutes) and provides useful and illustrative information about actuator construction, operating characteristics, and maintenance requirements.

Contact a valve application specialist for more information, or to discuss any of your fluid control application needs.


Wednesday, July 29, 2015

Pneumatic Actuator With Air Fail Safe Operation

Pneumatic actuator on industrial valve
Air Fail Safe Actuator
installed on industrial valve
Courtesy Hytork, EPM
Pneumatic actuators are used throughout the industrial process control field to provide remote or automated control of valve operation. This type of industrial valve actuator employs pressurized air to move a piston or diaphragm and apply force to the valve stem, opening or closing the valve. Since, by the general nature of their scale and content, industrial fluid processes tend to carry substantial risk related to safety and financial loss due to failure, the engineer’s task is to plan and design for safe operation, should a wide range of possible failure modes occur. Hytork, an Emerson Process Management brand, provides a solution for fail safe operation of pneumatic actuators.
The Hytork Air Fail Safe Acutator is intended for use on larger valves with high torque requirements. The actuator has a built-in air reservoir that provides reserve air capacity to safely close the valve when the input air pressure fails. The accumulator stores compressed air at the highest pressure seen at the device. The design of the Air Fail Safe actuator delivers a high torque level in a double rack and pinion arrangement that is inaccessible using spring based designs. Learn about the Hytork Air Fail Safe Actuator and discuss your potential applications with a product expert.