Compact Electric Control Valve Actuators

CML linear valve actuator
Image courtesy of Rotork

Rotork's CMA line of electric valve actuators are intended for use in industrial process control applications where precise response and positioning are key requirements. The variants of linear, rotary and quarter-turn actuators span a wide range of application requirements and support on-board programming and connection via any of several recognized communication protocols.

The compact actuators are available with enclosures rated for several environments, ranging from non-hazardous to hazardous. Low temperature operation to -40 degrees Celsius is provided with the inclusion of a low temperature option.

These are but a small recounting of the useful features incorporated into the product line. More detail is provided in the document included below. For best results, share your valve automation requirements and challenges with process valve automation specialists, combining your own process knowledge and experience with their valve automation expertise to develop effective solutions.

Rotork CMA Compact Electric Valve Actuators from CTi Controltech

Rotary and Linear Drives for Damper Control on Combustion Air and Flue Gas Applications

Pneumatic vane damper drive, one of several
variants available.
Image courtesy Rotork

Combustion air and flue gas damper drives fill a critical role requiring safety, accuracy and reliability above all else. It is critical to deploy the best drive technology to maximize combustion efficiency, minimize emissions and reduce installation costs.

Damper Operator (Drives) Types :

Damper drives can be one of three types: pneumatic, electric, or electro-hydraulic, as described below.

• Pneumatic. These damper operators are used whenever controls rely primarily on compressed air (pneumatic) for moving operators.
• Electric. These damper operators are used whenever controls rely primarily electricity as the power source.
• Electro-hydraulic. These damper operators are the same as the electric type described above, but also have a hydraulic system to position the damper.

A very important part of damper design is determination of damper torque, and sizing and selection of the damper actuator for the maximum torque. Actuator torque should be selected to provide the maximum torque required to operate the damper as well as to provide margin and allow for degradation over the life of the damper. Actuators should be evaluated for damper blade movement in both directions, at the beginning of blade movement, and while stroking blades through the full cycle of movement.

The Goal for Selecting the Best Drive Technology:

Reduced emissions, lower fuel consumption and improved boiler draft control.

Ways to achieve this goal:

• High speed continuous modulation of ID/FD fan and inlet guide vanes 
• Improved modulation and control of secondary air dampers 
• Improved automation and burner management 
• Quick response to plant demand 
• Improved reliability in high temperature environments 
• Precise damper and burner positioning 
• Simple commissioning and diagnostics 
• Low running costs, virtually maintenance free 
• Pneumatic, analog and bus network communications 

For more information, share your requirements and challenges with combustion experts. The combination of your facilities and process experience and knowledge with their application expertise will yield an effective solution.

The Application of Heat in Industrial Settings

Heat exchangers are found throughout industrial and
commercial settings in many sizes and types.

The measurement and control of heat related to fluid processing is a vital industrial function, and relies on regulating the heat content of a fluid to achieve a desired temperature and outcome.

The manipulation of a substance's heat content is based on the central principle of specific heat, which is a measure of heat energy content per unit of mass. Heat is a quantified expression of a systems internal energy. Though heat is not considered a fluid, it behaves, and can be manipulated, in some similar respects. Heat flows from points of higher temperature to those of lower temperature, just as a fluid will flow from a point of higher pressure to one of lower pressure.

A heat exchanger provides an example of how the temperature of two fluids can be manipulated to regulate the flow or transfer of heat. Despite the design differences in heat exchanger types, the basic rules and objectives are the same. Heat energy from one fluid is passed to another across a barrier that prevents contact and mixing of the two fluids. By regulating temperature and flow of one stream, an operator can exert control over the heat content, or temperature, of another. These flows can either be gases or liquids. Heat exchangers raise or lower the temperature of these streams by transferring heat between them.

Recognizing the heat content of a fluid as a representation of energy helps with understanding how the moderation of energy content can be vital to process control. Controlling temperature in a process can also provide control of reactions among process components, or physical properties of fluids that can lead to desired or improved outcomes.

Heat can be added to a system in a number of familiar ways. Heat exchangers enable the use of steam, gas, hot water, oil, and other fluids to deliver heat energy. Other methods may employ direct contact between a heated object (such as an electric heating element) or medium and the process fluid. While these means sound different, they all achieve heat transfer by applying at least one of three core transfer mechanisms: conduction, convection, and radiation. Conduction involves the transfer of heat energy through physical contact among materials. Shell and tube heat exchangers rely on the conduction of heat by the tube walls to transfer energy between the fluid inside the tube and the fluid contained within the shell. Convection relates to heat transfer due to the movement of fluids, the mixing of fluids with differing temperature. Radiant heat transfer relies on electromagnetic waves and does not require a transfer medium, such as air or liquid. These central explanations are the foundation for the various processes used to regulate systems in industrial control environments.

The manner in which heat is to be applied or removed is an important consideration in the design of a process system. The ability to control temperature and rate at which heat is transferred in a process depends in large part on the methods, materials, and media used to accomplish the task. Share your process control challenges with application specialists, combining your own knowledge and experience with their product application expertise to develop effective solutions.