Wednesday, August 31, 2016

Self Operated Mechanical Temperature Regulators

Self operated temperature regulator valve Mark 80 Jordan
Mark 80 Temperature Regulator
Jordan Valve
In process control applications, exceedingly close control with PID loops is not always necessary. There can also be instances where location or operational circumstance calls for temperature control, but not necessarily under the control of a centralized system. Self operated mechanical temperature regulators, with their reliable and simple operating scheme, can be well suited for these applications.

Self operated temperature regulators are basically valves with self contained actuation controlled by a filled system, or bulb. The valve portion of the assembly controls the flow of a fluid which impacts the process temperature. The process temperature is measured by a fluid filled bulb, connected via a capillary to a chamber containing a diaphragm. As the temperature of the process changes, the fluid in the bulb expands or contracts, changing the fluid pressure on the diaphragm. Pressure on the diaphragm causes movement, which is linked to the sliding gate trim of the valve, thus adjusting fluid flow. A spring provides a counteractive force on the diaphragm and allows for setpoint adjustment.

The self contained assembly requires no external power source to operate and requires little maintenance. Proper selection of line size, capillary length, bulb type, and temperature range are key elements in getting the right valve for the job. Application temperature ranges from -20 to +450 degrees Fahrenheit. You can see all the details in the datasheet included below.

Share your temperature control and fluid flow challenges with product application specialists, combining you own process expertise with their product application know-how to develop the most effective solutions.



Wednesday, August 24, 2016

Sample Gas Moisture Control

sample gas dryer with Nafion tubing
Sample Gas Dryer
Perma Pure
Sample gas used for analysis in process control operations will often need some conditioning in order to accommodate the input  needs of the analyzer. A common requirement is to maintain a certain moisture content in the gas sample, requiring either addition or removal of moisture from the sample stream.

It is advantageous, even necessary, that any conditioning done to the sample gas have no impact on the component(s) subject to analysis. One technology provides for specific removal or addition of moisture (water) in a simple fashion, with no impact on other sample constituents.

Perma Pure gas sample dryers and humidifiers use Nafion® tubing, with a selectively permeable membrane that permits only the passage of water molecules. By controlling relative vapor pressure around the exterior of the tube, moisture can be drawn from, or added to, the sample gas stream. The simple device employs no moving parts and the vapor pressure differential is easily achieved using shop instrument air or other sources readily available.

Share your gas analysis challenges and requirements with product application experts, combining your process knowledge with their product expertise to develop effective solutions.

instrument air purge gas diagram for sample gas drying
Sample gas dryer using instrument air



Thursday, August 18, 2016

Combustion Efficiency - In Situ Oxygen Transmitter

zirconium oxide based oxygen O2 transmitter for flue gas combustion
The Oxymitter shown with integral and
remote electronics
Emerson Process Management
Rosemount Analytical
Accurate control of combustion efficiency is a mainstay of fired boiler and other combustion operations. Reliable measurement of oxygen concentration in flue gas enables adjustment of the fuel to air ratio to produce efficient combustion, reducing cost and environmental impact. Since O2 sensors are located on an exhaust stack, generally a difficult location to access, high transmitter reliability and low maintenance requirements are beneficial.

The Oxymitter™, from Rosemount Analytical (div. of Emerson Process Management), is an in situ oxygen transmitter well suited for use in monitoring flue gas. The transmitter is applicable to all new installations and adaptable as a replacement for existing units. The zirconium oxide based sensing technology, along with advanced design, provide a host of useful features.

  • High accuracy measurement
  • Electronics mounted remotely, or on probe
  • Optional display
  • Optional wireless connectivity
  • Optional explosion proof ratings
  • Compatible with range of communications protocols
  • Fully field repairable
  • Variable probe insertion length
  • Optional Xi electronics provide additional functionality
The data sheet included below provides additional detail for the Oxymitter™. Share your combustion control challenges with product application specialists. A combination of your process knowledge and their product application expertise will produce an effective solution.



Thursday, August 11, 2016

Electro-Pneumatic Transducer Bridges Gap From Electric to Air Signals

electropneumatic current to air voltage to air transducer for process control signals
In this age of electronics, pneumatics are still widely employed in process control, and the benefit of using compressed air to deliver control signals is not likely to diminish. Providing a bridge between electrical signals from controllers and pneumatic signals required at the input of operating devices is the function of an electro-pneumatic transducer.

The transducers come in many different versions to accommodate a wide range of possible input signals and two output pressure ranges. The compact units can be mounted in several ways, and NEMA 4X enclosures are available for installation outdoors or in washdown areas.

Some common applications where electrical control signals will be converted to pneumatic for device control.

  • Valve actuators
  • Pneumatic valve positioners
  • Damper and louver actuators
  • Final control elements
  • Relays
  • Air cylinders
  • Web tensioners
  • Clutches and brakes
ControlAir Inc. manufactures a comprehensive line of electro-pneumatic transducers, with models ranging through differing feature levels and price points. Certain applications will call for special variants designed with immunity to shock and vibration or other conditions found throughout industrial installations. Contact a product specialist and share your control challenges. Combining your process knowledge and expertise with their product application experience will produce an effective solution.



Wednesday, August 3, 2016

Sliding Gate Valve Trim for Maximized Flow Control

process control valve sliding gate style
Sliding Gate Valve
Courtesy Jordan Valve
Fluid flow control in a process can present a number of challenges, large and small. In addition to selecting a properly sized control valve, your choice of trim design can contribute noticeably to overall positive performance. One candidate for fluid flow control is the sliding gate valve.

The trim of a sliding gate valve essentially consists of a fixed disc and a movable plate installed directly in the flow path. The disc and plate have precisely located and sized perforations, slots, or other openings. The valve actuation mechanism slides the plate across the face of the disc, progressively changing the alignment of the openings in the plate and fixed disc. This type of design can bring some benefits to the process and user.

  • Short stroke length provides fast response, reduces wear on packing and diaphragm, allows for a compact installed assembly
  • Straight-through flow pattern reduces turbulence, noise, erosion, valve chatter, and cavitation
  • Ease of maintenance, with fewer trim components that are easily changed
  • Self cleaning, self lapping seats
The video below provides a clear illustration of how the sliding gate valve trim works, through animation and exploded views of the valve components. Share your fluid flow control challenges with a valve specialist and combine your process expertise with their product application knowledge for an effective solution.