Wednesday, August 24, 2016

Hydrostatic Level Measurement

submersible pressure sensor transmitter
Submersible Pressure Transmitter
VEGA
Liquid level can be inferred by accurately measuring the pressure produced by the height of a fluid column and knowing the density of the liquid measured. The measurement is comparative in nature, referencing some external pressure as a zero point. The zero point can be the surrounding atmospheric pressure, tank pressure, or the pressure exerted by another column of liquid contained elsewhere.

There are uncountable application scenarios, each with its own set of special conditions. Proper instrument selection, installation and calibration are essential to generating reliable and accurate results.

The VEGA hydrostatic pressure transmitters are specially designed to provide level measurements across a wide range of liquids with different properties. Some units provide media temperature measurement as well. The product centers around three basic units, with numerous variants and options that can be used to configure an instrument for any application.

Browse the document included below to see application examples, setup instructions, and the extensive array of configurations available with these pressure transmitters from VEGA. Contact product specialists to share your application challenges and get effective solutions.


Wednesday, August 17, 2016

Steam Desuperheaters

steam desuperheater attemperator water injection type
Diagram of one type of steam desuperheater
Schutte & Koerting
Steam has been a preferred means of delivering energy for many decades. Whether used for propulsion, as when driving a turbine, or delivery of heat, steam has proven to be an acceptably reliable and safe means of energy transfer.

Steam can exist in a saturated or superheated state. When saturated, molecules are at the minimum energy level needed to maintain a gaseous state. Superheated steam is essentially steam that has additional sensible heat content beyond what is necessary to create saturated steam. Some processes, such as turbines, will operate best with superheated steam. Heat transfer processes will often provide their best efficiency with saturated steam. Whatever the case, there can be instances where it is preferential, or necessary, to reduce the superheat level of process steam.

Desuperheaters reduce the sensible heat content of steam through a number of methods, most that involve adding finely atomized water to the steam flow. The document included below outlines various construction methods and principles of operation for steam desuperheaters. The illustrations, diagrams, and explanatory content will provide a useful overview of this common industrial process, including application examples.



Wednesday, August 10, 2016

When to Use a Globe Valve for Fluid Process Control

heavy duty industrial control globe valve with pneumatic actuator
Heavy duty industrial globe valve with pneumatic actuator
Masoneilan brand of GE
Industrial process control often involves the regulation of fluid flow. There are almost uncountable types and variants of flow control valves, each with a particular set of attributes that can make it the advantageous choice to meet certain applications.

When the process calls for controlling flow over a range of possible values, known as throttling, a globe valve may be a good candidate for the application.

Globe valves are characterized by the change in direction of fluid flow as it passes through the valve and the plug or disk positioned in an opening through which fluid must pass. The plug is connected to a stem extending to the exterior of the valve body through the bonnet. Movement of the stem will reposition the plug in relation to the opening, providing a successively larger or smaller opening area through which fluid can pass.
diagram of globe valve
Simple globe valve diagram
Courtesy Wikipedia
Globe valves are available in tee, angle, and wye configurations, as well as an enormous range of special configurations to suit specific applications.
What are some potential advantages of globe valves?

  • Good throttling and shutoff capability
  • Comparatively easy maintenance
  • Comparatively short travel of plug from open to closed position
  • Seats can usually be resurfaced when worn
What are some limiting factors for globe valves?

  • Higher valve pressure drop than some other designs
  • No straight through fluid path
  • Comparatively higher actuator torque requirements to operate valve
When flow throttling capability is the overriding concern for an application, a globe valve could be a good candidate for consideration. Share your flow control challenges with product specialists. Combining your process knowledge with their product application expertise will produce effective solutions.



Wednesday, August 3, 2016

Fuel Air Ratio Controller for Combustion Efficiency

gas fired industrial boilers
Combustion efficiency reaps substantial cost savings
Steam and hot water use is prevalent throughout industrial processes. Production of these two media is most commonly accomplished with a boiler, many of which are heated by combustion of fossil fuel. Fuel fired boilers of a certain size become the focus of regulatory requirements for emissions. All boilers consume what would be construed by their owners as large amounts of costly fuel. Because of their high pressure and temperature, and the presence of a controlled combustion within an occupied facility, safety is a paramount concern.

There, fortunately, is a single solution that can help to attain useful goals with the three concerns of safety, fuel cost, and regulatory compliance. Applying an efficiency controller to manage the fuel to air ratio of the combustion system will deliver benefits far in excess of the cost to incorporate the necessary devices. The three basic goals for the fuel air controller are:
  • Maximize fuel efficiency
  • Minimize regulated emissions
  • Maintain safe operating condition
A good portion of all three goals can be accomplished through careful concerted control of combustion air supply and fuel supply. The fuel air ratio must be subject to continual adjustment in response to current air conditions (which can vary on a daily basis) and the level of O2 in the flue gas. Controlling the air fuel ratio supports the following goals:
  • Preventing excess fuel vapors from entering the flue and creating an unsafe condition
  • Providing the correct amount of air to effectively combust the fuel supplied to the burner
  • Preventing excess air flow from reducing net heat transfer to the feedwater
  • Maintaining regulated emissions within required limits
  • Limiting fuel consumption to the minimum necessary to meet demand
Fireye® is a leading manufacturer of flame safeguard controls and burner management systems for commercial and industrial applications throughout the world. Their products, the first of which was developed in the 1930's, enhance the safety and efficiency of all fuel fired burners.

There are numerous capabilities built in to the company's PPC4000 series of fuel air ratio controllers. Some of the more notable include:
  • Precise fuel air ratio attained using parallel control of servos to regulate fuel and air supplies.
  • User selected burner profiles
  • Alarm contacts
  • PID operation
  • An array of inputs and outputs to accommodate sensors and devices needed to monitor and control boiler operation
  • Compatible with other products that provide additional flame and burner monitoring safety
  • Multiple boiler sequencing and cold start thermal shock protection
  • On board boiler efficiency calculation
  • User interface, optional larger touchscreen interface
Glance through just the first two pages of the document below to get a full description of the capability of this compact and comprehensive controller. You can get more detailed information, or get a professional evaluation of your current system efficiency, by contacting the combustion experts at Classic Controls.