Friday, May 27, 2016

Drop-In Replacement Damper Drives for Boilers and Other Combustion Operations

Rotork brand pedestal mount pneumatic damper drive, Type K Series PM
Pedestal mount damper drive, PM Series
Courtesy Rotork
Damper drives are specialty actuators that position air and flue gas dampers on combustion based systems in industrial settings. They can be linear or rotary to meet certain application requirements. The damper positioning is a process control function that is used to increase efficiency, reduce maintenance, control harmful emissions, and lower fuel consumption.

With a very large base of legacy damper drives of the rotary type already installed throughout commercial and industrial markets, there is a need for drop-in replacements for older drives that are worn or not able to provide the level of performance accuracy needed to meet modern operating demands. Rotork, globally recognized manufacturer of valve and damper actuators, has developed a product series within their damper drive line that specifically addresses the drop-in replacement of legacy damper drives.

Rotork's PM and DM Series drives, a portion of the company's Type K Damper Drive line, provide rotary operation in the 30 to 100 degree range and are available as pedestal mount or direct mount versions. As a subset of this broad offering, the company has crafted the FasTrak Series, which are preconfigured as ready-made units to replace common, older legacy damper drives. Twelve models cover the most commonly occurring pneumatic or electric damper drive replacements. The manufacturer states that the FasTrak drives will:
  • Bolt to the floor where the old drive was mounted
  • The existing link rod and clevis will attach to the FasTraK drive lever
  • Simply verify envelope dimensions to assure that there are no external obstructions
A product catalog describing the full line of Type K drive is provided below. Share your combustion application challenges with a product specialist and work together to find the best solutions.


Tuesday, May 17, 2016

Specialty Transmitter Isolation Valve for Tanks and Vessels

transmitter isolation valve for process control tanks level transmitter
Transmitter Isolation Valve
Courtesy PBM Valve Solutions
Fluid process control applications frequently employ tanks and vessels as part of the processing chain or for storage and holding. Level transmitters can be installed on the tank to provide indication of liquid level. While there are numerous combinations of fittings and valves that could be used to mount and connect the transmitter to the tank, one manufacturer has designed a specialized valve intended to mate a transmitter to a tank fitting with great advantage.

The specialized transmitter isolation valve minimizes dead space to prevent media residue buildup. It can be configured to accommodate CIP and drainage without process interruption. Calibration ports and industry standard mountings allow for broad application throughout the fluid process control industries.

A cut sheet is provided below, and more information and application assistance is available from process control specialists.




Tuesday, May 10, 2016

Boiler Efficiency - Small Gains Can Bring Big Savings

industrial boiler room with equipment and boiler
Every boiler and steam system has a unique
set of efficiency challenges
There are numerous, actually about a half million, articles on the web about boiler efficiency. Because of the scale of even modest sized boilers, small increases in production efficiency can translate into very substantial monetary savings. Even when you have squeezed that final increment of efficiency from your boiler, a closer look will likely show there is something more you can do.
Increasing boiler and steam system efficiency is not a "one and done" proposition.
Boosting efficiency will undoubtedly involve controlling elements that were not controlled before, or at least controlling them in a more rigorous manner. This means additional instrumentation and controls that were not part of the system previously. Keeping those measurement and control elements in top working order is key to maintaining operating efficiency at stellar levels. The takeaway point here is that...
Higher efficiency operation is likely accompanied by increased system complexity.
Higher efficiency results from operating within a narrower set of conditions. Excess air, combustion temperature, flue gas composition, and more must be continuously monitored and maintained within the necessary envelope to keep the goal efficiency level throughout the varying demand levels on the system. With proper implementation, this additional complexity should not be an undue burden on the system operators. Automation and functionality built into modern measurement and control elements are capable of handling the normal operation and providing notice when conditions adversely vary from predicted or required ranges.
Increased maintenance activity is an integral part of reaping efficiency savings.
Steam systems, whether for heating a commercial building or driving an industrial process, generally involve extensive piping. The consumptive devices serviced by the system, most often where steam becomes condensate, are also part of the efficiency plan. Their productive use of the process steam contributes to overall savings. If an equipment unit, through the efforts of good maintenance and control, can perform its task with 95% of it previous consumption, that is a positive return on the effort and cost expended to boost performance.
Attaining elevated efficiency can result from added equipment, but maintaining high efficiency is a function of attitude and commitment. 
It is important that the managers, supervisors, technicians and contractors responsible for the day to day operation of the system consider efficient operation as a valuable and useful goal. Diligence, discipline, and attention to detail are solid elements of a successful maintenance program.

The US Department of Energy summarizes combustion efficiency on their website.
http://energy.gov/sites/prod/files/2014/05/f16/steam4_boiler_efficiency.pdf

Combustion Efficiency

Operating your boiler with an optimum amount of excess air will minimize heat
loss up the stack and improve combustion efficiency. Combustion efficiency
is a measure of how effectively the heat content of a fuel is transferred into
usable heat. The stack temperature and flue gas oxygen (or carbon dioxide)
concentrations are primary indicators of combustion efficiency.
Given complete mixing, a precise or stoichiometric amount of air is required
to completely react with a given quantity of fuel. In practice, combustion
conditions are never ideal, and additional or “excess” air must be supplied to
completely burn the fuel.
The correct amount of excess air is determined from analyzing flue gas oxygen
or carbon dioxide concentrations. Inadequate excess air results in unburned
combustibles (fuel, soot, smoke, and carbon monoxide), while too much results
in heat lost due to the increased flue gas flow—thus lowering the overall boiler
fuel-to-steam efficiency. The table relates stack readings to boiler performance.

Combustion Efficiency For Natural Gas















Here are some items that can impact boiler efficiency and steam system operating costs. While the list may point you toward some areas that need attention in your system, a good strategy is to consult a combustion specialist and share your concerns and goals for system operation. Their expertise will be an integral part of your good decision making.


  • Minimize losses due to leaks throughout the entire connected system.
  • Rigorously follow boiler and component manufacturer maintenance schedule recommendations.
  • Establish means to provide boiler blow-down when excess accumulation of dissolved solids occurs. Conductivity monitoring can be an effective indicator of dissolved solids.
  • Insulate all steam and condensate piping and traps. 
  • Establish steam system operation at the lowest effective pressure. Special condensate return accommodations may enhance ability to operate at lower pressure.
  • Perform timely maintenance of steam traps in accordance with best practices.
  • Use energy recovery units to heat makeup water with waste heat from flue gas.
  • Add variable speed drive controls to boiler feed pumps for lower energy consumption and finer control of feed flow.
  • Monitor flue gas O2  and temperature levels to determine combustion efficiency and optimize air-fuel ratio.
  • Monitor and control air flow and fuel flow using mass flow measuring and control devices for best accuracy.
  • On systems with multiple boilers, incorporate load sensing controls that will sequence and optimize the operation of the units in response to demand.
Certainly there is more detail involved in each item listed, plus numerous other potentially energy saving activities. By continuing to properly maintain your existing system and stay informed about new equipment and technology with promising application, you will keep your steam system operating at the top end of its efficiency range.

Thursday, May 5, 2016

Electromechanical Pressure, Differential Pressure and Temperature Switches - The Basics

Many industrial applications require the monitoring or control of pressure and temperature of a process. Pressure and temperature measurement can be accomplished either by transmitters, gauges, or switches. This post will provide a quick introduction to industrial electromechanical pressure switches and temperature switches.

Pressure Switch

An industrial pressure switch is made up of three main components:
  1. The sensor
  2. The housing
  3. The switching element.
Industrial process control pressure switch
Pressure Switch
The correct combination of each component assures proper application of the device for its intended use.

Sensor

The sensor is located above the pressure port and process connection. For pressure and differential pressure switches, there are several varieties of pressure sensors to choose. The most common types of pressure sensors are:

Metal Bellows - An accordion-like device that provides linear expansion and contraction based upon the application of pressure or vacuum. Bellows are excellent sensors because they provide good overall pressure range and are fairly sensitive to small changes in pressure.

Piston - A rod and o-ring combination that moves linearly in direct response to applied pressure. Piston sensors are normally only applied to only very high pressure ranges. They have very small surface areas and wide deadbands (the change in pressure required to change the position of the switch output).

Diaphragm - A thin, elastomer or metallic membrane, often with a rolled lip that allows for greater movement. The diaphragm has a large surface area and provides the most sensitivity to pressure change, making it ideal for low to mid-range pressure sensing.

Housing

Housings are classified and selected based on the atmosphere in which they’ll be used. Housing ratings are classified by several national and international agencies, such as NEMA and CENELEC. Very generally put, housings can be rated as general purpose, dust & water resistant, water tight, corrosion resistant and hazardous (explosive) environments. Proper selection of the housing is important to the operation and life expectancy of the device. In hazardous environments, proper selection is absolutely critical. If unsure about the housing classification, consultation with an applications expert is required.

Switching Element

The switching element refers to the signaling device inside the enclosure that responds to the movement of the sensor. It can be either electrical or pneumatic, and provides an on-off signal based upon the switch setpoint (as opposed to an analog, or proportional signal produced by transmitters).

The switching element is most times a “micro” type single pole, double throw (SPDT) electrical switch. These microswitches come in many configurations and electrical ratings, such as double pole, double throw (DPDT), 120/240 VAC, 12VDC, 24VDC, and hermetically sealed.

For the switching element and the sensor, it is very important to know the cycling rate (number switch state changes per unit of time) the instrument will see. Since both of these elements are mechanical, they will eventually wear out and need to be replaced. Switches are an economical and strong performing choice for low to medium cycle rates. For extremely high cycle rates, the use of solid state transmitters is a better choice.

Temperature Switches

An electromechanical temperature switch (sometimes called a thermostat) is, for the most part, a piston type pressure switch connected to a filled capillary and bulb sensing element. The thermal expansion of the media inside the bulb and capillary creates the pressure and linear movement upon the piston sensor of the switch. The bulb and capillary elements are often supplied in copper or stainless steel, and at various lengths.

There are many more details to selecting and applying electromechanical pressure and temperature switches. This post provides a very general introduction. It is always suggested to discuss your application with a qualified applications engineer so that you are assured to get the longest lasting, most economical and safest instrument possible.