Introduction to the Two-Wire Transmitter and the 4-20mA Current Loop


In two-wire 4-20mA control loops, we use 2-wire transmitters to convert various process signals representing flow, speed, position, level, temperature, pressure, strain, pH, etc., to 4-20mA DC for the purpose of transmitting the signal over some distance with little or no loss of signal. This paper reviews the operation of this transmission standard and its advantages, in particular as it relates to two-wire transmitters and the associated 4-20mA current loop.


This white paper is sponsored by Acromag.

Innovative Cleaning of Air Preheater Coils with Pressurized Liquid Nitrogen


Cleaning of air heaters in power plants or recovery boilers has been traditionally done with high pressure water, chemicals or steam. These techniques, while effective on moderate air-side fouling of heat exchange surfaces, are usually ineffective on more tenacious deposits that can develop in coal-fired plants with buildup of fly ash, dust and oil. If these deposits are not cleaned periodically, the heat transfer in the heaters is reduced, which in turn reduces boiler efficiency and increases a unit’s heat rate. Severe fouling on air preheaters and air heaters can even reduce a unit’s Mw output. This paper discusses the recent introduction of a highly effective method of cleaning air heaters utilizing pressurized liquid nitrogen (LN2). A success story at PPL Generation’s Brunner Island plant illustrates the effectiveness of this new technology.

White Paper brought to you by Conco Systems Inc.

The Practical Application and Innovation of Tube Cleaning Technology for Condensers


Maintaining clean condenser tubes is important for reliable, efficient power generation.  Two major problems result from tube fouling: (1) Loss of heat transfer, and (2) Under-deposit corrosion.  Internal tube fouling is nearly always detrimental to heat transfer, thus reducing the efficiency of steam condensing, resulting in a lower vacuum (higher pressure) and less efficient steam turbine operation. Under-deposit corrosion of tube material can result in through-wall leaks, permitting ingress of cooling water into high purity steam condensate.  Because poor vacuum conditions in the condenser can reduce electric generating capacity, and contaminants in steam condensate can cause significant damage to boiler tubing and steam turbine materials, measures to prevent fouling or remove foulants must be applied. Early identification of fouling characteristics and a fundamental knowledge of cleaning system capabilities are essential in determining the most effective cleaning technology. State-of-the-Art methods for off-line mechanical tube cleaning are presented, and their effects examined.

White Paper brought to you by Conco Systems Inc.

The Practical Application and Innovation of Cleaning Technology for Heat Exchangers


The fouling of heat exchangers not only has a negative impact on heat transfer efficiency but also may restrict the output or production capacity of the facility. Given the cooling medium and the process, heat exchangers may be lightly fouled with organic deposits or may be severely blocked from hardened process chemicals. The probability of success in cleaning the heat exchanger is dependent on the selection of the appropriate cleaning technology under the specific fouling conditions. Early identification of fouling characteristics and a fundamental knowledge of cleaning system capabilities are essential in determining the most effective cleaning technology and the frequency of cleaning required. Unique circumstances may require innovative solutions. State-of-the-art cleaning technologies for shell and tube heat exchangers and air-cooled heat exchangers are introduced. The practical application and innovation of cleaning technology is discussed. Methods for effective removal of various deposit types are presented.

White Paper brought to you by Conco Systems Inc.

The Advantages of Using Multiple Frequencies for Eddy Current Examination of Condenser Tubing


An essential element in the eddy current testing methodology is the use of multiple testing frequencies. A true volumetric inspection requires complete penetration of the tube wall from various perspectives. Since prime frequency is set to approximately thirty seven percent standard depth of penetration of the tube wall, additional frequencies are required to gain an accurate and detailed perspective of the defect.

This paper demonstrates the effects and advantages of utilizing multiple frequencies in the testing process to provide the analyst with sufficient information to call the defects with greater accuracy and reliability. Utilizing a multi-frequency test instrument and standard probes commonly used for testing condenser tubes, tube samples with various defects will be examined utilizing one, two, three and four frequencies. Defect acquisition rates will also be varied and the results reported. The information is useful for determining the number of frequencies required for an effective eddy current test.
White Paper brought to you by Conco Systems Inc.

The Practical Application SF6 and Helium Condenser Tube and Air In-leakage Detection


Many different methods are available for the detection of condenser tube and air in leakage. Once detected, it is necessary to locate the actual source of the problem so that it can be rectified and the health of the unit restored. The nature and severity of the leak largely determine the best method to be employed in locating its source.

The tracer gas technique has eliminated much of the guess work normally experienced when using less sophisticated methods, has resulted in less down time to perform leak detection, and has especially helped to reduce the increase in heat rate which is associated with air in leakage.

This paper presents the practical application and use of tracer gases to perform leak detection, compares this method with other techniques, and outlines the key elements which an engineer should consider when determining the most appropriate procedure and tracer gas to use in a given application.

White Paper brought to you by Conco Systems Inc.

Top 10 Tips for Secure Bolting


Achieving the safest, most secure bolted connection involves many factors. To help you achieve the best possible results we have summarised the in-depth know-how shared over the last ten issues of Nord-Lock's Bolted Magazine into ten bolting tips.


This White Paper is sponsored by Nord-Lock Inc.

Understanding Natural Gas Fuel Reliablity for Backup Power


Reliability of fuel supply tends to be of great concern for authorities having jurisdiction (AHJs). On-site fuel (most often diesel) is typically required for life-safety applications, and many mission-critical applications like 911 call centers specify it because it is perceived to be more reliable. Nonetheless, maintenance issues and delivery concerns of diesel fuel in an emergency, combined with the reliability and cost-effectiveness of natural gas, must be considered in a standby power system. NFPA and NEC offer provisions for the use of natural gas in standby power applications that had previously been the clear domain of diesel-fueled systems. There are also many ways to work with the AHJ to clear the way for the use of gaseous fuel in a standby power system.

White Paper brought to you by Generac Power Systems.