Cooling water systems that rely on cooling towers are a critical component at chemical process industries (CPI) facilities. However, during operation, these open recirculating systems concentrate the contaminants in the makeup water, and as a result, scale formation and biological fouling can occur. To manage this problem, all cooling water systems require proper chemistry control and monitoring. Unless prevented, corrosion and the build up of scale and microbial fouling can impact cooling efficiency and in extreme cases even lead to unit shutdown. This article examines some of the fundamental concepts and treatment options that should be considered to keep open, recirculating cooling systems clean.... http://www.che.com/processing_and_handling/operations_and_maintenance/Keeping-Cooling-Water-Clean_5005.html
The heat transfer sufaces of coal-fired process heaters and boilers often undergo severe fouling. If left intact, such deposits, consisting of slag from mineral matter contained in the coal, can reduce heat-transfer-surface availability, reduce thermal efficiency and cause corrosion. If the deposits are adherent and cannot be removed by conventional steam soot-blowers, shutdown and more rigorous cleaning is required. Maintenance personnel have been known to use shot cleaning as a means of removing stubborn deposits. This article proposes the installation of permanent, on-stream shot-blasting equipment for adherent deposit removal... http://www.che.com/processing_and_handling/operations_and_maintenance/The-Shotgun-Approach-Removal-of-Fouling-Deposits-on-Heat-Transfer-Surfaces-in-Coal-Fired-Process-Heaters-and-Boilers_4925.html
Organic-based thermal fluids provide relatively trouble-free service for significant periods of time. However, there comes a time when any fluid (either aromatic- or aliphatic-based) needs to be replaced. Since aromatic-based fluids generally cost more and are complicated to dispose of, they receive far more attention than aliphatic-based fluids when the time comes for replacement. Aliphatic-based fluids (manufactured with mineral oil, petroleum or poly alpha-olefins) are viewed less critically, since they are historically less expensive to purchase and are more easily handled as waste. As a result, these fluids are replaced more frequently than may be required. However, the recently rising costs of petroleum feedstocks have made these relatively low-cost hot oils more expensive to replace. To minimize the waste of good product, this article provides guidance on when to replace thermal fluids and how to achieve this using the most cost-effective method. (Part 1 of this report, p. 34, describes important considerations for avoiding overheating.)... http://www.che.com/processing_and_handling/operations_and_maintenance/Cover-Story-Part-2-Heat-Transfer-Fluids-Maintaining-the-System_4385.html
Improvements in performance can be achieved with the application of heat-transfer-enhancement devices — such as wire matrix inserts, twisted-tape inserts and helically coiled inserts — in the subcooled zone of a vertical thermosiphon reboiler. These enhancement devices reduce the required heat-transfer surface area, subcooled zone length and maximum temperature of the reboiler tube wall, while increasing the overall heat-transfer coefficient, subcooled-zone overall heat-transfer coefficient and average heat flux rate. All together, these benefits translate into a reduction in the size of the exchanger, the area of installation and the initial investment.... http://www.che.com/processing_and_handling/operations_and_maintenance/Engineering-Practice-Get-More-From-Vertical-Thermosiphon-Reboilers_4321.html
Water hammer — a high-pressure surge or wave created by the kinetic energy of the moving liquid — is not only a system issue, but primarily a safety concern. Understanding the nature and severity of water hammer in a steam-and-condensate system will allow prevention of its destructive forces. A better understanding will also help with the introduction of preventative measures into system designs, steam system startups, maintenance and installations, which can contribute to personnel safety, reduce maintenance costs, and reduce system downtime.
Tube plugging is probably the most frequently used maintenance and repair technique for the tube side of an exchanger. This article provides information on how to locate the positions of tube failures and discusses why it is important to know such information. It describes how to find out where the tubes failed and explains how to analyze what caused failures, seen from the tube side. Descriptions of several kinds of plugs and their uses and plugging techniques are included. Preparation of a plug map, a key to tubeside maintenance, is also discussed.... http://www.che.com/processing_and_handling/operations_and_maintenance/Maintaining-and-Repairing-Heat-Exchanger-Tubes_3731.html
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