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December 1, 2008
Lubricant contamination in gearbox bearing housings can substantially reduce gear life. In critical applications, dual-face, magnetic bearing-protector seals will keep contamination out (Figure 1). Dual-face, magnetic bearing protectors are preferred in many difficult applications, such as wet cooling tower gearboxes, while advanced rotating labyrinth seals are more universally applicable. Both users and...
http://www.che.com/technical_and_practical/Bearing-Housing-Protector-Seals-for-Gearboxes_4386.html
December 1, 2008
Engineers often need to fit experimental data to an empirical relationship for extrapolation or modeling without resorting to a full mathematical treatment based on physical principles or theory. The most widely used platform in science for doing this is MS Excel, and while its "off-the-shelf" Trendline tool is useful, it is limited to only 4 or 5 simple functions. Excel’s Solver add-in, on...
http://www.che.com/technical_and_practical/Engineering-Practice-Functions-for-Easier-Curve-Fitting_4387.html
December 1, 2008
The thermal conductivity of hydrocarbons is an essential parameter that needs to be known when designing heat transfer equipment. Presented here is a simple-to-use correlation that was developed for predicting thermal conductivities of liquid paraffin hydrocarbons, petroleum fractions and atmospheric natural hydrocarbon gases as a function of temperature and molecular weight or relative density. Results...
http://www.che.com/technical_and_practical/Engineering-Practice-Estimating-Thermal-Conductivity-of-Hydrocarbons_4388.html
November 1, 2008
Process modeling has progressed from the "molecule accounting" of steady-state flowsheeting packages to become a central platform for capturing and deploying chemical process industries’ (CPI) intellectual property (IP). Systematic modeling has moved center stage to help companies differentiate themselves from their competitors while also providing a set of tools with which it is possible...
http://www.che.com/technical_and_practical/Cover-Story-Process-Modeling-Moves-Center-Stage_4317.html
November 1, 2008
  Pressure relief systems are vital in the chemical process industries (CPI) for handling a wide variety of situations. They are used to prevent pressurization above a system’s design pressure; for venting during an unusual or emergency situation; and for normal depressurization during a shutdown, as examples. In some cases, such as when non-combustible gases including steam, air and nitrogen...
http://www.che.com/technical_and_practical/Pressure-Relief-System-Design_4319.html
November 1, 2008
Management is a process of managing risk; maintenance management is a process of managing risk for operational reliability. Since it is hard to manage what cannot be measured, effective maintenance management demands good data on machine health — a comprehensive condition monitoring program, carried out by skilled and determined personnel, using appropriate tools and technology. Condition-based...
http://www.che.com/technical_and_practical/Condition-Based-Maintenance-Management-Enhances-Reliability_4320.html
November 1, 2008
A very common heat exchanger in the chemical process industries (CPI) is the vertical thermosiphon reboiler (VTR; Figure 1). Due to size and fluid-flow restrictions, however, its heat transfer rate is often quite low. The subcooled region formed at the thermosiphon’s tube-bundle base usually causes reduction in the tubes’ average heat-transfer coefficient. Improvements in performance can be...
http://www.che.com/technical_and_practical/Engineering-Practice-Get-More-From-Vertical-Thermosiphon-Reboilers_4321.html
October 15, 2008
Pumps Centrifugal pumps with cast or forged steel casings are typically appropriate for systems with large flowrates Positive displacement pumps frequently can handle smaller flowrates of less than 100 gal/min Sealless pumps (canned motor or magnetic drive) avoid the installation of mechanical seals A typical centrifugal pump can be expected to deliver operational head of about: where g is gravitational...
http://www.che.com/technical_and_practical/Facts-at-Your-Fingertips-Heat-Transfer-System-Design_4238.html
October 15, 2008
  The perfect valve to control your process has been selected. The valve will pass your maximum flow. Everything is great, right? In some cases digging a little deeper might help. The control valve usually should not be the...
http://www.che.com/technical_and_practical/Feature-Report-Part-1-Using-Installed-Gain-to-Improve-Valve-Selection_4239.html
October 15, 2008
The role of valves in a process is far from insignificant. These components enable engineers to control the vitals of a process: temperature, pressure, concentration, and flow. In some cases, the failure of a valve could be catastrophic and in other cases just a headache, but whatever your situation, your material selection will surely be one of the most important elements in determining the reliability of...
http://www.che.com/technical_and_practical/Feature-Report-Part-2-Valves-and-Specialty-Metal-Materials_4240.html
October 15, 2008
Spray technology is a powerful tool used to achieve higher levels of overall process performance. Strategic decisions in selecting and employing spray technology can yield dramatic wins. Understanding sprays, drop size, and the strengths and characteristics of nozzle types and correctly positioning them are fundamental to the desired process "response" or result. The selection of a nozzle is a...
http://www.che.com/technical_and_practical/Feature-Report-Spray-Technology-Fundamentals-and-Applications-Game-Winning-Strategies_4241.html
October 15, 2008
This article presents the fundamental concepts of the discharge coefficient, KD, of a relief valve or a safety relief valve, and flow resistance factor, KR, of a rupture disk, and their proper use in sizing an emergency relief system. When these devices are used to protect a pressure vessel, they must be certified according to ASME code in the U.S. Both the discharge coefficient and the flow resistance...
http://www.che.com/technical_and_practical/Engineering-Practice-Discharge-Coefficients-and-Flow-Resistance-Factors_4242.html
October 15, 2008
As regulatory issues, environmental sensitivity, and longterm water supply concerns increase, the chemical process industries (CPI) are considering ways to reduce their water discharges. In fact, more and more companies are evaluating the viability of zero-liquid-discharge (ZLD) processes. This usually involves consideration of evaporation and crystallization technologies, which can be very expensive from...
http://www.che.com/technical_and_practical/Strategies-to-Minimize-Wastewater-Discharge_4243.html
September 15, 2008
Process engineers understand how to harness the power of closed-loop multi-variable control in their plants. The evolution of digital control in the chemical process industries (CPI) has provided that power. Yet digital control represents just one facet of optimization and improvement within operations. With increased digitization, the universes of process control and information technology (IT) are...
http://www.che.com/technical_and_practical/The-Path-to-the-Perfect-Plant_4170.html
September 15, 2008
The need to conserve water is becoming a common concern throughout the world. Whether this is due to the cost of water, availability of water, or environmental concerns, water conservation is becoming a major focal point, both in the public and private sector. In those areas where renewable water resources are limited, and in regions where there are significant environmental concerns and costs associated...
http://www.che.com/technical_and_practical/Feature-Report-Water-Reuse-and-Conservation-in-the-CPI_4171.html
September 15, 2008
Today, companies in the chemical process industries (CPI) are faced with increased operating expenses, reductions in the number of qualified workers, strong competition and the need to do more with less. To meet these challenges, many companies are making use of advancements in instrumentation and control technologies to optimize plant performance. These advancements often lie in improved electronic...
http://www.che.com/technical_and_practical/From-Tap-to-Transmitter_4173.html
September 15, 2008
Each compressed air system is typically composed of one or more compressors with a power source, control system, intake air filter, after cooler and separator, air receiver, air dryer, interconnecting piping and a distribution system to deliver air to points of application. Because the air leaving the compressor is generally saturated, any reduction in temperature will cause water to begin condensing...
http://www.che.com/technical_and_practical/Engineering-Practice-Predicting-Water-Content-of-Compressed-Air_4174.html
September 15, 2008
There are many criteria that the engineer considers when optimizing: maximization of product yield or quality; minimization of recycle flow or energy consumption; and economic indicators, such as maximization of profits, net present worth (NPW) and minimization of payback period (PBP). Instead of simply focusing on the most important criterion, it would be preferable to optimize the process for several...
http://www.che.com/technical_and_practical/Engineering-Practice-Optimize-your-Process-Plant-for-More-than-One-Objective_4175.html
August 15, 2008
  Caking occurs when an easy-flowing powder becomes cohesive after storage or transport, forming agglomerates comprised of individual particles that are bonded together. As a consequence, a powder that flowed freely during packaging may contain lumps when the package is opened by a customer; a silo that readily discharges a bulk material when in continuous operation may become plugged when its feeder...
http://www.che.com/technical_and_practical/Solids-Processing-Prevent-Caking-and-Unintended-Agglomeration_4084.html
August 15, 2008
Gate Gate valves are designed to operate fully open or fully closed; When fully opened, there is very little pressure drop across the valve, and when fully closed there is good sealing against pressure. With the proper mating of a disk to the seat ring, very little or no leakage occurs across the disk when the gate valve is closed. Gate valves open or close slowly, which prevents fluid hammer and...
http://www.che.com/technical_and_practical/Facts-at-your-Fingertips-Valves_4087.html
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