High operational problems

These systems, commercially known as Tberminol VP or Dowtherm A, differ from steam in some key areas which can result in operating problems unless handled properly in design (14). The low pressure—high temperature operation means that the AT/AP ratio at saturation is quite high for example, at 315°C the ratio is 25 times that of steam. This means that a pressure drop that would be nominal in a steam system (10 kPa (0.1 atm)), can not be tolerated if precise temperature control is needed. 

One operational problem with analog alarms is that noise in the variable can cause multiple alarms whenever its value approaches a limit. This can be avoided by defining a deadband on the alarm. For example, a high alarm would be processed as follows ... 

A design is only as effieient as the performanee of the seleeted eomponent materials. The eombustor liner and turbine blades are the most eritieal eomponents in existing high-performanee, long-life gas turbines. The extreme eonditions of stress, temperature, and eorrosion make the gas turbine blade a materials ehallenge. Other turbine eomponents present operational problem areas, but to a lesser degree. For this reason, gas turbine blade metallurgy will be diseussed for solutions to problem areas. Definition of potential solutions will also relate to other turbine eomponents. 

Sohre, J., Operating Problems with High-Speed Turbomachinery—Causes and Correction, 23rd Annual Petroleum Mechanical Engineering Conference, September 1968. 

Liquid level above seal pan in bottom of column. Poor stripping of bottoms product. High pressure drop across section. Board mounted instrument improperly calibrated. Level gauge in field not properly blown down or even checked. Operation problem. 

Operating problems. High-temperature operations create high maintenance requirements and can reduce equipment reliability. 

J. Dolbear (W. R. Grace) What are the incentives for high operating temperatures, and how are the mechanical design complications met In other words, with high temperatures and high steam concentrations, what are the problems in designing a mechanically workable reactor system ... 

Another operational problem that may develop concerns multiple LP steam-heating system installations in which an imbalance in waterside chemistry results in low TDS/chemical inhibitor in one boiler and high TDS/chemical inhibitor in a second unit. 

Boiler scales and corrosion product deposits also may form from the thermal breakdown of treatment chemicals. Breakdown products of chemicals such as sulfite, amines, hydrazine, and chelants often are steam-volatile, and subsequent reactions may produce corrosion debris that forms deposits and causes blockages. This problem typically occurs when chemical treatments selected for use are applied under unsuitable operating conditions (as when the boilers are highly rated or raise steam at particularly high operating pressure or temperature). 

The Ballestra Neutrex SV system (Fig. 10) has been developed to obtain, in a single process step, products with high AM at high purity. Neither solvents nor hydrotropes (sometime used to overcome viscosity and consequent high-pressure problems in the loop) are required to operate with these highly viscous products. 

As described above, the activity of a catalyst can be measured by mounting it in a plug flow reactor and measuring its intrinsic reactivity outside equilibrium, with well-defined gas mixtures and temperatures. This makes it possible to obtain data that can be compared with micro-kinetic modeling. A common problem with such experiments materializes when the rate becomes high. Operating dose to the limit of zero conversion can be achieved by diluting the catalyst with support material. 

Air entrainment and foaming in hydrocarbon liquids can cause operational problems with high-speed machinery in physical-chemical processes such as petroleum production, distillation, cracking, coking, and asphalt processing. 

The PULSAR units are high efficiency static aerators that have been developed for municipal wastewater treatment plants and have successfully been used over extended periods of time without any operational problems such as unstable operation or plugging up during intermittent operation of the air pumps (Chourda-kis, 1999). Data have been collected from a pilot plant unit at the Wastewater Treatment plant of the Industrial Park (Herakleion, Crete). A series of experiments were conducted for the determination of the mass transfer coefficient (kLa) and are shown in Figure 17.4. The data are also available in tabular form as part of the parameter estimation input files provided with the enclosed CD. 

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