Equipment rotating

Determination of reasonable parameters (due to optimized efficiency) of an SOFC-GT hybrid system also sets the necessary parameters of rotating 

The parameters of rotating machinery needed for the SOFC-GT can be achieved by a single-stage radial compressor and a two-stage axial turbine. A similar construction with very similar parameters is presented in Fig. 5.75 an exemplary compressor rotor is shown in Fig. 5.76. 

Calculations on off-design operation of air compressors are based on real device characteristics presented in the form of maps (for a single stage radial compressor see [30]) with parameters corresponding to the conditions of the SOFC-GT hybrid system concerned. Exemplary characteristics (map) of a compressor are shown in Fig. 5.77. 

The map presents the following parameters 1. Reduced pressure ratio  

The SOFC-GT works with a lower air excess factor than does the standard gas-turbine unit. This specific requirement means that the air compressor has a lowered flow capacity than is the case for the gas turbine standalone. 

American Petroleum Institute (API), Manual of Petroleum Measurement Standards. Chapter 8.2. Automatic Sampling of Petroleum and Petroleum Products. First Edition, API Washington, D.C., 1987. 

National Fire Protection Association (NFPA), NFPA 15. Fixed Water Spray Systems. NFPA, Quincy, MA., 1990. 

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A more sophisticated and increasingly popular method of on-condItion maintenance is to monitor the performance of equipment on-line. For example, a piece of rotating equipment such as a turbine may be monitored for vibration and mechanical performance (speed, inlet and outlet pressure, throughput). If a base-line performance is established, then deviations from this may indicate that the turbine has a mechanical problem which will reduce its performance or lead to failure. This would be used to alert the operators that some form of repair is required. 

Most rotating equipment includes electric motors or steam dryers that generate noise at a constant frequency. Air cooler fans are a source of noise that can be reduced by lowering the fan speed and increasing the number of blades. Pump motor noise can be reduced by including a shroud or fan cover that is accurately lined. Centrifugal compressor noise reduction can be achieved by blade design and the use of compressor pulsation noise reduction, silencers, and vibration isolation. 

The efficiency of the Rankine cycle itself can be increased by higher motive steam pressures and superheat temperatures, and lower surface condenser pressures in addition to rotating equipment selection. These parameters are generally optimized on the basis of materials of constmction as well as equipment sizes. Typical high pressure steam system conditions are in excess of 10,350 kPa (1500 psi) and 510 °C. 

Spinning-cup atomisers are used ia some plants to provide finer atomisation, allowiag smaller burner chambers and easier turndown, but with the burden of added rotating equipment. Rotary kiln burners were once popular to bum lower quaHty sulfur, but few are stiU ia operation. Spray burners can be operated intermittently and used at higher rates than rotary burners. 

Applications Two principal applications are rotating equipment oil coolers and compressor inter- and after-coolers. Although seemingly different applications, both rely on the shellside finning to enhance the heat transfer of low heat-transfer characteristic fluids. 

As a general nile, the direct-heat units are the simplest and most economical in construction and are emploved when direct contact between the solids and flue gases or air can be tolerated. Because the total heat load must be introduced or removed in the gas stream, large gas volumes and high gas velocities are usually required. The latter will be rarely less than 0.5 m/s in an economical design. Therefore, employment of direct rotating equipment with solids containing extremely fine particles is likely to result in excessive entrainment losses in the exit-gas stream. 

Auxiliary Equipment On direct-heat rotating equipment, a combustion chamber is required for high temperatures and finned steam coils are used for low temperatures. If contamination of the produc t with combustion gases is undesirable on direct-heat units, indirect gas- or oil-fired air heaters may be employed to achieve temperatures in excess of available steam. 

Rotating equipment, except brick-hned vessels, operated above ambient temperatures is usually insulated to reduce heat losses. Exceptions are direct-heat units of bare metal construction operating at high temperatures, on which heat losses from the shell are neces-saiy to prevent overheating of the metal. Insulation is particularly necessary on cocurrent direct-heat units. It is not unusual for product cooling or condensation on the shell to occur in the last 10 to 50 percent of the cylinder length if it is not well insulated. 

For best operation, the feed rate to rotating equipment should be closely controlled and uniform in quantity ana quality. Because sohds temperatures are difficult to measure and changes slowly detected, most rotating-equipment operations are controlled by indirect means. Inlet and exit gas temperatures are measured and controlled on direct-heat units such as direct dryers and kilns, steam temperature and pressure and exit-gas temperature and humidity are controlled on steam-tube units, and direct shell temperature measurements are taken on indirect calciners. Product temperature measurements are taken for secondaiy control purposes only in most instances. 

In applying power recovery, three basic problems are (1) hmitations in designing equipment to recover the power, (2) operating reluctance to consider rotating equipment that is not absolutely necessaiy, and (3) the way in which the economics of the installed system is evaluated. It is important to recognize that there has always been an opera-... 

Since centrifuges are subject to the hazards inherent in all rotating equipment, the designer should first consider whether other, safer methods of separation (such as decanters or static filters) can be used. If it is determined that a... 

Vibration is both a cause of problems and an effect of equipment problems. The potential destructive force of an out-of-balance load has led to setting lower shutdown limits on the magnitude of vibration than other rotating equipment. Flexible connections for process and utility lines become a must so these vibration problems are not transmitted to connected equipment. Flexible hoses with liners having concentric convolutions (bellows type) avoid the sharp points inherent with spiral metallic liners. By avoiding the sharp point the liner is less likely to cut the exterior covering. 

Use a Fast Data Logger for critical pieces of equipment that can change states quickly, e.g., major rotating equipment where the usual one-minute data storage interval is not adequate in case of trips... 

IRI 1991a. Vibration in Rotating Equipment. IRInformation Manual 6.0.8.1.0. Industrial Risk Insurers, Hartford, CT. 

As discussed in Chapter 2, The Toller Selection Process, evaluating the site s safe work practice procedures should have been a part of the review during the toller selection process. Still, new materials may indicate a need to revise or develop special procedures to address unique chemical and physical hazards. New hazards such as vacuum, ciyogenics, ultra-high pressure, or new rotating equipment could be introduced. Medical monitoring requirements or special handling and spill response procedures for the toll s raw materials and products may indicate a need to write or revise safe work practices. 

The Guidelines for Process Equipment Reliability Data with Data Tables covers a variety of components used in the chemical process industry, including electrical equipment, analyzers, instrumentation and controls, detectors, heat exchangers, piping systems, rotating equipment (pump, compressor, and fan), valves, and fire protection systems. 

The next graph (Figure 10-1) indicates the expected eontinuous running time of rotating equipment with inereasing misalignment. As you soon. see, the alignment improves and so does the service time. 

Since the first application of turbocompressors (Figure 4-1) in large-scale production of nitric acid as a raw material for fertilizers, explosives, plastics, and a variety of other chemical products, the requirements on processes as well as on rotating equipment have become increasingly demanding. Environmental as well as economic considerations have heavily influenced the development of such plants. 

Power applied to a rotating equipment train shaft must be balaneed by the power absorbed on that shaft to maintain a eonstant speed. However, these parameters are not truly dimensionless. Beeause the geometry of the expander is fixed, dimensions of length ean be eliminated by a eonstant eharaeteristie lengtli. Constants ean be dropped and ignored for eontrol purposes. The equation deseribing this is ... 

The present trend in rotating equipment is toward inereasing design speeds, whieh inereases operational problems from vibration lienee the importanee of vibration analysis. A thorough appreeiation of vibration analysis will aid in the diagnoses of rotor dynamies problems. 

A total analysis of high-speed rotating equipment requires a eomplex blend of performanee and vibration data. The trend toward total analysis is growing with the problems of an energy shortage and the need for maximum plant utilization. Performanee analysis is essential in the effieient utilization of turbomaehinery and, when eoupled with vibration analysis, is an unbeatable tool as a total diagnostie system. 

Stroh C.G., MacKenzie J.R., Rebstock, and Jordan, Options for Low Speed and Operating Speed Balancing of Rotating Equipment, Proceedings of the 25th Turbomachinery Symposium, Texas A M University, p. 253, 1996. 

Brown, Royce N., Selection and Specification of Process Compressors, in ASME 36th Petroleum Division Conference Publication, Enhanced Recovery and Rotating Equipment—A Workbook for Petroleum Engineers, New York American Society of Mechanical Engineers, 1980, pp. 57-64,... 

System designers often think dampers bloek airflow and are suitable to prevent baek drafts in idle towers. This is not the ease. Airfoil dampers simply hamper fan housing efficiency- they do not block airflow. Air Inlet Screens are always part of blow through, counterflow towers to protect people from rotating equipment. Some designs can be a hazard when accessible from the underside and require the specifier to call out additional screening. They can be a worthwhile accessory when there are nearby trees even when not required for safety reasons. Air inlet screens should be eliminated on towers utilizing inlet ductwork. Inlet ductwork may also make it necessary to block extraneous air entry such as from the underside when towers are elevated. 

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