Compressor drives

Bectric motor From a layout standpoint, elearic motors require the least amount of information to 

EXHIBIT 4 14 Single Stage or Multistage Horizontal Split-Case Compressor 

Gas turbine Seleaion of gas turbines, like any other drive system, is based on economics. The availability of gas in such remote areas as deserts and offshore platforms makes it a prime source of power in these locations. Gas turbines are used in various applications, including gas transmission, gas lift, liquid pumping, gas reinjection, and process compressors. Air is compressed in the gas turbine by the centrifugal compressor and is discharged into a reverse flow annular combuster in which fuel is injected through nozzles. The transition dua directs tfie hot gas into a gas gener- 

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Synchronous and induction motors cannot always be compared on an equal speed basis. In geared applications such as high-speed centrifugal compressor drives (above 3,600 rpm), the most economical induction moior speed is usually 1,800 rpm. The most economical synchronous motor speed for the same application might be 900 or 1,200 rpm, depend-... 

For 3,600-rpm compressor drives below 5,000 hp, simplicity of installation almost dictates using the two-pole induction motor. No gear e. required, and the overall electrical and mechanical installation is the simplest possible. 

In NEMA size ranges, motors with service factors are still available however, for compressor drives, it would be better if they were iiul Experience with operation into the service factor rating has not been sat isfactoiy. 

A relatively new innovation for use in electric motor compressor drives is the variable frequency power source. Fundamentally, the power source converts an existing three-phase source into DC then uses an inverter to convert back to a variable frequency supply. Thyristors or transistors are used to switch the output at the required frequency. 

It has been said that since the publication of API 613, Second Edition, the reliability of gears used in compressor drives has moved up several orders. This edition of API 613 mandated a conservative rating formula that was widely adopted in North America and to a more limited extent... 

Horsepower is the work done in a cylinder on the gas by the piston connected to the driver during the complete compression cycle. The theoretical horsepower is that required to isen-tropically (adiabatically) compress a gas through a specified pressure range. The indicated horsepower is the actual work of compression developed in the compressor cylinder(s) as determined from an indicator card. Brake horsepower (bhp) is the actual horsepower input at the crankshaft of the compressor drive. It does not include the losses in the driver itself, but is rather the actual net horsepower that the driver must deliver to the compressor crankshaft. 

A beat can occur as the sum or difference of two frequencies. The sum or difference of any resonant frequency and a compressor driving frequency must be equal to some low value, possibly only V2 cycle per sec or less. Therefore, only two frequencies or possible harmonics of these frequencies, which vary by a value of less than 2 cycles per sec, will be harmful as far as vibration is concerned for many, not all cases. It is important that risers be given close attention in... 

If compressor drive, give NEMA application number. 

Figure 14-14. Selection chart for centrifugal compressor drive. (Used by permission E-M Synchronizer, 200-SYN-52, 1958. Dresser-Rand Company.)...

Compressed air for the combustion is supplied by a centrifugal compressor drive by the power turbine. The extra power is available for mechanical drive or other equipment or for power generation, see Figures 14-37A-D. ... 

Woodward, G. C., and T. O. Kuivinen, High Efficiency Engine As a Compressor Drive, presented at AIChE. meeting, Lake Placid, NY, Sept. 26, (1955). 

The total compressor power input is the net power delivered to the compressor drive shaft by the prime mover system. This is... 

An important factor in obtaining an economical plant is the selection of an appropriate compressor drive. The most common power units are ... 

Choice of compressor drive (basis 1 kg water evaporated)... 

Smaller rotary positive displacement compressors are controlled with external bypass. Such equipment usually has a built-in relief valve that opens at a pressure short of damaging the equipment, but the external bypass still is necessary for smooth control. Large units may be equipped with turbine or gas engine drives which are speed adjustable. Variable speed gear boxes or belt drives are not satisfactory. Variable speed dc motors also are not useful as compressor drives. Magnetic clutches and hydraulic couplings are used. 

The three main compressor types are rotary, reciprocating, and centrifugal. The compressor drives can be constant or variable speed, and can be driven by electric motors, steam turbines, gas turbines, gasoline, or diesel engine drives. For a particular application, the type of compressor is selected by considering the required capacity and discharge pressure. 

COi Compressor Drive E = electric motor, ST = steam turbine e Air is needed to provide oxygen for passivation of stainless steel equipment. 

Figure 6.2 Pressurized motor, located in zone 1, as a gas compressor drive on SLEIPNER.

Figure 6.28 Active magnetic bearing for high speed compressor drives. The rotor shaft is positioned in both the vertical and horizontal axes by actively controlled magnetic fields, generated by four levitation coils.

Figure 6.29 Active magnetic bearing for a 23 OOOkW6300min 1 natural gas compressor drive. Mechanical backup bearings catch the rotor and brake it to standstill in case of active control malfunction.

Figure 6.31 Pressurized motor as a compressor drive in zone 1.

As an example for a large gas compressor drive unit, Fig. 6.60 shows a 3.2 MW synchronous motor, whose stator-rotor part and exciter set are... 

Includes steam for C02 compressor drive and steam for desorbtion/hydrolyzes section. 

Most chemical-plant-size compressors are electrically driven [43]. Moore [25] discusses the characteristics of squirrel-cage induction and synchronous electrical motors. Wound rotor induction motors have not been used for compressor drives. For 370 to 4500 kW (500 to 6,000 hp), the induction motors are the first choice. The squirrel-cage induction motor is the most coimnonly used driver in the process industries from 1/8 to 1,5000 hp (0.0932 to 1,120 kW [25]. From 15,000 hp (149 to 11,200 kw) the synchronous motor could be used [25]. If the compressor is operated at 7,500, 11,000, and 23,000 rad/s (1,200, 1,800 and 3,600 rpm), no step-up gears are required. The least costly speed for an induction motor is 1,000 rad/s (1800 rpm) so that this speed is usually selected. Step-up gears are used to obtain higher speeds. 

Compressor drives. Compressors and blowers in fluid cracking units may be either steam or electrically driven (209). Steam turbines were preferred over electric-motor drives in the design of early units, partly because of fear of a power failure. However, under some circumstances, the economics favor the use of electric motors. Several units have been built with electrically driven main air blowers, and at least one refiner has selected electric motors for the air blower, gas compressor,... 

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