Centrifugal compressors specifications

Motor-driven, multistage reciprocating compressors have reportedly been the most popular choice for aeroderivatives. Motor-driven, oil-fiooded screw compressors are also used in some cases. High horsepower, multistage centrifugal compressors, similar to those used at many pipeline compressor stations, may be required for the newer heavy-duty units if the distribution pipeline pressure is insufficient (see Pipelines). Gas turbines have more stringent fuel-gas specifications in terms of cleanliness than do gas-fired boilers. Thus oil- and water-knockout systems, coalescing filters, and fine-mesh filters are used. 

Centrifugal compressors in general are used for higher-pressure ratios and lower-flow rates compared to lower-stage pressure ratios and higher-flow rates in axial compressors. Figure 6-3 is a map for centrifugal compressors that shows the effect of specific speed (A ) and specific diameter (Z) ) on their... 

One way to decrease your reliability and cause problems is to not men tion fouling potential in centrifugal compressor specifications if proce.s.s experience exists. The experience may exist but not be recognized... 

The centrifugal compressor is well established for the compression of gases and vapors. It has proven its economy and uniqueness in many applications, particularly in which large volumes are handled at medium pressures. This compressor is particularly adaptable to steam turbine or other continuous speed change drives, as the two principles of operation and control are quite compatible. It is also adaptable to the electric motor, gas engine, and gas turbine with each installation being specific to a particular problem or process. Installation as well as operating costs can be quite reasonable. 

Figure 12-461, Part 1. Impeller geometry versus flow coefficient, dimensionless to define the flow-handling capability of a specific impeller (wheel) geometry, < = 0/(tt/4)(DA). (Used by permission Fullemann, J., Technical Report Centrifugal Compressors, 1963. Cooper Energy Services, Cooper-Cameron Corporation. All rights reserved.)...

Centrifugal compressors usually have specific speeds of 1,500-3,000 rpm at the high efficiency point. The axial flow fans and blowers are high specific-speed wheels mixed flow units are lower and the centrifugal compressor wheels are the lowest in specific speed range because they have narrow impellers. 

The mode of operation of a specific application should be the first consideration. The inherent design of each type of compressor defines the acceptable operating envelope or mode of operation that it can perform with reasonable reliability and life cycle costs. For example, a bullgear-type centrifugal compressor is not suitable for load-following applications but will prove exceptional service in constant-load and volume applications. 

Selection of a Centrifugal Compressor A hydrocarbon mixture with molecular weight 44.23 is raised from 41°F and 20.1 psia to lOO.Spsia at the rate of 2400lbmol/hr. Its specific heat ratio is k = 1.135 and its inlet and outlet compressibilities are estimated as zj = 0.97 and Zj = 0.93. A size of compressor will be selected from Table 7.6 and its expected performance will be calculated ... 

Centrifugal compressors can operate at speeds from 9,000 to 50,000 rpm, with single-stage compression ratios from 1.2 to 9, and efficiencies from 30 to 85%, depending upon the specific design and application. 

Row through the compressor section will be adiabatic, so that dq = 0, and the height difference will be negligible, so that dz — 0. Further, the difference between the inlet and outlet velocities is small for both axial and centrifugal compressors so that cdc 0. Accordingly the differential of specific work is given by ... 

Mechanical Specifications. API 617 is a standard and widely used mechanical specification for centrifugal compressors. Since this is a generalized specification, most compressor manufacturers have their own standard set of exceptions. Still, it provides common ground for comparison of different offers and can be recommended as a starting point to engineers specifying part of a chlorine plant. 

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