Equipment sizing compressors

Prepare/supervise preparation of piping or mechanical flow diagram (or P and ID), with necessary preliminary sizing of all pipe lines, distillation equipment, pumps, compressors, etc., and representation of all instrumentation for detailing by instrument engineers. 

When selecting and sizing compressors, care should be taken in determining which standard has been used to rate a compressor under consideration, particularly if the compressor has been produced abroad. All further discussions in this section will utilize only the API Mechanical Equipment Standards standard atmosphere. 

It can be easily seen that the equipment size, pressure drop, and hence cost have a direct bearing upon the air compressor power. It is important to obtain the correct optimization between equipment costs and power consumption. The values used in the example are for illustration purposes. An actual plant design would vary based upon the cost vs. power analysis. This is covered in more detail in Section 3.2.3. 

For pipe sizing, process equipment sizes are required. These include types and sizes of vessels, heat exchangers, pumps, compressors, intercoolers, scrubbers, silencers, floor space of lube and seal-oil console, furnace and heater details, control and switch house arrangements. 

Mapping Results. After Aspen IPE has mapped and sized the equipment items, it is prudent to check the results, especially for major equipment items such as towers, compressors, and chemical reactors. These items are usually very expensive, and consequently, it is a good practice to estimate equipment sizes independently for comparison with the Aspen IPE results. To view the Aspen IPE results for an equipment item, double click on the item on the IPE Workbook window or on its icon in the Process Flow Diagram. For example, the following component specification form, which contains some of the sizing results, is obtained for the depropanizer tower. 

Careful analysis of life cycle costs and equipment size is important. Little can be done to correct an error in compressor sizing without incurring significant expense. 

Another solution is to dilute the S5mgas by recycling product gas, thus reducing the temperature increase to what can be handled by a methanation catalyst [219] [423]. The higher the temperature increase, the lower the recycle ratio and sizes of equipment and compressor. 

The prototype power conversion equipment, particularly the rotating components, will undergo shop acceptance tests to the fullest extent possible. These are followed by field tests of the partially to fully integrated power conversion system to verify the turbo-machinery aerodynamics and the system hot functions. To limit power input for cost saving, the field tests are planned at partial system pressures and partial to full tuifiine inlet temperatures, using either conventional or nuclear heaters. For example, the FSNL (i.e. full speed, no load) test, which has the main objective of validating the full-size compressor aerodynamics and efficiency, may be carried out at selected partial or rated conditions as indicated on the compressor performance map (Fig. XVI-5). 

Motor-driven reciprocating compressors above about 75 kW (100 hp) in size are usually equipped with a step control. This is in reality a variation of constant-speed control in which unloading is accomplished in a series of steps, varying from full load down to no load. Three-step eontrol (full load, one-half load, and no load) is usually accomplished with inlet-valve unloaders. Five-step eontrol (fuU load, three-fourths load, one-half load, one-fourth load, and no load) is accomphshed by means of clearance pockets (see Fig. 10-91). On some machines, inlet-valve and clearance-control unloading are used in combination. 

The preceding chapters offered some general guidance on the sizing of the various types of compressors. Before the start of the specification, the equipment should be sized, at least in a preliminary manner. Actually, part of this may be integrated into the process calculation. However, after the process calculations are complete, a review of the equipment best suited to perform the task at hand should be made. 

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