Principles of Compression Analysis

Pressure-Volume Analysis

The purpose of this analysis is to:
• Detect mechanical problems before they become serious enough to cause significant damage to the machine,
• Evaluate compressor/engine performance in conjunction with P-T (Pressure-Time) and vibration analysis, and
• Automatically compute indicated horsepower, volumetric efficiency, compressor horsepower loading, and power loss.

Compressor Cylinders
Figure 800-1 is a simplified summary of a typical Pressure-Volume display and how it correlates to piston/valve actions. It gives the basic pattern and events relative to piston travel.

Typical Pressure Volume Display

Figure 800-2 represents one format to display the compression cycle. Note that it is similar to Figure 800-1, except for being reversed. Figure 800-2 also shows typical problems that can be detected (with interpretation).

Typical Compressor Cylinder Problems Identified with P-V Displays

Typical Compressor Cylinder Problems Identified with P-V Displays

Typical Compressor Cylinder Problems Identified with P-V Displays

Typical Compressor Cylinder Problems Identified with P-V Displays

Typical Compressor Cylinder Problems Identified with P-V Displays

Figures 800-3 and 800-4 further illustrate methods for detecting impending compressor valve problems.

Detection Patterns for Valve Problems


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