Planning

One thing that will become quickly evident, as aptly stated by Matthews [10] is "production plants are not test stands." As one pursues the task of getting an existing compressor ready for a field test, it becomes quite clear as to how true the statement is.

The applicable code procedures should be followed, particularly in regard to instrumentation. On an existing plant, this will require planning in advance of a scheduled shutdown. The pressure and temperature tap locations and installation details can all be developed with the compressor running. All details must be followed. When a drawing states, "deburr, do not chamfer" that is exactly what it means (see Figure 10-7),

Remove burrs on inside of pipe but do not chamfer edge of hole

< Vj" Swage Nipple (1" « V," Swage Nipple at Orifices)

< Vj" Swage Nipple (1" « V," Swage Nipple at Orifices)

Process Line Pipe Wall

^ V." 3000# Coupling ^^ (1" 3000# Coupling at

Orifices)

Process Line Pipe Wall

Figure 10-7. Typical pressure tap detail.

The necessary steps are a lot easier to accomplish if the compressor installation is still on the drawing board. This author's best field tests were run on units where the instrumentation was installed during plant construction. Sometimes, as plants are going through revisions for other reasons, it is possible to add the necessary compressor test equipment.

Part of the planning should include the evaluation of test uncertainty. This evaluation can be limited to a common sense approach based on available instrumentation and the locations relative to the ideal. A more sophisticated study can be made in which instrumentation accuracy and the impact of any inaccuracy on the measured parameters is evaluated. This is a complex task with the need being based on the motivation for the test. If the test is being performed to settle a dispute, a formal understanding of the uncertainty should be developed. Methods for evaluation of test uncertainty are found in ANSI/ASME PTC 19.1 [11].

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