The following speed margins are defined by API:
• Rated (Design) Speed: 100%
• Maximum Continuous Speed: 105% of Rated Speed
• Trip Speed: 110% of Maximum Continuous
• Overspeed: 115% of Maximum Continuous
Figure 200-28 identifies the impeller stresses at various rotational speeds. Reduced yield strengths required for corrosive gas will correspondingly reduce maximum head per stage through reduction in speed.
