NFPA 20, 10.10.12.1 requires an electric VFD fire pump controller to be set to lock out pump shaft critical speeds supplied by the pump OEM on vertical turbines. That probably should have applied to multistage, long shaft horizontals also like the 5 stage Peerless TUT fire pumps. VFDs typically have three to five "skip or jump" speed settings for this.

The pressure limiting controls on diesel engines appear to be an all mechanical (hydraulic, pilot actuated like a main relief valve) positioner fastened to the existing engines governor speed lever controls. There does not appear to be anything mentioned that I found in the literature that says you can do the same with skip speeds. The only way that I know would be an electronic positoner, the standard engine governor cannot be substituted for a electronic one per NFPA 20.

Does anyone know if these engines have the same ability as the VFDs or are people being careful not to put them on vertical pumps? I don't readily see where this is covered anywhere unless I overlooked something.