Can someone explain to a dumby the difference between intermittent and continuous horsepower and any way of calculating it?The reason is that I'm looking to repowering my forestry mulcher with a Cummins 6bt engine but the six I've found differ greatly in power from 158-230hp. Surely Cummins didn't make so many variations Cheers Tony
These definitions are as relates to a generator set but they should serve you as well. Continuous rating is what the engine will do on 24/7 basis. Intermittent (or Standby) rating is what it will do for 30 minutes maximum before it should be shut down. Usually used for emegergency generators that are only required to operate when the mains power fails. For example we had some generator sets that were rated 2.5MW Standby but only 2MW Continuous.
Why not? Nige explained it perfectly. A less technical way to think about it is the difference between a 2 liter car engine rated at 160HP and a 6 liter diesel rated the same HP, which makes more power, for how long? Or compare it to another rating, like the tractor pull rating on that Cummins, 1,200HP for 30 seconds
Actually I made a mistake in Post #2 above. After operating for 30 minutes at the Standby rating the engine does not have to be shut off, just backed off to its Continuous power rating. So as per my genset example above the set could produce 2.5MW for 30 minutes at which point it would have to be backed off to 2MW if it was required to run for longer than the 30 minutes. There is a thread somewhere about Cat 3208 Marine engines and while researching information for it we found that there were ratings available from 210BHP to 450BHP for what is effectively the same engine.
Cummins will make whatever any manufacturer asks for, so yes there are dozens of power ratings with different torque curves, HP ratings and governed RPM's...