The thing to understand about pressure washing is that you can control the aggressiveness of the washing by keeping the nozzle further from the work. In other words, the further you hold the nozzle from the surface being cleaned, the less impact (and cleaning power) you are using. If you have a very high pressure machine, you should keep it further from the work, but can cover more area (with a fan spray nozzle) while having the same cleaning power as a lower pressure machine used up close.
I have had good luck using a 3000 psi machine on equipment as long as I avoid getting up close an personal around electrical components and places where shafts extend out of housings. Use discretion in wielding the cleaning wand and you will be fine.