Steam Return HPR MPR LPR Condensate Piping

Recently I was looking at mechanical drawings and saw steam piping labeled HPS and HPR which stand for "High Pressure Steam" and "High Pressure Return" and I asked myself why would you want to return high pressure steam?

The answer is that you are not trying to return high pressure steam. You are returning the condensate from steam traps that are connected to high pressure steam supplies. HPR piping is condensate piping. However, this piping must be designed considering the possibility and probability that steam will be in the piping along with the condensate. Think "flash steam" and "live steam". Although only a small possibility that you do not want, if a steam trap fails, the steam in the condensate pipe could have as much pressure as the high pressure steam supply.

All the acronyms:
HPS High Pressure Steam
HPR High Pressure Return
MPS Medium Pressure Steam
MPR Medium Pressure Return
LPS Low Pressure Steam
LPR Low Pressure Return

C Condensate (This is not the preferred way to identify a steam condensate pipe.)
PC Pumped Condensate, this is condensate that has usually been collected in a condensate return tank at atmospheric pressure and then pumped back to the boiler plant. PC usually remains all liquid water and does not have the same level of safety hazard as "steam return" condensate piping.

OK that's the end of my story of not understanding the meaning of steam return. For more related info, here's a link. .