Main Steam Line Plug (MSLP)


Preferred Engineering’s Main Steam Line Plugs (MSLP) have been in use since the mid 1990’s. Trusted by over 12 sites to isolate their steam lines during refueling outages and facilitate MSIV maintenance and testing. Designed for easy and efficient installation our MSL Plugs cut Critical Path time significantly and reduce dose. 


  • Passive design requires no input energy to maintain a firm seal once installed.  

  • Dual seal offer redundant isolation. 

  • Polished Stainless Steel construction promotes effective decontamination. 

  • Visual verification aids offer positive feedback to operators of proper installation. 

  • Built in adjustability allows for Plugs to accommodate variations in nozzle geometry.