I have written several articles on the topic of when we store our flammable liquids BELOW their flash points with the aid of refrigeration and how that makes our “refrigeration/chiller” a critical utility if we wish to take credit for storing the flammable below its FP. I have also discussed processing a Class IIIB/Cat 4 flammable liquid within 30 degrees of its FP. However, this article is about a “utility process” used for heating a process, and the heat transfer fluid (HTF) is heated above its FP.
This process and analyzing its hazards can be tricky. When we look at the Safety Data Sheets and the Technical Datasheets, these fluids are almost always listed as “Non-Flammable” as their FPs are well over 200F. So at standard temperature and pressure (i.e., 68°F and 14.7 psi), the solution is indeed NOT flammable; however, we will be heating the solution to above its FP. This is a recognized hazard by OSHA, Insurance Providers, and NFPA; which insurance and NFPA 30 provide the user(s) some excellent DESIGN features to help PREVENT a LOPC event and PROTECTION and MITIGATION layers when the LOPC event occurs.
First and foremost, codes and standards manage these hazards by setting a tolerance against operating up to 30 degrees within the solutions FP.