Client Background
One of our clients, who operates a furnace, wanted to know if Limiting Oxygen Concentration (LOC) at high temperature would impact their safety case.
Client Problem
The main basis of safety for the operation was to reduce the atmospheric oxygen concentration to that below the limiting oxygen concentration (LOC) of each fuel being used to fuel the furnace. This was to avoid the injected fuel from igniting and producing an explosion. The process had many leaks and therefore not gas tight, meaning that control of the O2 levels by nitrogen blanketing was difficult, especially to the levels required to ensure safety.
Client Objectives
The question was asked by the client “how does temperature influence LOC?”. Since the fuel was being injected into the furnace at 150 °C, they wanted to know if these elevated temperature conditions would increase or decrease a materials LOC. If the elevated temperature conditions reduced a materials LOC, then it would mean that there was a high potential they would not be able to achieve the “new” reduced LOC conditions.
Insights and results
Testing Overview
Under normal testing conditions, the 20-litre sphere apparatus uses a cooling jacket, with circulating, chilled water regulate and cool the explosion vessel to ambient conditions after each test explosion has occurred, ready for the next test. The “cooling” jacket was adapted to be a heating jacket and used to regulate both the explosion vessel and dispersion cup to an elevated temperature, mimicking the client’s injection furnace.
Sigma-HSE found that
After modifying the equipment and carrying out the tests, we were able to confirm the client's safety case, proving that the LOC for a range of fuel was identical at high temperatures and that their current oxygen detection system and alarms around their inertion systems, would be sufficient.
