Spontaneous combustion of ferrous sulfide occurred after disassembling the short section of the outlet valve on the liquefied gas cylinder safety valve!
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This post was last edited by Refiner on 2018-6-11 07:51. Does anyone know the reason? Are there any good methods?
It’s definitely because the medium exiting the system contains sulfur. Either the liquefied gas contains sulfur, causing the safety valve to leak due to poor sealing, or the medium from the pressure relief system flows back to the outlet of the safety valve, resulting in the formation of ferrous sulfide. It is recommended to purge the system first before breaking the short circuit; spontaneous combustion is still manageable, but if the pipeline contains flammable materials, it becomes dangerous.
Where is that liquefied gas cylinder of yours? Logically, if ferrous sulfide is present, it should be before the product is refined. Our unit has a liquefied gas buffer tank for gas fractionation
After removing the rust, a blind plate can be installed; filling it with water is also an option
Your design of bypassing the outlet valve of this safety valve likely results in liquid accumulation at a point that is lower along the flare line. The reason for this is that the flare line sometimes discharges gas containing high levels of sulfur, which deposits at the short-circuit point located at the lower part of the safety valve of the liquefied gas tank; sometimes, prolonged cleaning of the flare line or nitrogen purging can lead to corrosion of ferrous sulfide at that short-circuit point. Solution: 1. Change the pipeline by bypassing the valve and moving it to the flare line bus at a lower position. 2. Pass steam through the valve bypass connection; normally, a blind flange is used on the steam line. By passing steam through the line before disassembling the valve bypass, spontaneous combustion of ferrous sulfide can be prevented when the valve section at the outlet of the liquefied gas tank’s safety valve is removed.