Regarding the safety issues of steam purging during the shutdown of light oil, why isn’t steam purging allowed for gasoline and liquefied gas?
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This post was last edited by 328104062 on 2015-9-1 00:14. Why isn’t it allowed to use steam for purging? Is static electricity being generated? (As a supplementary note: there is sufficient expansion space for that pipeline inside the device, so there’s no need to worry at all.) Then why are gas pipelines always purged with steam?
In our factory, light oil is first pushed out with water, and then purged with steam!
Liquefied gas also requires pressurization with water first, followed by purging with steam!
Liquefied gas and gasoline will vaporize when exposed to hot steam, causing the pressure to increase significantly. Effects: First, overpressure; second, if the pressure exceeds the steam pressure, backflow will occur. Gas is itself a gas, so there is no issue of vaporization.
It shouldn’t be a sealed system with steam applied, there should be a pressure release outlet
Light oils are volatile. When steam is used for line cleaning, the oil vaporizes in large quantities, forming explosive gases. Flowing at high speed driven by steam can easily generate static sparks, so using steam for cleaning poses a risk of explosion. If hot work is required on the pipeline, it is necessary to first use water to drive away most of the oil, followed by steam cleaning; hot work can only be carried out after the tests show satisfactory results. As there is no gasification phenomenon with gas, it is of course safer to purge with nitrogen first and then with steam. For crude oil, hot water can also be used to displace the oil, followed by steam purging. As for lubricating oil, it can be purged with relatively inexpensive compressed air; of course, steam purging is also required for hot work.
Regarding light oil purging, I agree with the view expressed above; as for other types of oil, it’s necessary to learn more about them
I usually drain all the oil, purge it with nitrogen once, and then introduce steam
Light oil is always pushed forward with water; using steam leads to intense vaporization, which not only causes backflow but also means that the installation simply cannot handle the volume of expansion resulting from the vaporization of light oil throughout the pipeline. For a medium like that in a dry gas system, it can be directly purged using steam.
There can be a situation where the vaporization rate is faster than the emission rate.
For the dry gas system as well, it is necessary to relieve pressure first before purging; it’s not possible to use steam at 1.0 MPa (usually around 0.8 MPa) to treat dry gas at 0.6 MPa, as there is also a process of condensation and temperature increase involved. This method can indeed dry the dry gas to the level required by the steam system, since the steam may be used in applications where lower pressures are sufficient.