What are the criteria for selecting the purging medium for pipelines? !

Inert gases such as nitrogen or steam are generally used for purging; they do not react with the medium inside the pipelines and meet the requirements for working on such systems

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The original poster was asking about the purging medium used after the installation is shut down, and the answer provided on the third floor referred to the purging done at the initial startup of a new installation. After filling with water, gasoline and liquefied gas should be purged with steam for 48 hours or more ；

What I’m asking is how to purge the device when it is shut down for inspection! ? I also searched on the forum, and most of it is related to purging and pressure testing!

A few days ago, an explosion occurred in our factory due to using wind for cleaning – are there any clear standards or regulations in place?

If the original poster does not specify the medium in question, it will be difficult for us to provide you with an accurate and detailed answer. Different devices, pipelines, media, and maintenance methods all determine the appropriate purging medium as well as the relevant standards to be followed. These standards are the result of hard work and experience. Since an incident has occurred, there must already be relevant standards in place. First of all, you need to describe things more clearly

Gas line, light oil line, heavy oil line..... What is the standard used (flash point? ! ) Classification, as well as the selection of purging method!

Generally, water flushing, inert gas or steam purging can be used. In general, it is strictly prohibited to use compressed air for purging flammable and explosive gas-liquid pipelines, as this can result in the formation of explosive gases (mixtures within their explosive range), which will explode upon contact with fire. After purging, it is advisable to use a combustible gas concentration detector for measurement if possible.

I quite agree with what was said on floor 7. If the prerequisites are unclear, it is impossible to provide appropriate advice. First, it is necessary to clarify the purpose of purging. Shutting down the plant for purging is not necessarily its only purpose (some factories may simply shut down due to market reasons and wait before restarting operations); another possible purpose is equipment inspection and maintenance. Different maintenance tasks require varying standards for purging, and these tasks may involve risks such as hot work or work in confined spaces. Secondly, the purge medium must be selected based on the process system, the properties of the materials within the system, as well as the material and characteristics of the equipment; it is possible to use a single purge medium, or multiple purge media may be employed. Third, for the task list, a corresponding preliminary purging plan (or scheme) should be developed. Previous solutions and the corresponding standards can be referred to. ), it is also possible that the second and third steps are combined into one step. Fourth, it is necessary to conduct a corresponding risk assessment, during which relevant risk factors will likely be taken into consideration. For example, the hazards of the purging medium, the risk of asphyxiation associated with the use of N2 gas, and the effects of pressure ； The use of steam can cause water hammer to damage equipment, excessive equipment temperature can lead to damage, negative pressure effects may occur after cooling, and personnel can suffer burns ； The effects of air pressure are taken into account, such as the risk of explosion resulting from its use as an oxidizing agent, and so on. Fifth, further refine the purging plan based on the risk assessment results, propose corresponding risk control measures, and finalize it.