1. Material selection (CF3, CF8, F304, or F304L) for this fluid service is critical and changes should be made with caution.
2. Flanged connections should be minimized and only used when required for component and equipment connections.
3. Threaded connections should only be allowed for instrument connections.
4. The minimum temperature may govern the design of this piping system and require impact testing for certain material and welding procedures.
5. Nitrogen is lethal and any leakage is serious.
One important difference between N2 and air is that N2 can kill people without warning by displacing air, as bimr has noted. I would just list that as the #1 concern. Its density is almost the same as air so there is little tendency to mix without positive ventilation.
It is not uncommon to use brazed systems of heavy gauge Cu tube for inert gas service also.
Though welded stainless tube is most common.
Where we have enclosed spaces with inert gas service we install O2 sensors. Ar is the same story.
Thank you again, actually I also had great information from the N2 suppliers in my area who were glad to share more information and they supply the taks to their clients and all the engineering. Reading the document I found that N2 is heavier than air so in case of leaks it would tend to stay in the room
¨It is to be noted, that the use of inert cryogenic liquids such as nitrogen or helium is accompanied by
two primary hazards:
• The fluids are very cold (-196°C for nitrogen and -269°C for helium) and can cause serious cold
burns on contact with the skin.
• Once vaporised both products will generate a large volume of cold inert gas (e.g. 1 litre of liquid
nitrogen will yield 680 litres gaseous product) that will displace ambient air, causing oxygen
deficiency and may accumulate in low points.¨
So plain ventilation may not be enougth and air extractors may be needed?
The only reason that N would be heavy is because it is cold, it has the same density as air. It doesn't take much ventilation to assure that you have enough oxygen.
Story.
Small single story manufacturing plant that used a lot of Argon (very dense).
Air compressors in the basement.
Came to work on Monday and had not compressed air. Restarted compressors (from upstairs) and they would trip the overloads in just a couple of minutes.
Process Engineer started to walk down into the basement to check the compressors.
Fortunately he was a scuba diver, he realized that he was starting to breath very rapidly and was aware that he wasn't getting any oxygen.
He got back upstairs before he asphyxiated.
And argon regulator failed, filled the basement with Ar. The Ar is so dense that it displaced all of the air, and overloaded the compressors because it takes more power to compress it.
Result was we put in fans for ventilating the basement and added oxygen sensors in the basement with the display upstairs.
End of story.
In the world of liquid gasses N is the easiest and safest to handle. I hate liquid oxygen, it is the most dangerous and my least favorite.
Cold nitrogen is heavier than just like cold air is heavier than (warmer) air. Gaseous N2 is slightly lighter than air at the same temperature because it has a molecular weight of 28 rather than 32 for pure oxygen, which is 20% of air. So you statement is very misleading without the qualifiers.
Good point Composite, in our case with around 30° C average ambient temperature if we had a N2 leak it would be much colder than air so it would be denser than air probably. But in general designs I believe that exhausting N2 is not such a great issue?
