Ventilation in Area with N2 bottle leak
Ventilation in Area with N2 bottle leak
(OP)
Hi,
We are buliding a vessel, with approx 20 200 litres bottles, each containing Nitrogen at 180 barg.
The plan is to have a two speed fan system to purge the area in the event of N2 leakage and a low level O2 alarm, say 19% O2.
My question is; Can I simply calculate the N2 volume added to the air, and then calculate how much air I need to flow through the room to clear/dilute the N2 rich air, or do I need to add some fancy factors for the N2 that are not displaced straight away.
I was looking at the simple way, saying that x volume if Nitrogen added (at atm pressure) will result in:
Air needed = X N2 x 79/21.
Does this make any sense at all ?
cheers
Even
We are buliding a vessel, with approx 20 200 litres bottles, each containing Nitrogen at 180 barg.
The plan is to have a two speed fan system to purge the area in the event of N2 leakage and a low level O2 alarm, say 19% O2.
My question is; Can I simply calculate the N2 volume added to the air, and then calculate how much air I need to flow through the room to clear/dilute the N2 rich air, or do I need to add some fancy factors for the N2 that are not displaced straight away.
I was looking at the simple way, saying that x volume if Nitrogen added (at atm pressure) will result in:
Air needed = X N2 x 79/21.
Does this make any sense at all ?
cheers
Even





RE: Ventilation in Area with N2 bottle leak
I would suggest using the same methods.
RE: Ventilation in Area with N2 bottle leak
It definately is a code issue, so at least provide the minimum cfm/sq.ft. required, and watch where your air flow paths are, via. high and or low inlets and outlets.
Steve
RE: Ventilation in Area with N2 bottle leak
RE: Ventilation in Area with N2 bottle leak
RE: Ventilation in Area with N2 bottle leak
RE: Ventilation in Area with N2 bottle leak
1. Room Size and Ventilation
The Procedure Assessment (COSHH-related) will take into account the location of work and room size. Staff should be made aware of the increased risk of oxygen depletion in a small room. The volume of the room, volume of cryogenic liquid, and room ventilation, should be considered collectively. If the room is mechanically ventilated, a contingency plan should be developed which identifies, in the event of a possible failure of the air handling system, how personnel would be notified.
Cold rooms are poorly ventilated small rooms and must not be used for the storage of liquid nitrogen vessels.
The risk assessment should calculate the oxygen concentration in the room which results from the loss of the entire contents of the liquid vessel in a short period of time (i.e. the worst case scenario). The resulting oxygen concentration is calculated using the following formula:
%O2 = 100 x Vo
Vr
Where for nitrogen,
Vo = 0.21 (Vr – Vg)
Vg = gas release, in litres spilled x 683, divided by 1000 to convert to m3
Vr = room volume in cubic metres.
If oxygen levels could fall below 18%, suitable control measures should be implemented. For example, where practicable, filling or storing vessels in a more suitable, better ventilated room, fitting a permanent oxygen monitor, or the use of smaller storage vessels should be considered.
Note: In all cases, only the minimum volume possible of cryogenic liquid should be handled.
Worked examples of calculations for liquid nitrogen can be found in the BCGA Code of Practice CP30 or obtained from the College Health and Safety Office.
RE: Ventilation in Area with N2 bottle leak
Good luck,
RE: Ventilation in Area with N2 bottle leak