What is the gas composition in a tank with a SF6 leak?

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  • Thread starter Thread starter Graaf van Vlaanderen
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Discussion Overview

The discussion revolves around the gas composition in a tank containing air and SF6 gas, particularly after a leak in a SF6 gas HV circuit breaker. Participants explore the implications of adding SF6 to a tank already filled with air at atmospheric pressure.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant assumes that after a leak, only air remains in the tank and questions the percentage composition of air and SF6 when SF6 is added to the tank at a specific overpressure.
  • Another participant prompts for clarification on how to calculate the composition based on the provided numbers.
  • A participant proposes a calculation method based on constant temperature and volume, suggesting that the total pressure is the sum of atmospheric pressure and the pressure of SF6, leading to a percentage calculation for SF6.
  • A later reply confirms the calculation method proposed by the previous participant.
  • One participant expresses an expectation that SF6 would pool at the bottom of the tank, introducing a potential complication to the gas distribution assumption.

Areas of Agreement / Disagreement

Participants generally agree on the calculation method for determining the percentage of SF6, but there is disagreement regarding the physical behavior of SF6 in the tank, particularly concerning its pooling behavior.

Contextual Notes

Assumptions regarding the behavior of gases under pressure and the effects of temperature changes are not fully explored. The implications of SF6 pooling at the bottom of the tank introduce uncertainty in the gas distribution model.

Graaf van Vlaanderen
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We discovered a leak in a SF6 gas HV circuit breaker. Since we don't know when the leak occurred due to temperature changes I assume there is only air left in the tank.
Here is my question. Suppose I have a tank with a fixed volume filled with air at the same pressure as the atmospheric pressure. When we add SF6 gas up to 0.2bar over pressure, what would then be the percentage of each gas (air and SF6) in the tank?
 
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You have three numbers; what do you calculate from them?
 
Well, I consider T and V constant, hence ntot = n(air) + n(SF6) => ptot = p(atm) + p(SF6)
Hence %SF6 = (0.2/1.2)*100. Not sure this is correct.
 
You got it.
 
But I'd expect all the SF6 will pool on the bottom of the tank.
 

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