Compressor shelter내의 HC 누출로 인한 화재/폭발 예방 방안 (1): Hierarchy of Controls

Compressor shelter와 같은 building 내부에 설치된 설비로 부터 HC 이 누출된다면 이는 화재,폭발로 이어질 수 있다. 이를 위해 누출된 HC이 최대한 희석되어 LEL 이하로 유지되도록 혹은 누출된 HC을 최대한 빨리 감지하여 비상조치를 수행할 수 있어야 한다. H2 compressor shelter의 ventilation 측면에서 shelter design시 고려할 사항과 H2 누출을 감지하기 위한 detector의 위치를 선정하는 내용을 위주로 가이드를 제안하겠다. 

 

Hazard and Risk 

HC (H2 포함) 누출 및 축적 으로 인한 화재/폭발 

 

Compressor shelter와 같이 빌딩내 Gas leak 시, 사고 예방을 위한 방안은 아래와 같으며, 본 posting에서는 Passive와 active 방안을 중점적으로 다루고자 한다.  

• ISD
  • HC inventory 최소화, 운전 온도/압력 최소화, flange/valve와 같은 leak source 최소화 등. 
  • Natural ventilation 효과를 통해 HC이 축적되지 않도록 외부 설치 (outdoor) 
• Passive: Building design- Passive ventilation 
• Active:
  • Listen and watch for alarms: leak detection (Gas detector placement) 
  • Active ventilation 및 system shutdown/isolation 등.
• Procedure 
  • Listen for the sound of high-pressure gas escaping
  • Use portable hydrogen detectors
  • Check for small leaks by applying a soap bubble solution on the surface of areas where leaks are suspected

Inherently Safer Design

Avoid using hazardous materials when possible

• Minimize the quantity of hazardous materials
• Control the operating conditions (temperature, pressure, concentration, etc.) to reduce hazards
• Design facilities and equipment using:
  • inherent safety features and
  • fail safe designs
• Choose safer locations and consider:
  • outdoor installation: Natural ventilation. HC 축적 최소화 
  • access control : 인명피해 최소화 
  • safety barriers: 다단계의 안전장치 
  • remote operation (separation distance): Escalation 예방, 인명피해 최소화 

Passive Ventilation  

Indoor - building design for ventilation 

Proper ventilation can reduce the likelihood of a flammable hydrogen-air mixture from forming in an enclosed area.

 

Active Ventilation 

If sufficient passive ventilation is not sufficient, active (mechanical, forced) ventilation can be used to prevent the accumulation of flammable mixtures. Active ventilation can be used to ensure sufficient air flow is maintained to keep the concentration of hydrogen below that which will burn in air. 

 

Leak/Gas/Flame Detection System

Instrumented leak detection techniques include:

• Hydrogen (or flammable gas) detectors installed where leaking hydrogen is likely to concentrate
• Monitoring piping pressures or flow rates changes
• Locating hydrogen piping within another pipe (double containment) and monitoring the annulus for leaks

Procedure 

• Listen for the sound of high-pressure gas escaping 
• Use portable hydrogen detectors 
• Check for small leaks by applying a soap bubble solution on the surface of areas where leaks are suspected 정기적으로 검사 

References

[1] H2tools.org - ventilation, leak detection 

[2] OSHA standards CFR 1910.103