2022/05/17

【數據中心設計】CDCP 學習筆記 - 數據中心 (Part 10) - Data Centre Design - Water Supply & Fire Protection

Water supply in a Data Centre

  • Fire suppression
  • Sanitary facilities
  • Makeup water for cooling
  • Cleaning
  • General facilities maintenance (gardens etc.)


Backup water supply: Water storage tanks

  • for the fire suppression installation
  • for makeup water for cooling towers
  • for chilled water backup (buffer storage)
  • for off-peak chilled water storage (thermal storage)


Backup water supply: Well water / Retention pond

Well water

  • Cleanliness
  • Supply capability
  • Drilling could be very expensive

Retention pond

  • Fixed quantity
  • Large area required
  • Water temperature varies
  • Water quality checks on a regular basis


Fire protection and safety

  • originate from electrical sources
    • Equipment (overheating, zinc whiskers or dead shorts)
    • Electrical distribution (wiring, loose connections, sparks)
    • Light fixtures
  • Bad connections, overloading and dust are contributing factors
  • During various data centre audits it is proven that a high percentage of data centres have (potential) issues with fire protection


Requirements for Data Centre fire suppression

  • Detect as early as possible
  • Safe for humans (as much as possible)
  • Environmentally friendly
  • Effective for fires in the data centre and supporting facilities
  • Do not, or minimize, damage to sensitive equipment
  • Comply with national and building code


Standards

  • NFPA 75 / NFPA 72
  • NFPA 2001 / ISO 14520
  • Local codes


Detection systems

  • VESDA (Very Early Smoke Detection Apparatus)
  • HSSD (Highly Sensitive Smoke Detection)
    • Works via air sampling
    • 1000 times more sensitive than standard smoke detectors
    • Care must be taken, especially during building works such as hacking, drilling, etc.


Smoke detectors for fire panels
  • Ionization detectors(較Photoelectric detector更靈敏)
    • Uses low radiation (harmless) material (americium-241)
    • When smoke enters the detector the ions create an electrical path setting alarm condition
  • Photoelectric detector
    • Uses a light source (i.e. LED etc.) and photocell
    • When smoke enters, deflection of light will activate photocell triggering an alarm
  • Sprinklers act as detection and activation
    • Slow, typically activates at 70 degrees or higher
    • accidental damage will result in immediate water problems
  • Concealed sprinkler systems
    • More attractive finish / Less risk of damage
    • The cover plate drops off at 57 Celsius and the deflector drops down
    • Sprinkler head activates at 70 Celsius or higher

Fire suppression system

Wet / Dry sprinkler system 考慮因素

  • Preferred to have dry pipe principle (pre-action)
  • Not harmful to humans
  • Environmentally friendly
  • Effective
  • Leaves water damage —— Drainage piping
  • Slow response
  • Widely used in data centres as a secondary system
  • Compulsory under most building codes for high-rise buildings


Fire suppression systems: 

  • Halon 1301 —— banned in most countries, depletes the ozone layer
  • Carbon Dioxide —— lowest-priced, not allowed in most countries in occupied areas
  • FM200 —— widely used in data centres, harmful gas will develop when FM200 is burned
  • Novec —— cost-effective, clear gas, environmentally safe, cylinders need to be close to the hazard area, containers can be refilled on site
  • Inergen —— more appropriate for the larger computer rooms, 10 times more space compared to FM200
  • Argonite —— reduces oxygen levels down to approx. 12.5%, loud noise generated
  • FE13 —— allows high nozzles (up to 8 metres, other 4 metres)
  • Pyrogen —— 氣溶膠滅火劑, no piping and no pressure cylinders required


Best practices for main fire suppression

  • Install VESDA/HSSD type of system
  • Use any of the gas-based systems as the primary fire suppression system
  • Use a pre-action sprinkler as a secondary system
  • Ensure that the room is properly sealed
  • Ensure that gas content is enough to achieve concentration levels required
  • Create extraction vents
  • Proper maintenance

理想情況下,火災當然需要被盡可能快地探測到,因此快速的反應系統,如VEDSA是最合適的。氣體滅火系統作為主要系統,對數據中心的設備幾乎沒有傷害。如果法例要求,水系統可以作為後備系統來配置。

房間需要被密封,一旦滅火氣體被釋放,氣體可以被控制在房間內。需要留意的是,滅火氣體亦有可能會從電纜盤的孔中洩漏。滅火氣體的量需要仔細計算,滅火的氣體量需要一個濃度的要求,氣體量不能過少也不能太多。

另外,需要配備抽風系統,以便在排除氣體後能夠將氣體抽出房間。


Handheld extinguishers —— Class C (for Data centres)

  • Fires involving energized electrical equipment such as appliances of all kinds, motors, computers etc.
  • Extinguishers contain carbon dioxide, Halon, dry chemical or liquid extinguishing agent
  • Note: The indicator of classes can vary per country, class C can be indicated by class E


Signage and safety

  • Exit / Emergency signs to be located at: (可以跟BS 5266設計)
    • Every escape door
    • In pathways leading to doors (arrows)
    • Must be visible from all areas in the hazard area
  • Evacuate area immediately
  • Alarm bell
  • Strobe light
  • Gas release abort - (Telephone / Intercom)
  • Gas manual release


Regulatory requirements / Best practice

  • EPO (Emergency Power Off)(防止火勢擴散)
  • Auto unlock doors - Doors should use the swing-out principle (code permitted)
  • Escape routes should be clear and within the distance required by law
  • (Automatic) the shutdown of air conditioners - Country dependent, check regulation
  • Integration with existing building fire panel
  • Gas manual release and gas abort buttons
  • Fulfil local fire-codes


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