【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