E2-E3: ELECTRICAL CHAPTER-13 FIRE PROTECTION SYSTEM- EVOLVING TRENDS AND APPLICABILITY TO DATA CENTRE

Transcription

1 E2-E3: ELECTRICAL CHAPTER-13 FIRE PROTECTION SYSTEM- EVOLVING TRENDS AND APPLICABILITY TO DATA CENTRE BSNL, India For Internal Circulation Only Page: 1

2 Fire Protection System- Evolving Trends & Applicability to Data Centers 1.0 Introduction: The objective of this chapter is to understand the evolving trends in fire detection and extinguishing system, and to discuss its possible application in Telecom installations. A telecom installation with high concentrations of cables and electronics switching equipment within relatively small areas constitutes a HIGH RISK installation. 2.0 Objective: At the end of this Chapter, participants will be able to under stand : Evolving Trends in fire Detection System Modern Trends in Fire Extinguishing System Fire fighting for data Centers 3.0 Evolving Trends In Fire Detection System: The modern trend is to provide one of the following automatic fire detection systems for protecting the Telecom installations. - High Sensitivity Smoke Detection System [HSSD] - Linear Heat Detection Cables [LHD] - Analogue Addressable Intelligent System. 3.1 HSSD System Description: High sensitivity smoke detector is a relatively new form of smoke detector. It is an aspirating detection system which comprises of : - Pipe work to collect samples of Air from the protected area. - High sensitivity Detector capable of detecting smoke concentrations as low as 0.01% per meter. - A fan to draw air through the pipe network. - A display and control card to show increased smoke levels in increments from 1-10 and provide the necessary alarm outputs. HSSD system provides smoke detection sensitivities up to 500 times greater than conventional point detectors. Fig. (1) Illustrates the incipient stages of fire and contrast the relative response of detectors. BSNL, India For Internal Circulation Only Page: 2

3 Fig -1 BSNL, India For Internal Circulation Only Page: 3

4 3.1.1 HSSD Principle Of Operation: HSSD is a digital particle counter utilizing advance optics and electronics. A fan through a ducting / pipe system continuously draws air from the high value components. A laser is focused by a lens assembly to provide a high intensity spot of light within the centre of the air stream. This spot is 100 micron in diameter, which provide good light intensity to be scattered by a particle entering at this point. Focused at this point is the light receive optics which transfers the photons of lights scattered by each particle to the receive electronics. The throughput of particles is effectively counted through integration circuitry, which then convert the digital system to an analogue where smoke density is displayed on 1 to 10 segments Bar Graph. The electronic of the system ignores pulses generated from particles over 10 microns, thus, effectively, discriminating against false alarms due to dust or environmental conditions. The system has been used in some Telecom System has FM approval. applications in West. M/S KIDDE UK 3.2 Linear Heat Detection Cables: LHD System Description: Linear heat detection [LHD] cable based system provides economical temperature monitoring thereby fire detection capabilities at the precise point of risk. They are reliable, flexible and have ability to detect abnormal temperature variations of fire before the break out. LHD system is a continuous heat detection cable capable of measuring and reporting adverse changes in temperature at a spot location. Linear Heat detection is - Continuous heat detector in the form of cable. - Analogue [Alarm line] averaging heat detector or rate of rise. - Digital [KIDDE BICC] Point of risk heat detector Fixed temperature LHD Principle Of Operation: Analogue [Alarm Line]: Alarm Line high resistance sensor cable is a 4-core cable. Two cores are used for monitoring and two cores for sensing temperature changes. An increase in temperature reduces the resistance value of the cable. This value is measured by associated electronic interfaced unit, which provides the alarm indication once the predetermined alarm level has been reached. The cable senses the rate of rise of temperature and not the fixed temperature. BSNL, India For Internal Circulation Only Page: 4

5 Digital [KIDDE BICC]: Digital heat sensor cable is a twin conductor cable with temperature sensitive insulation. The cable operates by melting [thereby short-circuiting] once the temperature of sensor cable is exceeded. Unlike analogue [alarm line] the operating temperature is fixed within the temperature rating of the temperature sensitive insulation. The temperature alarm setting depending upon the outer sheet of the cable used and the requirement can be seen as under: ALARM COATING 70 ºC Polythene 90 ºC Polythene 113 ºC PVC 180 ºC PVC 238 ºC Fluoro Polymer The digital cables can be directly connected into a fire panel as a zone. These cables can be effectively installed to protect the cable runways or the telecom racks. M/S KIDDE UK LHD has FM approval. 3.3 Analogue Address Intelligent Fire Surveillance System: System Description: - Analogue The feedback from the sensors is in the form of Analogue Counts. The value of these counts changes depending upon fire, fault, dust conditions and can be analyzed by the micro processor. - Addressable The detectors have a fixed address which can be read by the control panel and the sensor can be addressed by the control panel. - Intelligent The micro processor in the control panel provides the intelligence and the decision making is through this micro processor. The system hardware [Fig -2] depends upon the actual requirement and usually has combination of the following: [a] Control panel [b] Sensors [c] Bells/ Sounders [d] System Wiring and Fittings. [e] Power Supply Unit. BSNL, India For Internal Circulation Only Page: 5

6 [f] Optional Items :- Repeater Control Unit, External status Interface, Personal Computer/ Networking. Control Panel : The Control panel [As shown in Fig -3] is having micro- processor on a PCB that automatically controls the system. The control panel holds a combination of electronic circuit cards as per the site requirements for pulse bells and sensors. They also provide interface to external facilities through peripherals printed circuit boards. The key pad on the control panel enables certain supervisory function to be undertaken. It also provides for authorized only coded access to enable certain system functions to be interrogated for maintenance. Access to the control panels itself is by key. A built in printer is a standard item on the control panel. BSNL, India For Internal Circulation Only Page: 6

7 BSNL, India For Internal Circulation Only Page: 7

8 Fig -2 Fig -3 BSNL, India For Internal Circulation Only Page: 8

9 Sensors: As per the site requirement combination of following sensors also termed as field units/input devices is provided: - Analogue Addressable ionization smoke detectors with dual ionization chamber. - Analogue Addressable optical smoke detectors, photo electric type using internal infrared light source. - Analogue Addressable fixed temperature, heat detector and rate of rise hear detectors. - Analogue addressable manual call Point / Break glass Unit :- With frangible glass, splinter protected for activation by manually breaking the glass. Bells / Sounders: The externally wired bells and electronic sounders/ PA system provide audible warning to emergencies. The Bells/Sounders can create disturbances on the system and thus, have to be properly chosen. System Wiring And Fittings: Two wire cable is used for linking the sensors and the control panel and for the PA system / interface unit etc. etc. The wiring is looped [Fig. 4.0] and in some cases, a standby [loop] is also provided so as to make the system fool proof. Fittings such as short circuit isolators are fixed at strategic position to isolate sensors section in case of break or fault. Generally one isolator is provided for every 20 devices. Power Supply Unit: Two 12 volts sealed lead acid batteries provide the 24volt DC supply to operate the system. The batteries are on constant charge from an integral Charging unit fed through AC MAINS. Optional Items: Repeater control unit for monitoring of system at strategic or remote locations can be provided. Status interface can be provided for linking the system with personal computer., in networking or external building management system Principle Of Operation: The Analogue addressable intelligent fire surveillance system uses state of- theart microprocessor control with built in Software program to maintain automatic two ways communication with a large number of remote sensors which detects fire and smoke. The system provides for an activation signal to be transmitted by any sensor to BSNL, India For Internal Circulation Only Page: 9

10 the control unit and also enables the operational readiness of each sensor to be routinely monitored. The detectors used in the system are addressable analogue detectors. Unlike the conventional detectors, the analogue detector does not operate on the threshold basis. The analogue voltage signal produced by the activation of the detector is converted into a analogue count by the electronic circuitry and transmitted to the control panel on interrogation. The unique address [1 to 126] of the sensor provided by means of XPERT CARD/ DIL [DUAL INPUT LINE] switch [Fig. 5] is read by the microprocessor whenever the sensor is addressed by the control panel. Built in programmes address and interrogate in turn each sensor in the system.the interval between addressing any sensor is 2 to 3 seconds depending upon the number per loop. Each sensor responds with a signal indicating that it is in operational readiness. Though the principle of operation may vary from manufacturer to manufacturer, a commonly employed method is on the pulse position modulation principle. Each and every detector is scanned by the pulses generated [Fig. 6.0] from the control panels and feedback is processed by the control panel to generate the required signals. Intelligent pulses of 5 to 9 volts are super-imposed on the DC supplies volts on the two wires. Since there is a constant communications between the Control Panel and the various detectors, the exact condition of the detector is conveyed to the Panel in the form of an Analogue count [1 to 126]. It gives the information that the detector is non-functional / fault/ dead [count of 1 to 12], normal/ healthy [15 to 40]. A count of 40 to 55 is a prealarm stage which is generally due to non-maintenance of the detectors or the poor environmental conditions. This information is extremely important because timely action by the supervisor can prevent the false-alarm. A condition beyond 55 is generally an alarm condition. It is this feature of the intelligent system which is the most important, useful and powerful in comparison to the conventional system. The programmes routinely execute supervisory commands within the control unit to validate the operational readiness of the electronic circuits. On switching on, the control unit automatically calibrates each sensor against its ambient temperature or particular level as appropriate, ensuring constant sensitivity of sensors throughout the systems. The calibration, together with lamp testing is performed routinely every day at a fixed time ( say 1200 hours) through system software. The system is able to discriminate between a false alarm and the real fire conditions by analyzing various fire characteristics and environmental conditions [Fig. 7.0] BSNL, India For Internal Circulation Only Page: 10

11 3.3.4 Advantages Of Analogue Addressable System: Large number of detectors in one loop and flexibility Status Display Programming For Exact Location Of Fire Adjustment Of Detector Sensitivity Dirty Pre-Warning For Detectors Simple Cabling Origin / Flow Of Fire Can Be Ascertained Discrimination Between Genuine Fire And Other Conditions Isolation Of Faulty Detectors / Output Devices/ Areas Under Mtce. Logging Of Past Events Ease Of Maintenance 4.0 Modern Trends In Fire Extinguishing Systems: - Fire Trace Extinguishing System. - Halon Alternative Extinguishing System (A) Total Flooding Agents (B) Portable Fire Extinguishers - Wet Riser & Sprinklers 4.1 Fire Trace Extinguishing System: System Description: The system consists of following: - A specialized flexible Fire detection and Fire extinguishing Delivery tube. - The tube is wrapped around or installed within the Protected equipment Exchange Racks, cabinets etc. etc. - [Avoiding surface above 80 ºC] - Fire extinguishing media cylinder connected at one end of the tube, thus, the tube is charged with extinguishing media Principle Of Operation: When an area is overheated or should a small fire take place the tube adjacent or above the fire will soften and burst at hottest point allowing swift and accurate delivery of the extinguisher directly to the source of the fire. BSNL, India For Internal Circulation Only Page: 11

12 4.1.3 Fire Trace Advantages: The system does not require Electricity / or battery supply for operating the detection system. It has no wiring, detectors or control panel. It can be connected to any extinguishing agent depending upon application and has been approved by LOSS PREVENTION CONTROL BOARD 4.2 Halon Alternative Extinguishing System: Halon is a very effective fire extinguishing agent. However, because of the high ozone depletion potential, its use has to be phased out as per the provisions in Montreal protocol without comprising with Fire safety. As per Government of India Ministry of Home affairs & DGCD [Fire Cell] letter dated , the following HALON alternatives have been identified. [A] [B] Alternative For Halon 1211 Portable Fire Extinguishers Are: (I) ABC Powder extinguisher. (II) Co2 squeeze grip type extinguisher. (III) HCPC based compounds like NAF P IV, Halotron, FE-36 etc. Alternative For Halon 1301 Fixed Fire Protection Systems Are: [i] CO2 fire extinguishing in-cabinet and subfloor systems, including low Pressure CO2 systems. [ii] Inert gas extinguishing systems [nitrogen based] [iii] Water mist fire extinguishing system. [iv] Fast response sprinklers. [v] Halocarbons such as HFC 227 (FM-200), PE-13, HCFC blends, The HALON alternatives as above can be classified under[nafs 111] following categories. [I] Traditional Fire Protection Agents: [Ii] Halocarbon Agents [Iii] Inert Gases [Iv] Water Mists [V] Powdered Aerosols 4.3 Wet Riser & Sprinklers: These are continued to be provided for high-rise buildings and basements as per local Fire byelaws and Fire Protection manual of the department. BSNL, India For Internal Circulation Only Page: 12

13 5.0 Fire Fighting In Data Centre A complete and thorough fire protection strategy in the data center seems like an obvious priority. Protection = Detection + Suppression. The ideal protection strategy should include a smoke detection package with a fire suppression system. There are a variety of possibilities to choose from in both categories. Detection. Typically, detection is cross-zoned using both photoelectric and ionization type spot detectors. Cross zoning allows the end user protection against false discharges of the suppression system, by requiring one of each type of detector to be in alarm, prior to the initiation of a discharge. High sensitivity smoke detection is also an option. Suppression. There are multiple options to choose from for both suppression agents, and suppression systems. Some suppression agent brands you'll want to consider: FM-200, Inergen, Argonite, Novec Also, because these halon alternatives are a more mature product set now, several applications specific systems are available. For example, 'in-cabinet' systems for protection of a small closet or cabinet spaces. The FM-200 agent is a popular halon replacementtypesystem. Fm 200 Based Fire Extinguishing System The FM-200 extinguishing system include the following components: Agent storage container with cylinder valve. FM-200 agent. Discharge nozzle (s). Electronic control head for master cylinder (s) and pressure operated control head for slave cylinder(s) as releasing devices. Mounting brackets. Discharge hoses. EL Check valves on manifold. Actuation hoses for slave cylinder(s) Master cylinder adapter kit for slave cylinder system Any other required for the completeness of the system Any other required for the completeness of the system. The Heptafluropropane - CCF 3 CHFCF 3 (FM-200), is a clean Fire suppression agent. FM-200 is stored in seamless storage containers. The FM-200 Fire Suppression System includes a detection and control switch provision for both pre-alarm and automatic agent release. BSNL, India For Internal Circulation Only Page: 13

14 The detection and control system used to trigger the FM-200 suppression employs multiple smoke detectors. A single detector in one zone activated, shall cause an alarm signal to be generated. Another detector in the second zone activated, shall generate a pre-discharge signal and start the pre-discharge condition. The suppression sub-system provides high- speed release of FM-200 Based on the concept of total flooding fire protection for enclosed areas. A uniform extinguishing concentration shall be seven- (7) percent v/v concentration of FM-200 at 70 degree F. The system discharge time shall be 10 seconds or less, in accordance with NFPA Standard The discharge nozzles are located in the protected volume in compliance to the limitation with regard to the spacing, floor and ceiling coverage etc. The nozzle locations are such that the design concentration is established in all parts of the protected volumes. The FM- 200 discharge shall be activated by an output directly from the FM-200 Gas Release control panel, which will activate the Electric control head based releasing device. FM- 200 agent is stored in the container as a liquid, having a natural vapor pressure of 66.4 psi at 77 degree F. To aid release and distribution, the container shall be super pressurized to 360 psi(g) at 70 degree F with dry nitrogen. The FM-200 valve, operating actuators is an Electric (Solenoid) type, and is capable of resetting manually. Provision is provided on the Electric Control Head for a Manual Lever for over-ride in case of failure of the Electrical components. The Electric Control Head ( Actuator ) operates at 24 VDC. The Electric Control Head should be capable of being functionally tested for periodic servicing requirements, and without any need to replace consumable parts. The system flow calculations are carried out on certified software, suitable for the particular container being offered for the project.the releasing device is also capable of direct mechanical actuation, providing a means of discharge in the event of total electrical malfunction. Provided with a manual lever and a face plate with clear instruction of how to mechanically activate the system. In all cases, FM-200 cylinders is fitted with a manual mechanical operating facility that requires two-action actuation to prevent accidental actuation. FM-200 storage cylinders is provided with a safety rupture disc. An increase in internal pressure due to high temperature ruptures the safety disc and allow the contents to vent before the rupture pressure of the container is reached. The contents do not vented BSNL, India For Internal Circulation Only Page: 14

15 through the discharge piping and nozzles. FM-200 containers is equipped with a pressure gauge to display internal pressure. The gauge is an integral part of the container and shall be color-coded for fast referencing of pressure reading. Brass Discharge nozzles is used to disperse the FM-200. The nozzles are of brass with female threads and available in ½ through 2 sizes. FM-200 Gas Release Panel: The FM-200 release signal output shall be from the Microprocessor based Main Fire Alarm Control panel with battery charger and battery stand-by. This panel is not of the zone card type, but shall have the entire operational logic on a microchip. The panel should be capable of enhanced features such as printer and computer interface, auto dialer interface, by addition of extra cards on the motherboard. Release of FM-200 agent is accomplished by an electrical output from the FM-200 Gas Release Panel to the Electric control head release device and is in accordance with the requirements set forth in the current edition of the National Fire Protection Association Standard BSNL, India For Internal Circulation Only Page: 15

16 Question 1. Write the advantages of Analogue Addressable Microprocessor based Fire Detection System as compared to conventional system. 2. Which type of Fire Fighting and detection systems should be used in Data centre of BSNL 3. Briefly describe Fire Trace Extinguishing system. What are the Advantages? 4. Briefly describe High Sensitivity Smoke Detection system (HSSD) system used in fire protection system. Mention the advantages also. 5. What is Linear Heat Detection system (LHD). Write down the principle of operation. 6. Write down the Halon Alternative Fire Extinguishing systems. 7. List down the categories in which HALON alternatives can be classified. 8. List down the components of FM-200 Fire Extinguishing system. 9. Write short Notes on FM Gas Release Panel. 10. What is the difference between Digital Linear heat Detection system and Analogue Linear heat Detection system. BSNL, India For Internal Circulation Only Page: 16