TABLE 3: AIRFLOW LEAKAGE THROUGH OPEN FINAL EXIT DOOR
TABLE 4: AIRFLOW LEAKAGE THROUGH NON-FIRE FLOOR ROOMS
TABLE 5: AIRFLOW LEAKAGE THROUGH PRESSURISED LIFT SHAFT WALLS
Practical Example #01 CLASS E SYSTEM - STAIRCASE & LOBBY PRESSURISED 900m2
MODE 1 - ALL DOORS CLOSED Stairs There will be no flow through Stairs/Lobby Doors Leakage Area = 1 x Double Door at exit AE = 0.03m2 -TABLE 2 Airflow required to (Stairs) = Q = 0.83 AE -EQUATION 4 = 0.83 (0.03) x 500.5 = 0.176m3/s -EQUATION 5 + 50% = 0.264m3/s Lobbies - TABLE 2 Leakage Area = 7 x Single doors opening out at 0.02 = 0.14m2 Airflow required to (Lobbies) = Q = 0.83 AE 50 0.5 = 0.83 (0.14) x 50 0.5 = 0.82m3/s - EQUATION 4 + 50% = 1.23m3/s - EQUATION 5 Total Airflow Required Mode 1 = 1.23 + 0.264 = 1.494m3/s
MODE 2 - PRESSURE CRITERION Airflow through open exit door 1.6m2 = 4.36m3/s - TABLE 3 (2 doors & Vent) Airflow through two open accommodation doors 900 m2 = (2 x 0.574) = 1.148m3/s - TABLE 4 Add Mode 1 = 1.494m3/s Total Airflow = 4.36 + 1.148 + 1.494 = 7.002m3/s Airflow to Stairs = (7.002-1.230) = 5.772m3/s Airflow to Lobbies = 1.230m3/s
MODE 2 - VELOCITY CRITERION Airflow through open Fire Floor Door = 1.6 x 0.75 = 1.20m3/s - EQUATION 1 Airflow through open exit door = 4.36m3/s - TABLE 3 (2 doors & Vent) Airflow through open accommodation door 900m2 = 0.574m3/s - TABLE 4 Add Mode 1 = 1.494m3/s Total Airflow =7.628m3/s Airflow to Stairs = (7.628-1.230) = 6.398m3/s Airflow to Lobbies =1.23m3/s Note: (Mode 2 - Velocity Criterion Determines Fan Duty) CALCULATE AREA OF PRESSURE RELIEF Area of Pressure Relief =
CALCULATE AREA OF AIR/SMOKE RELIEF VENT - EQUATION 1 Airflow to Fire floor = 1.20m3/s - EQUATION 1 Area of air/Smoke Relief Vent=Q/2.5 = 1.2/2.5 =0.48 m2 Fan Duty Required = 7.628m3/s @ 50 Pa + System Area of Pressure Relief = 1.09m2 Area of Air/Smoke Release Vent = 0.48m2 Airflow to Stairs = (7.628-1.230) = 6.398m3/s Airflow to Lobbies =1.23m3/s
PRACTICAL EXAMPLE #02 CLASS B SYSTEM - FIRE FIGHTING STAIRS & LIFT 900m2
MODE 1 - PRESSURE CRITERION ALL DOORS CLOSED Stairs (No airflow across stair/lobby doors) -TABLE 2 - EQUATION 4 Leakage area = 1 double Door At Exit = 0.03m2 - EQUATION 5 Airflow to stairs = Q = 0.83 AE 50 0.5 = 0.176m3/s + 50% = 0.264m3/s Lobbies (No airflow across lift/lobby doors) - TABLE 2 Leakage area = 7 single doors opening - EQUATION 4 - EQUATION 5 out at 0.02 m2 = 0.14 m2 Airflow to lobbies = Q = 0.83 x 0.14 x 500.5 = 0.821 m3/s + 50% = 1.232 m3/s
Lift Shaft - TABLE 2 Leakage area = 1 lift top vent = 0.10m2 - TABLE 5 Walls 21m high = 0.12m2 - EQUATION 4 Total Leakage = 0.10 + 0.12 = 0.22 m2 Airflow to Lift Shaft = Q = 0.83 x 0.22 x 50 0.5 = 1.29m3/s Total Airflow Mode 1 = 1.29 + 1.23 + 0.264 = 2.78m3/s
CLASS B SYSTEM - FIRE FIGHTING STAIRS & LIFT
MODE 3 - FIRE FIGHTING - VELOCITY CRITERION REFERENCE - TABLE 2 LIFT SHAFT - (Lift door open on one floor) - TABLE 2 - TABLE 5 Leakage Area - AE - 1 - Open Lift Door (2m high x 1m wide) = 0.15m2 Lift Top Vents = 0.10m2 Lift Shaft Walls (21m high) = 0.12m2 Airflows - Q = 0.83 AE 50 0.5 - EQUATION 4 Open Lift Door = 0.88 m3/s Lift top vents = 0.58 m3/s Lift shaft walls = 0.71 m3/s Total Airflow to lift shaft = 2.17 m3/s Note of which 0.88 m3/s will leak into the lobby and contribute to the total airflow. Total Airflow to lift shaft = 2.17m3/s - 0.88m3/s = 1.29m3/s
CALCULATED TOTAL AIRFLOW REQUIRED - MODE 3 Airflow to fire floor = (1.6 m2 x 2.0m/s) = 3.2m3/s - EQUATION 1 - TABLE 3 (2 Doors & Vent) Airflow through open exit door = 5.93m3/s = 2.17m3/s Airflow to lift shaft TOTAL AIR FLOW = 3.2 + 5.93 + 2.17 + 1.49 = 12.79 m3/s minus airflow through lift door = 0.88 m3/s = 11.91 m3/s
CALCULATE AREA OF PRESSURE RELIEF Fan Duty Required = 11.91m3/s @ 50 Pa + System Resistance Pressure Relief = 1.56 m2 Area of Air/Smoke Release Vent = 1.28 m2
Design Criteria ACCORDING NFPA The Staircase Pressurization calculation is usually based on the following design criteria: Δp min. = min. pressure difference = 0.18 in wg between staircase and adjacent accommodation space Δp max. = max. pressure difference = 0.37 in wg between staircase and adjacent accommodation space Airflow velocity of not greater than 200 fpm (~1 m/s) through doors when 3 doors are open Maximum Force required to open any door at the door handle shall not exceed 30 lbs (133 N).
Problems & Issues
SCHEMATIC DIAGRAM
PRESSURE RELIEF DAMPER PRESSURE RELIEF DAMPER SUPPLY POINT
PRESSURIZATION FAN
MOTORIZED FIRE DAMPER
ELECTRICAL POWER SUPPLIES (Primary and Secondary) General Electrical power supplies (primary & secondary) shall be in accordance with prEN 12101-10. All primary and secondary electrical supplies to: a) Pressure differential system supply fans and any associated relief air path equipment. b) Depressurization fans and any associated supply make-up air equipment. Change over between the primary power supply and the secondary power supply shall be automatic.
Requirements for Electrical Cables Electrical cables for the pressure differential systems shall comply with the following: a) Fire-resisting cables meeting the temperature and time criteria b) Enclosed with fire-resisting construction, or installed external to the building where the cables cannot be endangered by fire c) Cables protected from fire shall comply with the classification temperature/time of the component that they serve. d) Fire alarm control systems and damper control systems, etc.
Requirements for Distribution Ductwork for Pressure Differential Systems – Installation •Ductwork shall be tested and classified in accordance with prEN 13501-3 or prEN 13501-4 and shall have a classification performance appropriate to the design criteria according to prEN 12101-7. •The ductwork construction shall be in accordance with the EN 1505 and EN 1506. •The air intake shall always be located away from any potential fire hazards. Air intakes shall be located on or near ground level (but well away from basement smoke vents) to avoid contamination by rising smoke. If this is not possible, air intakes shall be positioned at roof level. •When an air intake is distant from the fan, air shall be ducted from the intake to the fan. Where an air intake is not at roof level, a smoke detector shall be provided in the intake duct or within the immediate vicinity of the supply ductwork in order to cause the automatic shut down of the pressure differential system if substantial quantities of smoke are present in the supply. An override switch shall be provided for fire brigade purposes •Fire dampers shall not be used in pressure differential system supply ductwork. If such ductwork penetrates a fire-resisting compartment, the ductwork shall be protected with suitable fire resisting material. •Air supply grilles shall not be located near any major leakage path from a pressurized zone.
Maintenance
Actuation and Control Manual system - override switches for the pressurization system shall be located at the following locations: a) The building services plant room and the pressure differential system equipment plant room (if separate). b) Near the building entrance at a location agreed with the regulatory authority. Automatically In systems where the operation of the air release system is automatic, its actuation shall be by the same signal that actuates the rest of the system. Systems shall be operational within 60 s of detection of smoke. Where a dual operating system is not permitted for firefighting purposes, the system shall automatically enter the firefighting mode on starting up.
REFUGE AREA
References 1. على كودة الوقاية من الحريق2007 ) لعام1( التعديل رقم 2. BS 5588-4, 1998 3. BS EN 12101-6, 2005 4. NFPA 92 5. FLAKT WOODS: Smoke Control by Pressurization.
Alaa Sabha
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