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GB 51251-2017: Technical standard for smoke management systems in buildings
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Technical standard for smoke management systems in buildings
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GB 51251-2017
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Basic data | Standard ID | GB 51251-2017 (GB51251-2017) | | Description (Translated English) | Technical standard for smoke management systems in buildings | | Sector / Industry | National Standard | | Classification of Chinese Standard | P16 | | Word Count Estimation | 135,157 | | Date of Issue | 2017-11-20 | | Date of Implementation | 2018-08-01 | | Regulation (derived from) | The Ministry of Housing and Urban-Rural Development Announcement No. 1741 of 2017 | | Issuing agency(ies) | Ministry of Housing and Urban-Rural Development of the People's Republic of China; General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China | GB 51251-2017: Technical standard for smoke management systems in buildings---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order.
1 General
1.0.1 This standard is formulated for the purpose of rationally designing building smoke prevention and exhaust systems, ensuring construction quality, standardizing acceptance and maintenance management, reducing fire hazards, and protecting personal and property safety.
1.0.2 This standard applies to the design, construction, acceptance and maintenance management of smoke prevention and exhaust systems for new, expanded and rebuilt industrial and civil buildings. For industrial and civil buildings with special purposes or special requirements, if there are special provisions in professional standards, those provisions can be followed.
1.0.3 The design of building smoke prevention and smoke exhaust system should take effective technical measures in consideration of the characteristics of the building and the development law of fire smoke, so as to achieve safety, reliability, advanced technology and reasonable economy.
1.0.4 The equipment of the building's smoke prevention and smoke exhaust system should be selected in accordance with the current relevant national standards and relevant access systems.
1.0.5 In addition to implementing this standard, the design, construction, acceptance and maintenance management of the building's smoke prevention and smoke exhaust system should also meet the requirements of the current relevant national standards.
2 Terminology and symbols
2.1 Terminology
2.1.1 smoke protection system
Prevent fire smoke from accumulating in stairwells, front rooms, and refuge floors (rooms) by adopting natural ventilation, or prevent fire smoke from invading stairwells, front rooms, and refuge floors (rooms) by using mechanical pressurized air supply. Room) and other space systems, the smoke prevention system is divided into natural ventilation system and mechanical pressurized air supply system.
2.1.2 smoke exhaust system
A system that uses natural smoke exhaust or mechanical smoke exhaust to exhaust fire smoke from rooms, aisles and other spaces to the outside of the building, and is divided into natural smoke exhaust systems and mechanical smoke exhaust systems.
2.1.3 direct irrigation mechanical pressurization without air shaft
There is no air supply shaft, and the air supply mode is directly mechanically pressurized by the fan to the stairwell.
2.1.4 natural smoke exhaust
Utilize the buoyancy of the fire hot smoke flow and the external wind pressure to directly discharge the smoke in the building to the outside through the opening of the building.
2.1.5 natural smoke exhaust window (mouth) natural smoke vent
The openable outer window or opening with smoke exhaust function can be opened by automatic, manual, temperature-controlled release, etc.
2.1.6 smoke plume
The mixed smoke flow formed by the smoke entraining the surrounding air during a fire. According to the flow of flame and smoke, the smoke plume can be divided into axisymmetric smoke plume, balcony overflow smoke plume, window type smoke plume, etc.
2.1.7 Axisymmetric smoke plume axissymmetric plume
A smoke plume that does not come into contact with surrounding walls or obstacles during its ascent, and is not disturbed by airflow.
2.1.8 Balcony spill plume
The smoke plume overflows from the door (window) beam of the fire room, flows along the balcony or horizontal protrusion outside the fire room, and overflows to the edge of the balcony or horizontal protrusion to the adjacent tall space.
2.1.9 window plume
The smoke plume that overflows from openings such as doors, windows, etc. of a room or compartment where a fire with restricted ventilation occurs, into an adjacent tall space.
2.1.10 draft curtain
Made of non-combustible materials, it is vertically installed under the roof, beam or ceiling of the building, and can form a certain smoke storage space in the event of a fire.
2.1.11 smoke reservoir
Located on the top of the building space, it is a space for accumulating fire smoke formed by smoke-retaining vertical walls, beams or partition walls. The height of the smoke storage bin is the design smoke layer thickness.
2.1.12 Clear height clear height
The height from the lower edge of the smoke layer to the indoor ground.
2.1.13 Mass flow rate of plume
The mass of the plume passing through a horizontal section at a certain height per unit time, in kg/s.
2.1.14 Combination fire and smoke damper
Installed on the pipe of the mechanical smoke exhaust system, it is usually open, and it will be closed when the temperature of the smoke in the smoke exhaust pipe reaches 280°C during a fire, and it can meet the requirements of smoke leakage and fire resistance integrity within a certain period of time Fire-stop valve. It is generally composed of valve body, vane, actuator and temperature sensor.
2.1.15 smoke damper
Installed at the end of each branch pipe (smoke inlet) of the mechanical smoke exhaust system, it is usually closed and meets the air leakage requirements. It can be opened and closed manually or electrically in case of fire, and it plays the role of smoke exhaust. It is generally composed of valve body, vane, actuator and other components.
2.1.16 smoke exhaust inlet
Inlet for flue gases in a mechanical fume extraction system.
2.1.17 fixed window fixed window for fire forcible entry
Installed in a place with a mechanical smoke prevention and exhaust system, the window sash is fixed and cannot be opened at ordinary times. It is only convenient for manual demolition in the event of a fire to exhaust the smoke and heat in the fire.
2.1.18 fusible daylighting band (window) fusible daylighting band
It is made of materials that can melt by itself at 120°C to 150°C without producing molten droplets. It is installed in the upper part of the building space and is used to discharge smoke and heat in the fire site.
2.1.19 Independent anteroom
Antechamber connected only by an escape staircase.
2.1.20 Shared front room shared anteroom
(residential building) scissor stairwell The front room when two stairwells share the same front room.
2.1.21 Combined anteroom
The front room when the front room of the smoke-proof stairwell is shared with the front room of the fire elevator.
2.2 Symbols
2.2.1 Calculation of geometric parameters
A - the effective air leakage area of each evacuation door;
Ak - cross-sectional area of the door to open;
Ao - total area of all air inlets;
Am - the area of the door;
Af - the area of a single air supply valve;
Ag - the total area of the evacuation door in the front room;
Al - the total area of the evacuation door in the stairwell;
Av - cross-sectional area of natural smoke exhaust window (port);
AW——window opening area;
B——The dimension of the long side of the air duct;
b——the distance from the opening to the edge of the balcony;
dm - the distance from the handle of the door to the latch;
db——thickness of the smoke layer below the lowest point of the suction port of the smoke exhaust system;
D - the diameter of the air duct;
H—clear height of the space;
H'——For a single-story space, take the net building height of the smoke exhaust space; for a multi-story space, take the floor height of the highest evacuation floor;
Hl - the height from the fuel surface to the balcony;
HW - the height of the window opening;
Hq——minimum clear height;
ω——the opening width of the fire source area;
W——the spreading width of smoke plume;
Wm - the width of a single door;
Z - the height from the fuel surface to the bottom of the smoke layer;
Zl——flame limit height;
Zb - the height from the lower edge of the balcony to the bottom of the smoke layer;
Zw - the height from the upper edge of the window opening to the bottom of the smoke layer.
2.2.2 Calculation of air volume and wind speed
g - acceleration of gravity;
Lhigh——The allowable air leakage volume per unit time of the air duct per unit area of the high pressure system;
Lj——the mechanical pressurized air supply volume in the stairwell;
Llow——The allowable air leakage volume per unit time of the air duct per unit area of the low pressure system;
Lmid——The allowable air leakage volume per unit time of the air duct per unit area of the medium pressure system;
Ls——the mechanical pressurized air supply volume of the front chamber;
L1——When the door is opened, the air supply volume required to reach the specified wind speed value;
L2——When the door is opened, the total amount of air leakage from other door gaps under the specified wind speed value;
L3——the total amount of air leakage of the normally closed air supply valve that is not opened;
Mρ—mass flow rate of smoke plume;
ν——wind speed of door opening section;
V - smoke exhaust volume;
Vmax——The maximum allowable smoke exhaust volume of the exhaust port.
2.2.3 Calculate pressure, heat and time
Cp - constant pressure specific heat of air;
F' - the total thrust of the door;
Fdc—the force required to overcome the door closer at the door handle;
M - the opening torque of the door closer;
P0 - gas density at ambient temperature;
P——The maximum allowable pressure difference of the evacuation door;
P air duct - the working pressure of the air duct system;
△P——the average pressure difference for calculating air leakage;
Q——heat release rate;
Qc - the convective part of the heat release rate;
t——fire growth time;
T - the average absolute temperature of the smoke layer;
T0 - the absolute temperature of the environment;
ΔT——The difference between the average temperature of the smoke layer and the ambient temperature.
2.2.4 Calculation coefficients
α——fire growth coefficient;
αw—correction coefficient of window plume;
γ - smoke exhaust position coefficient;
C0 - air inlet flow coefficient;
Cv——flow coefficient of natural smoke exhaust window (port);
K - convective heat release factor in the flue gas;
n——exponent.
2.2.5 Computing other symbols
N1 - the number of floors where the designed evacuation door is opened;
N2 - the number of air leakage evacuation doors;
N3 - the number of air leakage valves.
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