Fire smoke exhaust fans are usually the main smoke prevention and exhaust facilities of high-rise civil buildings. They are indispensable for high-rise civil buildings to ensure the safety of people’s lives and properties. However, due to the lack of understanding of the structure, function and performance of smoke prevention and exhaust facilities by some design and construction personnel, The incomplete understanding of the national norms and standards often leads to some problems in the design and construction. Here are a few details.
1. Natural smoke exhaust facilities cannot achieve the purpose of smoke exhaust
Natural smoke exhaust is an economical, simple, easy-to-operate, and convenient way to maintain and manage smoke. However, some projects are not carried out in accordance with specifications during the design and construction process, which often results in natural smoke exhaust facilities not equipped with exhaust after the completion of the project. To analyze the effects of smoke, the main reasons are as follows:
1. The setting position of the natural smoke exhaust window is improper. Considering the natural smoke exhaust effect, the smoke exhaust window should be installed as close to the upper part of the wall as possible. At present, a considerable number of natural smoke exhaust windows are not installed on the upper part of the wall, but at the lower part. The distance from the ceiling and the ceiling is large, which is not conducive to nature. Exhaust smoke.
2. The opening area of the natural smoke exhaust window does not meet the specification requirements. The national standard "Code for Fire Protection Design of High-Rise Civil Buildings" clearly stipulates the window area of the natural smoke exhaust part, but because some designers did not carefully calculate according to the requirements of the code, or calculate the area of the fixed window in the area of the smoke exhaust window Within this, the area of smoke exhaust windows in some projects did not meet the specification requirements, which directly affected the smoke exhaust effect.
3. The structure of the natural smoke exhaust window is unreasonable. Some make the smoke exhaust window into a fixed window that cannot be opened, some make the upper part of the window into a fixed window, and set the openable smoke exhaust window in the lower part of the window, which seriously affects the smoke exhaust function.
4. The smoke exhaust window with high installation height lacks an easy-to-open operating mechanism. According to the requirements of the specification, the smoke exhaust window should have a device that is easy to open, but some of the smoke exhaust windows with high installation height and difficult to open are not equipped with an opening operation device, and the smoke exhaust window is opened under adverse fire conditions.
2. It is difficult to form the residual pressure required by the mechanical pressurized air supply and smoke prevention facilities, and the smoke exhaust effect of the mechanical smoke exhaust facilities is not obvious
The phenomenon that the air volume and residual pressure value of the air supply vents and smoke exhaust vents do not meet the requirements of the specification is common in engineering. The wind speed of some air supply vents and smoke exhaust vents is even close to zero. The reasons for this phenomenon are more complicated, mainly including: The following aspects:
1. Improper fan selection. According to the requirements of the code, the mechanical pressurized air supply volume of the smoke-proof staircase and the front room, the shared front room and the front room of the fire elevator room shall be determined by calculation. When the calculated value is inconsistent with the value specified in the code, the two shall be calculated. The larger value is determined, and some designs are directly determined according to the value given by the specification, which often results in the selected fan air volume and pressure being too small, which cannot meet the requirements; some designs adopt a combined ventilation and mechanical smoke exhaust system, but the construction is not The design requires the use of a two-speed fan; some construction units do not order the fan according to the design model, but purchase a fan with a smaller power specification, resulting in a serious shortage of fan air volume.
2. The mechanical pressurized air supply system and the natural smoke exhaust facility are set repeatedly. For a type of public building with a building height of more than 50 meters and a residential building with a building height of more than 100 meters, according to the requirements of the "High Regulations", a mechanical pressurized air supply system should be installed. Some projects also use natural smoke exhaust at the same time. , In the event of a fire, when the mechanical pressurized air supply system and the natural smoke exhaust window are opened at the same time, it is difficult to form a positive pressure in the smoke-proof staircase, and the smoke-proof effect cannot be achieved.
3. The pressure difference adjustment device is not designed for the combined positive pressure air supply system. According to the requirements of the specification, the smoke-proof stairwell and the shared front room with mechanically pressurized air supply should be provided with independent air supply systems. When the same system must be shared, automatic pressure difference should be set on the branch duct leading to the shared front room. Adjusting device. Many currently designed co-positive pressure air supply systems are not designed with pressure difference adjustment devices, and cannot form a stairwell with a higher residual pressure value than the front room.
4. The smoke-proof zone does not set up smoke-proof facilities according to the requirements of the regulations. A considerable part of the project, especially large shopping malls where mechanical smoke exhaust is installed, did not install smoke blocking walls under the ceiling according to the requirements of the specification. Although some basements use building beams as smoke blocking facilities, the smoke exhaust system of the smoke exhaust system is not It is installed on the ceiling or the wall close to the ceiling according to the specification, but under the beam.
5. The air supply outlet setting does not meet the requirements. Some vertical smoke prevention and exhaust systems use fixed louvered normally open air outlets for air outlets. The size of the air outlets is basically the same, resulting in serious imbalances in the air volume and speed of the air outlets on each layer, and the air volume at the air outlet farther from the fan is insufficient, even at the end The wind speed and volume of the air supply outlet are close to zero.
6. The construction quality of the duct shaft is poor and the air leakage is serious. There are quite a lot of projects because the ventilation shaft is not plastered, the pipeline connection is not tight, the normally closed air outlet is not tightly closed, and the air leakage is very serious, resulting in the wind speed and air volume of the air supply outlet and the exhaust outlet not meeting the specification requirements. Some construction units even Cancelling the air duct connecting the vertical shaft to the ceiling air outlet and using the ceiling space instead of the air duct often results in the air duct air velocity being close to zero.
At the same time, the exhaust outlet of the fan of the smoke exhaust system is installed indoors, which causes the smoke to be discharged from the indoor to the indoor in the case of a fire, which not only loses the smoke exhaust function, but may also cause the spread of the fire.
3. The power distribution of the smoke prevention fan does not meet the requirements of the specification
One is that the power supply and distribution of wind turbines cannot meet the load level requirements of high-rise civil buildings. Some power supply lines are not connected to the fire power supply, but to the floor lighting distribution box. Some designs use single-circuit power distribution lines, and some designs do not have an automatic terminal power switch device, which can not reach the first or second power supply. Dedicated dual circuits for load requirements, with provisions for automatic end switching devices.
The second is that the installation of open distribution lines does not meet the requirements. The power distribution lines of some smoke prevention and exhaust fans wear PVC plastic pipes, and some metal pipes are not painted with fire-resistant coatings, which do not meet the requirements of the fireproof performance of the pipes.
4. The parts where mechanical smoke prevention and exhaust facilities should be installed are not set according to the requirements of the specification
1. Smoke-proof stairwells and front rooms of high-rise civil buildings with podiums, front rooms of fire-fighting elevator rooms or shared front rooms, when the upper part of the podium can be opened for natural smoke exhaust, the skirt part does not have natural smoke exhaust When conditions are met, its front room or shared front room is not equipped with a positive pressure air supply system as required by the specification.
2. There is no natural smoke exhaust in the inner walkway over 20 meters. Some designers think that it has natural smoke exhaust conditions because of the natural smoke exhaust in the front room of the smoke-proof stairwell connected to it. Mechanical smoke exhaust facilities are not installed in accordance with the specifications. .
Countermeasure
In response to the above-mentioned problems, the fire supervision department should strengthen the supervision and management of the design and construction of building smoke prevention and exhaust facilities from the following aspects:
1. The business guidance and training for the design and construction personnel of smoke prevention and exhaust facilities should be strengthened. Local fire departments generally attach great importance to the professional design and construction of fire alarms, electrical, and fixed (automatic) fire extinguishing facilities. The professional design and construction personnel of fire extinguishing facilities are often ignored during the training process.
2. The system that the construction of smoke prevention and exhaust facilities is undertaken by the construction unit of the fire protection facilities should be implemented. Smoke prevention and exhaust facilities are an important part of building automatic fire protection facilities. According to regulations, their construction should be undertaken by the construction unit of fire protection facilities. However, at present, the construction of smoke prevention and exhaust facilities in many projects is installed by professional air-conditioning construction units.
3. When reviewing construction drawings, the construction review personnel of the fire protection supervision department should pay attention to the review of the design of smoke prevention and exhaust facilities, and focus on the setting of natural smoke exhaust windows, window area, mechanical smoke prevention and exhaust facilities, and fans The selection, the setting of the air supply and exhaust outlets, and the smoke prevention zones are reviewed. At the same time, the supervision and management of the smoke prevention and exhaust facilities should be strengthened during the construction, and the smoke prevention and exhaust facilities should be listed as an important content of the construction supervision and inspection, so as to be timely If problems are found, guide and urge the construction unit to carry out rectification.
1. Natural smoke exhaust facilities cannot achieve the purpose of smoke exhaust
Natural smoke exhaust is an economical, simple, easy-to-operate, and convenient way to maintain and manage smoke. However, some projects are not carried out in accordance with specifications during the design and construction process, which often results in natural smoke exhaust facilities not equipped with exhaust after the completion of the project. To analyze the effects of smoke, the main reasons are as follows:
1. The setting position of the natural smoke exhaust window is improper. Considering the natural smoke exhaust effect, the smoke exhaust window should be installed as close to the upper part of the wall as possible. At present, a considerable number of natural smoke exhaust windows are not installed on the upper part of the wall, but at the lower part. The distance from the ceiling and the ceiling is large, which is not conducive to nature. Exhaust smoke.
2. The opening area of the natural smoke exhaust window does not meet the specification requirements. The national standard "Code for Fire Protection Design of High-Rise Civil Buildings" clearly stipulates the window area of the natural smoke exhaust part, but because some designers did not carefully calculate according to the requirements of the code, or calculate the area of the fixed window in the area of the smoke exhaust window Within this, the area of smoke exhaust windows in some projects did not meet the specification requirements, which directly affected the smoke exhaust effect.
3. The structure of the natural smoke exhaust window is unreasonable. Some make the smoke exhaust window into a fixed window that cannot be opened, some make the upper part of the window into a fixed window, and set the openable smoke exhaust window in the lower part of the window, which seriously affects the smoke exhaust function.
4. The smoke exhaust window with high installation height lacks an easy-to-open operating mechanism. According to the requirements of the specification, the smoke exhaust window should have a device that is easy to open, but some of the smoke exhaust windows with high installation height and difficult to open are not equipped with an opening operation device, and the smoke exhaust window is opened under adverse fire conditions.
2. It is difficult to form the residual pressure required by the mechanical pressurized air supply and smoke prevention facilities, and the smoke exhaust effect of the mechanical smoke exhaust facilities is not obvious
The phenomenon that the air volume and residual pressure value of the air supply vents and smoke exhaust vents do not meet the requirements of the specification is common in engineering. The wind speed of some air supply vents and smoke exhaust vents is even close to zero. The reasons for this phenomenon are more complicated, mainly including: The following aspects:
1. Improper fan selection. According to the requirements of the code, the mechanical pressurized air supply volume of the smoke-proof staircase and the front room, the shared front room and the front room of the fire elevator room shall be determined by calculation. When the calculated value is inconsistent with the value specified in the code, the two shall be calculated. The larger value is determined, and some designs are directly determined according to the value given by the specification, which often results in the selected fan air volume and pressure being too small, which cannot meet the requirements; some designs adopt a combined ventilation and mechanical smoke exhaust system, but the construction is not The design requires the use of a two-speed fan; some construction units do not order the fan according to the design model, but purchase a fan with a smaller power specification, resulting in a serious shortage of fan air volume.
2. The mechanical pressurized air supply system and the natural smoke exhaust facility are set repeatedly. For a type of public building with a building height of more than 50 meters and a residential building with a building height of more than 100 meters, according to the requirements of the "High Regulations", a mechanical pressurized air supply system should be installed. Some projects also use natural smoke exhaust at the same time. , In the event of a fire, when the mechanical pressurized air supply system and the natural smoke exhaust window are opened at the same time, it is difficult to form a positive pressure in the smoke-proof staircase, and the smoke-proof effect cannot be achieved.
3. The pressure difference adjustment device is not designed for the combined positive pressure air supply system. According to the requirements of the specification, the smoke-proof stairwell and the shared front room with mechanically pressurized air supply should be provided with independent air supply systems. When the same system must be shared, automatic pressure difference should be set on the branch duct leading to the shared front room. Adjusting device. Many currently designed co-positive pressure air supply systems are not designed with pressure difference adjustment devices, and cannot form a stairwell with a higher residual pressure value than the front room.
4. The smoke-proof zone does not set up smoke-proof facilities according to the requirements of the regulations. A considerable part of the project, especially large shopping malls where mechanical smoke exhaust is installed, did not install smoke blocking walls under the ceiling according to the requirements of the specification. Although some basements use building beams as smoke blocking facilities, the smoke exhaust system of the smoke exhaust system is not It is installed on the ceiling or the wall close to the ceiling according to the specification, but under the beam.
5. The air supply outlet setting does not meet the requirements. Some vertical smoke prevention and exhaust systems use fixed louvered normally open air outlets for air outlets. The size of the air outlets is basically the same, resulting in serious imbalances in the air volume and speed of the air outlets on each layer, and the air volume at the air outlet farther from the fan is insufficient, even at the end The wind speed and volume of the air supply outlet are close to zero.
6. The construction quality of the duct shaft is poor and the air leakage is serious. There are quite a lot of projects because the ventilation shaft is not plastered, the pipeline connection is not tight, the normally closed air outlet is not tightly closed, and the air leakage is very serious, resulting in the wind speed and air volume of the air supply outlet and the exhaust outlet not meeting the specification requirements. Some construction units even Cancelling the air duct connecting the vertical shaft to the ceiling air outlet and using the ceiling space instead of the air duct often results in the air duct air velocity being close to zero.
At the same time, the exhaust outlet of the fan of the smoke exhaust system is installed indoors, which causes the smoke to be discharged from the indoor to the indoor in the case of a fire, which not only loses the smoke exhaust function, but may also cause the spread of the fire.
3. The power distribution of the smoke prevention fan does not meet the requirements of the specification
One is that the power supply and distribution of wind turbines cannot meet the load level requirements of high-rise civil buildings. Some power supply lines are not connected to the fire power supply, but to the floor lighting distribution box. Some designs use single-circuit power distribution lines, and some designs do not have an automatic terminal power switch device, which can not reach the first or second power supply. Dedicated dual circuits for load requirements, with provisions for automatic end switching devices.
The second is that the installation of open distribution lines does not meet the requirements. The power distribution lines of some smoke prevention and exhaust fans wear PVC plastic pipes, and some metal pipes are not painted with fire-resistant coatings, which do not meet the requirements of the fireproof performance of the pipes.
4. The parts where mechanical smoke prevention and exhaust facilities should be installed are not set according to the requirements of the specification
1. Smoke-proof stairwells and front rooms of high-rise civil buildings with podiums, front rooms of fire-fighting elevator rooms or shared front rooms, when the upper part of the podium can be opened for natural smoke exhaust, the skirt part does not have natural smoke exhaust When conditions are met, its front room or shared front room is not equipped with a positive pressure air supply system as required by the specification.
2. There is no natural smoke exhaust in the inner walkway over 20 meters. Some designers think that it has natural smoke exhaust conditions because of the natural smoke exhaust in the front room of the smoke-proof stairwell connected to it. Mechanical smoke exhaust facilities are not installed in accordance with the specifications. .
Countermeasure
In response to the above-mentioned problems, the fire supervision department should strengthen the supervision and management of the design and construction of building smoke prevention and exhaust facilities from the following aspects:
1. The business guidance and training for the design and construction personnel of smoke prevention and exhaust facilities should be strengthened. Local fire departments generally attach great importance to the professional design and construction of fire alarms, electrical, and fixed (automatic) fire extinguishing facilities. The professional design and construction personnel of fire extinguishing facilities are often ignored during the training process.
2. The system that the construction of smoke prevention and exhaust facilities is undertaken by the construction unit of the fire protection facilities should be implemented. Smoke prevention and exhaust facilities are an important part of building automatic fire protection facilities. According to regulations, their construction should be undertaken by the construction unit of fire protection facilities. However, at present, the construction of smoke prevention and exhaust facilities in many projects is installed by professional air-conditioning construction units.
3. When reviewing construction drawings, the construction review personnel of the fire protection supervision department should pay attention to the review of the design of smoke prevention and exhaust facilities, and focus on the setting of natural smoke exhaust windows, window area, mechanical smoke prevention and exhaust facilities, and fans The selection, the setting of the air supply and exhaust outlets, and the smoke prevention zones are reviewed. At the same time, the supervision and management of the smoke prevention and exhaust facilities should be strengthened during the construction, and the smoke prevention and exhaust facilities should be listed as an important content of the construction supervision and inspection, so as to be timely If problems are found, guide and urge the construction unit to carry out rectification.