Engineering quality of fire dampers and smoke exhaust valves

1. The main uses of fire dampers and smoke exhaust valves Most high-rise and other modern buildings are equipped with ventilation, air conditioning and smoke prevention and exhaust systems. Once a fire occurs, the pipes in these systems will become channels for the spread of flames and smoke. In order to prevent the fire from spreading and expanding through the air ducts, the installation requirements for fire dampers and smoke exhaust valves are clearly stipulated in the “Fire Protection Code for Design of Buildings” GBJ16-87 and the “Fire Protection Code for Design of High-Rise Civil Buildings” GB50045-95. Fire dampers are used in the supply and return air ducts of ventilation and air-conditioning systems. They are usually open. When a fire occurs and the gas temperature in the pipe reaches 70°C, it will close automatically. It can meet the requirements of fire resistance stability and fire resistance within a certain period of time. Integrity requirements, acting as a smoke and fire barrier. The smoke exhaust valve is used on the smoke exhaust system pipe or the suction inlet of the smoke exhaust fan. It is usually closed. When a fire occurs, the valve is opened manually or automatically through the fire alarm signal, and the smoke exhaust is coordinated according to the system function. When the smoke in the pipe It automatically closes when the air temperature reaches 280°C, and can meet the requirements of fire resistance stability and fire resistance integrity within a certain period of time, acting as a smoke and fire barrier. ​

2. The important role of fire dampers and smoke exhaust valves in ventilation, air conditioning and smoke prevention and exhaust systems

Fire dampers include gravity fire dampers, fire control valves, fire vents, pneumatic fire dampers, smoke fire dampers, electronic automatic smoke fire dampers and other products; smoke exhaust valves include smoke exhaust fire dampers, plate smoke exhaust vents (ceiling ), smoke exhaust vents for shafts and other products. Fire dampers and smoke exhaust valves are important components in ventilation, air conditioning and smoke prevention and exhaust systems. They play an important role in the system in the following three aspects:

2.1. Smoke and fire prevention function

In the air supply system, the air sent by the blower must be distributed to the branch pipes through the main pipe; in the smoke exhaust system, after the smoke flows from the branch pipe to the main pipe, it enters the smoke exhaust fan and is discharged. When a fire occurs in a building, in the ventilation and air-conditioning systems, in order to prevent the fire from spreading through the air supply system, when the gas temperature in the air supply system reaches 70°C, the fuse on the fire damper mechanism is activated and the valve is quickly closed. Cut off the path for smoke and fire to spread along the air duct. Similarly, in the smoke exhaust system, when a fire occurs, the smoke exhaust valve is opened to exhaust smoke. In order to cut off the flow of high-temperature smoke in the smoke exhaust pipe and prevent the fire from spreading to another fire protection zone, when the temperature of the exhaust smoke reaches At 280°C, the smoke exhaust fire damper and the fuse on the smoke exhaust outlet are activated, and the valves must automatically close to prevent smoke exhaust. It can be seen that fire dampers and smoke exhaust valves achieve the function of isolating smoke and preventing fire when they are connected when they are connected and disconnected when they are disconnected. ​

2.2. Regulatory effect

In the pipeline design of ventilation and air conditioning systems, despite calculations, if the operating conditions of the actual project change, it is necessary to adjust the air volume of each part of the system through fire dampers, conduct system debugging, and adjust the opening of the valves. Fix it and distribute it reasonably to meet the design requirements.

2.3. Start the no-load function

When installing and debugging all centrifugal fans and fire-fighting smoke exhaust axial fans in ventilation, air conditioning and smoke exhaust systems, for the sake of safety, the starting current of the motor should be minimized, usually without load, and this is achieved by temporarily cutting off the pipeline through a valve. ​

3. Quality requirements in engineering applications

3.1. Product quality requirements

At present, there are many manufacturers of fire protection and smoke exhaust products. Our fire supervision, construction approval department and design department should strictly control the products and allow Party A to choose products with complete “three certificates” and qualified products, that is, they must have the manufacturer’s our factory certificate, Product sales license from the public security fire protection agency, product inspection report from the National Fireproof Building Materials Quality Supervision and Inspection Center. Product performance and quality can be reflected from the national inspection report and product technical parameters, which are based on the national standards “Fire Damper Test Method” GB15930-1995 and “Smoke Exhaust Fire Damper Test Method” GB15931-1995. Its product quality requirements are reflected in 5 aspects:

3.1.1. Temperature sensor action performance test

The temperature-sensing elements of fire dampers and smoke exhaust valves are tested at the prescribed temperatures of constant-temperature water baths and oil baths respectively, and through non-action and action tests to check whether they can be closed accurately at the required temperature. ​​​

3.1.2. Close reliability test

After 250 closing operations on the test bench, the test piece should be able to be closed flexibly and reliably from the open position, and each component should have no obvious wear, deformation, or damage that affects its sealing performance. This is used to check the reliability of the shutdown. ​

3.1.3. Salt spray test

The test piece is sprayed with salt spray in a salt spray box. The test piece should be able to reliably close from the open position to test the corrosion resistance of the valve in actual engineering. 3.1.4. Air leakage test Under the specified pressure difference condition between the front and rear of the valve body, the air leakage per unit area of the test piece shall not exceed 700Nm3/(h·m2) to test the sealing performance of the valve after closing. ​

3.1.5. Fire resistance test

Through the fire resistance test, the fire resistance of the valve is determined based on two indicators: the closing capacity within the specified time and the air leakage per unit area. ​

In addition, the technical parameters of the product require that its fire resistance limit is 3h. ​

3.2. Installation quality requirements

During the daily fire inspection and project acceptance work, the author found that due to installation and construction quality problems, the fire smoke exhaust valve did not open properly or was faulty, and the smoke exhaust valve, smoke exhaust outlet, fire damper, and fire vent were difficult to reset. This should attract the attention of the construction party and pay attention to the following installation requirements. ​ 3.2.1. Fire dampers and smoke exhaust valves should be constructed strictly according to the drawings, and separate supports and hangers should be installed to prevent the air ducts from deforming at high temperatures and affecting the function of the valves. ​

3.2.2. When the valve is installed on the ceiling or in the air duct, an access hole should be provided on the ceiling plate or the air duct wall. Generally, the size of the access hole is not less than 450×450mm. When conditions are limited, access holes on the ceiling can also be used. Reduced to 300×300mm. ​

3.2.3. The air duct between the fire damper and the firewall (or floor) should be made of steel 4130 plates with δ ≥ 1.5mm. It is best to use refractory insulation or non-combustible material protection outside the air duct to ensure the safety of the firewall. Fire resistance. ​

3.2.4. There should be a clear space of 350mm on the side of the valve’s operating machinery to facilitate maintenance. ​​

4. Some problems existing in fire prevention and smoke exhaust valve projects

During my daily fire protection construction review, project inspection and acceptance work, I found some problems with fire protection and smoke exhaust valves, as follows, for reference by colleagues. ​

4.1. The supply and return air ducts of the fire control room are not equipped with fire dampers where they pass through the wall. ​​

During the construction review process, it was discovered that the supply and return air ducts of the fire control room in some engineering design drawings did not have fire dampers where they passed through the wall, which was inconsistent with Article 6.2.2 of the “Design Code for Automatic Fire Alarm Systems” GB50116-98. The purpose of setting up a fire damper is to ensure the fire safety of the fire control room. ​

4.2. The fire control equipment has imperfect control and display functions for smoke prevention and smoke exhaust facilities. According to Article 6.3.9 of the specification GB50116-98: After the fire alarm is confirmed, the air conditioning supply to the relevant parts must be stopped and the electric fire protection must be turned off. valve, and receive its feedback signal; at the same time, start the smoke prevention and exhaust fans, smoke exhaust valves, etc. in the relevant parts, and receive its feedback signal. Some engineering linkage controls cannot control smoke exhaust valves and smoke exhaust outlets in separate areas, and some cannot receive their feedback signals and cannot reflect the opening and closing status of valves.

4.3. The pipeline network gas fire extinguishing system does not have a pneumatic fire damper. ​​

Article 6.3.4.3 of GB50116-98 requires: “During the delay phase, fire doors and windows should be automatically closed, the ventilation and air conditioning system should be stopped, and fire dampers in relevant parts should be closed.” This requires that pneumatic fire dampers must be installed in the gas fire extinguishing system of the pipeline network. Fire damper, linked with fire control equipment. This function does not exist in individual projects. ​

4.4. There is no remote control when air supply and smoke exhaust share the same air duct.

When some building basements and parking lots use air ducts for air supply and smoke exhaust, we found that the stop valves in front of the air blower and smoke exhauster can only be manually operated on site and cannot be remotely controlled from the control room. Normally, when the air blower is working, the cut-off valve at its front end The valve is open. In the event of a fire, people need to go to the scene to close the stop valve in front of the fan. This is very impractical and directly affects the smoke exhaust system. Therefore, it is recommended to add remote control function to its stop valve. ​

5. System linkage debugging and maintenance management. Fire dampers and smoke exhaust valves are not independent smoke-proof and fire-retardant products in actual projects, but have their own unique linkage logic relationships in the entire fire linkage control system. Therefore, in order to ensure that it plays a role in the fire protection system, before the system is accepted, it must be fully debugged according to the linkage requirements to make the ventilation, air conditioning and smoke prevention and exhaust systems meet the specification requirements. After acceptance, a dedicated person should conduct planned daily maintenance and management to ensure that the valve body is in normal condition and can perform its function of preventing smoke and fire.