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The security measures of the central computer room include preventing illegal intrusion into the network, lightning protection, grounding, fire prevention, blackout prevention, anti-static electricity, etc. These are all essential and important conditions for ensuring the safe operation of the equipment.
I. UPS power supply system design
The effective operation of building intelligent systems depends on the normal power supply, especially the room should not be blacked out, because the engine room is the head of the intelligent building. As we all know, when a computer suddenly loses power while it is working, it may cause data loss. So the power system in the computer room is very important. For the general distribution system of intelligent buildings, normal blackouts or accidental blackouts are allowed, but they are not allowed for the central engine room. The general solution is divided into two parts. The first is that the front-end AC power source is used to introduce two-way mains electricity. When conditions permit, additional generators can be added to provide multi-channel power supply and improve the reliability of power supply. Second, there is no interruption in the equipment room. Power UPS, with a certain DC battery pack as a backup power supply, can ensure power supply. The former is a traditional way to improve power supply reliability, and the latter is a method that has been increasingly applied in recent years with the rapid development of information technology.
There are two types of UPS power supply available. One is online, that is, the UPS is always in the power supply state, and it is working all the time. The UPS has replaced the utility power supply for the computer network equipment. The second type is backup type, which means that the computer network equipment usually supplies power from the mains, and only when the mains power is out of power, it immediately turns to the UPS. There is a zero-crossing problem in standby power supply, that is, when the utility power fails, no matter what kind of closing mode, it can not avoid the instant no power problem. Mains electricity is 50HZ, Pentium IIPC is more than 500MHZ, apparently, in the moment of power outage, the computer may lose data. The specific method is to divide and conquer: if there is a normal power outage, there must be a notice in advance and the UPS can be put in advance; if it is a fault (short-circuit, grounding) power failure, the current on the inductor cannot jump, the voltage on the capacitor cannot jump, and the UPS can The automatic access is set to be less than the trip current value, ie, the UPS is already connected before the circuit is disconnected.
UPS power is developing towards high power, low noise, intelligence, and networking. This is exactly what the central computer room needs. High-power UPS power supply (such as 20, 30, 60KVA and above) mostly has the function of parallel redundancy, and the newly emerged hot-swappable and modular battery array further improves the reliability of power supply. This is because the "array structure" was previously used in a "disk array" of a computer network, which proves to be beneficial to the improvement of reliability.
Second, the application of anti-static floor
Anti-static electricity mainly refers to the timely elimination of electrostatic charges generated in various places inside the computer room. Triboelectricity is a natural phenomenon. The accumulation of static electricity can cause accidents and endanger the safety of electronic equipment and personal safety. Therefore, the room should use anti-static floor, discharge static electricity through the ground. The floor is generally 0.3m away from the ground. In order to guarantee the construction quality, the engine room project shall be undertaken by the unit that has the qualification for construction of the engine room project.
Third, the large number of electronic devices work in the engine room lightning protection and grounding design <br> <br> central office lower voltage, higher precision equipment, poor tolerance of lightning, once suffered, often huge losses. Therefore, there is a higher level of lightning protection here, which requires higher measures to prevent various lightning strikes. There are many kinds of lightning strikes. The lightning protection measures in the engine room are mainly directed to direct lightning and induced lightning. The general practice is to install lightning rods and lightning conductors on the roof of the building to prevent direct lightning strikes. Connect the main bars of the whole structure in the building to form equal-voltage Faraday cages and equalizing rings to prevent side-impact lightning. (High-rise buildings are at a height of 30 meters and above. The three-story ring beam reinforcement is connected with the main reinforcement in the column to form a pressure equalization ring; the foundation pile conductors are interconnected at the building foundation to form a good grounding and ground potential distribution within the building. In addition, the metal equipment on the surface of the building and the metal pipes entering the home are well connected with the grounding grid to ensure the equipotentiality within the building.
To prevent the intrusion of high-voltage lightning waves into the equipment room, various anti-overvoltage devices can be used at the front end of the equipment room. For example, a three-stage lightning protection device in front of a network device can effectively divide the voltage limit to prevent the intrusion of induced lightning waves. The third-level refers to the front end of the power supply terminal, UPS terminal, server, or distribution frame. In addition, antenna feeders, signal lines, and data communication lines that are introduced into the room outdoors should be equipped with lightning arresters at home.
The grounding system includes lightning protection grounding, AC work grounding, DC grounding, PE protection grounding, shield grounding, and antistatic grounding. The latter three can be interconnected. The grounding method generally adopts the joint grounding method. That is, the lightning protection grounding, the protection grounding, and the work grounding are directly connected with the grounding net. The total grounding resistance should be less than 1 ohm, that is, the so-called zero grounding resistance. Special grounding devices can also be set when conditions permit.
In the digital circuit, the logic ground of the equipotential surface and the signal ground of the analog circuit providing the reference potential become the DC ground. The reference potential of the DC grounding system is derived from the total equipotential copper bar. In engineering, an insulated copper conductor with a cross-sectional area of ​​35 mm2 can be used to route the protection pipe to the weak electrical equipment as a DC ground.
There are many AC and DC filters in electronic devices, which are used to prevent interference voltages of various frequencies from invading through power lines so as not to affect the operation of low-level signal devices. The grounding of the AC-DC filter is called power grounding. The power grounding system is used to lead from the distribution box to the weak electrical equipment with an insulated copper core wire with cross-sections such as phase conductors. This grounding wire is connected to the N-wire (ie neutral) in the TN-S five-wire system.
Shield grounding and antistatic grounding are used to solve electromagnetic radiation and electromagnetic interference problems. With the increasing number of high-frequency communication facilities in smart buildings, anti-jamming is increasingly important. Electromagnetic interference is the parasitic electrical energy radiated by the electronic system. It can reduce the accuracy of data transmission, increase the bit error rate, affect the clarity, and cause electromagnetic pollution. In order to prevent external electromagnetic interference, the shielded wire or threaded metal tube inside and outside of the electronic device and the device is grounded and shielded in the entire process. This is called shielded grounding. In general, the environment in the equipment room is relatively dry, and static electricity is easily generated, which in turn causes interference to electronic equipment. The ground used for this purpose is grounded against static electricity. The general practice of shielding grounding and antistatic grounding is to lead the PE weak mains from the building's total equipotential copper bar, and set weak equipotential copper bars on each floor. The outer casing of the electronic device, metal pipe and antistatic grounding are all equal to this potential. Copper rows meet.
In addition to the above measures, the security facilities of the computer room should also have access control, anti-theft, CCTV monitoring, firewall software, and fire alarms.
Fourth, the room design standard <br> <br> central room can be divided into preliminary design stage design, civil engineering design, detailed design layout and decoration, design and as-built drawings joint trial. The preliminary plan should determine the composition, main functions, and macro requirements of the computer room. The civil design determines the location, area, shape, height and so on. Deepening the design of the machine room to determine the plane, facade layout, decoration specific practices, mechanical and electrical equipment selection, lighting and so on. The design of the central engine room is mainly in accordance with the specifications of GB50174-93 Computer Room Design Standards. The main contents involved include construction standards, electrical systems, construction environment, fire prevention, anti-accident prevention, and destruction.
The architectural profession must first select the location of the central engine room. From the economic point of view, it is necessary to avoid the high-value golden area; from the technical point of view, it should be close to the middle section of the system line, and it should also be as close to the weak electric shaft as possible to facilitate the introduction of trunk lines such as the urban telephone network, cable television network and fiber optic data network into the equipment room; Considering that it is not required to be adjacent to rooms with potential hazards, such as toilets and gas rooms, in the upper and lower quarters, the height and ceiling height of the rooms should be taken into consideration. Attention should be paid to the shape, orientation, natural ventilation and lighting conditions, size, etc. of the location; in addition, the central engine room should be The relative locations of computer rooms such as the telephone room, fire control room and television picking and weaving room should also be taken into account. Although there are many of these factors, only a few are hard. For example, ceiling height of Class A smart buildings must be 2.7m, B and C levels are 2.6m and 2.5m; however, the net height of the central engine room and other weak machine rooms must not be lower than 2.7. m, not divided into A, B, C grade. In a comprehensive view, the location of the engine room is generally preferred on the second floor, and on the top floor or the basement floor of the podium. The reason is that the central engine room can be on duty with the fire control room of the first floor (internal transfer) when it is on the second floor. The top floor of the podium is closer to each antenna and the cable is centered. The ground floor is generally close to the main building equipment room.
The structural professional should pay attention to the position, weight, size and shape of the UPS battery, determine its ground bearing capacity (around 800KG/M2), and leave holes and configure lintels. In addition to the mechanical structure, the structural profession must form a "Faraday cage" at the engine room, so that the engine room maintains the equipotential voltage in the engine room when all kinds of lightning strikes are involved, including the induction of lightning, eliminating the step voltage and achieving the goal of protecting people and machines.
Equipment professionals should pay attention to design standards and construction standards for heating, ventilation, and air conditioning that are higher than those of ordinary offices. The related parameters of the equipment room environment are, for example, suitable temperature, humidity, oxygen content, carbon dioxide content, and dust. Content (cleanliness) and so on.
V. Room environment design
The environmental requirements of the engine room are naturally higher than those of general offices. It requires not only adequate illumination, but also proper temperature, humidity, oxygen content, carbon dioxide content, dust content (cleanliness), etc. during normal operation. One of its environmental monitoring higher than the performance of the general office is different construction standards. The national standard of the engine room is divided into A and B levels.
Unlike traditional comfort air conditioners, the precision air conditioner used in the engine room strictly controls the evaporation pressure in the evaporator, and increases the amount of air supply so that the surface temperature of the evaporator is higher than the air dew point temperature. Therefore, it is not necessary to dehumidify, and the generated cooling capacity is all used for cooling. Reduced moisture loss and improved economic efficiency. Due to the large amount of air supply, on the one hand, the air supply difference is small. On the other hand, the high frequency of air exchange in the engine room makes the entire air circulation in the entire engine room. The equipment in the equipment room can be evenly cooled. At the same time as the air circulation is good, a dedicated air filter provided by the precision air conditioner can effectively filter out the dust in the air and make the room cleanliness meet the requirements.
The computer room precision air conditioning system is generally equipped with a humidification system, a dedicated high-efficiency dehumidification system, and an electric heating compensation system. Through microprocessor processing of data sent by sensors, the temperature and humidity of the equipment room can be precisely controlled. In general, the air conditioning system does not have a humidification system. Can control the temperature, and the accuracy is low, can not meet the needs of the engine room. In addition, due to the good airtightness of the engine room and many heating devices, continuous operation, and constant operation, high reliability requirements, the general air conditioning system is difficult to perform, especially in winter, the general air conditioning is difficult due to the low outdoor condensing pressure, and the precision air conditioning system With a controlled outdoor condenser, the normal operation of the refrigeration cycle can be guaranteed.
Computer room lighting and fire fighting design
The electrical profession should pay attention to the lighting design, power equipment location, number of stations and monitoring requirements, as well as integrated grounding lead connections. The electrical load of the central engine room belongs to level 1, and a dedicated two-terminal terminal shall be used for mutual power supply circuits. The wires shall be fire-resistant or flame-retardant copper wires, and the batteries shall be closed type products. Distribution system components, materials, selection margin should be slightly larger to prevent electrical fires. When the engine room is in normal operation, not only its environmental monitoring is high, but also sufficient illumination is needed. The standard for artificial lighting in the central engine room is 150-300LX, medium is 400LX, and high is 500-750LX.
Fire design includes smoke alarm and gas fire extinguishing. Smoke alarms are mainly in the form of ceiling and cable smoke detectors. The protection radius of ceiling smoke sensation is generally not more than 5.8m, and it is not less than 0.5m away from the wall, tuyere and girder. Cable smoke detectors can be laid along walls. The fire damper shall be installed at the wall through the duct of the machine room (automatically closed when the ambient temperature reaches 70°C). The function of the gas fire extinguishing system is similar to that of a sprinkler system in an ordinary office. Its design points include the selection of the system type structure, the determination of the extinguishing agent concentration, the gas injection time, the amount of the extinguishing agent, and the immersion time. The types of gas fire extinguishing systems are mainly carbon dioxide fire extinguishing systems and haloalkan fire extinguishing systems. In addition, indoor and outdoor DC power dual-power emergency lights, fire accident broadcasts, 119 special fire-fighting telephones, fire alarm buttons and other fire-fighting facilities are also provided. Room decoration materials should meet the requirements of the relevant fire code.
I. UPS power supply system design
The effective operation of building intelligent systems depends on the normal power supply, especially the room should not be blacked out, because the engine room is the head of the intelligent building. As we all know, when a computer suddenly loses power while it is working, it may cause data loss. So the power system in the computer room is very important. For the general distribution system of intelligent buildings, normal blackouts or accidental blackouts are allowed, but they are not allowed for the central engine room. The general solution is divided into two parts. The first is that the front-end AC power source is used to introduce two-way mains electricity. When conditions permit, additional generators can be added to provide multi-channel power supply and improve the reliability of power supply. Second, there is no interruption in the equipment room. Power UPS, with a certain DC battery pack as a backup power supply, can ensure power supply. The former is a traditional way to improve power supply reliability, and the latter is a method that has been increasingly applied in recent years with the rapid development of information technology.
There are two types of UPS power supply available. One is online, that is, the UPS is always in the power supply state, and it is working all the time. The UPS has replaced the utility power supply for the computer network equipment. The second type is backup type, which means that the computer network equipment usually supplies power from the mains, and only when the mains power is out of power, it immediately turns to the UPS. There is a zero-crossing problem in standby power supply, that is, when the utility power fails, no matter what kind of closing mode, it can not avoid the instant no power problem. Mains electricity is 50HZ, Pentium IIPC is more than 500MHZ, apparently, in the moment of power outage, the computer may lose data. The specific method is to divide and conquer: if there is a normal power outage, there must be a notice in advance and the UPS can be put in advance; if it is a fault (short-circuit, grounding) power failure, the current on the inductor cannot jump, the voltage on the capacitor cannot jump, and the UPS can The automatic access is set to be less than the trip current value, ie, the UPS is already connected before the circuit is disconnected.
UPS power is developing towards high power, low noise, intelligence, and networking. This is exactly what the central computer room needs. High-power UPS power supply (such as 20, 30, 60KVA and above) mostly has the function of parallel redundancy, and the newly emerged hot-swappable and modular battery array further improves the reliability of power supply. This is because the "array structure" was previously used in a "disk array" of a computer network, which proves to be beneficial to the improvement of reliability.
Second, the application of anti-static floor
Anti-static electricity mainly refers to the timely elimination of electrostatic charges generated in various places inside the computer room. Triboelectricity is a natural phenomenon. The accumulation of static electricity can cause accidents and endanger the safety of electronic equipment and personal safety. Therefore, the room should use anti-static floor, discharge static electricity through the ground. The floor is generally 0.3m away from the ground. In order to guarantee the construction quality, the engine room project shall be undertaken by the unit that has the qualification for construction of the engine room project.
Third, the large number of electronic devices work in the engine room lightning protection and grounding design <br> <br> central office lower voltage, higher precision equipment, poor tolerance of lightning, once suffered, often huge losses. Therefore, there is a higher level of lightning protection here, which requires higher measures to prevent various lightning strikes. There are many kinds of lightning strikes. The lightning protection measures in the engine room are mainly directed to direct lightning and induced lightning. The general practice is to install lightning rods and lightning conductors on the roof of the building to prevent direct lightning strikes. Connect the main bars of the whole structure in the building to form equal-voltage Faraday cages and equalizing rings to prevent side-impact lightning. (High-rise buildings are at a height of 30 meters and above. The three-story ring beam reinforcement is connected with the main reinforcement in the column to form a pressure equalization ring; the foundation pile conductors are interconnected at the building foundation to form a good grounding and ground potential distribution within the building. In addition, the metal equipment on the surface of the building and the metal pipes entering the home are well connected with the grounding grid to ensure the equipotentiality within the building.
To prevent the intrusion of high-voltage lightning waves into the equipment room, various anti-overvoltage devices can be used at the front end of the equipment room. For example, a three-stage lightning protection device in front of a network device can effectively divide the voltage limit to prevent the intrusion of induced lightning waves. The third-level refers to the front end of the power supply terminal, UPS terminal, server, or distribution frame. In addition, antenna feeders, signal lines, and data communication lines that are introduced into the room outdoors should be equipped with lightning arresters at home.
The grounding system includes lightning protection grounding, AC work grounding, DC grounding, PE protection grounding, shield grounding, and antistatic grounding. The latter three can be interconnected. The grounding method generally adopts the joint grounding method. That is, the lightning protection grounding, the protection grounding, and the work grounding are directly connected with the grounding net. The total grounding resistance should be less than 1 ohm, that is, the so-called zero grounding resistance. Special grounding devices can also be set when conditions permit.
In the digital circuit, the logic ground of the equipotential surface and the signal ground of the analog circuit providing the reference potential become the DC ground. The reference potential of the DC grounding system is derived from the total equipotential copper bar. In engineering, an insulated copper conductor with a cross-sectional area of ​​35 mm2 can be used to route the protection pipe to the weak electrical equipment as a DC ground.
There are many AC and DC filters in electronic devices, which are used to prevent interference voltages of various frequencies from invading through power lines so as not to affect the operation of low-level signal devices. The grounding of the AC-DC filter is called power grounding. The power grounding system is used to lead from the distribution box to the weak electrical equipment with an insulated copper core wire with cross-sections such as phase conductors. This grounding wire is connected to the N-wire (ie neutral) in the TN-S five-wire system.
Shield grounding and antistatic grounding are used to solve electromagnetic radiation and electromagnetic interference problems. With the increasing number of high-frequency communication facilities in smart buildings, anti-jamming is increasingly important. Electromagnetic interference is the parasitic electrical energy radiated by the electronic system. It can reduce the accuracy of data transmission, increase the bit error rate, affect the clarity, and cause electromagnetic pollution. In order to prevent external electromagnetic interference, the shielded wire or threaded metal tube inside and outside of the electronic device and the device is grounded and shielded in the entire process. This is called shielded grounding. In general, the environment in the equipment room is relatively dry, and static electricity is easily generated, which in turn causes interference to electronic equipment. The ground used for this purpose is grounded against static electricity. The general practice of shielding grounding and antistatic grounding is to lead the PE weak mains from the building's total equipotential copper bar, and set weak equipotential copper bars on each floor. The outer casing of the electronic device, metal pipe and antistatic grounding are all equal to this potential. Copper rows meet.
In addition to the above measures, the security facilities of the computer room should also have access control, anti-theft, CCTV monitoring, firewall software, and fire alarms.
Fourth, the room design standard <br> <br> central room can be divided into preliminary design stage design, civil engineering design, detailed design layout and decoration, design and as-built drawings joint trial. The preliminary plan should determine the composition, main functions, and macro requirements of the computer room. The civil design determines the location, area, shape, height and so on. Deepening the design of the machine room to determine the plane, facade layout, decoration specific practices, mechanical and electrical equipment selection, lighting and so on. The design of the central engine room is mainly in accordance with the specifications of GB50174-93 Computer Room Design Standards. The main contents involved include construction standards, electrical systems, construction environment, fire prevention, anti-accident prevention, and destruction.
The architectural profession must first select the location of the central engine room. From the economic point of view, it is necessary to avoid the high-value golden area; from the technical point of view, it should be close to the middle section of the system line, and it should also be as close to the weak electric shaft as possible to facilitate the introduction of trunk lines such as the urban telephone network, cable television network and fiber optic data network into the equipment room; Considering that it is not required to be adjacent to rooms with potential hazards, such as toilets and gas rooms, in the upper and lower quarters, the height and ceiling height of the rooms should be taken into consideration. Attention should be paid to the shape, orientation, natural ventilation and lighting conditions, size, etc. of the location; in addition, the central engine room should be The relative locations of computer rooms such as the telephone room, fire control room and television picking and weaving room should also be taken into account. Although there are many of these factors, only a few are hard. For example, ceiling height of Class A smart buildings must be 2.7m, B and C levels are 2.6m and 2.5m; however, the net height of the central engine room and other weak machine rooms must not be lower than 2.7. m, not divided into A, B, C grade. In a comprehensive view, the location of the engine room is generally preferred on the second floor, and on the top floor or the basement floor of the podium. The reason is that the central engine room can be on duty with the fire control room of the first floor (internal transfer) when it is on the second floor. The top floor of the podium is closer to each antenna and the cable is centered. The ground floor is generally close to the main building equipment room.
The structural professional should pay attention to the position, weight, size and shape of the UPS battery, determine its ground bearing capacity (around 800KG/M2), and leave holes and configure lintels. In addition to the mechanical structure, the structural profession must form a "Faraday cage" at the engine room, so that the engine room maintains the equipotential voltage in the engine room when all kinds of lightning strikes are involved, including the induction of lightning, eliminating the step voltage and achieving the goal of protecting people and machines.
Equipment professionals should pay attention to design standards and construction standards for heating, ventilation, and air conditioning that are higher than those of ordinary offices. The related parameters of the equipment room environment are, for example, suitable temperature, humidity, oxygen content, carbon dioxide content, and dust. Content (cleanliness) and so on.
V. Room environment design
The environmental requirements of the engine room are naturally higher than those of general offices. It requires not only adequate illumination, but also proper temperature, humidity, oxygen content, carbon dioxide content, dust content (cleanliness), etc. during normal operation. One of its environmental monitoring higher than the performance of the general office is different construction standards. The national standard of the engine room is divided into A and B levels.
Unlike traditional comfort air conditioners, the precision air conditioner used in the engine room strictly controls the evaporation pressure in the evaporator, and increases the amount of air supply so that the surface temperature of the evaporator is higher than the air dew point temperature. Therefore, it is not necessary to dehumidify, and the generated cooling capacity is all used for cooling. Reduced moisture loss and improved economic efficiency. Due to the large amount of air supply, on the one hand, the air supply difference is small. On the other hand, the high frequency of air exchange in the engine room makes the entire air circulation in the entire engine room. The equipment in the equipment room can be evenly cooled. At the same time as the air circulation is good, a dedicated air filter provided by the precision air conditioner can effectively filter out the dust in the air and make the room cleanliness meet the requirements.
The computer room precision air conditioning system is generally equipped with a humidification system, a dedicated high-efficiency dehumidification system, and an electric heating compensation system. Through microprocessor processing of data sent by sensors, the temperature and humidity of the equipment room can be precisely controlled. In general, the air conditioning system does not have a humidification system. Can control the temperature, and the accuracy is low, can not meet the needs of the engine room. In addition, due to the good airtightness of the engine room and many heating devices, continuous operation, and constant operation, high reliability requirements, the general air conditioning system is difficult to perform, especially in winter, the general air conditioning is difficult due to the low outdoor condensing pressure, and the precision air conditioning system With a controlled outdoor condenser, the normal operation of the refrigeration cycle can be guaranteed.
Computer room lighting and fire fighting design
The electrical profession should pay attention to the lighting design, power equipment location, number of stations and monitoring requirements, as well as integrated grounding lead connections. The electrical load of the central engine room belongs to level 1, and a dedicated two-terminal terminal shall be used for mutual power supply circuits. The wires shall be fire-resistant or flame-retardant copper wires, and the batteries shall be closed type products. Distribution system components, materials, selection margin should be slightly larger to prevent electrical fires. When the engine room is in normal operation, not only its environmental monitoring is high, but also sufficient illumination is needed. The standard for artificial lighting in the central engine room is 150-300LX, medium is 400LX, and high is 500-750LX.
Fire design includes smoke alarm and gas fire extinguishing. Smoke alarms are mainly in the form of ceiling and cable smoke detectors. The protection radius of ceiling smoke sensation is generally not more than 5.8m, and it is not less than 0.5m away from the wall, tuyere and girder. Cable smoke detectors can be laid along walls. The fire damper shall be installed at the wall through the duct of the machine room (automatically closed when the ambient temperature reaches 70°C). The function of the gas fire extinguishing system is similar to that of a sprinkler system in an ordinary office. Its design points include the selection of the system type structure, the determination of the extinguishing agent concentration, the gas injection time, the amount of the extinguishing agent, and the immersion time. The types of gas fire extinguishing systems are mainly carbon dioxide fire extinguishing systems and haloalkan fire extinguishing systems. In addition, indoor and outdoor DC power dual-power emergency lights, fire accident broadcasts, 119 special fire-fighting telephones, fire alarm buttons and other fire-fighting facilities are also provided. Room decoration materials should meet the requirements of the relevant fire code.
During the production of highway painting, put glass bead into paint based on the ratio of 18-25% (weight percentage), so that the highway paint can still keep reflectivity during wear and friction. The ratio is refer to the specification of Communication Industry Standard of the People`s Republic of China No. JT/T280-2004, the standards which is different in different countries and areas.
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The appearance of glass bead should be colorless, loosen and spherical particle, should be clean without impurity, and without agglomeration |
According to the specification of Communication Industry Standard of the People`s Republic of China No.GB/T24722-2009, the granulometry is shown in the table below:
The glass bead can be produced based on the standard of countries or areas, such as EN1423/1424, AASHTO M247, BS6088, JIS R3301 and KS L2521 etc.
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