Chemicals, petroleum, coal and other occupational operating environments have the risk of explosive gases or dust. Therefore, it is necessary to install explosion-proof cameras. Ensuring a safe environment for industrial production is the primary meaning of the existence of explosion-proof surveillance cameras. Now the factory pays more and more attention to production safety, and the requirements for operating power are getting higher and higher. The factory must improve production safety, improve production power, rational use of human resources, and explosion-proof cameras have played a great role. Today Briefly introduce the relevant knowledge of explosion-proof monitoring equipment.
How to choose explosion-proof surveillance lenses
The principle of selecting a lens for an explosion-proof camera is like a general camera, with 4-25MM lens optional. First of all, the appropriate lens is selected according to the interval and scale to be monitored on site. For example, the monitored object is about 30 meters away from the device point, then a 12MM or 16MM lens should be selected. If you want to see more clearly, then choose 16MM lens, vague, choose 12MM lens. In practice, the lens has a theoretical length value. The number of millimeters of the lens multiplied by 2 is equal to the interval of the measured object. The disadvantage of the lens is that it does not look far and wide, and it does not look wide. The smaller the number of millimeters of the lens, the larger the size, and the shorter the interval.
Second, the explosion-proof camera device
1. Under the conditions of satisfying the requirements of the field of view of the supervision policy, the height of the device: the height of the indoor camera is preferably 2.5 to 5m, and the outdoor is preferably 3.5 to 10m; The camera is at opposite corners, and the optical axis of the camera is 45 degrees with the two walls of the elevator and the ceiling.
2. Pay attention to the camera and its supporting devices to prevent damage and be harmonious with the surrounding environment.
3. In a strong electromagnetic disturbance environment, the camera unit should be insulated from the ground.
4. Outdoor installations shall adopt lightning protection measures.
5. The camera device must be sturdy to avoid monitoring screen shake.
6. It is necessary to adjust the infrared lamp at night. At night, the imaging direction of the infrared beam is adjusted by an imaging device (such as a monitor). And can be useful to adjust the lens aperture setting.
7. The height of the infrared lamp device should not exceed 4 meters. Too high will affect the reflectivity of light. The viewing angle should be 20 degrees from the top to the bottom, and the reflectivity will decrease when the elevation is too large.
8. Infrared cameras, try to avoid direct light sources, because the power control part of the infrared lamp is based on the photoresistor installed on the infrared lamp board to control whether the operating power of the infrared lamp is on or not.
9. In the field of view of the infrared camera, try to avoid all black objects, open areas, water and other objects that absorb infrared light. The infrared lamp supporting the CCD camera is to reflect infrared light on the object to the CCD camera lens to form a picture. If infrared light is absorbed or weakened, it will greatly reduce the useful illumination of infrared lamps
10. It is necessary to ensure the operation target of the infrared lamp (see the product manual for details). For example, the power supply power of the infrared lamp must be higher than the operating power of the infrared lamp itself.
11. The user must first read the operation manual carefully when using infrared light, especially the precautions to ensure the safety of personal equipment. Check whether the above-mentioned supporting aspects meet the requirements, and whether the influencing factors to be considered are considered. If the requirements are not met, the equipment used can be adjusted in time.
12. Be careful not to touch the lens and CCD target surface during the installation process, and do not let the dust float on the camera.
13. PTZ device:
1) The device of the gimbal should be strong, and there should be no shaking when rolling.
2) According to the product skills and system planning requirements, check whether the scale of the rolling viewpoint of the gimbal is satisfactory.
3) The decoder should be installed in the vicinity of the gimbal or in the ceiling (but there must be a manhole).
14. Avoid exposing the equipment to large motors such as elevators, pumps and fluorescent columns, and various high-power radio equipment environments.
15. It is very important to choose a good BNC head. A bad BNC head will make you die better, without exaggerating.
Third, the device of the line part
1. Video cable: SYV75-3 video cable generally transmits within 300 meters, 75-5 transmits within 500 meters, and 75-7 can transmit 800 meters; other requirements concern the quality of CCTV coaxial cable, RG59U, RG6 and RG11 are required to be 100% copper core and 95% copper woven shielding layer. The maximum resistance of the line loop cannot exceed 15 ohms. When the interval exceeds 500 meters, it is necessary to consider the use of optical cable transmission.
2. Power cord: The flame-retardant cable should be selected, and the protective sheath is relatively strong. Under the premise of saving engineering costs, use a thick point as much as possible to reduce the attenuation of the power supply.
3. Control line: Generally use shielded 2 * 1.0 cable, RVVP2 * 1.0.
4. Threading pipe: In general, PVC pipe is sufficient. Galvanized steel pipe should be used for underground or explosion-proof projects.
1. The orientation of the console and cabinet (rack) devices should meet the planning requirements, and the devices should be stable and sturdy to facilitate operation and protection. The net clearance between the opposite and side of the cabinet frame and the wall should meet the repair requirements.
2. All devices for controlling, displaying and recording terminal equipment should be stable and easy to operate. In the meantime, the monitor (screen) should avoid direct light from outside, and when it is unavoidable, it should adopt the method of avoiding light. Ventilation and heat dissipation shall be provided for the equipment installed in the console and cabinet (rack), and the connection between the internal connector and the equipment shall be reliable.
3. All the cables in the control room should be provided with cable troughs and cable entry holes according to the orientation of the equipment. They should be neatly arranged, bundled, numbered, and permanently marked.
4. The equipment of the operating environment security system that controls the equipment is required to be installed in a clean air-conditioned room, and is required to be installed in a standard 19 "rack. There should be appropriate space between the equipment, and forced ventilation fans must be used.
5. Ensure that the front, neutral and ground wires of the power supply in the monitoring room are connected in accordance with the standard. With the monitoring center equipment (supervisor, hard disk recorder, matrix, video distributor) open, use the analog multimeter to communicate the voltage level to measure the voltage to ground of the above equipment casing and the video cable connector connected to the camera. The higher the voltage, the more easily the video output part of the camera is damaged. When the voltage is not zero, avoid plugging or unplugging the video cable while the power is on.
V. Attentions for installation:
1. Installation explosion-proof cameras should pay attention to the orientation of the installation: local installations that avoid strong light should be selected, which is useful when the demand for wide dynamics is high or the photography is ambiguous.
2. Select the device according to the performance of the camera. If the night vision monitoring function is completed by white light, it is best to choose the device where the light is dark and there is a necessary device.
3. For the cameras with no infrared function, they need to be installed in a bright environment.
4. The cables should be routed as far as possible.
5. In case of disturbance, you need to pay attention to strengthening the device to prevent the picture from being ambiguous.
Six, some precautions in equipment protection
In the process of protecting the explosion-proof monitoring system equipment, some conditions should be taken into consideration to make the equipment operate normally, and the first thing to do is to prevent moisture, dust, corrosion, lightning, and disturbance.
1, moisture-proof, dust-proof, anti-corrosion
Regarding the various collection equipment of the explosion-proof monitoring system, because the equipment is directly placed in a dusty environment, it will directly affect the operation of the explosion-proof equipment. It is necessary to do a good job of protection against moisture, dust and corrosion. If the explosion-proof camera is hung on the shed for a long time, the explosion-proof shield and explosion-proof glass will soon be covered with a layer of dust, carbon ash, etc., which is dirty and black and corrosive, which seriously affects the viewing function. Explosion-proof equipment causes damage, so it is necessary to do a good job of dust-proof and anti-corrosion protection of explosion-proof cameras. In some areas with heavy moisture, it is necessary to adjust the device orientation and equipment protection during the protection process to improve the equipment's ability to prevent moisture. Together with high-humidity zones, dehumidification methods must often be adopted to deal with moisture problems.
2.Lightning protection and anti-interference
Anyone who has only been engaged in the protection of the electromechanical system knows that in the thunderstorm climate, it is common for explosion-proof equipment to be struck by lightning, which creates a great safety hazard for the normal operation of explosion-proof monitoring equipment. Therefore, explosion-proof monitoring equipment has It is necessary to pay great attention to the problem of lightning protection. The first method of lightning protection is to make a lightning protection grounding network for equipment grounding. An inductive grounding network with a ground resistance of less than 1 ohm should be prepared according to the isoelectric body plan, and the lightning protection grounding of the weak electrical system and the electrical lightning protection grounding network should be eliminated. Mixed practices to avoid clutter from the power ground grid to disturb the equipment. Anti-interference is the first to adhere to the strong and weak electrical separation guidelines when wiring, separate power cables from communication cables and video cables, and strictly follow the wiring standards for communication and power occupations.
Seven, simple handling
1.How can I not see pictures in explosion-proof monitoring?
First check whether there is any problem with the camera imaging. If there is no problem with imaging, please check the power of the camera;
If the power is normal, check the transmission equipment of the camera (such as optical transceiver);
If the transmission equipment is good, then check the connection of the transmission line;
If the connector of the transmission cable is good, then check the transmission cable;
If there is no problem with the transmission cable, check the signal access device;
If the signal access device is good, check the system settings of the signal access device.
2. Vague picture of explosion-proof camera
Maybe the focal length of the lens is not adjusted properly;
Oil, dirt or dust on glass, lens or CCD;
If it is vague at night, in order to save costs, some manufacturers plan shortcomings. The infrared lamp is too close to the lens, forming a reflection, and the infrared lamp is too close to the camera. These types of products are not good at night.
3.The explosion-proof camera is installed at the scene. Why is there no picture?
Check whether the power supply of the explosion-proof camera is well connected and whether the power supply voltage is satisfactory;
Whether the BNC head or video cable is outstanding in touch;
If you use a manual iris lens, you need to check whether the iris is open, and the automatic iris lens needs to be adjusted; the LEVEL potentiometer can make the iris in a proper orientation.