"Construction and Transportation" Expressway Mechanical and Electrical Equipment Installation Key Technologies and Construction Technology

The normal operation of the expressway needs support from many aspects, and the electromechanical equipment occupies an important position in it. In order to exert the application advantages of the electromechanical equipment, it should be installed in place during the construction. In this regard, it is worthwhile for engineers to conduct in-depth discussions on the installation of mechanical and electrical equipment.

1. Project Overview

The main line project of the Hebei section of Yanchong Expressway includes service areas, tunnel management offices, ramp toll stations and other parts. In engineering projects, the workload of the tunnel monitoring system is relatively large, including multiple links such as joint design of construction drawings, equipment configuration, testing, operation, quality inspection, and delivery. The installation of mechanical and electrical equipment is the key construction content, and its construction quality should be guaranteed.

2. Key construction technologies

2.1 Cable trough and bridge installation

Choose manufacturers that meet the qualification requirements, form a stable cooperative relationship, and purchase high-quality wire ducts and bridges. The installation of the wire duct has a great impact on other links. No matter how the bridge is installed, it is necessary to ensure that the wire duct can effectively pass through the floor hole, and its size should meet the requirements. For metal trunking, it is especially critical to ensure good electrical connection. Fix the wire trough in a reasonable way to ensure that the wire trough in each installation link is stable and the contact performance of each node is good.

Damage to equipment lines is a common problem in the installation of electromechanical equipment, which can easily lead to safety accidents. In this regard, it is necessary to do a good job of monitoring the equipment cables and connect them to the ground network of the monitoring equipment room. When installing the wire trough, pay attention to the distinction between the strong and weak wire troughs. The distance between the two should be ≥20cm, and they do not interfere with each other. During the laying of the horizontal trunking, the principle of separate laying of strong and weak currents should be followed to avoid crossing, and the level error of the trunking should be minimized after installation. The equipment installation cabinet uses plastic trunking, and other parts use metal trunking.

2.2 Installation of electromechanical equipment

To determine the installation range of electromechanical equipment, the equipment box and the cabinet should be mainly considered. To maintain a stable operation state, high-efficiency heat dissipation can be achieved. The design drawings have a guiding role, and the installation of electromechanical equipment should strictly follow the requirements. The principle of separation of strong and weak electricity must be followed when wiring in the cabinet. It should be tidy and beautiful on the premise of normal use. The binding spacing of strong and weak lines is set to 25cm, so that it can be stably placed in the wire groove.

The composition of electromechanical equipment contains some special devices, and the installation of this part should select specific tools to avoid welding operations. The function of the screw is to enhance the stability of the equipment, it cannot be damaged, it needs to be screwed into the designated position and tightened. Part of the wire trough is set in the console, where the strong and weak electricity should be separated from each other, and a number of weak wire troughs are added to reduce the adverse effects of electromagnetism.

2.3 Optical cable laying and installation

The installation of the optical cable should refer to the position of the cable, and the two have a parallel positional relationship. After the optical cable is laid, it should be straightened to make it smooth, and there should be no problems such as twisting or damage. In order to provide good conditions for the normal operation of electromechanical equipment, all optical cables must be connected to the terminal junction box. For manholes, the junction box used here should have good waterproof performance and be equipped with a repeated opening function to reduce the difficulty of subsequent maintenance. The use of optical cables is easily affected by many factors and is accompanied by signal attenuation. For this, the optical cables need to be connected outside the manhole.

The optical fiber fusion splicer is an important device for the successful completion of the splicing operation, and the installation of each link must be supported by the corresponding tools. Attention should be paid to the selection of tools. After the splicing process, sealing measures should be taken immediately to isolate the external air to prevent the mixing of moist air. internal wear and tear. All operation information in the process of optical cable connection must be effectively recorded, strengthen the inspection of each section of optical cable, summarize the results and submit them to the owner to avoid information fraud or missing.

3. Monitoring system construction process

3.1 Field equipment foundation and grounding construction

(1) Foundation pit construction. After the measurement, the position of the foundation pit is determined, and the supervision engineer is arranged for further inspection to ensure that the size and the geology of the location meet the construction requirements. Based on the construction base surface, the excavation depth is strictly controlled, and the error between the final pit depth and the design standard should be controlled within -50~+100mm. During the excavation process, protection should be done to ensure the stability of the pit wall and slope; the pumice water on the base surface should be effectively treated to avoid water accumulation or water seepage. Taking the pit opening as the benchmark, the soil is piled up 1m away from its periphery. If it is saturated soil, it should keep a farther distance from the pit opening. Level the pit base, and take tamping measures after it is correct.

(2) Ground wire production and installation. Pay attention to the selection of materials. It is more appropriate to use galvanized flat steel for the ground connection line. After the welding surface is effectively cleaned, the welding operation can be organized. Taking the width of the flat steel as a reference, the resulting lap length should reach 2 times the value ( flexibly increase according to the actual situation). The quality of the welding seam is good, no virtual welding may occur, and anti-corrosion measures should be taken. For the laying operation of the grounding electrode, the key point in this link is to ensure that the grounding electrode is kept straight and the bottom of the trench is sufficiently flat. In some cases, the grounding resistance exceeds a reasonable range, which can be solved by increasing the number of grounding electrodes. The distance between the grounding electrodes of each group is 5m. If it is not possible to increase the number of grounding electrodes due to the restrictive construction terrain, a feasible way is to use a resistance reducing agent to adjust the resistance value to a reasonable range.

(3) Foundation pouring and maintenance. Check the pre-set formwork and reinforcement again, effectively deal with the formwork gap, and evenly brush the release agent on the formwork. The pouring site should be supervised by a commissioner to strengthen the inspection of concrete performance, such as whether the color is uniform, whether the stones are effectively wrapped by the slurry, etc. The base structure is formed after pouring, and experimental blocks are made, numbered and dated. Keeping the bottom of the pit clean and free of water accumulation is an important prerequisite for smooth pouring. Concrete is poured from a specific height, and considering that the mixture is prone to segregation, the free height should not exceed 2m.

The pouring operation should be continuous, and the interruption in the middle should be avoided as much as possible. If it is forced to pour intermittently due to special circumstances, the time should be as short as possible. After the completion of the pouring construction, the maintenance work should be organized within the following 12 hours, and the method of watering should be selected. When the site temperature is high or the windy and dry weather is encountered, the watering and maintenance should be started within 3 hours of the end of the pouring, so as to avoid a large amount of concrete loss. water. When pouring, the position of the flange should be adjusted so that it is centered with the foundation structure, and it should be properly embedded in the foundation. The anchor bolts must be stable during the whole process of pouring, and the verticality cannot be changed. The exposed part of the concrete should not be directly exposed to the outside world, and it needs to be covered. The concrete surface should always be kept in a relatively moist state during the curing process, and 28d is more suitable for curing.

(4) Installation inspection and testing. It is required that the foundation and the buried depth of the ground wire should be consistent with the design requirements, and the basic structure has the dual characteristics of good quality and beautiful appearance. To detect ground resistance, use a high-precision ground resistance tester to obtain accurate data.

3.2 Camera installation and construction

(1) Hoisting. The camera gantry should be lifted by a crane, and a commissioner should be arranged to check the position and adjust it so that it is aligned with the foot of the column base, and the deviation is controlled within a reasonable range.

(2) Fasten. After correction, the number of exposed bolts on the upper end of the nut should be reasonably controlled, 4~5 buckles are appropriate, pay attention to the inspection of the root of the anchor bolt, and do not directly contact the bottom of the reserved hole; improve the stability of the camera column base as much as possible The part that is closely attached to the foundation should account for 70% of the total area. Check the exit lines of each camera column, and their directions should be consistent; hoist objects according to the specifications; clean the site in depth.

(3) The installation of the camera and its accessories. Make preparations before installation, create a video switching matrix system and connect it to the room, and control the working status of the lens through the keyboard, such as the change of focal length, the adjustment of the aperture, the movement of the focus point, etc. After trial control, improve it shortcomings. The assembly of the camera should be done on the ground, the purpose is to reduce the amount of high-altitude work; put the cables, all power cables should be effectively connected, and the reserved length should be controlled. The cable is stable enough not to be affected by the tension. If the reserved length is unreasonable, the life of the cable will be shortened. The exposed part of the cable is covered with a hose to achieve effective protection; adjust the position of the camera so that the plane and height are reasonable enough. After finishing the installation of the equipment, do the cleaning work, run it with power on, and use the external device (keyboard) to control the lens to make it perform specific operations.

(4) Installation inspection and testing. The camera should meet the requirements of position accuracy and stability, considering the working conditions of the maximum rated wind speed, and a stable picture can still be displayed in the monitor at this time. Check the outlet hole of the steel pipe, it should be smooth enough and free of burrs. The camera pan needs to be flexible enough, so the camera cable should be reasonably slack. Check the incoming and outgoing cable terminals to determine the seal there.

4. Control of key points of electromechanical equipment installation

The installation of electromechanical equipment should focus on the condition of the control box to ensure that the box meets the requirements of flatness and verticality. The installation of the on-site controller is easily affected by the environment. It needs to be completed in sunny and dry weather. The internal composition is thoroughly checked, and the actual operating condition is clarified by on-site testing.

The installation of electromechanical equipment must be prepared in the early stage. During the processing of the wiring cord, attention should be paid to the inspection of the intermediate joint of the cable. It must be maintained in a dry state to prevent a large amount of moisture from infiltrating into it, otherwise it will cause adverse effects on subsequent installation operations. . Soldering and tinning should be completed according to relevant specifications, which will affect the installation quality of each component.

  5 Conclusion

The stable operation of the expressway depends on many factors. The installation of mechanical and electrical equipment has a great impact on it. The construction unit needs to form an accurate understanding of this work, clarify the possible problems in the construction, select the appropriate installation technology, and install various types of equipment. The mechanical equipment is in place to provide effective support for the operation of the expressway.

Written by: Cai Peng, China Consulting Technology Transportation Engineering Group Co., Ltd.

(Reprinted from the 11th issue of "China High-tech" magazine in 2020