Through the network to solicit the opinions and reasons of the professional peers of the instrument and control industry, the following questions were summarized in combination with the previous engineering design experience:
1.The size of the project (related to the amount of investment) is based on the different project implementation conditions, and the cable laying method is selected. Small projects have less investment, short cycle, quick results, and are more economical and practical to pull alone. Large projects have a lot of investment, long cycle, slow effect, and the use of junction boxes can save instrument cables, cable trays, structural support materials, labor construction costs and other expenses.
2.Engineering Practicality Perspective. The cable laying method of the single-pull instrument is simple, and it is easy to troubleshoot the problem of the instrument and find the cause of the fault point. It is more convenient for field instrumenters to maintain. However, for engineering designers, there is also a problem, the filling rate of the instrument cable to the slot box is more serious, the cable well between the control room and the cabinet will be larger, and there are more cables entering the cabinet room, and it is more difficult to sort out in the later stage.
3.Regulatory compliance perspective. From the industry standard specification (SH, HG) automation instrument selection design specifications, instrument piping and wiring design specifications. The junction box can be used in the scene where the instrument points are concentrated, which effectively avoids the complexity and diversification of the ground laying and aerial laying of more instrument cables. Moreover, too many instrument conduits also cause great safety hazards. The safety inspection needs to pay attention to the box material, explosion-proof type, protection level, anti-corrosion level, wire inlet method, terminal port specifications and other information of the junction box.
To sum up, according to the actual application and experience of the project, the overall planning and reasonable layout in the early stage of project construction, and actively negotiate a stable project implementation plan with the design institute engineering company.