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Bridge tray cleaning
Bridge
The cable tray is divided into trough type, tray type, ladder type, mesh format and other structures, and consists of brackets,
brackets and installation accessories. It can be erected independently or laid on various buildings and pipe corridor brackets,
reflecting the characteristics of simple structure, beautiful shape, flexible configuration and convenient maintenance. All parts
need to be galvanized and installed on the open-air bridge tray outside the building. If it is near the seaside or belongs to a
corrosion area, the material must have the characteristics of corrosion resistance, moisture resistance, good adhesion, and high
impact resistance.
Load characteristics
1. Load of cable tray
The loads of the cable tray are divided into static loads, dynamic loads and additional loads.
Static load refers to the type of cables laid in the cable tray, the number of cables, the outer diameter weight/unit length of each
cable, and the list is determined according to the different routes laid by the cable.
Dynamic load refers to the weight of construction and maintenance personnel during the installation and maintenance of cable
trays. For light cable trays, dynamic loads are generally not considered, that is, people on the tray are not allowed to stand
(travel) on the tray. If people on the tray need to be considered, the span should be appropriately reduced. Additional loads
are only outdoors, which refer to the loads formed by ice, snow, wind and electromagnetic forces. They are related to the natural
meteorological conditions of the installation site and the properties of the charged bodies. They should be calculated based
on various conditions in the design.
2. Steps to select a bridge
(1) Determine the width, number of layers, type and spacing of support points, and the distribution of cables on each layer of bridge.
Bridge design
Bridge design
(2) Calculate the uniform load (kN/m2) of each layer of cable, and preliminarily determine the model and specifications of the bridge.
(3) Verify the bridge strength based on the maximum cable total average load value. The verification formula is as follows:
QUsage =q1+q2
Where: q1 --The uniform distribution load of the cable (the maximum value of the uniform distribution load of each layer) (kN/
m2), the uniform load is the load of the pallet, ladder or cable duct;
q2--Consider the weight of the person is equivalent to uniform distribution load (kN/
When calculating the value of m2), q2, the weight of a person is generally calculated as p=90kg.
The bending distance of concentrated load and uniform load is shown in Figure 2
Convert according to the conditions where the maximum bending distance is equal:
Where: P--1 person's load (kg)
ι--1 support point spacing (if the fulcrum distance is not equal, the maximum value is taken) (m)
q2--1 The equivalent uniform load of humans (kg/m)
Based on the bridge model, specification and fulcrum spacing preliminarily determined above, check the manufacturer's
sample information and repeatedly check the distance and bridge model until the load requirements are met.
(4) Deflection
There are no clear regulations on how to determine the deflection value. It is obvious that reducing the winding should be considered in heavy load areas, which means that the amount of steel will increase accordingly. Therefore, when calculating, as long as the maximum allowable stress of the steel is fully utilized and sufficient safety factor is ensured, it is generally appropriate to have a ratio of the maximum deflection to the span (spacing between support points) to be 1/250~1/150.
Bridge grounding
According to the relevant regulations of the specifications, the galvanized cable tray is well grounded.
(1) Contact resistance of each fixing bolt on the direct plate of the galvanized cable tray
It should be less than 0.005Ω. At this time, the cable tray can be used as a grounding trunk (the powdered cable tray should not be used as a grounding trunk). The resistance value of each cable tray can be calculated according to the following formula:
r=ρ·L/S
Where: ρ =15×10Ω-6 /cm (20℃);
L=The length is calculated as 100mm;
S=cross area cm2.
(2) The unit resistance value of the ladder mounted on the pallet is shown in Table 2.
Table 2 Unit resistance value of ladder mounted on pallet
(3) The unit resistance value of the cable duct is shown in Table 3
(4) When the cable tray is installed and connected as a whole, the resistance of each ladder (or each cable tray) is:
R=L(r+1/3r’)
Where:
R--the ladder edge, that is, the total resistance of the full length (mΩ);
r--Unit length resistance of ladder (mΩ/m)
| Class | maximum particles/m3 | FED STD 209E equivalent | |||||
| >=0.1 µm | >=0.2 µm | >=0.3 µm | >=0.5 µm | >=1 µm | >=5 µm | ||
| ISO 1 | 10 | 2 | |||||
| ISO 2 | 100 | 24 | 10 | 4 | |||
| ISO 3 | 1,000 | 237 | 102 | 35 | 8 | Class 1 | |
| ISO 4 | 10,000 | 2,370 | 1,020 | 352 | 83 | Class 10 | |
| ISO 5 | 100,000 | 23,700 | 10,200 | 3,520 | 832 | 29 | Class 100 |
| ISO 6 | 1,000,000 | 237,000 | 102,000 | 35,200 | 8,320 | 293 | Class 1,000 |
| ISO 7 | 352,000 | 83,200 | 2,930 | Class 10,000 | |||
| ISO 8 | 3,520,000 | 832,000 | 29,300 | Class 100,000 | |||
| ISO 9 | 35,200,000 | 8,320,000 | 293,000 | Room Air | |||
| maximum particles/m3 | |||||
| Class | >=0.5 µm | >=1 µm | >=5 µm | >=10 µm | >=25 µm |
| Class 1 | 3,000 | 0 | 0 | 0 | |
| Class 2 | 300,000 | 2,000 | 30 | ||
| Class 3 | 1,000,000 | 20,000 | 4,000 | 300 | |
| Class 4 | 20,000 | 40,000 | 4,000 | ||
桥架和线缆的清洗和除尘：
梯式桥架中的线缆表面和内侧。
‚梯式桥架中固线器和横梁。
③梯式桥架中中的线缆。
备注：桥架和线缆的清洗工艺和流程：
First use a vacuum cleaner with an anti-static brush to absorb large dust particles on the cable.
‚Use a quick spray gun, use a dedicated online cleaner for communication equipment, and a high-power hair dryer to clean the
dust on the cable surface. Finally, spray special electrostatic elimination liquid to eliminate static electricity from the cable.
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