CECS : 3191 Steel Cable Tray Engineering Design Specification CECS31:91
Some standard content:
China Engineering Construction Standardization Association Standard
Steel Cable Tray Engineering Design Specification
CECS31:91
Editor: China Engineering Construction Standardization Association Electrical Engineering Committee Approval: China Engineering Construction Standardization Association Approval Date: December 27, 1991
Chapter I General Provisions
Article 1.0.1 In the design, manufacture and engineering use of steel cable trays (hereinafter referred to as cable trays), the relevant national technical guidelines and policies must be implemented, and the technology should be advanced, economically reasonable, safe and applicable, and the quality should be ensured. Article 1.0.2 This specification applies to the design, construction, manufacture, testing and inspection of cable trays for industrial and civil buildings.
Article 1.0.3 Cable tray products should be tested and certified by the national cable tray professional quality inspection agency. Article 1.0.4 When cable trays are used in cable laying projects, in addition to complying with this specification, they should also comply with the provisions of relevant national standards.
Chapter 2 Bridge
Section 1 Name Definition, Structural Type and Variety Article 2.1.1 Bridge is a general term for a continuous rigid structural system consisting of trays, straight sections of ladders, bends, accessories, supports and hangers, etc., used to support cables. Article 2.1.2 Bridges may include the following structural types: 1. Perforated tray: a trough-shaped component consisting of a bottom plate with holes and sides, or a component made by punching and bending a whole steel plate.
2. Non-perforated tray: a trough-shaped component consisting of a bottom plate and sides, or a trough-shaped component made by bending a whole steel plate. 3. Ladder: a trapezoidal component consisting of sides and several crosspieces. 4. Assembled tray: a component that is connected into a tray by bolts or plug-in methods by any combination of perforated components suitable for the project site.
Article 2.1.3 Bridges may include the following structural varieties: 1. Straight section refers to a rigid straight section that cannot change direction or size and is used to directly support cables. 2. An elbow is a rigid non-linear component that can change direction or size and is used to directly support cables. It can include the following types:
1. Horizontal elbow: a component that changes the direction of trays and ladders in the same horizontal plane, divided into four types: 30°, 45°, 60°, and 90°;
2. Horizontal tee: a component that connects trays and ladders in three directions separated by 90° in the same horizontal plane, divided into two types: equal and variable width;
3. Horizontal cross: a component that connects trays and ladders in four directions separated by 90° in the same horizontal plane, divided into two types: equal and variable width;
4. Upper elbow: a component that allows trays and ladders to change from a horizontal plane to a horizontal plane. Components that change direction upward are divided into four types: 30°, 45°, 60°, and 90°;
5. Lower bend: Components that change the direction of pallets and ladders from the horizontal plane to the downward direction, which are divided into four types: 30°, 45°, 60°, and 90°;
6. Vertical tee: Components that connect pallets and ladders in three directions separated by 90° on the same vertical plane, which are divided into two types: equal and variable width;
7. Vertical cross: Components that connect pallets and ladders in four directions separated by 90° on the same vertical plane, which are divided into two types: equal and variable width;
8. Variable diameter straight: Components that connect pallets and ladders of different widths or heights on the same plane. Article 2.1.4 Bridge accessories refer to components that are used to connect between straight segments, between straight segments and bends to form a continuous and rigid bridge system, which are necessary for connecting and fixing or supplementing the functions of straight segments and bends, and may include: 1. Straight connecting plates, which can be referred to as direct plates. 2. Hinged connecting plate, which can be referred to as hinged plate, is divided into horizontal and vertical types. 3. Continuous hinged plate, which can be referred to as soft joint plate. 4. Variable width connecting plate, which can be referred to as variable width plate. 5. Variable height connecting plate, which can be referred to as variable height plate. 6. Telescopic connecting plate, which can be referred to as telescopic plate. 7. Turning connecting plate, which can be referred to as bending connecting plate. 8. Upper and lower connecting plates, which can be referred to as upper and lower connecting plates, are divided into four types: 30°, 45°, 60° and 90°. 9. Cover plate.
10. Partition plate.
11. Pressure plate.
12. Terminal plate.
13. Downlead.
14. Vertical shaft.
15. Fasteners.
Article 2.1.5 Support and hanger refers to the components that directly support pallets and ladder racks, which can include: 1. Support arm: a rigid component that directly supports pallets and ladder racks and is fixed at one end, which is divided into snap-on type and bolt-fixed type. 2. Column: The component that directly supports the bracket arm, which is divided into I-beam, channel steel, angle steel, and special-shaped steel columns. 3. Hanger: The rigid component that suspends the tray and ladder rack, which is divided into round steel single and double rod type; angle steel single and double rod type; I-beam single and double rod type; channel steel single and double rod type; special-shaped steel single and double rod type. 4. Other fixed brackets: such as vertical, inclined and other fixed brackets. Section 2 Models and Specifications
Article 2.2.1 The content of the bridge model may contain the name, specification, load level, and anti-corrosion layer category: 1. Name: It can be expressed in uppercase Latin letters. 2. Specifications: The straight sections and bends of the tray and ladder rack are marked with width and height in turn; accessories and supports and hangers are marked with the dimensions of one or several main technical characteristics.
3. Load levels: A, B, C, and D. 4. Anti-corrosion coating categories: painted or baked (Q), electrogalvanized (D), powder sprayed (P), hot-dip galvanized (R), powder sprayed after electrogalvanizing (DP), hot-dip galvanized after painting (RQ), other (T). Among them, the load level and anti-corrosion coating category may not be indicated in the model, and can be uniformly described in words. Article 2.2.2 The commonly used specifications and size series of pallets and ladder racks in width and height can be seen in Table 2.2.2. Common specifications of pallets and ladder racks
Degree (mm)
Note: The symbol △ represents the commonly used specifications.
Article 2.2.3 The standard length of a single straight section of a pallet and ladder rack can be 2, 3, 4, and 6m. Article 2.2.4 The commonly used inner bending radius of pallets and ladder racks is as follows: 1. Bending shape: The radius R of the inscribed circle of the two inner right-angled sides is 300, 600, and 900mm. 2. Arc shape: 300, 600, and 900mm. Article 2.2.5 The ventilation hole area at the bottom of the perforated tray should not be greater than 40% of the total bottom area. 100
Article 2.2.6 The center spacing of the straight section ladder crosspieces and the center spacing of the 1/2 length of the ladder bend crosspieces are both 200-300mm, and the width of the crosspiece is 20-50mm.
Article 2.2.7 The opening position or welding position of the support and hanger column fixed bracket should meet the requirements of 200, 250, 300, and 350 center distances between layers when the tray and ladder are set in multiple layers. 200
Article 2.2.8 The specifications and dimensions of various accessories and supports and hangers should be determined in accordance with the bridge series under the condition of meeting the corresponding load.
Section 3 Technical Requirements
Article 2.3.1 Cable trays and ladder racks should be made of cold-rolled plates. Hot-rolled plates can also be used if the strength requirements are met. The material should comply with the Q235A steel in the GB700 standard "Technical Conditions for Ordinary Carbon Structural Steel" and the relevant provisions of the GB716 standard "Cold-rolled Steel Strip for Ordinary Carbon Structural Steel" and the GB912 standard "Technical Conditions for Ordinary Carbon Steel and Low Alloy Steel Thin Plates".
Article 2.3.2 The minimum allowable plate thickness for trays and ladder racks can be seen in Table 2.3.2. Table 2.3.2 The minimum allowable plate thickness for trays and ladder racks Width of trays and ladder racks (mm)
400～800
Minimum allowable thickness (mm)
Article 2.3.3 The surface anti-corrosion layer material should comply with the provisions of the relevant current national standards. Article 2.3.4 The welding rods for manual welding shall comply with the standard of "Carbon Steel Welding Rods" GB5117, and it is advisable to use E4300~E4313 welding rods.
Article 2.3.5 The material of ordinary bolts shall comply with the standard of "Technical Conditions for Ordinary Carbon Structural Steel" GB700. The material of fasteners such as Q235A steel rivets shall comply with the standard of "Technical Conditions for Hot-rolled Round Steel for Ordinary Carbon Steel Rivets" GB715. Article 2.3.6 Under the condition of a simply supported beam with a span of 2m for the support and hanger, the rated uniformly distributed load of the pallet and ladder rack is divided into four levels, see Table 2.3.6 for details.
Load level table of pallets and ladder racks 2.3.6
Load level
Rated uniformly distributed load kN/m
(kgf/m)
Article 2.3.7 The structure of pallets, ladder racks, supports and hangers shall meet the requirements of strength, calculation method, please refer to Appendix 1.
Stiffness and stability, and its calculation
Article 2.3.8 The bearing capacity of the bridge shall be verified in accordance with the provisions of the load test in Article 2.4.1. The load when the bridge rack initially produces permanent deformation divided by the safety factor of 1.5 shall not be less than the rated uniformly distributed load. Article 2.3.9 Various types of supports and hangers shall be able to withstand the rated uniformly distributed load and their own weight of the corresponding specifications and number of layers of pallets and ladder racks.
Article 2.3.10. The load-bearing accessories such as connecting plates and connecting bolts shall be compatible with the structural strength of the main body of pallets, ladder racks, brackets, etc.
Section 2.3.Article 11 The manufacturer shall provide a curve or data table showing the relationship between different spans and allowable uniformly distributed loads for various types and specifications of pallets and ladder racks.
Article 2.3.12 The relative deflection of pallets and ladder racks when bearing rated uniformly distributed loads shall not be greater than 1/200. Article 2.3.13 The ratio of the maximum deflection value of the bracket fixed to the crossbar or side wall of the hanger when bearing the rated load of the pallet and ladder rack to its length shall not be greater than 1/100.
Article 2.3.14 The manufacturer shall provide the deflection values of pallets and ladder racks of various types and specifications under different loads and support and hanger spans.
Article 2.3.15 When pallets and ladder racks need to bear short-term additional concentrated loads, they shall comply with the provisions of the second paragraph of Article 3.3.2.
Article 2.3.16 The technical quality of hot-dip galvanizing anti-corrosion treatment shall comply with the provisions of Table 2.3.16. Table 2.3.16 Galvanizing thickness
(adhesion)
average value
zinc layer adhesion
uniform zinc layer
bridge components
bolts and rods (diameter ≥10mm)
≥65μm(460g/m2)
≥54μm((460g/m2)
score, crosshatch or hammer test, the zinc layer should not peel off or bulge The copper sulfate test should not expose iron after 4 times
The surface of the zinc layer should be uniform, free of burrs, overburning, dust, scars, local non-galvanized (diameter more than 2mm) and other defects, and there should be no zinc nodules that affect installation. The coating of the thread should be smooth and the bolted joints should be able to be screwed into Article 2.3.17 The technical quality of electrogalvanizing anti-corrosion treatment should comply with the provisions of Table 2.3.17 and Table 2.4.2. Electrogalvanizing technical quality index table 2.3.17
Galvanized layer thickness
Bridge Component
≥12μm(84g/m2)
(Adhesion）
Surface passivation
Zinc layer adhesion
≥M14
M8～M12
≥12μm(84g/m2）
≥9μm(63g/m)
≥6μm(42g/m)
After passivation treatment, there should be a good passivation film (white, rainbow, grass green , dark green)
The zinc layer should not peel off in the line and grid test. The surface of the zinc layer should be smooth, uniform and dense. There should be no defects such as peeling, bubbles, spots, partial unplating, scratches, etc.
Article 2.3.18 The technical quality of spray powder anti-corrosion treatment shall comply with the provisions of Table 2.3.18 and Table 2.4.2. Technical quality indicators of spray powder
Thicknessum
Adhesion level
Impact strengthJ
(kgf - cm)
Flexibility
Corner coverage%
Epoxy resin powder
(≥50)
Uniform and smooth, no bubbles, no cracks, uniform color Article 2.3.19 The technical quality of paint anti-corrosion treatment shall comply with the provisions of Table 2.3.19 and Table 2.4.2. Paint technical quality index table 2.3.19
Strength levelwww.bzxz.net
Impact strength J (kgf·cm）
(≥50)
(≥50)
Flexibility
Coverage %
Flat, smooth, uniform, no peeling, no bubbles or blisters Article 2.3.20 For bridges with composite anti-corrosion treatment after galvanizing and then spraying powder or painting, the thickness, adhesion and appearance of the galvanized layer shall meet the technical quality indicators of Table 2.3.16 or Table 2.3.17; the surface spraying and painting layers shall meet the requirements of Table 2.3.18, 2.3.19 and Table 2.4.2 respectively. Article 2.3.21 For bridges with other anti-corrosion treatments such as zinc-nickel alloy and high passivation, they shall be tested and verified in accordance with Article 2.4.2, and shall have clear technical quality indicators and testing methods. Article 2.3.22 The tensile strength, yield and other mechanical properties of the weld shall not be lower than those of the main material, the weld surface shall be uniform, and there shall be no defects such as leaking welding, cracks, slag inclusions, burn-through, arc pits, etc., and shall meet the third-level requirements of the GBJ205 standard of "Code for Construction and Acceptance of Steel Structure Engineering". Article 2.3.23 Limit deviation of geometric dimensions of pallets and ladders: length (single standard length) shall not be greater than JS16 level; width shall not be greater than JS18 level; height shall not be greater than JS17 level. Article 2.3.24 Allowable deviation of bolt hole diameter and hole spacing: bolt hole diameter can be 1.5mm (when the screw diameter is not greater than M16) or 2mm (when the screw diameter is not less than M20) larger than the nominal diameter of the screw, and the bolt hole accuracy shall not be lower than H14 level. 2. Allowable deviation of hole spacing of bolt connection holes: 0.7mm between two adjacent holes in the same group; 1.0mm between any two holes in the same group; 1.2mm between end holes of two adjacent groups. Article 2.3.25 When the bridge system is used to form a grounding loop, the joint resistance value shall be measured in accordance with Article 2.4.5, and shall not be greater than 0.00033Q.
Section 4 Tests
Article 2.4.1 Load test and deflection measurement may be in accordance with the provisions of Appendix 2. Article 2.4.2 Artificial environment test for anti-corrosion layer may be in accordance with the provisions of Table 2.4.2. Artificial environment test items and cycles
Alternating damp heat
Chemical corrosion
Gas test
Ultraviolet cold
Condensation test
GB2423.4 test Db
GB2423.17 test Ka
GB2423.33 test kch
Light 70℃8h
Condensation 50℃4h||tt ||Light wavelength 275~00um
Relative humidity 95%~100%
General 0 class 1 class 2 class 0
Ordinary damp heat medium corrosion strong corrosion light corrosion
Corrosion type corrosion type corrosion
Relative humidity in the cooling stage 35%
Note: ① UV condensation test illumination 70℃h, condensation 50℃ 4h, a total of 12x as 1 cycle, the rest is 24h as 1 cycle.
② Environmental condition level, please refer to Appendix VII.
Article 2.4.3 Galvanized layer performance test shall meet the following requirements: 1. Thickness (adhesion): measured according to Appendix III "weight method", or according to the provisions of GB4955 "Measuring the thickness of metal coating layer by anodic dissolution coulometric method" and GB4956 "Measuring the thickness of non-magnetic coating layer on magnetic substrate by magnetic method". 2. Adhesion: Except for the plate thickness greater than 8mm, which is measured by the "hammer method" in Appendix 5, the rest are measured by the "scribing and scratching method" specified in the "Method for Testing Adhesion Strength of Metallic Coatings (Electrodeposited Layers and Chemically Deposited Layers) on Metal Substrates" GB5270.
3. Uniformity: According to the provisions of Appendix 4. Article 2.4.4 The coating performance test shall meet the following requirements: Thickness: According to the provisions of the "Determination of Paint Film Thickness" GB1764 or the "Magnetic Method for Measuring the Thickness of Non-magnetic Coatings on Magnetic Metal Substrates" GB4956.
2. Adhesion: According to the provisions of the "Determination of Paint Film Adhesion" GB1720. 3. Flexibility: According to the provisions of the "Determination of Paint Film Flexibility" GB1731. 4. Impact strength: According to the provisions of the "Determination of Paint Film Impact Resistance" GB1732. Article 2.4.5 The connection resistance test of pallets and ladders shall be in accordance with the provisions of Appendix 6. Section 5 Inspection
Article 2.5.1 The items to be inspected before the product leaves the factory are: 1. Appearance quality (full inspection).
2. Dimensional accuracy (spot inspection).
3. Anti-corrosion layer thickness and adhesion (spot inspection). 4. Welding surface quality (full inspection).
5. Hot-dip galvanizing layer uniformity (spot inspection). Article 2.5.2 Type inspection shall be carried out in any of the following situations: 1. Trial and final evaluation of new bridge products; 2. After formal production, the materials, structure and process have changed significantly; 3. The product is resumed after being discontinued for one year;
4. The national quality inspection agency or certification organization requires the product to be type inspected. Article 2.5.3 The type inspection items shall include the relevant inspection items in Sections 3 and 4 of this standard. Article 2.5.4 Product sampling and judgment:
1. The samples shall be randomly sampled, and the number of samples to be inspected shall be 2% of each batch of products, but shall not be less than 3 pieces. Only 1 piece of sample is allowed for load test.
2. If there is one unqualified sample in each batch of product samples, the second sample of the same batch of products can be taken for inspection. If it still fails, the batch of products will be considered unqualified.
3. For the quality of the anti-corrosion layer, it is allowed to directly inspect the product or the sample made of the same material and the same process. Section 6 Pricing, Marking, Packaging, Storage Article 2.6.1 The straight section of the pallet and ladder rack should be priced by unit length (m), and other parts should be priced by piece or weight. Article 2.Article 6.2 Each batch of products should be equipped with an appropriate number of marks on the main components. The content may include: model, specification, manufacturer name.
Article 2.6.3 The content of the product outer packaging mark may include: product name (including model and specification when necessary), manufacturer name, factory date (year, month), project name or code, recipient unit name, gross weight, net weight. Article 2.6.4 The mark should be clear and not easily damaged. Article 2.6.5 The product packaging should be able to prevent mechanical damage during transportation, and should be selected according to the transportation method and component specifications and shapes. Appropriate packaging methods, such as angle steel or flat steel, wooden boards, foam concrete packaging boxes, etc. The packaging box should be easy to hoist and transport. It can also be packaged according to classification or engineering area (section) according to user requirements. Article 2.6.6 The packaging box should be accompanied by a packing list, product certificate and factory inspection report. Article 2.6.7 The storage place of the bridge frame should be dry and covered, and should be protected from corrosion by corrosive substances such as acids, salts and alkalis.
Article 2.6.8 The various components of the bridge should be stacked in categories, and the layers should be separated by appropriate soft cushions to avoid heavy pressure. Chapter 3 Bridge Engineering Design
Section 1 Bridge Type and Variety Selection
Article 3.1.1 When it is necessary to shield the cable loop of electrical interference, or to protect the environment from external influences such as oil, corrosive liquids, flammable dust, etc., a covered non-perforated pallet should be selected. Article 3.1.2 When it is necessary to assemble in accordance with local conditions, it is advisable to use assembled pallets. Article 3.1.3 Except for the cases of Articles 3.1.1 and 3.1.2, perforated pallets or ladder racks can be used. Article 3.1.4 When other structural types of bridges are selected except Article 2.1.2, the requirements of Articles 2.3.1 to 2.6.8 should be met.
Article 3.1.5 In environments where dust is easily accumulated and other coverings are required or outdoor places, it is advisable to have a cover. Article 3.1.6 In public passages or outdoor crossing sections, pads should be added to the bottom ladder, or trays should be used in this section. Article 3.1.7 When low-voltage power cables and control cables share the same tray or ladder, partitions should be installed between them; appropriate bends should be provided at the branching, leading up and down points of the tray or ladder;
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