Technical Specification and Application Guide for Steel Grating in PV Plant Maintenance Walkways
——Product Selection and Performance Requirements Based on 25-Year Design Life
Abstract
As the scale of global photovoltaic power plants continues to expand, maintenance walkways, as an integral part of plant infrastructure, require material selection that directly impacts operational safety and maintenance costs throughout the facility’s lifecycle. Steel grating, characterized by high structural strength, excellent light transmission, and ease of installation, is widely used in PV plant platforms and maintenance access pathways.
This article focuses on the steel grating product itself, systematically elaborating technical requirements for PV applications from five dimensions: structural selection, open area ratio design, load parameters, anti-corrosion treatment, and installation specifications. Selection comparison tables based on environmental classifications and application scenarios are provided. All technical parameters reference relevant standards including ISO 14122, GB/T 13912, and GB 50797, and are verifiable through product test reports.
Chapter 1: Application Scenarios of Steel Grating in PV Plants
PV plant maintenance walkways refer to access pathways used by maintenance personnel for cleaning, inspecting, and repairing PV modules. Main applications include:
Inter-array maintenance walkways: Located between PV array rows for personnel access
Inverter/transformer station platforms: Operational platforms around equipment
Rooftop PV access pathways: Permanent maintenance routes on sloped or flat roofs
The common requirements for steel grating products in these scenarios are: while ensuring load-bearing safety, minimize shading of PV modules to the greatest extent possible, and provide durability matching the plant’s service life.
Chapter 2: Steel Grating Structural Selection and Specifications
2.1 Product Structure Composition
Steel grating consists of load-bearing bars and cross bars (twisted square bars) welded at intersections. Main structural parameters include:
Load-bearing bar: Height h (mm) × thickness b (mm) – determines load capacity
Bar spacing: Center-to-center distance between adjacent load-bearing bars (mm) – determines open area ratio
Cross bar spacing: Center-to-center distance between adjacent cross bars (mm) – affects lateral stiffness
2.2 Recommended Specifications for PV Scenarios
Based on load requirements and installation conditions of different applications, the following specifications are recommended:
| Application Scenario | Recommended Type | Bar Size (mm) | Bar Spacing (mm) | Cross Bar Spacing (mm) | Unit Weight (kg/m²) | Section Modulus (cm³/m) |
|---|---|---|---|---|---|---|
| Ground-mounted PV (standard) | G405/40/150 | 40×5 | 40 | 150 | 29.8 | 24.0 |
| Rooftop PV (light duty) | G325/30/100 | 32×5 | 30 | 100 | 29.3 | 17.5 |
| High wind/heavy load areas | G505/40/150 | 50×5 | 40 | 150 | 37.2 | 37.5 |
| Temporary access (light duty) | G303/30/100 | 30×3 | 30 | 100 | 18.5 | 6.2 |
Selection Notes:
G405/40/150 (40mm bar height) is the mainstream choice for ground-mounted PV plants, meeting 3.0kN/m² load requirements at 1200mm support spacing
Due to roof load limitations, G325/30/100 (30mm bar height) is recommended for rooftop plants, with support spacing controlled within 800mm
Suffix “S” in type designation (e.g., G323/30/100S) indicates serrated anti-slip bars, recommended for walkways with slope >5°
2.3 Anti-slip Performance Requirements
Photovoltaic maintenance access involves working at heights, and anti-slip performance is a key safety indicator:
Slip resistance level: According to DIN 51130 standard, should achieve R12 level (no slip at inclination ≥12°)
Implementation methods: Serrated bars (surface indented) or embedded corundum sand on bar surface
Test method: Pendulum friction coefficient tester, wet-state friction coefficient ≥0.6
Chapter 3: Open Area Ratio and Light Transmission Performance
In PV scenarios, the open area ratio of steel grating directly affects shading of underlying modules. It should be clarified that: open area ratio is an inherent structural property of the steel grating product, determined by bar spacing and cross bar spacing, independent of PV modules.
3.1 Definition and Calculation of Open Area Ratio
Open area ratio = (1 – projected shading area/total area) × 100%
For standard steel grating, open area ratio can be approximately calculated as:
Open area ratio ≈ (bar spacing – bar thickness)/bar spacing × (cross bar spacing – cross bar diameter)/cross bar spacing
3.2 Open Area Ratio Comparison for Different Specifications
| Type | Bar Spacing (mm) | Bar Thickness (mm) | Theoretical Open Area Ratio | Measured Light Transmittance (Vertical Illumination) |
|---|---|---|---|---|
| G405/40/150 | 40 | 5 | 42% | 85% |
| G325/30/100 | 30 | 5 | 37% | 78% |
| G303/30/100 | 30 | 3 | 40% | 82% |
| Close-spaced type (25mm spacing) | 25 | 5 | 32% | 70% |
Technical Notes:
Measured light transmittance exceeds theoretical open area ratio because oblique light can pass through more gaps
40% open area ratio represents an engineering balance between structural strength and light transmission performance
For photovoltaic applications, prioritize flat steel spacing of ≥40mm.
3.3 Load-bearing Bar Orientation Requirements
The orientation of load-bearing bars should be parallel to the PV module row direction for the following reasons:
Parallel arrangement produces broken line shadows, avoiding continuous shadow bands
Continuous shadow bands can cause hot spot effects in PV modules
Shading from cross bars (6mm diameter) is negligible
Chapter 4: Load Performance Parameters
The load capacity of steel grating is determined by bar height, thickness, steel grade, and support spacing. The following are technical indicators that products should meet upon delivery.
4.1 Design Load Values
| Load Type | Design Value | Reference Standard | Application Scenario |
|---|---|---|---|
| Uniformly distributed live load | ≥3.0 kN/m² | ISO 14122-2 | Personnel access and light tools |
| Concentrated load | ≥1.5 kN (acting on 100mm×100mm area) | ISO 14122-2 | Single person maintenance |
| Maintenance vehicle load | ≥5.0 kN/m² | GB 50797 | Areas permitting light equipment access |
| Wind load | ≥1.5 kN/m² (adjust per project location) | ASCE 7/GB 50009 | Open area PV plants |
Data Source: GB 50797 “Design Code for Photovoltaic Power Plants” Clause 6.8.3 specifies that PV platform load capacity shall not be less than 5000N/m², with safety factor not less than 2.5.
4.3 Deflection Control Standards
Maximum deflection limit: ≤L/200 (L = support span)
Permanent set requirement: After unloading, permanent set ≤0.2% of span
Control purpose: To prevent weld fatigue under long-term loads and ensure structural stability over a 25-year service life
Chapter 5: Anti-corrosion Treatment and Weathering Performance
As outdoor metal components, the anti-corrosion performance of steel grating is fundamental to 25-year service life. PV plants are often located in deserts, coastal areas, and rooftops with significantly different corrosion risks.
5.1 Environmental Corrosion Classification (ISO 12944 Standard)
| Corrosion Category | Environment Description | Applicable Areas | Recommended Anti-corrosion Solution | Coating Thickness Requirements |
|---|---|---|---|---|
| C3 | Medium | Inland deserts, general industrial areas | Hot-dip galvanizing | Zinc coating ≥85μm |
| C4 | High | Coastal areas (within 5km), industrial pollution zones | Hot-dip galvanizing + seal coat | Zinc coating ≥100μm |
| C5 | Very high | Marine environments, high salt spray areas | Stainless steel 316L | — |
5.2 Hot-dip Galvanizing Technical Requirements
Applicable standards: GB/T 13912 / ISO 1461
Coating thickness: For bar thickness 5mm, average coating ≥100μm, local ≥85μm
Adhesion requirements: Coating does not peel or expose bare metal upon hammer testing
Appearance requirements: Surface shall be continuous, complete, free from uncoated areas, bubbles, or coarse particles
5.3 Service Life Expectancy of Different Anti-corrosion Solutions
| Anti-corrosion Treatment | Applicable Environment | Expected Service Life | Maintenance Interval |
|---|---|---|---|
| Hot-dip galvanizing (100μm) | C3 | 25 years | Visual inspection every 10 years |
| Hot-dip galvanizing (85μm) | C3 | 20 years | Inspection every 8 years |
| Hot-dip galvanizing + seal coat | C4 | 20-25 years | Inspection every 8 years |
| Stainless steel 316L | C5 | 25+ years | Maintenance-free |
5.4 Edge Protection Requirements
All cut ends and hole edges shall be coated with zinc-rich repair paint (dry film zinc content ≥92%)
Welded areas shall receive secondary anti-corrosion treatment using cold galvanizing spray or epoxy zinc-rich primer
Chapter 6: Installation Specifications and Fixing Systems
6.1 Fixing Component Specifications
| Fixing Component Type | Material Requirement | Specification | Quantity Requirement |
|---|---|---|---|
| Clips/bolts | Stainless steel 304/316 | M10 (minimum) | At least 4 per panel |
| Anti-lift clips | Stainless steel 304 | Matched to grating | Enhanced spacing in wind zones |
6.2 Installation Technical Requirements
Support beam spacing: ≤80% of manufacturer certified span (safety margin)
Support beam precision: Top surface elevation deviation ≤±3mm
Overlap length: Steel grating overlap with support structure ≥40mm
Tightening torque: M10 stainless steel bolts, torque 35-40N·m
Expansion joint allowance: 10mm gap every 30m continuous length
6.3 Construction Protection Requirements
Anti-corrosion coating shall not be damaged during installation
Hot-dip galvanized components should not be cut or holed on site; if cutting is unavoidable, anti-corrosion repair shall be performed
Hole enlargement by gas cutting is prohibited
After installation, welding slag and drilling debris shall be cleaned to prevent corrosion sources
Chapter 7: Product Selection Quick Reference Table
| Selection Dimension | Ground-mounted (Inland) | Ground-mounted (Coastal) | Rooftop PV | High Wind Area |
|---|---|---|---|---|
| Recommended Type | G405/40/150 | G405/40/150 | G325/30/100 | G505/40/150 |
| Bar Specification | 40×5mm | 40×5mm | 32×5mm | 50×5mm |
| Open Area Ratio | 42% | 42% | 37% | 42% |
| Anti-corrosion Solution | HDG 100μm | HDG 120μm + seal coat | HDG 85μm | HDG 100μm |
| Fixing Requirements | M10 stainless, 4 points | M10 stainless 316, 4 points | Special clamps (waterproofing preserved) | Anti-lift clamps, enhanced spacing |
| Reference Weight | 29.8kg/m² | 29.8kg/m² | 29.3kg/m² | 37.2kg/m² |
| Maximum Support Spacing | 1200mm | 1200mm | 800mm | 1500mm |
Appendix: Referenced Standards
GB 50797-2012 “Design Code for Photovoltaic Power Plants” (2024 Edition)
GB/T 13912 “Metallic coatings—Hot dip galvanized coatings on fabricated iron and steel articles—Specifications and test methods”
ISO 14122-2 “Safety of machinery—Permanent means of access to machinery—Part 2: Working platforms and walkways”
ISO 1461 “Hot dip galvanized coatings on fabricated iron and steel articles—Specifications and test methods”
ISO 12944 “Paints and varnishes—Corrosion protection of steel structures by protective paint systems”
GB/T 51368-2019 “Technical standard for building photovoltaic system application”
GB 50009 “Load code for the design of building structures”
Appendix: Technical Parameter Quick Reference Table
| Type | Bar Size (mm) | Bar Spacing (mm) | Open Area Ratio (%) | Unit Weight (kg/m²) | Section Modulus (cm³/m) | Recommended Max Span (m) |
|---|---|---|---|---|---|---|
| G253/30/100 | 25×3 | 30 | 40 | 18.5 | 6.2 | 0.8 |
| G303/30/100 | 30×3 | 30 | 40 | 22.1 | 9.8 | 1.0 |
| G325/30/100 | 32×5 | 30 | 37 | 29.3 | 17.5 | 1.2 |
| G405/40/150 | 40×5 | 40 | 42 | 29.8 | 24.0 | 1.5 |
| G505/40/150 | 50×5 | 40 | 42 | 37.2 | 37.5 | 1.8 |
| G505/50/150 | 50×5 | 50 | 48 | 31.6 | 37.5 | 1.8 |
Conclusion
The application of steel grating in PV plants fundamentally represents the technical adaptation of industrial products to specific use scenarios. Selection should return to the product’s own performance parameters—structural specifications determine load capacity, open area ratio determines light transmission performance, and anti-corrosion treatment determines service life.
The technical parameters provided in this article are sourced from relevant national standards and industry specifications, verifiable through product test reports and type inspection reports. EPC contractors and procurement personnel are advised to explicitly reference the standards listed herein in technical specifications to ensure purchased products meet the performance requirements for 25-year PV plant operational cycles.
Technical Note: Data in this article is based on standard steel grating products of Q235B material with hot-dip galvanizing. Load parameters for stainless steel products are identical, with weight increased by approximately 3%. For project-specific load verification calculations, structural engineers should perform assessments based on site conditions.
