Welding Process Standards for Solar Mobile Lighting Trailers

Welding Process Standards for Solar Mobile Lighting Trailers

For outdoor emergency lighting, construction projects, and events, solar mobile lighting trailers are favored by international buyers due to their zero-emission, mobile nature, and stable battery life. Welding processes, as a critical link connecting the trailer frame, light poles, and solar panel supports, directly determine the product's load-bearing capacity, wind and earthquake resistance, and service life. For international wholesale buyers focused on long-term partnerships, standardized welding processes are not only a key indicator of product quality but also a key guarantee for mitigating post-sales risks and ensuring operational safety. This article will detail the welding process standard system for solar mobile lighting trailers from four perspectives: process foundations, key component standards, testing specifications, and compliance requirements.

I. Basic Core Standards for Welding Processes: Comprehensive Control from Materials to Personnel

Standardization of welding processes begins with source control; oversight at any step can lead to structural hazards. When international buyers are evaluating suppliers, they should focus on the following basic standards:

(I) Compatibility of Welding Materials and Parent Metals
The core load-bearing structure of solar mobile lighting trailers is typically constructed of Q235B carbon structural steel or Q355 low-alloy high-strength steel, while the poles and brackets are typically constructed of 6061-T6 aluminum alloy. Welding material selection must adhere to the principle of "equal strength matching":

When welding steel, low-carbon steel (Q235B) should be paired with E43 series electrodes (such as E4303) or ER50-6 solid wire. Low-alloy steel (Q355) should be paired with E50 series electrodes (such as E5015) or ER55-B2 solid wire. Ensure the weld strength is at least 85% of the parent material.

Aluminum alloy welding requires ER4043 or ER5356 aluminum welding wire. ER5356, due to its greater crack resistance, is more suitable for outdoor, high-stress connections on light poles.

Welding materials must have a clear Material Certificate (MTC) and must be stored in a humidity ≤ 60% and temperature ≥ 5°C to prevent moisture absorption and rust on the electrodes, which can affect weld quality. (II) Compliance Standards for Welding Equipment and Environment

Professional equipment and environment are prerequisites for process stability. Welding scenarios that meet international standards should meet the following requirements:
Preferably, metal arc welding (MIG/MAG) equipment is used. Its welding efficiency is over 30% higher than manual arc welding, and its weld appearance is more aesthetically pleasing. The equipment must be equipped with a current and voltage stabilizer to ensure that the welding current fluctuation range is ≤±5A and the voltage fluctuation range is ≤±1V.

The welding environment must be protected from wind, rain, and dust. Outdoor work requires a windproof shelter (wind resistance rating ≥ 5). Indoor work requires ventilation of ≥10m³/person/hour, and the ambient temperature must be no less than 0°C (low-temperature welding requires preheating the base metal to 100-150°C).

Equipment must be calibrated regularly, with calibration intervals not exceeding 12 months. Calibration records must be traceable and comply with ISO 9001 quality management system requirements. (III) Welding Personnel Qualification Standards

Welding is a process that combines craftsmanship with standards. The operator's qualifications directly determine weld quality:

All welders must hold a nationally or internationally recognized welding qualification certificate (such as China's "Special Equipment Welding Operator Certificate" or the EU's EN 287-1 certificate). The welding methods (such as MIG welding) and parent material types (such as steel and aluminum alloys) covered by the certificate must be consistent with the actual work being performed.

Welders must undergo regular skill assessments, with a recurring period of no more than 24 months. These assessments cover weld visual inspection and practical non-destructive testing.

For welding critical load-bearing parts, experienced personnel with at least five years of experience welding similar products must be designated, and a "one person, one code" traceability system must be implemented.

II. Welding Process Standards for Critical Parts: Targeted Solutions to Structural Load Requirements

Different parts of solar mobile lighting trailers fulfill different functions, such as load-bearing, wind resistance, and fixation. Therefore, welding procedures must be precisely designed based on their load characteristics. The following is a detailed explanation of the process standards for three core components:

(I) Frame and chassis welding: The "first line of defense" for load-bearing safety

As the load-bearing core of the trailer, the frame and chassis must bear the combined weight of the solar panels, battery pack, and lighting equipment (typically 1-3 tons) and withstand bumps and impacts during movement. Therefore, its welding standards are particularly stringent:

Main beam butt welding utilizes "double-sided V-groove welding" with a groove angle of 60°±5°, a blunt edge thickness of 2-3mm, and an assembly gap of 2-4mm. Multi-layer, multi-pass welding is required. The current for the first weld pass is controlled at 180-200A, and the current for subsequent passes is gradually increased to 220-250A, ensuring a weld penetration depth of ≥70% of the parent material thickness.

The crossbeam and main beam are connected using "fillet welds," with a leg height of at least 8mm. The weld must be continuous and full, with no interruptions permitted. The welding sequence must follow the "center first, then the ends," and the "longitudinal first, then the transverse" approach. The principle of "to reduce welding deformation" must be adhered to.

Weld appearance must meet the following requirements: free of defects such as cracks, incomplete penetration, and slag inclusions; undercut depth ≤ 0.5mm; weld reinforcement ≤ 3mm; 100% ultrasonic testing (UT) of main beam butt welds must be performed in accordance with ISO 17640, with defects not exceeding Level II. (II) Welding of Light Pole and Base: A Key Support for Wind and Earthquake Resistance
Light poles are typically 4-8 meters tall and must withstand lateral forces from winds exceeding force 10 when used outdoors. The weld between the pole and the base is a stress concentration point. The process standards are as follows:
The base of the pole and the base flange are welded using a circumferential seam. When the flange thickness is ≥16mm, a single-sided V-groove (angle 50°±5°) is required. Welding is performed using submerged arc welding (SAW) at a speed of 30-40cm/min to ensure uniform weld penetration.
To enhance the connection strength, 4-6 reinforcing ribs are added between the pole and flange. Continuous fillet welds are used to connect the ribs to the pole and flange. The weld leg height is ≥6mm, and the gap between the rib and the pole is ≤1mm.
After welding, the pole must be inspected for verticality, with a verticality deviation of ≤1‰ (i.e., no more than 8mm for an 8-meter pole). The circumferential seam is also inspected. 100% radiographically tested (RT) in accordance with ASME BPVC Section V standards, with defects not exceeding Level III.

(III) Solar Panel Bracket Welding: The "Structural Guarantee" for Stable Power Generation

Solar panel brackets must ensure that the solar panels are always oriented toward the optimal sunlight and withstand long-term wind and rain erosion. Their welding must balance strength and rust resistance:

T-joint welding is used for bracket crossbeams and longitudinal beams, preferably using MIG welding with a welding current of 160-180A and a voltage of 22-24V. The weld seam should be smooth and avoid sharp corners that could cause stress concentration.

All welded areas must undergo surface treatment: first, remove welding slag and spatter, then sandblast to remove rust (to Sa2.5 grade), and finally apply cold-dip galvanizing with a zinc content of ≥96% and a coating thickness of ≥80μm.

After bracket welding, a load test is performed. A load of 1.2 times the rated weight (typically 20-30kg per solar panel) is applied to the solar panel mounting location for 24 hours. The welds are then inspected for deformation and cracking.

III. Welding Quality Inspection and Traceability System: Full-Process Risk Management

For buyers, a traceable quality inspection system is key to ensuring consistent quality during bulk purchases. Welding quality inspection for solar mobile lighting trailers must cover the entire process: before, during, and after welding.

(I) Pre-weld Inspection: Preventing Potential Hazards

Before welding, a comprehensive inspection of the base metal, welding materials, and groove dimensions is required:

The base metal surface must be free of rust, oil stains, cracks, and other defects, and thickness deviation must comply with the GB/T 709 standard (tolerance ±0.5mm).

Welding materials must be verified to ensure consistency between the material certificate and the actual model. Welding rods must be dried (acidic electrodes should be dried at 100-150°C for 1 hour; alkaline electrodes should be dried at 350-400°C for 2 hours).

Groove dimensions should be inspected with a weld gauge, with a deviation of no more than ±1mm. Assembly clearances should be inspected with a feeler gauge. Any deviations from the specified requirements will require reprocessing. (II) In-Weld Inspection: Real-Time Process Control

Quality inspectors conduct regular inspections during the welding process:

Monitor parameters such as welding current, voltage, and speed to ensure they meet the requirements of the process documentation, recording parameter data every 30 minutes;

Check welder compliance with operational standards, such as preheating and interpass cleaning procedures;

Test interpass temperatures during multi-layer welding. Interpass temperatures for steel welding must not exceed 300°C, and for aluminum alloy welding must not exceed 150°C.

(III) Post-weld Inspection: Comprehensive Quality Verification
Post-weld inspection is divided into two categories: visual inspection and non-destructive testing:

Visual inspection: All welds must be 100% inspected using a combination of visual inspection and weld gauges, with a focus on defects such as cracks, incomplete penetration, undercuts, and weld bumps. The appearance acceptance standard complies with GB/T 19418-2019.

Non-destructive testing: Key areas (frame main beams and light pole circumferential seams) must undergo 100% ultrasonic testing (UT) or radiographic testing (RT). General areas (bracket crossbeams) must undergo 20% sampling testing. The test results must be reported in a written report.

Mechanical testing: One sample from each batch undergoes weld tensile and bend testing. The tensile strength must be no less than the parent material standard value, and the bend test must be crack-free (bend angle ≥ 180°). (IV) Quality Traceability System: Fully traceable and traceable

Establish a full-chain traceability system from materials to finished products:

Assign a unique traceability code to each batch of base metal and welding materials, linking information such as material certification and procurement batch;

During the welding process, record the operator, equipment number, welding time, and parameter data to form a "welding process card";

Finished products are accompanied by a "Quality Traceability Report" containing all test records and traceability code information. Purchasers can scan the code to access the complete process flow.

IV. International Compliance and Industry Certification: Aligning with Global Procurement Standards

When selecting suppliers, buyers should focus on whether their welding processes meet the compliance requirements and industry certification standards of their target markets:

EU market: Requires compliance with EN 1090 steel structure welding certification, CE certification for welding processes, and weld quality that meets EN ISO 3834 standards;

North American market: Requires compliance with AWS D1.1/D1.2 welding specifications (AWS D1.1 for steel, AWS D1.2 for aluminum alloys), and suppliers must be AISC (American Institute of Steel Construction) certified;

Globally recognized standards: ISO 3834 welding quality system certification is a key requirement. This certification covers the entire process, including welding personnel, equipment, processes, and testing, and is an authoritative credential demonstrating a company's welding capabilities. In addition, for outdoor use of solar mobile lighting trailers, some countries require welds to pass salt spray corrosion testing (e.g., ASTM B117 standard, test time ≥ 500 hours, coating corrosion area ≤ 5%) to ensure product durability in harsh environments such as coastal areas and high humidity.