The rainy season presents unique challenges for welding operations. High humidity, condensation, and moisture ingress are not just discomforts—they are direct threats to weld integrity. Moisture introduced into the weld zone can lead to hydrogen-induced cracking, porosity, and embrittlement. Additionally, damp conditions significantly increase the risk of electric shock and render shielding gas less effective. This article outlines practical control measures to maintain welding quality during wet weather.
1. Environmental Standards for Welding (Do Not Weld If Conditions Are Not Met)
- National standards mandate that welding must not proceed when relative humidity exceeds 90%, in rain or condensation, or during high winds without protection.
- Humidity control: For indoor or sheltered areas, use industrial dehumidifiers to maintain workshop humidity at or below 80%. For pressure vessels and low-alloy steels, the requirement is stricter at ≤70%; for low-hydrogen welding, optimal conditions are ≤60%. Outdoor operations require fully enclosed rain- and wind-proof shelters—roofs with drainage, fire-resistant fabric enclosures, and 15cm water barriers at the base, supplemented by dehumidifiers and warm-air blowers. If visible water droplets or condensation appear on the workpiece surface, do not start welding.
- Wind speed management: The rainy season often brings gusts. For SMAW, wind speed must be ≤8 m/s. For gas-shielded welding (MIG/TIG), the limit is ≤2 m/s. Exceeding these limits requires windbreaks; otherwise, shielding gas is blown away, causing widespread porosity.
- Rainy day restrictions: Moderate to heavy rain, fog, or humid weather generally requires stopping outdoor work. Only fully enclosed shelters are permitted, and care must be taken to prevent slanting rain from entering the groove.
2. Moisture Protection and Drying of Welding Consumables
- Storage: Consumable warehouses must maintain constant temperature and dehumidification at ≤60% humidity. Materials should be stored 50cm above the floor and 30cm from walls to prevent ground moisture absorption. Low-hydrogen electrodes, SAW fluxes, and flux-cored wires must be kept in sealed packaging and used within the day of opening; any leftover must be re-dried.
- Field issue rules: Each welder should carry only half a container of electrodes, keeping the holding oven covered at all times. Return unused rods to the drying oven at the end of the shift—do not leave them exposed overnight.
3. Pre-Weld Cleaning and Drying of Base Metal and Grooves
- Cleaning scope: Treat 20-50mm on both sides of the joint—grind to a metallic sheen, removing rust, oil, water stains, paint, and moisture-induced flash rust.
- Condensation removal: For thin sheets and stainless steel, use low-temperature flame heating (≤150°C) to dry surface moisture without causing overheating or oxidation. For thick plates, high-strength steel, and low-temperature vessel steel, use electric heating blankets to preheat the groove and surrounding 50mm uniformly, eliminating adsorbed moisture. Workpieces exposed to rain must be allowed to stand and dried before welding.
- After groove preparation, weld as soon as possible. If more than 30 minutes elapse, reapply drying and condensation removal.
4. Process Optimization for Humid Conditions
- Preheating and interpass temperature: For general carbon steel, increase preheat to 80-100°C. For thickness ≥30mm, high-strength steel, or Cr-Mo steel, raise to 120-180°C. Interpass temperature should not fall below the preheat level to prevent condensation during cooling. For low-alloy steels, keep interpass below 250°C. Tack welds should follow the same preheat requirements—use longer tack lengths and more frequent tacks to prevent cracking.
- Welding technique: Use short-arc operation to reduce moisture entrainment. For gas-shielded processes, increase shielding gas flow by about 10% to compensate for humid air interference. For thick plates with multiple passes, clean slag after each pass and cool to interpass temperature before proceeding. During rainy periods, try to weld continuously to minimize stops and starts.
5. Equipment and Electrical Safety
- Welder protection: Place welders at least 30cm above ground and cover with waterproof sheeting. Ensure no water accumulation inside shelters. All cables and connections should be insulated with protective sleeves; replace damaged cables immediately.
- Electrical safety: Welders must wear insulated rubber gloves and waterproof insulated boots. Do not operate with wet gloves or clothing. Ensure reliable grounding and test earth leakage protectors daily. In damp areas, do not change electrodes or adjust current while the machine is live. For water-cooled TIG torches, ensure water lines are leak-proof to prevent short circuits.
- Gas supply: Keep argon and CO₂ cylinders elevated and dry. Regularly drain regulators and blow out condensation from gas lines.
6. Red Lines – Conditions That Must Stop Work
Work must stop immediately if any of the following conditions exist:
- No rain shelter, exposed to rain or drifting moisture.
- Ambient humidity exceeds 90%, or condensation/water droplets are visible on the workpiece.
- Gas-shielded welding with wind speed >2 m/s and no wind protection.
- Low-hydrogen electrodes not properly dried or left exposed for extended periods.
- Welding groove not cleaned/dewatered or not preheated.
- Damaged cables or extensive water accumulation on the shop floor.
Post time: Jul-20-2026