Fabrication and Welding Requirements for Marine Bollards

1. Welding Preparation Requirements

• Welding materials (welding rods, wires, fluxes) shall be compatible with the base material of the bollard, and shall be accompanied by quality certificates. They shall be baked in accordance with the product instructions before use, and stored in an insulation bucket for immediate use to avoid dampness or deterioration. Low-hydrogen electrodes shall be used for important welding parts to prevent welding cracks.
• The base material (steel plate, forging) of the bollard shall be free of defects such as cracks, inclusions and corrosion. Before welding, the welding surface, groove and its surrounding 20-30mm area shall be thoroughly cleaned to remove oil, rust, oxide scale and other impurities, ensuring the welding surface is dry and clean.
• Welders must pass the qualification examination and hold a valid certificate, and shall only perform welding within the scope of their approved qualifications. For the first time using steel, welding materials and welding methods, welding process qualification shall be carried out to determine the welding process parameters.
• The welding groove shall be processed in accordance with the design drawings and relevant standards (such as CCS "Rules for Classification of Steel Sea-Going Ships"), and the groove size, angle and assembly gap shall meet the requirements to ensure full penetration of the weld seam. The assembly gap shall be uniform, and the misalignment shall not exceed the allowable range of the standard.
• When the ambient temperature is lower than 0℃, preheating measures shall be taken. The preheating temperature shall be determined by process test, and the preheating area shall be more than 1.5 times the thickness of the workpiece on both sides of the weld seam, and not less than 100mm. Wind shielding measures shall be taken when the wind force exceeds level 4 to avoid affecting the welding quality.

2. On-site Welding Operation Requirements

• Welding shall be carried out in strict accordance with the approved welding process specifications (WPS), and the welding current, voltage, welding speed and arc length shall be strictly controlled. The arc length of acid electrodes shall generally be 3-4mm, and that of alkaline electrodes shall be 2-3mm to ensure uniform weld thickness and width.
• Continuous welding shall be adopted for all weld seams of the bollard; spot welding, intermittent welding and missing welding are strictly prohibited. For long welds (longer than 1m for manual arc welding), segmented back welding or skip welding shall be adopted to reduce welding deformation. The joints of each weld layer shall be staggered by not less than 30mm.
• For fillet welds and butt welds of the bollard (such as the connection between the bollard body and the base, the connection between the bollard cap and the body), full penetration welding shall be adopted to ensure the welding strength. The weld leg size shall not be less than 1/4 of the thickness of the thinner base material, and the allowable deviation of the weld leg size shall be 0-4mm.
• During welding, the welding angle shall be reasonably adjusted. When the thickness of the two workpieces is equal, the angle between the welding electrode and the workpiece shall be 45°; when the thickness is unequal, the angle between the electrode and the thicker workpiece shall be appropriately increased to ensure sufficient fusion of the weld seam and the base material.
• The arc striking and arc ending shall be standardized. Arc striking shall be carried out on the arc striking plate or the weld seam area, and random arc striking on the non-weld seam surface of the bollard is prohibited. When ending the arc, the arc pit shall be filled fully, and the arc shall be drawn back in the opposite direction of welding to prevent arc pit cracks and undercutting. After welding, the arc striking plate shall be cut off by gas cutting and ground flat.
• During multi-layer welding, the welding direction of each layer of weld bead shall be consistent, and the slag shall be thoroughly cleaned after each layer of welding before the next layer of welding to avoid slag inclusion defects. The interlayer temperature shall be controlled in accordance with the process requirements to prevent welding cracks.
• Symmetrical welding shall be adopted for symmetrical structures of the bollard, and double welders shall perform welding synchronously to reduce welding deformation. The overall welding sequence shall follow the principle of welding from the center to the surrounding, and from the middle of the weld seam to both ends.

3. Welding Quality Inspection Requirements

• Visual Inspection: After welding, the weld seam shall be clean and free of welding slag and spatter. The weld surface shall be smooth and continuous, without defects such as cracks, pores, slag inclusion, undercutting, incomplete penetration and unfilled arc pits. The shape of the weld seam shall be regular, and the transition between the weld seam and the base material shall be smooth without obvious steps.
• Non-destructive Testing (NDT): Key weld seams (such as full penetration welds of the bollard body and base) shall be subject to non-destructive testing in accordance with the requirements of the classification society (CCS/BV/LR, etc.) and design drawings. Ultrasonic testing (UT) shall be the main method, and ray testing (RT) shall be adopted when ultrasonic testing cannot determine defects. The inspection grade shall meet the requirements of GB11345 or GB3323, and the flaw detection ratio of primary full penetration welds shall be 100%.
• Dimensional Inspection: After welding, the overall dimensions, verticality, levelness and position deviation of the bollard shall be inspected to ensure they are consistent with the design drawings. The ellipticity of the bollard body shall be strictly controlled, and special tooling can be used for correction if necessary to ensure the overall accuracy meets the standards.
• Weld Strength Test: Sampling test shall be carried out according to the specified ratio. The tensile strength, impact toughness and other performance indicators of the weld seam shall not be lower than the minimum value of the base material. The test plate welding qualification rate shall not be less than 95%.

4. Post-welding Treatment Requirements

• After welding, the welding slag, spatter and welding marks on the surface of the bollard shall be thoroughly cleaned, and the weld seam and its surrounding area shall be ground and polished to make the surface smooth and consistent with the overall appearance of the bollard.
• For weld seams that fail the inspection, they shall be marked, and repair welding shall be carried out in accordance with the repair process specifications. The number of repair welding shall not exceed the allowable times specified by the standard, and re-inspection shall be carried out after repair welding until it is qualified. The repair process shall be recorded in detail.
• Post-weld heat treatment shall be carried out for thick-walled bollards or important weld seams to eliminate welding stress, improve the toughness of the weld seam and prevent welding cracks. The heat treatment temperature and holding time shall be determined according to the base material and welding process, and the heat treatment record shall be kept intact.
• After post-welding treatment, anti-corrosion coating shall be applied to the bollard surface in a timely manner. The coating shall be uniform and dense, without bubbles, peeling and other defects, to enhance the corrosion resistance of the bollard in the marine environment.