Procurement personnel often encounter rust or weld seam leakage in stainless steel sheaths of explosion-proof electric heaters within a short period. Although 316L stainless steel welded pipes contain molybdenum and have strong resistance to chloride ion corrosion, in actual working conditions, if the medium contains high concentrations of chloride ions or the equipment is in a humid environment for a long time, pitting corrosion or stress corrosion cracking may still occur. In addition, if the weld seams of the welded pipe have defects such as lack of fusion or porosity, they will become channels for medium penetration.
To address the above issues, when selecting models, attention should be paid to the weld seam quality and surface treatment of the welded pipe. It is recommended to require suppliers to provide non-destructive testing reports for weld seams and confirm that the welded pipe has undergone solution treatment or pickling passivation to restore corrosion resistance. For scenarios with highly corrosive media, consider increasing the wall thickness of the welded pipe or using duplex stainless steel, but economic feasibility must be evaluated.
During installation and maintenance, avoid scratching the surface of the welded pipe or direct contact with carbon steel to prevent galvanic corrosion. Regularly check the sealing performance at the connection between the welded pipe and the flange. If leakage is found, replace the sealing gasket or re-weld in a timely manner. For outdoor or washing environments, the protection level should not be lower than IP65; for coastal scenarios, IP66 is recommended, and check whether the flameproof surface of the junction box is rusted.
Procurement personnel also need to verify the explosion-proof certificate of the entire machine and confirm that the explosion-proof marking matches the usage area. When 316L welded pipe is used as a heating element sheath, ensure that it, together with the internal magnesium oxide insulation filling and nickel-chromium alloy heating wire, meets the low surface power density design to avoid local overheating accelerating corrosion.
