Before selection, verify three basic data points: installation space, medium temperature, and power supply conditions. In pipeline tracing and equipment preheating applications, common issues with sheathed electric heaters center on uneven surface temperature and short-term pitting of the sheath. Setting parameters accurately during the selection stage can reduce later maintenance workload.
The common outer diameter range of the sheath is Φ12mm to Φ20mm. The thinner the pipe diameter, the higher the power density per unit length, and the surface load must be reduced accordingly. For media such as clean water or weakly corrosive liquids, a stainless steel sheath may be selected; when the medium contains chloride ions or is acidic, the material grade should be verified and a corrosion allowance reserved. Uneven surface temperature of the pipeline is mostly related to power distribution and installation spacing. During selection, the pipe diameter and insulation layer thickness should be provided to facilitate determining the power per meter.
The common power range for similar products is 1kW to 6kW, with a voltage of 220V or 380V. Three-phase power supply is suitable for occasions with larger power and the need to balance loads; single-phase power supply is suitable for low-power tracing. The wiring method must be confirmed together with the on-site distribution cabinet capacity and cable specifications to avoid local overheating of the sheath caused by starting current and line voltage drop.
The sheath should avoid direct rigid contact with the pipe wall and leave clearance for thermal expansion; the junction box should be positioned for easy inspection and kept away from areas with standing water and direct steam impingement. Record the surface temperature and current values during the initial commissioning period as a baseline for subsequent inspections. When pitting occurs on the sheath, first recheck the medium composition and surface temperature, then determine whether the power density needs adjustment or the material needs replacement.
