A coating-line operator in Liaoning Province needed warmer make-up air during winter to stabilize drying conditions. Because solvent vapor could be present in the wider process area, the owner required a disciplined hazardous-area review and dependable airflow interlocks. This article describes an illustrative application, not a confirmed project for a named customer.

The concept used an explosion-proof duct-heating assembly upstream of the controlled process zone. The thermal duty was based on minimum winter inlet temperature, air mass flow, and target discharge temperature. The design limited element surface temperature and arranged the elements to promote even airflow across the duct section.

The proposed sequence started the fan, proved airflow, opened the required dampers, and then enabled heater stages. Loss of airflow or a high-temperature signal removed power immediately. A run-on period allowed the fan to carry away residual heat after normal shutdown. Filters and access panels were positioned for regular inspection.

The scenario highlights the importance of system responsibility. The heater manufacturer can provide a customized assembly and technical data, while the coating-line designer must define solvent conditions, ventilation philosophy, area classification, temperature limits, and functional safety requirements. Clear interfaces between these parties reduce risk during commissioning.

The coating-line owner would first define the expected solvent types, concentration range, ventilation modes, and maximum safe air temperature. These inputs are essential because the heater cannot be selected independently of the overall explosion-protection and ventilation strategy. The line designer would also review what happens during filter blockage, fan failure, emergency stop, and production changeover.

During commissioning, technicians would measure airflow across several operating modes and confirm that each heater stage follows the intended sequence. Temperature uniformity downstream of the heater could be checked at multiple points. If the profile is uneven, changes to duct transitions, straightening devices, dampers, or sensor locations may be more effective than increasing electrical power.

Call to Action

Discuss your application with Runkel. Send the medium or gas composition, flow or volume, inlet and target temperatures, pressure, voltage, installation dimensions, control requirements, and hazardous-area information to info@runkel.cn, or visit www.runkel.cn.