Explosion-proof duct heaters are used where air or a compatible gas must be heated in or near a classified industrial area. Applications may include process ventilation, drying, preheating, make-up air, anti-condensation duty, and temperature control for packaged equipment. The heater is typically installed in a duct or engineered housing with terminals, sensors, and protective devices selected for the site conditions.

A safe design requires dependable airflow across every energized element. The inquiry should include gas composition, normal and minimum flow, inlet and outlet temperatures, duct dimensions, operating pressure, ambient temperature, particulate loading, hazardous-area classification, and the maximum allowable sheath or discharge temperature. If the gas contains solvent vapor or other combustible components, the owner and qualified safety engineer must define the applicable design basis.

Runkel can customize element arrangement, housing dimensions, mounting flange, sheath material, power stages, terminal enclosure, and sensor package. Staged or modulating control can reduce temperature overshoot when demand changes. A dedicated high-temperature limit and airflow proving device should be considered independently of the normal control loop.

During installation, avoid uneven inlet profiles immediately downstream of elbows, dampers, or fans unless flow straightening is provided. Confirm that the fan starts and airflow is proven before the heater can energize, and that the heater turns off before airflow stops. Routine inspection should focus on terminals, insulation resistance, deposits, filters, sensors, and evidence of hot spots.

Pressure drop is often a project constraint. The heater frame, element quantity, element spacing, and support arrangement must provide adequate heat-transfer area without obstructing the gas stream excessively. The supplier should receive the allowable pressure-drop limit together with minimum and maximum flow. If the duct carries particulate matter, access for inspection and cleaning becomes especially important.

Temperature sensors should represent the actual risk and control objective. A downstream process sensor may provide normal control, while a separate high-limit sensor monitors the heater outlet or another critical point. In some designs, additional element-sheath sensing is considered. Sensor response time, mounting depth, radiation effects, and mixing distance should be reviewed with the system designer.

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.