Electric Class A Truck Oven for Recycled Magnet Demagnetization

The project required a cart-loaded batch oven for the controlled thermal demagnetization of recycled magnet material. The customer work in magnetic materials and recycled rare-earth processing created the need for a robust oven platform capable of handling dense product loads while delivering repeatable high-temperature batch performance.

APPLICATION REQUIREMENT

• The project required a batch demagnetization oven for recycled magnets.
• The oven had to support a thermal process that removed magnetism from recycled magnetic material before downstream handling and subsequent processing.
• The system had to provide a controlled batch environment suited to magnetic-material processing rather than general low-temperature drying.

WORK CHAMBER / LOAD REQUIREMENT

• Required work chamber: 48 in W × 48 in D × 60 in H.
• The oven had to support cart-loaded batches rather than hand-loaded shelf processing.
• The documented cart package provided a 1,500 lb capacity flatbed cart with a 40 in × 40 in load surface.
• The loading system had to accommodate dense and potentially irregular recycled magnet loads in a repeatable transport format.

OPERATOR / ACCESS REQUIREMENT

• The oven had to allow front loading and unloading through two swing doors.
• The process required a guided cart-loading arrangement using the oven’s insulated floor guide tracks.
• Product positioning and fixturing had to be arranged to minimize restrictions to airflow passage through the oven.

QUALITY / CONTROL REQUIREMENT

• The process required repeatable high-temperature batch performance within the stated work-area uniformity.
• The system required programmable temperature control to support defined demagnetization profiles.
• The oven had to provide a stable thermal environment for consistent recycled magnet processing from batch to batch.

SAFETY / ENVIRONMENTAL REQUIREMENT

• The oven had to be configured as a Class A oven.
• The documented design basis established a maximum volatile load of 0.32 gal/batch (o-xylene basis).
• The process required powered exhaust, purge sequencing, and airflow proving before heat could be enabled.
• Because of the site elevation, the allowable VOC basis was reduced by 4%.

SITE / UTILITY REQUIREMENT

• Required electrical service: 460V / 3PH / 60Hz.
• Design elevation: 1,135 ft.

The project required a high-temperature forced-convection batch process capable of thermally demagnetizing recycled magnet material in a controlled Class A oven environment.

TEMPERATURE REQUIREMENT

• Operating temperature basis: approximately 750°F to 800°F.
• Maximum temperature basis: 800°F.
• Required work-area uniformity: ±10°F.

PROCESS BASIS

• The thermal process basis was demagnetization of recycled magnets.
• The process required a sustained high-temperature thermal environment appropriate for removing magnetic strength from recycled magnet feedstock.
• The oven had to deliver that performance in a repeatable batch format across cart-loaded product.

AIRFLOW / HEAT-TRANSFER REQUIREMENT

• Airflow direction basis: full horizontal airflow.
• The process required forced-convection heat transfer across the full cart-loaded work zone.
• Using the documented recirculation airflow and chamber cross-sectional area in the airflow direction, the first-pass chamber air velocity is approximately 105 FPM.

HEAT-INPUT REQUIREMENT

• Heat source: electric resistance heat.
• Installed heat basis: 54 kW total.
• Heating arrangement basis: two 27 kW heater banks.
• The process required controlled staged heat delivery through the temperature-control system.

VENTILATION REQUIREMENT

• The process required Class A exhaust and purge sequencing.
• Powered exhaust basis: 550 CFM.
• Maximum volatile load basis: 0.32 gal/batch (o-xylene basis).
• Airflow proving had to be satisfied before heat could be enabled.

CONTROL / SEQUENCING REQUIREMENT

• Primary control basis: ramp/soak temperature control.
• Minimum purge time basis: 3 minutes.
• Documented operating sequence:
• Start exhaust fan.
• Start recirculation fan.
• Complete purge.
• Turn on heater bank(s).
• Run at temperature or programmed profile.

COOLDOWN REQUIREMENT

• The process required continued fan operation during cooldown.
• The source package states that fans are not to be shut down while oven temperature is above 250°F.

To satisfy those requirements, Precision Quincy configured the project as a 74-800 electric Class A truck oven with full horizontal airflow, powered exhaust, guided cart loading, and interlocked high-temperature controls.

OVERALL CONCEPT

• One electric Class A truck oven.
• Cart-loaded batch configuration for recycled magnet demagnetization.
• Compact high-temperature oven platform sized for guided flatbed-cart loading.

HEATING ARCHITECTURE

• Heat source: electric resistance heat.
• Total installed heat: 54 kW.
• Heating split into two 27 kW heater banks.
• Each heater bank built from nine 3,000 W elements.
• Heater power controlled through solid-state relays with backup contactors.

AIRFLOW ARCHITECTURE

• Airflow pattern: full horizontal airflow.
• Recirculation system based on a 13.5 in × 5 in fan assembly delivering 2,100 CFM at 2 in. W.c..
• Fresh-air damper integrated into the oven airflow system.

EXHAUST / VENTILATION ARCHITECTURE

• Class A exhaust based on a PQ1 exhauster delivering 550 CFM at 1 in. W.c..
• Exhaust and recirculation airflow are monitored through airflow switches.
• Purge timer and interlocked safety logic prevent heater operation until safe operating conditions are met.

CHAMBER / SHELL ARCHITECTURE

• Internal work chamber: 48 in W × 48 in D × 60 in H.
• 6-inch insulated wall construction.
• Standard wall insulation: 6 in of 6 lb mineral wool.
• Heat-chamber wall insulation: 5 in of 6 lb mineral wool plus 1 in of 8 lb Superwool.
• Interior: unpainted aluminized steel.
• Exterior finish: PQ Blue.
• Control enclosure finish: ANSI 61 gray.
• The oven includes an insulated floor with cart guide tracks.

DOOR / LOADING ARCHITECTURE

• Two swing doors.
• Flatbed cart with 1,500 lb capacity.
• Cart load surface: 40 in × 40 in.
• Cart construction: mild steel, unpainted.
• Cart running gear: two swivel casters and two rigid casters, each 6 in diameter.

CONTROLS ARCHITECTURE

• Watlow F4T ramp/soak controller for primary temperature control.
• Gefran 650L excess-temperature controller.
• NEMA 1 UL 508A open industrial control panel.
• Separate operator controls for exhaust fan, recirculation fan, heater bank #1, and heater bank #2.
• Panel indication includes purge complete, fan on, and heater-bank on status lights.
• Enclosure layout includes a panel cooling fan, USB port, and 100A non-fused disconnect switch.

SAFETY ARCHITECTURE

• Applicable standards basis: NFPA 79, NFPA 86, UL 508A.
• Safety logic includes:
• Exhaust airflow proving
• Recirculation airflow proving
• Timed purge before heat enable
• Excess-temperature shutdown
• Heat shutdown if required safe operating conditions are not met