Electric Class B Cabinet Oven for Pre-Heating and Stress Relief of Aluminum and Steel Parts

The project required a shelf-loaded batch oven sized for controlled thermal processing of aluminum and steel parts. The process was pre-heating and stress relief, requiring repeatable temperature control in a compact cabinet format.

APPLICATION REQUIREMENT

• The project required a batch process oven for aluminum and steel parts.
• The oven had to support pre-heating and stress-relief processing.
• The oven had to support shelf-loaded product or fixtures in a cabinet chamber.

WORK CHAMBER / LOADING REQUIREMENT

• Required work chamber: 48 in W × 30 in D × 48 in H.
• The loading package included two 100 lb shelves.
• Shelf adjustment: 3-inch centers.
• The loading arrangement had to support multiple part and fixture positions within the cabinet chamber.

OPERATOR / ACCESS REQUIREMENT

• The oven had to allow front loading and unloading through two swing doors.
• Trays, product positioning, and fixturing had to be arranged to minimize airflow restriction through the oven.
• The oven had to fit a standard industrial shipping and receiving environment based on 12 ft W × 16 ft H dock-door access.

QUALITY / CONTROL REQUIREMENT

• The customer needed repeatable thermal processing within the stated work-zone uniformity.
• The process required controlled temperature measurement at the work area.
• The oven had to provide an independent excess-temperature safety limit.

SAFETY / ENVIRONMENTAL REQUIREMENT

• The process was Class B.
• VOC loading was not permitted.
• The process used gravity exhaust rather than powered Class A exhaust architecture.

SITE / UTILITY REQUIREMENT

• Required electrical service: 460V / 3PH / 60Hz.
• Design elevation: less than 1000 ft.

The project required a controlled moderate-temperature batch heating process based on horizontal forced convection, electric resistance heat, and Class B operation.

TEMPERATURE REQUIREMENT

• Operating temperature: 250°F to 550°F.
• Maximum temperature: 550°F.
• Required work-zone uniformity: ±10°F.

AIRFLOW / HEAT-TRANSFER REQUIREMENT

• Airflow direction: full horizontal airflow.
• The process required forced-convection heating across the work chamber.
• Chamber air velocity was 150 FPM, which provided the heat transfer rate required for the process.

HEAT-INPUT REQUIREMENT

• Heat source: electric resistance heat.
• Installed heat: 18 kW total.
• Heating arrangement: eighteen 1000 W elements.
• The process required controlled heater operation through the temperature-control system.

VENTILATION REQUIREMENT

• Exhaust arrangement: gravity exhaust.
• The process was Class B with no VOCs allowed.
• The oven includes a 6-inch square exhaust opening and a fresh-air damper.

CONTROL / MEASUREMENT REQUIREMENT

• Primary temperature control: SSI 804 temperature controller.
• Independent excess-temperature protection: Geffran 650L.
• The control system uses Type J thermocouples to monitor the work area and excess-temperature condition.

COOLDOWN REQUIREMENT

• Fans are not to be shut down while oven temperature is above 250°F.
• The controller can be configured to shut down fans and reset once oven temperature falls below 250°F.

To satisfy those requirements, Precision Quincy configured the project as a 40B-550 electric Class B cabinet oven with horizontal airflow, electric heat, insulated cabinet construction, and interlocked controls.

OVERALL CONCEPT

• One electric Class B cabinet oven.
• Compact front-loading batch configuration.
• Shelf-loaded work chamber sized for flexible metal-parts loading.

HEATING ARCHITECTURE

• Heat source: electric resistance heat.
• Total installed heat: 18 kW.
• Heating built from eighteen 1000 W elements.
• Heater power controlled through solid-state relays with associated switching and protection hardware.

AIRFLOW ARCHITECTURE

• Airflow pattern: full horizontal airflow.
• Recirculation system based on a 9.94 in × 6 in fan wheel delivering 1500 CFM at 2 in. W.c..
• Recirculation motor: 1.5 HP.
• Louver openings provide airflow setup adjustment.

EXHAUST / VENTILATION ARCHITECTURE

• Exhaust arrangement: gravity exhaust.
• Exhaust opening: 6-inch square opening.
• A fresh-air damper is integrated into the oven body.

CHAMBER / SHELL ARCHITECTURE

• Internal work chamber: 48 in W × 30 in D × 48 in H.
• 4-inch insulated wall construction.
• Insulation: 4 in of 6 lb mineral wool.
• Interior: unpainted aluminized steel.
• Exterior finish: PQ Blue.
• Control enclosure finish: ANSI 61 gray.
• Approximate oven weight: 1250 lb.
• The oven includes a 4-inch insulated floor.

DOOR / LOADING ARCHITECTURE

• Two swing doors.
• Shelf package includes two 100 lb shelves.
• Shelf adjustment is based on 3-inch centers.
• The installation includes four floor anchors.

CONTROLS ARCHITECTURE

• SSI 804 for primary temperature control.
• Geffran 650L for excess-temperature protection.
• NEMA 1 UL508A open industrial control panel.
• Control package includes disconnect, fusing, motor starter / protector, solid-state relays, control transformer, airflow switch input, and enclosure cooling fan.

SAFETY ARCHITECTURE

• Applicable standards: NFPA 79, NFPA 86, UL508A.
• Safety logic includes:
• Recirculation airflow proving
• Excess-temperature shutdown
• Heat shutdown if required safe operating conditions are not met
• Controlled fan shutdown below 250°F when enabled

SHIPPING / INSTALLATION ARCHITECTURE

• The oven was shipped assembled on 4x4 lumber or larger as required on a flatbed truck.