Electric Class A Cabinet Oven for EMI/RFI Shielding Product Batch Processing

The project required a shelf-loaded batch oven sized for controlled thermal processing in a compact production format. Based on the source package and customer background, the oven supported an EMI/RFI shielding manufacturing environment involving shielding products, shielding gaskets, conductive shielding materials, or related fabricated shielding components.

APPLICATION REQUIREMENT

• The project required a batch process oven for shielding-related production work.
• The oven had to support shelf-loaded product or fixtures in a manufacturing environment handling custom or variable product forms.
• The work area had to be large enough to handle multiple load arrangements within one cabinet chamber.

WORK CHAMBER / LOADING REQUIREMENT

• Required work chamber: 55 in W × 30 in D × 60 in H.
• The oven needed to support multiple shelf elevations for different product heights and batch arrangements.
• The documented shelf package included one 500 lb bottom shelf, one 250 lb shelf, and two 100 lb shelves.
• Maximum shelved oven capacity had to be 750 lb evenly distributed.

OPERATOR / ACCESS REQUIREMENT

• The oven had to allow front loading and unloading through two swing doors.
• The loading arrangement had to work with a 12-inch stand for practical loading height.
• Trays, product positioning, and fixturing had to be arranged to minimize airflow restriction through the oven.

QUALITY / CONTROL REQUIREMENT

• The customer needed repeatable thermal processing within the stated work-zone uniformity.
• The process required programmable temperature control for defined thermal cycles.
• The machine had to arrive factory wired, tested, temperature surveyed, and balanced before shipment.

SAFETY / ENVIRONMENTAL REQUIREMENT

• The oven had to be configured as a Class A oven.
• The documented maximum volatile load basis was 0.21 gal/batch o-xylene.
• The customer process required powered exhaust and purge logic for safe handling of volatile, toxic, or otherwise undesirable fumes.

SITE / UTILITY REQUIREMENT

• Required electrical service: 230V / 3PH / 60Hz.
• Shipping and receiving dock door basis: 12 ft W × 16 ft H.

The project required a controlled moderate-temperature batch heating process based on horizontal forced convection, Class A ventilation, and programmable heat control.

TEMPERATURE REQUIREMENT

• Operating temperature basis: 350°F.
• Maximum temperature basis: 350°F.
• Required work-zone uniformity: ±10°F.

AIRFLOW / HEAT-TRANSFER REQUIREMENT

• Airflow direction basis: full horizontal airflow.
• The process required forced-convection heating across the work chamber.
• Using the documented recirculation airflow and the chamber cross-sectional area in the airflow direction, the first-pass chamber air velocity is approximately 96 FPM.

HEAT-INPUT REQUIREMENT

• Heat source: electric resistance heat.
• Installed heat basis: 24 kW total.
• Heating arrangement basis: two 12 kW heater banks.
• The process required controlled heater-bank operation through the temperature-control system.

VENTILATION REQUIREMENT

• The process required Class A exhaust and purge sequencing.
• Powered exhaust basis: 225 CFM.
• Maximum volatile load basis: 0.21 gal/batch o-xylene.
• The process required ventilation to be proven 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 40D-350 electric Class A cabinet oven with horizontal airflow, powered exhaust, flexible shelving, and interlocked controls.

OVERALL CONCEPT

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

HEATING ARCHITECTURE

• Heat source: electric resistance heat.
• Total installed heat: 24 kW.
• Heating split into two 12 kW heater banks.
• Each heater bank built from twelve 1000 W elements.
• Heater power controlled through solid-state relays with backup contactors.

AIRFLOW ARCHITECTURE

• Airflow pattern: full horizontal airflow.
• Recirculation system based on an RB fan assembly delivering 1200 CFM at 2 in. W.c..
• Final drawing package identifies adjustable louver openings for airflow setup.

EXHAUST / VENTILATION ARCHITECTURE

• Class A exhaust based on a PQ1 exhauster delivering 225 CFM.
• Fresh-air damper integrated into the oven body.
• Purge timer and airflow switches interlocked with the heat system.

CHAMBER / SHELL ARCHITECTURE

• Internal work chamber: 55 in W × 30 in D × 60 in H.
• 2-inch insulated wall construction.
• Insulation: 2 in of 6 lb mineral wool.
• Interior: unpainted aluminized steel.
• Exterior finish: PQ Blue.
• Control enclosure finish: ANSI 61 gray.
• Approximate oven weight: 1450 lb.

DOOR / LOADING ARCHITECTURE

• Two swing doors.
• 12-inch oven stand.
• Shelf package includes one 500 lb bottom shelf, one 250 lb shelf, and two 100 lb shelves.
• Shelf adjustment based on 3-inch centers.

CONTROLS ARCHITECTURE

• Watlow F4T ramp/soak controller for primary temperature control.
• Gefran 650L for excess-temperature protection.
• NEMA 1 UL508A open industrial control panel.
• Separate operator controls for exhaust fan, recirculation fan, and each heater bank.
• Panel includes purge complete, fan on, and heater-bank on indication.
• Enclosure layout includes cooling fan and panel-mount USB port.

SAFETY ARCHITECTURE

• Applicable standards basis: NFPA 79, NFPA 86, UL508A.
• 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

SHIPPING / INSTALLATION ARCHITECTURE

• Proposal package states the oven is shipped assembled on 4x4 lumber or larger as required and shipped on a flatbed truck.
• Shipping basis is FOB Origin / PPA.