Heavy-Duty Gas-Fired Batch Curing Oven with Rotating Roller System

A motor manufacturer required a reliable thermal processing solution for curing epoxy coatings on large stator assemblies. The application imposed demanding requirements across load capacity, temperature uniformity, safety compliance, and site constraints.

APPLICATION & PRODUCT TYPE

• Product: epoxy-coated motor stator assemblies (large, heavy cylindrical components).
• Process: batch curing in a controlled thermal environment to polymerize epoxy coatings.
• Stators are cylindrical; rotation during curing is required for uniform coating distribution across the part surface.

LOAD REQUIREMENTS

• Maximum batch load: 11,000 lb per batch.
• Maximum individual part weight: up to 5,500 lb per part.
• Loading method: top-loading via an overhead door; overhead lifting equipment (customer-supplied) positions stators onto powered rollers inside the oven.

THERMAL REQUIREMENTS

• Operating temperature: 350°F typical.
• Maximum temperature capability: 400°F.
• Temperature uniformity: ±10°F at operating setpoint across the work area.

VOC / SAFETY COMPLIANCE REQUIREMENT

• VOC loading: 1.0 gallon per batch of standard solvent emitted during epoxy cure.
• Required: NFPA 86 Class-A oven compliance with appropriate exhaust, purge, and safety interlock systems.

SITE CONDITIONS

• Fuel: natural gas heating specified.
• Electrical service: 460V / 3-phase / 60 Hz.
• Site altitude: 1,170 feet above sea level (requires combustion system altitude adjustment).

ACCESSIBILITY CONSTRAINTS

• Equipment must enter facility through a 12' × 16' dock door.

These thermal process requirements were developed to meet the customer's curing process needs for epoxy-coated stator assemblies, based on the application conditions and operating parameters.

TEMPERATURE REQUIREMENTS

• Normal operating temperature: 350°F.
• Maximum temperature capability: 400°F.

LOAD / PRODUCT PARAMETERS

• Batch capacity: 11,000 lb per batch.
• Individual part: up to 5,500 lb per part.
• Part geometry: cylindrical stators; rotation throughout the cure cycle ensures all surfaces receive consistent thermal exposure.

HEAT INPUT REQUIREMENT

• Required heat input: 500,000 BTU/hr.
• Direct-fired natural gas; Maxon OvenPak 405 burner.

AIRFLOW DELIVERY

• Full horizontal airflow (front-to-back) through the oven chamber.
• Recirculation fan: 4,000 CFM at 4.5" WC static pressure, 5 HP TEFC, belt-driven.
• Supply and return ductwork: 18-gauge aluminized steel with adjustable slot nozzles for airflow balancing.

EXHAUST REQUIREMENTS (CLASS-A VOC REMOVAL)

• Class-A exhaust fan: 1,225 CFM at 1" WC static pressure, 1.5 HP ODP motor.
• Exhaust discharge: vertical (customer to vent outside building per applicable code).
• Exhaust wheel material: mild steel, polished and ground.

TEMPERATURE UNIFORMITY

• ±10°F from setpoint at operating temperature, ensuring complete and even epoxy cure across the full load.

To deliver the thermal process requirements (which deliver the customer process requirements), PrecisionQuincy settled on the following equipment concept and architecture for the batch curing oven.

OVERALL CONCEPT

• Class-A, natural gas-fired, top-loading batch curing oven.
• Direct-fired heating via Maxon OvenPak 405 at 500,000 BTU/hr.
• Oven chamber: 117" W × 36" L × 41" H (100 cu ft interior volume).
• Overall equipment dimensions: 206.5" W × 70.5" L × 121.25" H.
• Total equipment weight: approximately 6,125 lb.

DOOR SYSTEM

• Top-loading door: 4-inch thick insulated construction with aluminized steel interior and exterior.
• Operation: electric winch with gearbox; self-locking in the up position for safety.
• Safety devices: door slack sensor; pneumatically actuated safety latch to prevent door from falling in the up position.
• Seal: high-temperature door seal gasket around full perimeter.

PRODUCT ROTATION SYSTEM

• Two 8-inch diameter powered rollers; variable speed 1.2 to 12 RPM.
• Drive: tensioner sprocket system with manual lead-screw adjustment for belt maintenance.
• Drip pans: aluminized steel positioned beneath rollers to contain process residue (varnish/epoxy runoff).
• End-of-oven access: access pan slides out at the end of the oven for removal of drip panels/trays during maintenance.

HEATING / AIRFLOW ARCHITECTURE

• Side-mounted heat chamber houses the burner and supply fan assembly.
• Supply fan: belt-driven, 4,000 CFM at 4.5" WC static pressure, 5 HP TEFC motor, mild steel polished wheel.
• Airflow pattern: full horizontal (front-to-back) via 18-gauge aluminized steel supply and return ductwork with adjustable slot nozzles.
• Class-A exhaust fan: 1,225 CFM, 1.5 HP ODP motor, vertical discharge.

CONSTRUCTION / SHELL ARCHITECTURE

• Structural steel frame (not insulated panel construction); an extremely robust and stable platform.
• 16-gauge internal pans designed to accommodate thermal expansion/contraction while minimizing through-metal paths.
• 16-gauge exterior cladding (mild steel).
• Wall thickness: 6 inches with 6-pound density mineral wool insulation.
• Finish: Precision Quincy Blue industrial enamel on body and door; white control panel.

CONTROLS ARCHITECTURE

• Temperature controller: Watlow F4T.
• Thermocouple type: Type J.
• Control enclosure: E1 enclosure; UL 508A open industrial control panel.
• Safety interlocks: heater box hi-limit (digital/manual reset), work area hi-limit (digital/manual reset), airflow switches on supply and exhaust fans, purge timer (Karl Dungs MPA4112), flame safeguard.
• Gas train: Karl Dungs double blocking valves with mixer and proportional control.

SAFETY SYSTEMS

• NFPA 86 and OSHA compliant.
• Class-A exhaust system for continuous VOC removal during cure cycle.
• Door slack sensor and pneumatically actuated safety latch on door system.
• Hi-limit controllers (heater box and work area) with manual reset.
• Airflow switches on both supply fan and exhaust fan as safety interlocks.

OTHER NOTED ATTRIBUTES

• Utilities: 460V / 3-phase / 60 Hz, 20 FLA; natural gas at 400 CFH @ 1 PSI.
• Site altitude adjustment: combustion system configured for 1,170 feet above sea level.
• Equipment dimensions designed to pass through a 12’ × 16’ dock door for installation.