1965 Orr & Sembower 350 HP 3‑pass firetube natural‑gas boiler

Specs
Year: 1965
Make: Orr & Sembower
Model: 3HG
Boiler Type: Firetube (three‑pass design, packaged)
Power: 350 HP
Capacity: 11,716,250 BTU/hr
Max Working Pressure: 15 psi
Heating Surface: 1,750 sq ft
Gas Consumption Rate: 13,825 cu ft/hr
Voltage – Motors: 208 V, 3‑phase
Voltage – Controls: 120 V, 1‑phase

Installed Options
Natural gas burner assembly
Electric motor drive system
Inline pressure regulators and gas control valves
Low-pressure gauge package
Exhaust stack lift frame

Feature Spotlight
• Classic three‑pass design for consistent combustion efficiency
• 350 HP capacity ideal for medium industrial steam applications
• Rugged build with service access front and rear
• 1,750 sq ft heating surface delivers high output steam delivery
• Utility-ready natural gas input with inline isolation valves

Machine Overview
This is a 1965 Orr & Sembower 3HG packaged firetube boiler rated at 350 HP and configured for natural gas operation. Its three-pass firetube layout and 11.7 MMBTU/hr burner firing rate make it well suited for steady-state steam production. The boiler has a 15 psi design pressure, 1,750 sq ft of heating surface, and is powered via a 208 V, 3-phase motor with 120 V, 1-phase controls. The unit appears intact and piped for inline service with valve redundancy and stack suspension in place.