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Steam Boilers

Low-Pressure Steam Boilers:

Low-pressure steam boilers are designed to operate at pressures below 15 pounds per square inch gauge (psig). They are commonly used in heating applications and small-scale industrial processes. These boilers generate steam by heating water to its boiling point, which typically occurs at 212°F (100°C) at atmospheric pressure. The steam produced in low-pressure boilers has a lower energy content compared to high-pressure steam, but it is still capable of performing various tasks such as space heating, humidification, and certain industrial processes that do not require high-pressure conditions. Low-pressure steam boilers are relatively simpler in design and operation compared to their high-pressure counterparts, making them more affordable and easier to maintain.

High-Pressure Steam Boilers:

High-pressure steam boilers are designed to operate at pressures above 15 psig, typically ranging from 75 psig to several thousand psig. They are commonly used in power generation, large-scale industrial processes, and certain specialized applications. High-pressure boilers are capable of producing steam at higher temperatures and pressures, which allows for greater energy transfer and more efficient power generation. These boilers require robust construction, advanced control systems, and sophisticated safety measures due to the higher pressures involved. High-pressure steam is utilized in various industries for processes such as steam turbine-driven electricity generation, chemical reactions, heating of large industrial spaces, and powering heavy machinery. These boilers are generally more complex and expensive to install and maintain, but they offer higher efficiency and power output compared to low-pressure steam boilers.


Our Unilux boilers are the first and only 5-pass, bent-tube boilers that operate at 85% efficiency, standard. The tangent tube design allows for unsurpassed convective internal pumping and maximum heat transfer. Standard design pressure is 160 PSI / ASME Section I, with higher pressures available.

  • Flexible burner selection <9ppm, <30ppm, etc.

  • Useable heated water in under 15 minutes

  • Easy access to boiler controls for safety and serviceability

  • Easy fireside access for inspection and service

  • Available as field-erect (FE) units that don’t require on-site welding (ASME Section I and IV)

  • Industrial grade materials throughout

  • 25-year standard warranty against thermal shock damage

Our Unilux boilers have the greatest size range of standard product available in this design and can be used wherever heated water is required.

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Low Pressure [15 psig] - Available | 30 - 950 BHP
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High Pressure - Available | 30 -900 BHP
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EVOLV High Pressure - Available | 800 -1600 BHP
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Low Pressure [15 psig] - Available | 15 - 200 BHP

3-pass firetube boiler operates at high efficiencies due to effective heat transfer across all heating surfaces. Submerged combustion chamber improves water circulation and adds to direct heating surface.

Compact design fits through a 36″ doorway and occupies a small footprint per boiler horsepower. Front and rear water legs eliminate the need for side connections.

Built, inspected, and stamped in accordance with Section IV of the ASME code.


Tubes are rolled and flared to facilitate maintenance*.

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U-Type Flex Joint design minimizes the destructive effects of differential stress as furnace expands at a greater rate than tubes during firing.


Structural steel skid with slots for forklift handling.

Custom fabricated bent steel turbulators insure positive furnace pressure necessary for highest noncondensing combustion efficiencies (83% +/-)..


Smokeboxes are easily removed for transporting boilers through existing elevators and stairwells. Bolted and gasketed construction provides convenient access to tubesheets for inspection, cleaning, and tube maintenance.

All flue gas reversing chamber surfaces except for rear access door are water-cooled, insuring maximum heat transfer efficiency and minimal thermal shock. Removable rear door provides easy access to furnace interior.

* Welded tubes available upon request.

  • 85.6% Thermal efficiency

  • On/Off, Low/High/Off, Low/High/Low, or Full Modulation

  • With or without tankless heater

  • Packaged or knock-down

  • Gas, Oil or Gas/Oil

  • Complies to LEED

  • 15 psig Steam Boiler

  • 1010 - 5845 MBH Input

  • 24-145 H.P.

  • Single or multiple boiler systems

88 Steam Commercial Gas & Oil Boiler

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Low Pressure [15 psig] - Available | 24 - 145 BHP
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