Firetube Boilers - Two Pass Wet-Back (SG)

Steam Boilers

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Product Description

The SG Firetube Boilers are our direct fired two pass wet back boilers.  The burner fires down the center of the firetube, which is located on the lower half of the boiler.  The flame travels down the firetube and enters the inversion chamber.  The exhaust gases then travel from the inversion chamber through the combustion tubes and exit the boiler through the exhaust stack.  The wet back design refers to water at the back of the boilers inversion chamber thus eliminating the need for refractory. Another feature is that the tubes are both expanded and welded to the tube-sheets.

The SG Firetube Boilers are only available in a two pass design.  The two pass design has a more balanced heat transfer from the tube to the water than a three pass design.  The optimized heat transfer lessens the thermal stresses on the structure and helps mitigate cracking or deformation.  In comparison, the third pass of a three pass boiler has negligible heat transfer improvement while it has the potential to expose the tubes to corrosion (dew point).

The SG can be supplied with a variety of forced draft burners provided by some of the world’s leading burner manufactures.  This allows us to utilize a variety of fuels, meet stringent emissions requirements, and even allow our customers the opportunity to select the burner of their choice.

The SG-PA is our high efficiency option of the SG Firetube Boiler.  The SG-PA is constructed in a horizontal orientation and is supplied with a combustion air preheater at the burner side of the heater.

The SG-ECO is our feed water preheater option of the SG Firetube Boiler.  The feed water preheater utilizes an economizer to preheat the water entering the steam generator.  This in turn, enables the customer to obtain optimum performance of the generator by supplying the necessary feed water temperatures to the Firetube Boiler.

The SG, SG-PA, and SG-ECO Firetube Boilers are designed and constructed to various local code requirements around the world.  The most common codes are ASME with National Board registration for the United States, CRN for Canada, and CE/PED/TUV/DIN for Europe. Additional code requirements may be met if necessary.

Package and containerized systems are available for both the SG, SG-PA, and SG-ECO Firetube Boilers.  These package systems can be customized to meet each of our customers’ needs, including but not limited to: control panel, feed water pumps, feed water treatment, deaerator, feed water tanks, ladders and platforms, and ancillary components.  These auxiliary components are typically fabricated in the USA for USA/Canada installations.


Firetube Boilers In General

Firetube boilers are a form of large water content boilers used to provide customers with steam as a heat transfer media.  Typically, the quality of steam provided by these units is much higher than forced circulation steam generators.  The higher quality of steam mitigates the use of steam separators or steam accumulators.

Product Specifications

Capacity Range:

  • 425 to 1,761 BHP(4150 to 17,280 kW)

Steam Production:

  • 14,500 to 60,760 lb/hr (6,600 to 27,600 kg/hr)

Operating Pressures:

  • 174 to 435 psi (12 to 30 bar)

Fuel Option:

  • Natural Gas
  • #2 Fuel Oil/Diesel
  • Light Fuel Oils
  • LPG
  • Dual Fuel
  • Additional Fuel Options Available


  • Horizontal

Two Pass, Wet Back Design

Combustion Air Preheater Optional

  • Model SM-PA

Economizer Optional

  • Model SM-ECO

Model Overview

Summary by model
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Model Thermal Capacity
Thermal Capacity
Thermal Capacity
Flow Rate
Model Steam Production
Steam Production
Steam Production
(From and at 212°F)
BHP Thermal Capacity
UM 30 300 661 735 21 206
UM 50 500 1,102 1,224 36 353
UM 100 1,000 2,205 2,449 71 697
UM 150 1,500 3,307 3,673 106 1,040
UM 200 2,000 4,409 4,898 142 1,393
UM 300 3,000 6,614 7,347 213 2,090
UM 400 4,000 8,818 9,796 273 2,678
Model Steam Capacity
Steam Capacity
BHP Thermal Capacity
HP 50 500 1,102 32 314
HP 100 1,000 2,205 64 628
HP 150 1,500 3,307 96 942
HP 200 2,000 4,409 128 1,256
HP 300 3,000 6,614 192 1,884
HP 400 4,000 8,818 256 2,512
Model Steam Production
Steam Production
Steam Production
(From and at 212°F)
BHP Thermal Capacity
SG 600 6,000 13,228 14,693 411 4,032
SG 800 8,000 17,637 19,591 545 5,347
SG 1000 10,000 22,046 24,489 682 6,691
SG 1200 12,000 26,455 29,387 818 8,025
SG 1500 15,000 33,069 36,733 1,025 10,056
SG 2000 20,000 44,092 48,978 1,314 12,891
SG 2200 22,000 48,502 53,876 1,598 15,677
SG 2500 25,000 55,116 61,222 1,633 16,021
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Additional Details

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Please call us at 770-777-2570 or contact us for more information.


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