Using the Boiler Design Software a fire tube boiler design was optimized delivering the following
  • reduced number of tubes (as few as 75 in 4 MW/400 HP boiler, down from up to 237 as found
    in same-sized Scotch Marine designs)
  • up to 70% of released heat from combustion taken up in furnace (more than 50 % more than in
    conventional Scotch Marine design)
  • no refractory lining made possible by unique cooled door design
  • reduced efficiency degradation at reduced boiler load
  • absence of tubesheet cracking as result of reduced temperature on tubesheet by cooled door.

In 1999, Tucson Medical Center (TMC,, Tucson, Arizona, USA installed three such
boilers of 4 MW/400 HP, 150 psi/10 bar, 6-metric ton steam per hour capacity. Data indicate a
consistent up to 15 percentage points seasonal efficiency increase over previous boilers. The boilers
carry serial numbers 001, 002 and 003 indicating first of the kind ones. Significantly improved part
load efficiency and no tubesheet cracks have been observed as of 2017 after 18 years of operation.
Letter of testimonial is available
here. Existing fire tube boilers can be retrofitted to this design.

Animated file showing the boiler principle is available
here. Instructions: Download the file and run it.
Icon on desktop will be created. Double click it to run the animation.
View on fire tube steam boilers of advanced design at Tuscon Medical Center, Arizona, U.S.A. (pipe
delivering steam from the cooled door visible)
Inner view on cooled door. Transverse plate prevents hot flue gas coming in touch with uncooled
steam area (above) from the cooled area below when door is closed.
Rear view with rear smoke box and stack connector.
Boiler plate with National Board number 001 indicating first of the kind boiler.
Boiler Design Software
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