Modulatic High Pressure Compact Steam Boiler

Vapor Power High Pressure
Compact Steam Boilers

The Modulatic® Line

Low Cost, High Pressure for Industrial Applications

Single Pass Water Tube Units, 300 BPH and 3100 psig 10, 350 lbs/hour


Modulatic High Pressure Compact Steam Boiler

Key Features of The Modulatic® High Pressure Compact Steam Boiler

  • Rapid start up - from cold start to full load in five minutes.
  • Low cost coil replacement - multiple coil design permits damaged coil replacement.
  • High quality steam - guaranteed 99% + dry steam.
  • Minimum prepurge energy loss - smaller size unit allows proper prepurge in seconds.
  • Minimal soot problems - separate combustion chamber prevents coating coils with partially burned fuels.
  • Simplified fuel switching - only have to turn selector, no burner changes required.
  • Low fuel requirements - air preheating and refractory lined chamber for complete combustion.
  • Minimum off-on cycling - turndown ratios up to 10 to 1 for handling wide range of loads.
  • Quick response to load changes - cycle time of less than one minute.
  • Low installation costs - packaged, compact units require only 60% of floor space needed for firetube boilers.
  • Complete line - nine sizes to permit proper selection. Safe design - no latent energy in the unit. Risk of catastrophic failure is eliminated.
  • Long life expectancy, rugged design and components, ASME design.
  • Coils are designed for a minimum of 1000 psi in thicker coil walls for longer life.
  • Easy access to burners - end mounted burner is simple to maintain.

The Modulatic® High Pressure Compact Steam Boiler
Operating Concept

The Modulatic® steam generator is a once through, forced circulation, water tube boiler in which water under pressure circulates at high velocity through a series of coils while forced draft combustion gases travel across the outside of the coils. The hot gases envelope the entire tube surface, making maximum use of both radiant and convective heat to achieve very high heat transfer rates. Water is forced by the feedwater pump into the series connected multiple coil assembly where 90% of the water is converted to steam. The steam and the remaining 10% unevaporated water are carried from the boiler to the separator (where unevaporated water is separated form the steam), providing 99%+ dry steam output. Solids collect at the separator bottom and are blown out when the blow down valve is opened. Close tracking of load variations is possible through use of a patented bypass regulator which continuously senses steam pressure.

The control changes feedwater volume to the coils in response to every change in steam demand. This modulated flow of feedwater varies the amount of steam output without the thermal shock of on-off feedwater pump action experienced in conventional boilers.

In addition, a patented servo fuel control accurately adjusts fuel and air for the most efficient combustion mixture by continually monitoring changes in the feedwater flow. Inefficient burner cycling is eliminated, fluctuating demands are satisfied and steam pressure is held constant. The design is such that the boiler cannot be fired without water being fed into the coils.


An integral control panel contains all controls and indicators necessary for the safe operation of the unit. A programmed operating sequence is also incorporated for simplified startup.

Free Start-Up Service

A qualified service representative is on hand for two consecutive days during start-up to assure trouble-free operation and provide on-site operator training.

Built to Meet Standards

Every unit is built to ASME Standards, Hartford inspected and National Board registered. Coast Guard, American Bureau of Shipping, Factory Mutual, Industrial Risk Insurers, Lloyds and other approvals are also available upon request.

Factory Tested

All units are fire tested for up to three days at the factory, with their individual controls to assure proper operation and to allow for control adjustments, which avoid installation delays.

The Modulatic® High Pressure Compact Steam Boiler
General Specifications


Boiler - Sectionalized coil tube type, forced circulation, forced draft fired.

Operating Pressures - adjustable from:

  • 5-13 psig 400-810 psig
  • 100-250 psig 400-1500 psig
  • 200-540 psig 500-2700 psig

Consult factory for special operating pressure ranges.


  • Air atomized burner for #2 fuel oil.
  • Multi-orificed burner for natural gas or LPG.
  • Combination of above for dual fuel applications.
  • Burners available to meet Low NOx regulations.

Electric Power

  • Main - 230 or 460 VAC, 3 Ph, 60 Hz Control - 120 VAC, 1 Ph, 60 Hz, factory wired.
  • Special voltages are available on request.
  • Ignition Electric spark ignited, interrupted gas pilot on most units.
  • Direct electric spark optional on #2 oil units where permitted.

Safety Controls

Programmed flame safeguard control with flame detector, coil temperature control, low water cut-off control, steam pressure control.

Optional Equipment

Automatic Blowdown, Stack Switch, Automatic Multiple Boiler Control, Annunciator Systems and equipment to meet special codes.

The Modulatic® High Pressure Compact Steam Boiler
Data and Dimensions

High Pressure Compact Steam Boilers

** Based on #2 fuel oil at 141,000 Btu per U.S. gallon and natural gas of 1000 Btu per cubic foot heat content. 0 - Based on 300 PSIG design unit.

* All models except 18 BHP are available as oil fired, gas fired or combination gas/oil units. 18 BHP unit has off-on automatic control. All units are 240v or 480v, 3 phase, 60 cycle, 120 VAC control power factory wired. Other voltages on request.

Application Assistance

With over 50 years experience in the design and manufacture of steam generators, and thousands of operating units, Vapor stands ready to assist with any specific application. Computer simulation of process systems and heat loss analysis are available to ensure the proper system for your application.