Schmidt-Hartmann Boiler

Schmidt-Hartmann boiler working operation is similar to an electric transformer. Two pressures are used to effect an interchange of energy.

In the primary circuit, the steam at 100 bar pressure is produced from the distilled water. This steam is passed through a submerged heating coil which is located in a steam generator (evaporator drum) as shown in the figure. The high-pressure steam in this coil possesses sufficient thermal potential and steam at 60 bar pressure with a heat transfer rate of 2.5 kW/m°C is generated in the evaporator drum.

Schmidt hartmann boiler

Schmidt-Hartmann Boiler. Image source: Slideshare

The steam produced in the evaporator drums (steam generator) from impure water is further passed through the superheater and the super-heated steam produced in the super-heater is supplied to the prime mover. The high-pressure condensate formed in the submerged heating coil is circulated through a low-pressure feed heater on its way to raise the feed water temperature to its saturation temperature. Therefore, only latent heat is supplied in the evaporator drum.

Natural circulation is used in the primary circuit and this is sufficient enough to effect the desired rate of heat transfer and to overcome the thermo-siphon head of height about 2 to 10 meters.

In normal circumstances, the replenishment of distilled water in the primary circuit is not required as every care is taken in design and construction to prevent leakages. But as a safeguard against leakage accidental loss, a pressure gauge and safety valve are fitted in the Schmidt-Hartmann boiler’s circuit.


  1. The salt deposited in the evaporator drum (steam generator) due to the circulation of impure water can be easily cleaned by blowing off the water with pressure or by removing the submerged coil from the drum.
  2. There is rare chance of overheating or burning the highly heated components of the primary circuit as there is no danger of salt deposition as well as there is no chance of interruption to the circulation either by rust or any other material. The highly heated parts run very safe throughout the life of the boiler.
  3. The wide fluctuations of load are easily taken by Schmidt-Hartmann boiler without undue priming or abnormal increase in the primary pressure due to high thermal and water capacity of the boiler.
  4. The absence of water risers in the evaporator drum and moderate temperature difference across the heating coil allow evaporation to proceed without priming.
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