Boilers Safety System

By Lars Josefsson

Marine boiler plants require adequate control systems to raise steam, maintain design conditions for steady steaming, secure the boiler units and detect promptly malfunctions and failures. The automatic control arrangement on a shipboard boiler is divided into two parts:

• Boilers Safety system that controls that all values are within the predetermined limits and give automatic alarm if some of them are not, and also initiate an automatic burner trip in case of a dangerous situation.
• Continuously control of the different parameters for water level control, steam pressure control, fuel oil pressure control, fuel oil temperature control, blowdown control, superheat temperature control etc.

The combustion control system maintains constant steam pressure by controlling the flow of air and oil to the burner. More advanced combustion controls the air and oil loading simultaneously but with a slight lag between air and oil, so at increased boiler load, the air will lead the oil, and at decreased boiler load the oil will lead the air. Such an arrangement makes it possible to minimize the emission of smoke during maneuvering. All the classification societies have special requirement for marine applications due to the environment and the fact that one can't escape from an accident nor get service when the ship is sailing at sea. A boiler just has to work.