recovery from the gases, the EGB wilI be larger in size and it wilI thus have a larger water volume inside the tubes.Due to increased steam production and water volume of the EGE, the OFB, steam receiver, has to be enlarged in order to obtain larger steam space and to withstand level variations which occur when the main engine starts and stops. When the main engine starts, and consequently the steam production takes place, the water in the EGB will expand and will be pressed from the EGE to the OFB where the water leivel increases. On the contrary, when the main engine stops, the steam production interrupts. The circulating water pump will then fill up the EGE with water that results in a decrease of the water level in the OFB. In case of a too small OFB compared with the steam production and the water content of the EGE, the water level variations in the OFB will be unacceptable and they will cause repeated, undesired high and low level alarms.