Q.Explain working of Steam Drum?

Total solids concentration in the steam at steam manifold outlet shall not exceed 0.5 ppm during steady operation at MCR.  Fabricator must indicate the maximum acceptable total dissolved solids concentration in the boiler water when operating normal drum water level.

The normal water operating level in the steam drum shall be not less than 25 mm (1") below the drum center line.  In the drum, the surface area of the normal operating water level shall be sized based on 100% MCR, such that the maximum surface release rate shall not exceed 3,900 kg/m²h (800 lb/ft²h).

Water hold-up between fabricator's stated normal water level and top downcomer level shall be sufficient to enable operating at 100% MCR for at least five minutes in the event of loss of boiler feed water supply.  This resident time design shall include ramping rate of 20% MCR per minute.

The water surge volume in the steam drum shall be adequate to accommodate the resultant swell from increase in load of 20% of MCR per minute without actuating the low water level cut-off.