Posted by rosmadi b zakaria on July 27, 2001 at 04:53:05:
In Reply to: Re: Boiler System Design posted by Raymond on September 01, 2000 at 14:09:48:
: : Incase of High Pressure Boiler Installation it is suggested to have a suction head of 1 kg per cm.sq this results in the de-aerator and feed water tank being installed at the heigt of 10 mts.
: : I wud like to know that why it is essential to have this arrangement ?
: : Anish
: The water in a thermal dearator is at its boiling point. The slightest reduction in pressure due to friction in the transporting lines will cause the water to start vaporising. This means cavitation when trying to pump this water. The only way to avoid this is provide a sufficient static head. The height you need to provide at the suction of the pump. Should be to its minimum, the NPSH imposed by the pump manufacturer plus the maximum friction loses expected in the suction lines, valves and suction filters. I would suggest that you put a safety margin on top of that. You do not want to damage your boiler feed water pump and play with its reliability. So yes, as a common practice dearators are placed 7 to 10 meters above the boiler feed water pump suction.
: A matter of fact this is true for all processed liquids pumped at their boiling points.
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