Description

CONSIDERATIONS

When a steam control valve is throttling to meet a reduced heat load, the steam pressure falls inside the heat exchanger. This steam pressure falling is sometimes considerable for several different reasons and the lack of differential pressure across the steam trap reduces it’s discharge capacity, causing accumulation of condensate inside the heat exchanger, resulting in a stall condition.
In presence of these considerations, it is recommended that before any steam trap selection and sizing for this kind of systems, to determine whether or not stall will occur. The non observance of this procedure may cause serious troubles on the systems, causing malfunction and equipment damage. Typically most of heat exchangers are selected from a standard production range available and they are often oversized, in other words, after the calculation the designer select the available model which area covers the calculated area, which in addition to other safety factors normally considered during the system design and heat exchanger calculation, results on over sizing. Over sizing heat exchangers increase the heat transfer capability above the required needs and for that reason the required steam pressure (and correspondent temperature) will be lower when compared with a correctly sized unit. They must be in consequence subject to a specific analysis.