Function and main types of steam traps
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Author:alliance
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Published time: 2018-05-24
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The purpose of installing the steam traps is to obtain fast heating of the product and equipment by keeping the steam lines and equipment free of condensate, air and non-condensable gases. A steam trap is a valve device that discharges condensate and air from the line or piece of equipment without discharging the steam.
The purpose of installing the steam traps is to obtain fast heating of the product and equipment
by keeping the steam lines and equipment free of condensate, air and non-condensable gases.
A steam trap is a valve device that discharges condensate and air from the line or piece of equipment
without discharging the steam.
Functions of Steam Traps
The three important functions of steam traps are:
• To discharge condensate as soon as it is formed.
• Not to allow steam to escape.
• To be capable of discharging air and other incondensible gases.
Types of Steam Traps
There are three basic types of steam trap into which all variations fall, all three are classified by
International Standard ISO 6704:1982.
Thermostatic (operated by changes in fluid temperature) - The temperature of saturated
steam is determined by its pressure. In the steam space, steam gives up its enthalpy of
evaporation (heat), producing condensate at steam temperature. As a result of any further heat
loss, the temperature of the condensate will fall. A thermostatic trap will pass condensate when
this lower temperature is sensed. As steam reaches the trap, the temperature increases and the
trap closes.
Mechanical (operated by changes in fluid density) - This range of steam traps operates by
sensing the difference in density between steam and condensate. These steam traps include 'ball
float traps' and 'inverted bucket traps'. In the 'ball float trap', the ball rises in the presence of
condensate, opening a valve which passes the denser condensate. With the 'inverted bucket
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Bureau of Energy Efficiency 63
trap', the inverted bucket floats when steam reaches the trap and rises to shut the valve. Both
are essentially 'mechanical' in their method of operation.
Thermodynamic (operated by changes in fluid dynamics) - Thermodynamic steam traps rely
partly on the formation of flash steam from condensate. This group includes 'thermodynamic',
'disc', 'impulse' and 'labyrinth' steam traps.