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 Steam Trap Operating Characteristics
TABLE 8-2.
Inverted
Bimetallic
Bellows
Bucket
F&T
Disk
Thermostatic
Thermostatic
Characteristics
Intermittent
Continous
Intermittent
Continuous
Semimodulating
Method of operation
(discharge)
Poor
Excellent
Excellent
Poor
Excellent
Operates against back
pressure
Good3
Fair
Excellent
Excellent
Excellent
Venting capability
Good
Poor to good
Excellent
Good
Fair
Load change response
Fair to good
Handles dirt
Good
Poor to good
Excellent
Poor
Poor5
Poor
Freeze resistance
Excellent
Excellent
Good
Water hammer resistance
Poor
Excellent
Poor
Excellent
Excellent
Handles startup loads
Fair
Poor
Fair
Excellent
Excellent
Suitable for superheat
Yes
Yes
Yes
No
No
5F to 30F
50F to 100F
Steam
Condensate subcooling
Steam
Steam
temperature
temperature
temperature
Closed*
Open
Open'
Usual failure mode
Closed
Open
1
4
Can be intermittent on low loads.
Can fail closed due to dirt.
2
5
Can fail open due to wear.
May be insulated for excellent resistance.
3
Not recommended for very low pressure.
Steam Trap Selection Guide
TABLE 8-3.
Primary Choice1
Alternate Choice
Application
Special
Considerations
Float and thermostatic
Inverted bucket
Steam Mains
Energy conservation
and
Response to slugs of condensate
Thermostatic in
Branch Lines
Ability to handle dirt
locations where
Variable load response
freezing may occur
Ability to vent gases
Failure Mode (open)
Float and thermostatic
Inverted bucket
Steam Separators
Energy conservation
(large vent)
Variable load response
Thermostatic (above
Response to slugs of condensate
125 psig)
Ability to vent gases
Ability to handle dirt
Failure Mode (open)
Float and thermostatic
Inverted bucket
Unit Heaters
Energy conservation
(constant pressure)
(constant pressure)
and
Resistance to wear
Air Handling
Resistance to hydraulic shock
Units
Float and thermostatic
Thermodynamic
Ability to purge system
(variable pressure)
(variable pressure)
Ability to handle dirt
Thermostatic traps should be used in any application where freezing temperatures may occur.
8-16
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